Merge branch 'frontend/filetree' into 'main'

feat: frontend/Filetree

Closes #2

See merge request EmmaVandewalle/writand!37

app/build.gradle

@@ -5,6 +5,7 @@ plugins {
     id 'kotlinx-serialization'
     id "kotlin-kapt"
     id 'com.google.protobuf' version '0.9.4'
+    id "kotlin-parcelize"
 }
 
 android {
@@ -13,7 +14,7 @@ android {
 
     defaultConfig {
         applicationId "be.re.writand"
-        minSdk 26
+        minSdk 30
         targetSdk 34
         versionCode 1
         versionName "1.0"
@@ -65,9 +66,10 @@ dependencies {
     implementation "androidx.compose.ui:ui-tooling-preview:$compose_ui_version"
     implementation "androidx.compose.material3:material3:1.2.1"
     implementation 'androidx.test:core-ktx:1.6.1'
-    implementation 'com.google.ar:core:1.44.0'
+    implementation 'com.google.ar:core:1.45.0'
     implementation 'androidx.navigation:navigation-runtime-ktx:2.7.7'
     implementation 'androidx.navigation:navigation-compose:2.7.7'
+    implementation 'androidx.documentfile:documentfile:1.0.1'
     testImplementation 'junit:junit:4.13.2'
     androidTestImplementation 'androidx.test.ext:junit:1.2.1'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.6.1'

app/src/main/AndroidManifest.xml

@@ -2,20 +2,26 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools">
 
+    <!--    Manage storage permission: we should fall into the category where this is allowed -->
+    <!--    https://developer.android.com/training/data-storage/manage-all-files#all-files-access-google-play -->
+    <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
+    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
+    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
+
     <application
         android:name=".WApplication"
         android:allowBackup="true"
         android:dataExtractionRules="@xml/data_extraction_rules"
         android:fullBackupContent="@xml/backup_rules"
         android:icon="@mipmap/ic_launcher"
-        android:label="@string/app_name"
+        android:label="Writand"
         android:supportsRtl="true"
         android:theme="@style/Theme.Writand"
-        tools:targetApi="31">
+        tools:targetApi="31"
+        android:hardwareAccelerated="true">
         <activity
             android:name=".MainActivity"
             android:exported="true"
-            android:label="@string/app_name"
             android:theme="@style/Theme.Writand">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />

app/src/main/java/be/re/writand/MainActivity.kt

@@ -1,22 +1,109 @@
 package be.re.writand
 
+import android.app.AlertDialog
+import android.content.ActivityNotFoundException
+import android.content.Intent
+import android.net.Uri
 import android.os.Bundle
+import android.os.Environment
+import android.provider.Settings
+import android.util.Log
+import android.widget.Toast
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
+import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Surface
 import androidx.compose.ui.Modifier
+import androidx.core.app.ActivityCompat
 import androidx.navigation.compose.rememberNavController
 import be.re.writand.navigation.WNavGraph
+import be.re.writand.screens.filetree.WFiletree
 import be.re.writand.ui.theme.WritandTheme
+import be.re.writand.utils.directorypicker.DirectoryPicker
 import dagger.hilt.android.AndroidEntryPoint
 
 @AndroidEntryPoint
-class MainActivity: ComponentActivity() {
+class MainActivity : ComponentActivity() {
+    private val picker = DirectoryPicker(this)
+    private val EXTERNAL_STORAGE_PERMISSION_CODE = 100
+    private val EXTERNAL_STORAGE_PERMISSION = Settings.ACTION_MANAGE_APP_ALL_FILES_ACCESS_PERMISSION
+    private var hasPermission = false
+
+    private fun requestPermission() {
+        when {
+            Environment.isExternalStorageManager() -> {
+                Toast.makeText(this, "Permission granted", Toast.LENGTH_LONG).show()
+                hasPermission = true
+            }
+
+            ActivityCompat.shouldShowRequestPermissionRationale(
+                this,
+                EXTERNAL_STORAGE_PERMISSION
+            ) -> {
+                val builder = AlertDialog.Builder(this)
+                builder.setMessage("This app requires access to files to do its job")
+                    .setTitle("Permission required")
+                    .setCancelable(false)
+                    .setPositiveButton("Ok") { dialog, _ ->
+                        ActivityCompat.requestPermissions(
+                            this,
+                            arrayOf(EXTERNAL_STORAGE_PERMISSION),
+                            EXTERNAL_STORAGE_PERMISSION_CODE
+                        )
+
+                        dialog.dismiss()
+                    }
+                    .setNegativeButton("Cancel") { dialog, _ ->
+                        dialog.dismiss()
+                    }
+                    .show()
+            }
+
+            // permission is not yet granted, ask user for permission
+            else -> {
+                val launcher =
+                    registerForActivityResult(ActivityResultContracts.StartActivityForResult()) {
+                        Toast.makeText(
+                            this,
+                            "Permission: ${Environment.isExternalStorageManager()}",
+                            Toast.LENGTH_LONG
+                        ).show()
+                        hasPermission = Environment.isExternalStorageManager()
+                    }
+
+                try {
+                    val intent =
+                        Intent(EXTERNAL_STORAGE_PERMISSION, Uri.parse("package:$packageName"))
+                    val builder = AlertDialog.Builder(this)
+                    builder.setTitle("Permission is required")
+                        .setMessage("Writand needs permission to access the filesystem.")
+                        .setCancelable(false)
+                        .setPositiveButton("Ok") { dialog, _ ->
+                            launcher.launch(intent)
+                            dialog.dismiss()
+                        }
+                        .setNegativeButton("Deny") { dialog, _ ->
+                            dialog.dismiss()
+                        }
+                        .show()
+
+                } catch (e: ActivityNotFoundException) {
+                    Log.e("PERMISSION", "${e.message}")
+                    TODO("Permission: support legacy operation when $EXTERNAL_STORAGE_PERMISSION is not supported")
+                }
+            }
+        }
+    }
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
+
+        requestPermission()
+
         setContent {
             WritandTheme {
                 // A surface container using the 'background' color from the theme

app/src/main/java/be/re/writand/data/local/FileManagerLocal.kt

@@ -1,86 +0,0 @@
-package be.re.writand.data.local
-
-import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.withContext
-import java.io.File
-import java.nio.file.Files
-import java.nio.file.NotDirectoryException
-import java.nio.file.Path
-import java.nio.file.Paths
-import java.util.PriorityQueue
-import java.util.Queue
-import kotlin.io.path.deleteExisting
-import kotlin.io.path.exists
-import kotlin.io.path.isDirectory
-import kotlin.io.path.name
-
-class FileManagerLocal : IFileManager {
-
-    /**
-     * Checks if a directory is empty.
-     * Requires API 26!
-     *
-     * @param[path] The path of the directory to be checked.
-     * @return returns true if the directory is empty. If [path] points to a file,
-     * false is immediately returned.
-     */
-    fun isDirectoryEmpty(path: Path): Boolean {
-        if (!path.isDirectory()) return false
-        return Files.list(path).count() == 0L
-    }
-
-    override suspend fun create(name: String, basePath: Path) {
-        if (!basePath.isDirectory()) throw NotDirectoryException(basePath.name)
-
-        val fullPath = Paths.get(basePath.toString(), name)
-        withContext(Dispatchers.IO) {
-            val res = fullPath.toFile().createNewFile()
-            if (!res) throw FileAlreadyExistsException(
-                fullPath.toFile(),
-                reason = "File already exists."
-            )
-        }
-    }
-
-    override suspend fun delete(path: Path) {
-        // path is a directory and is not empty, delete everything in this directory
-        if (path.isDirectory() && !isDirectoryEmpty(path)) {
-            val queue: Queue<Path> = PriorityQueue()
-            queue.add(path)
-
-            while (!queue.isEmpty()) {
-                val top = queue.poll()!!
-                if (top.isDirectory() && !isDirectoryEmpty(top)) {
-
-                    // add all the elements of the current directory to the queue
-                    for (dir in top.iterator()) {
-                        queue.add(dir)
-                    }
-
-                    // add the directory back into the queue (top is not an empty directory)
-                    queue.add(top)
-                } else {
-
-                    // top is a file or an empty directory
-                    top.deleteExisting()
-                }
-            }
-        } else {
-            path.deleteExisting()
-        }
-    }
-
-    override suspend fun move(from: Path, to: Path) {
-        withContext(Dispatchers.IO) {
-            Files.move(from, to)
-        }
-    }
-
-    override suspend fun rename(path: Path, newName: String) {
-        move(path, Paths.get(path.parent.toString(), newName))
-    }
-
-    override suspend fun walk(root: Path): FileTreeWalk {
-        return File(root.toUri()).walkTopDown()
-    }
-}

app/src/main/java/be/re/writand/data/local/filemanager/FileManagerLocal.kt

@@ -0,0 +1,141 @@
+package be.re.writand.data.local.filemanager
+
+import be.re.writand.utils.FileNode
+import be.re.writand.utils.GenerateId
+import be.re.writand.utils.WFileTreeAbstraction
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import java.nio.file.Files
+import java.nio.file.NotDirectoryException
+import java.nio.file.Path
+import java.nio.file.Paths
+import java.util.LinkedList
+import java.util.Queue
+import java.util.Stack
+import javax.inject.Inject
+import kotlin.io.path.deleteExisting
+import kotlin.io.path.isDirectory
+import kotlin.io.path.name
+
+class FileManagerLocal @Inject constructor(
+    private val generator: GenerateId
+) : IFileManager {
+
+    /**
+     * Checks if a directory is empty.
+     * Requires API 26!
+     *
+     * @param[path] The path of the directory to be checked.
+     * @return returns true if the directory is empty. If [path] points to a file,
+     * false is immediately returned.
+     */
+    fun isDirectoryEmpty(path: Path): Boolean {
+        if (!path.isDirectory()) return false
+        return Files.list(path).count() == 0L
+    }
+
+    override suspend fun create(name: String, fileType: FileType, basePath: Path): ULong {
+        if (!basePath.isDirectory()) throw NotDirectoryException(basePath.name)
+        val id = generator.generateUUID(name)
+
+        val fullPath = Paths.get(basePath.toString(), name)
+        withContext(Dispatchers.IO) {
+            val res = when (fileType) {
+                FileType.FILE -> {
+                    fullPath.toFile().createNewFile()
+                }
+
+                FileType.DIRECTORY -> {
+                    fullPath.toFile().mkdirs()
+                }
+            }
+            if (!res) throw FileAlreadyExistsException(
+                fullPath.toFile(),
+                reason = "File already exists."
+            )
+        }
+        return id
+    }
+
+    override suspend fun delete(path: Path) {
+        if (path.isDirectory() && !isDirectoryEmpty(path)) {
+            val queue: Queue<Path> = LinkedList()
+            queue.add(path)
+
+            while (!queue.isEmpty()) {
+                val top = queue.poll()!!
+                if (top.isDirectory() && !isDirectoryEmpty(top)) {
+                    val files = top.toFile()!!.listFiles()!!
+
+                    // add all the elements of the current directory to the queue
+                    for (dir in files) {
+                        queue.add(dir.toPath())
+                    }
+
+                    // add the directory back into the queue (top is not an empty directory)
+                    queue.add(top)
+                } else {
+
+                    // top is a file or an empty directory
+                    top.deleteExisting()
+                }
+            }
+        } else {
+            path.deleteExisting()
+        }
+    }
+
+    override suspend fun move(from: Path, to: Path) {
+        withContext(Dispatchers.IO) {
+            Files.move(from, to)
+        }
+    }
+
+    override suspend fun rename(path: Path, newName: String) {
+        move(path, Paths.get(path.parent.toString(), newName))
+    }
+
+    override suspend fun initFiletree(root: Path): WFileTreeAbstraction {
+        val index: HashMap<ULong, Path> = HashMap()
+        if (!root.isDirectory()) throw IllegalArgumentException("Provided argument is not a directory.")
+        val stack = Stack<Pair<Path, FileNode>>()
+        val rootId = generator.generateUUID(root.name)
+        val rootNode = FileNode(item = rootId, parent = null)
+        stack.push(Pair(root, rootNode))
+
+        index[rootId] = root
+
+        while (!stack.isEmpty()) {
+            val (path, node) = stack.pop()
+            // if it is a directory, we can go 1 level deeper
+            // else we hit a leaf node and can stop this "recursive call"
+            if (path.isDirectory()) {
+                val files = path.toFile()!!.listFiles()!!
+                for (child in files) {
+                    val id = generator.generateUUID(child.name)
+                    val childPath = child.toPath()
+
+                    // add this file to the index
+                    index[id] = childPath
+
+                    val childNode = FileNode(item = id, parent = node)
+                    node.children.add(childNode)
+                    stack.push(Pair(childPath, childNode))
+                }
+
+                // sort the children to follow the structure: alphabetically sorted and directories before files
+                node.children.sortWith(
+                    compareBy<FileNode> { index[it.item]?.isDirectory() }
+                        .reversed()
+                        .thenBy { index[it.item]?.name }
+                )
+            }
+        }
+        return WFileTreeAbstraction(index, rootNode)
+    }
+
+    override suspend fun read(path: Path): String {
+        val file = path.toFile()
+        return file.readLines().joinToString(separator = "\n")
+    }
+}

app/src/main/java/be/re/writand/data/local/filemanager/FileType.kt

@@ -0,0 +1,9 @@
+package be.re.writand.data.local.filemanager
+
+/**
+ * Simple enum to show which type a given object represents.
+ */
+enum class FileType {
+    FILE,
+    DIRECTORY
+}

app/src/main/java/be/re/writand/data/local/filemanager/IFileManager.kt

@@ -1,39 +1,39 @@
-package be.re.writand.data.local
+package be.re.writand.data.local.filemanager
 
-import java.nio.file.Path
+import be.re.writand.utils.WFileTreeAbstraction
+import java.io.IOException
 import java.nio.file.InvalidPathException
 import java.nio.file.NotDirectoryException
-import java.io.IOException
+import java.nio.file.Path
-import java.io.IOError
 
 /**
- * An interface to handle the File trees.
+ * An interface to handle file operations.
- * File is used to mention both real files and directories at the same time.
+ * "file" is used to mention both real files and directories at the same time.
  */
 interface IFileManager {
     /**
-    * Create a new File.
+     * Create a new file and assign an id to it.
-    * @param[name] the name of the new File.
+     * @param[name] the name of the new file.
-     * @param[basePath] the path where the new File should be created in.
+     * @param[basePath] the path where the new file should be created in.
      * @throws InvalidPathException
      * @throws FileAlreadyExistsException
      * @throws NotDirectoryException
      * @throws IOException
      * @throws SecurityException
      * */
-    suspend fun create(name: String, basePath: Path)
+    suspend fun create(name: String, fileType: FileType, basePath: Path): ULong
 
     /**
-     * Delete a File.
+     * Delete a file.
      * Symbolic links are followed.
-     * @param[path] the path pointing to the File to be deleted.
+     * @param[path] the path pointing to the file to be deleted.
      * @throws NoSuchFileException
      */
     suspend fun delete(path: Path)
 
     /**
-     * Move a File to a different location.
+     * Move a file to a different location.
-     * If the File to be moved is a symbolic link, then the link itself is moved instead of the
+     * If the file to be moved is a symbolic link, then the link itself is moved instead of the
      * target of the link.
      * @param[from] the start location.
      * @param[to] the destination.
@@ -45,7 +45,7 @@ interface IFileManager {
 
     /**
      * Rename a file to a new name
-     * @param[path] the path to the File to rename
+     * @param[path] the path to the file to rename
      * @param[newName] the new name to be given to [path]
      * @throws FileAlreadyExistsException
      * @throws IOException
@@ -54,11 +54,15 @@ interface IFileManager {
     suspend fun rename(path: Path, newName: String)
 
     /**
-     * Walk the directory and build a File tree.
+     * Walk the directory and build a file tree together with an index to enable fast searching.
-     * @throws NullPointerException
+     * @throws IOException
-     * @throws IllegalArgumentException
-     * @throws IOError
-     * @throws SecurityException
      */
-    suspend fun walk(root: Path): FileTreeWalk
+    suspend fun initFiletree(root: Path): WFileTreeAbstraction
+
+    /**
+     * Read a file in memory.
+     * @param[path] the path to the file to be read
+     * @throws IOException
+     */
+    suspend fun read(path: Path): String
 }

app/src/main/java/be/re/writand/di/DatabaseModule.kt

@@ -1,12 +1,15 @@
 package be.re.writand.di
 
 import android.content.Context
+import be.re.writand.data.local.filemanager.FileManagerLocal
+import be.re.writand.data.local.filemanager.IFileManager
 import be.re.writand.data.local.db.ProjectsDao
 import be.re.writand.data.local.db.ProjectsDatabase
 import be.re.writand.data.repos.settings.IUserSettingsRepository
 import be.re.writand.data.repos.settings.UserSettingsRepository
 import be.re.writand.data.repos.tos.ITOSRepository
 import be.re.writand.data.repos.tos.TOSRepository
+import be.re.writand.utils.GenerateId
 import dagger.Module
 import dagger.Provides
 import dagger.hilt.InstallIn
@@ -47,4 +50,9 @@ class DatabaseModule {
     fun provideTOSRepository(@ApplicationContext context: Context): ITOSRepository {
         return TOSRepository(context)
     }
+
+    @Provides
+    fun provideFileManager(generateId: GenerateId): IFileManager {
+        return FileManagerLocal(generateId)
+    }
 }

app/src/main/java/be/re/writand/di/GeneratorModule.kt

@@ -0,0 +1,20 @@
+package be.re.writand.di
+
+import be.re.writand.utils.GenerateId
+import dagger.Module
+import dagger.Provides
+import dagger.hilt.InstallIn
+import dagger.hilt.components.SingletonComponent
+
+/**
+ * Enable dependency injection for the generator class.
+ */
+@InstallIn(SingletonComponent::class)
+@Module
+class GeneratorModule {
+
+    @Provides
+    fun provideGenerator(): GenerateId {
+        return GenerateId()
+    }
+}

app/src/main/java/be/re/writand/domain/files/CreateFileUseCase.kt

@@ -0,0 +1,24 @@
+package be.re.writand.domain.files
+
+import be.re.writand.data.local.filemanager.FileType
+import be.re.writand.data.local.filemanager.IFileManager
+import java.nio.file.Path
+import javax.inject.Inject
+
+/**
+ * Use case to create a new file / directory on the filesystem.
+ * @param[manager] an object implementing the [IFileManager] interface.
+ */
+class CreateFileUseCase @Inject constructor(
+    private val manager: IFileManager
+) {
+
+    /**
+     * @param[name] the name of the new file / directory.
+     * @param[type] the type conforming [FileType].
+     * @param[root] the root directory where the new file / directory must be placed in.
+     */
+    suspend operator fun invoke(name: String, type: FileType, root: Path): ULong {
+        return manager.create(name, type, root)
+    }
+}

app/src/main/java/be/re/writand/domain/files/InitFiletreeUseCase.kt

@@ -0,0 +1,22 @@
+package be.re.writand.domain.files
+
+import android.content.Context
+import be.re.writand.data.local.filemanager.IFileManager
+import be.re.writand.utils.WFileTreeAbstraction
+import java.nio.file.Paths
+import javax.inject.Inject
+
+/**
+ * Use case to read the contents of a directory.
+ * @param[fileManager] an object implementing the [IFileManager] interface.
+ * @param[context] the context of the application.
+ */
+class InitFiletreeUseCase @Inject constructor(
+    private val fileManager: IFileManager,
+    private val context: Context
+) {
+    suspend operator fun invoke(pathString: String): WFileTreeAbstraction {
+        val path = Paths.get(pathString)
+        return fileManager.initFiletree(path)
+    }
+}

app/src/main/java/be/re/writand/domain/files/MoveFileUseCase.kt

@@ -0,0 +1,23 @@
+package be.re.writand.domain.files
+
+import be.re.writand.data.local.filemanager.IFileManager
+import java.nio.file.Path
+import javax.inject.Inject
+
+/**
+ * Use case to move a file to a new directory.
+ * @param[manager] an object implementing the [IFileManager] interface to handle the filesystem operation.
+ */
+class MoveFileUseCase @Inject constructor(
+    private val manager: IFileManager
+) {
+
+    /**
+     * Perform the move action.
+     * @param[item] the item which is moved.
+     * @param[destination] the destination directory.
+     */
+    suspend operator fun invoke(item: Path, destination: Path) {
+        manager.move(item, destination)
+    }
+}

app/src/main/java/be/re/writand/domain/files/ReadFileContentsUseCase.kt

@@ -0,0 +1,18 @@
+package be.re.writand.domain.files
+
+import be.re.writand.data.local.filemanager.IFileManager
+import java.nio.file.Path
+import javax.inject.Inject
+
+/**
+ * Use case for reading in the contents of a file.
+ * @param[manager] an object implementing the [IFileManager] interface to handle the filesystem operation.
+ */
+class ReadFileContentsUseCase @Inject constructor(
+    private val manager: IFileManager
+) {
+
+    suspend operator fun invoke(path: Path): String {
+        return manager.read(path)
+    }
+}

app/src/main/java/be/re/writand/domain/files/RemoveFileUseCase.kt

@@ -0,0 +1,17 @@
+package be.re.writand.domain.files
+
+import be.re.writand.data.local.filemanager.IFileManager
+import java.nio.file.Path
+import javax.inject.Inject
+
+/**
+ * Use case for reading in the contents of a file.
+ * @param[manager] an object implementing the [IFileManager] interface to handle the filesystem operation.
+ */
+class RemoveFileUseCase @Inject constructor(
+    private val manager: IFileManager
+) {
+    suspend operator fun invoke(root: Path) {
+        manager.delete(root)
+    }
+}

app/src/main/java/be/re/writand/screens/components/Buttons.kt

@@ -1,9 +1,11 @@
 package be.re.writand.screens.components
 
+import androidx.compose.foundation.border
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material3.Button
 import androidx.compose.material3.ButtonDefaults
+import androidx.compose.material3.MaterialTheme
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
@@ -34,3 +36,63 @@ fun WButton(
         WText(text = text, color = Color.Black, modifier = Modifier.padding(5.dp))
     }
 }
+
+/**
+ * A button to represent an action with consequences.
+ * This buttons has a red highlight to make sure the user is sure when confirming the action.
+ * @param[text] the text to show inside the button.
+ * @param[modifier] the modifier applied to this button.
+ * @param[onClick] a function to be executed when confirmation is given.
+ * @param[enabled] controls if this button is enabled or not.
+ */
+@Composable
+fun WDangerButton(
+    text: String,
+    modifier: Modifier = Modifier,
+    onClick: () -> Unit,
+    enabled: Boolean = true
+) {
+    Button(
+        onClick = onClick,
+        modifier = modifier,
+        colors = ButtonDefaults.buttonColors(containerColor = Color.Red),
+        shape = RoundedCornerShape(10.dp),
+        enabled = enabled
+    ) {
+        WText(text = text, color = Color.White, modifier = Modifier.padding(5.dp))
+    }
+}
+
+/**
+ * A button without a fill color.
+ * @param[text] the text to show inside the button.
+ * @param[modifier] the modifier applied to this button.
+ * @param[onClick] a function to be executed when confirmation is given.
+ * @param[enabled] controls if this button is enabled or not.
+ */
+@Composable
+fun WBorderButton(
+    text: String,
+    modifier: Modifier = Modifier,
+    onClick: () -> Unit,
+    enabled: Boolean = true
+) {
+    Button(
+        onClick = onClick,
+        modifier = modifier.border(
+            width = 2.dp,
+            color = MainGreen,
+            shape = RoundedCornerShape(10.dp)
+        ),
+        colors = ButtonDefaults.buttonColors(containerColor = Color.Transparent),
+        shape = RoundedCornerShape(10.dp),
+        enabled = enabled
+    ) {
+
+        WText(
+            text = text,
+            color = MaterialTheme.colorScheme.onPrimary,
+            modifier = Modifier.padding(5.dp)
+        )
+    }
+}

app/src/main/java/be/re/writand/screens/components/DragAndDrop.kt

@@ -0,0 +1,183 @@
+package be.re.writand.screens.components
+
+import android.util.Log
+import androidx.compose.foundation.gestures.detectDragGesturesAfterLongPress
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.BoxScope
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.LazyListScope
+import androidx.compose.foundation.lazy.rememberLazyListState
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.CompositionLocalProvider
+import androidx.compose.runtime.compositionLocalOf
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.input.pointer.pointerInput
+import androidx.compose.ui.layout.boundsInWindow
+import androidx.compose.ui.layout.onGloballyPositioned
+import androidx.compose.ui.unit.IntSize
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.zIndex
+
+/**
+ * Currently this is unused, but the goal is to implement this feature into the filetree.
+ * based on: [this video](https://www.youtube.com/watch?v=ST99k8qK6SM)
+ */
+
+internal class DragTargetInfo {
+    var isDragging: Boolean by mutableStateOf(false)
+    var dragPosition by mutableStateOf(Offset.Zero)
+    var dragOffset by mutableStateOf(Offset.Zero)
+    var draggableComposable by mutableStateOf<(@Composable () -> Unit)?>(null)
+    var dataToDrop by mutableStateOf<Any?>(null)
+}
+
+internal val LocalDragTargetInfo = compositionLocalOf { DragTargetInfo() }
+
+@Composable
+fun <T> DragTarget(
+    modifier: Modifier = Modifier,
+    dataToDrop: T,
+    onStartDragging: () -> Unit,
+    onStopDragging: () -> Unit,
+    content: @Composable () -> Unit
+) {
+    var currentPosition by remember { mutableStateOf(Offset.Zero) }
+    val currentState = LocalDragTargetInfo.current
+
+    Box(
+        modifier = modifier
+            .onGloballyPositioned {
+                currentPosition = it.windowToLocal(Offset.Zero)
+            }
+            .pointerInput(Unit) {
+                detectDragGesturesAfterLongPress(
+                    onDragStart = {
+                        onStartDragging()
+                        currentState.dataToDrop = dataToDrop
+                        currentState.isDragging = true
+                        currentState.dragPosition = currentPosition + it
+                        currentState.draggableComposable = content
+
+                        Log.d("DRAGGING", "states has been set")
+                    },
+                    onDrag = { change, dragAmount ->
+                        change.consume()
+                        currentState.dragOffset += dragAmount
+                    },
+                    onDragEnd = {
+                        onStopDragging()
+                        currentState.dragPosition = Offset.Zero
+                        currentState.isDragging = false
+                    },
+                    onDragCancel = {
+                        onStopDragging()
+                        currentState.dragPosition = Offset.Zero
+                        currentState.isDragging = false
+                    }
+                )
+            }
+    ) {
+        content()
+    }
+}
+
+@Composable
+fun <T> DropItem(
+    modifier: Modifier = Modifier,
+    content: @Composable (BoxScope.(isInBound: Boolean, data: T?) -> Unit)
+) {
+    val dragInfo = LocalDragTargetInfo.current
+    val dragPosition = dragInfo.dragPosition
+    val dragOffset = dragInfo.dragOffset
+    var isCurrentDropTarget by remember { mutableStateOf(false) }
+
+    Box(
+        modifier = modifier.onGloballyPositioned {
+            it.boundsInWindow().let { rect ->
+                isCurrentDropTarget = rect.contains(dragPosition + dragOffset)
+            }
+        }
+    ) {
+        val data =
+            if (isCurrentDropTarget && !dragInfo.isDragging) dragInfo.dataToDrop as T? else null
+        content(isCurrentDropTarget, data)
+    }
+}
+
+@Composable
+fun DraggableScreen(
+    modifier: Modifier = Modifier,
+    content: @Composable BoxScope.() -> Unit
+) {
+    val state = remember { DragTargetInfo() }
+    CompositionLocalProvider(
+        LocalDragTargetInfo provides state
+    ) {
+        Box(modifier = modifier.fillMaxSize()) {
+            content()
+            if (state.isDragging) {
+                var targetSize by remember { mutableStateOf(IntSize.Zero) }
+                Box(modifier = Modifier
+                    .graphicsLayer {
+                        val offset = state.dragPosition + state.dragOffset
+                        scaleX = 1.3f
+                        scaleY = 1.3f
+                        alpha = if (targetSize == IntSize.Zero) 0f else .9f
+                        translationX = offset.x.minus(targetSize.width / 2)
+                        translationY = offset.y.minus(targetSize.height / 2)
+                    }
+                    .onGloballyPositioned {
+                        targetSize = it.size
+                    }) {
+                    state.draggableComposable?.invoke()
+                }
+            }
+        }
+    }
+}
+
+@Composable
+fun DraggableLazyColumnScreen(
+    modifier: Modifier = Modifier,
+    content: LazyListScope.() -> Unit
+) {
+    val state = remember { DragTargetInfo() }
+    CompositionLocalProvider(
+        LocalDragTargetInfo provides state
+    ) {
+        val listState = rememberLazyListState()
+        LazyColumn(
+            state = listState,
+            modifier = modifier.fillMaxSize(),
+            contentPadding = PaddingValues(10.dp)
+        ) {
+            content()
+        }
+        if(state.isDragging) {
+            var targetSize by remember { mutableStateOf(IntSize.Zero) }
+            Box(
+                modifier = Modifier
+                    .zIndex(1.0f)
+                    .graphicsLayer {
+                        val offset = state.dragPosition + state.dragOffset - Offset(0f, listState.firstVisibleItemScrollOffset.toFloat())
+                        alpha = if (targetSize == IntSize.Zero) 0f else .9f
+                        translationX = offset.x - targetSize.width / 2
+                        translationY = offset.y - targetSize.height / 2
+                    }
+                    .onGloballyPositioned {
+                        Log.d("DRAGGING", "original targetsize = $targetSize, new value = ${it.size}")
+                        targetSize = it.size
+                    }) {
+                state.draggableComposable?.invoke()
+            }
+        }
+    }
+}

app/src/main/java/be/re/writand/screens/components/WLoadingIndicator.kt

@@ -1,13 +1,17 @@
 package be.re.writand.screens.components
 
+import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
 import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.MaterialTheme
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.unit.dp
 
@@ -23,7 +27,7 @@ fun WLoadingIndicator() {
         verticalArrangement = Arrangement.Center,
         horizontalAlignment = Alignment.CenterHorizontally
     ) {
-        CircularProgressIndicator(modifier = Modifier.padding(vertical = 10.dp))
+        CircularProgressIndicator(modifier = Modifier.padding(vertical = 10.dp), color = MaterialTheme.colorScheme.tertiary)
 
         WText(text = "while( !( succeed = try() ) );", textAlign = TextAlign.Center)
     }

app/src/main/java/be/re/writand/screens/components/WPopup.kt

@@ -0,0 +1,70 @@
+package be.re.writand.screens.components
+
+import androidx.compose.foundation.border
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.absoluteOffset
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.Scaffold
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.AbsoluteAlignment
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.platform.LocalConfiguration
+import androidx.compose.ui.unit.Dp
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.window.Dialog
+import androidx.compose.ui.window.DialogProperties
+import be.re.writand.ui.theme.MainGreen
+
+/**
+ * A custom pop up which lets you style it however you want.
+ * @param[titleBar] a composable for the title bar of this popup.
+ * @param[bottomBar] a composable for the bottom bar.
+ * @param[width] the width of the entire pop up.
+ * @param[height] the height for this pop up.
+ * @param[onDismiss] a function to be executed when the pop up must hide.
+ * @param[modifier] the modifier for further styling, applied on the outer box of this component.
+ * @param[children] a composable with the content inside the pop up.
+ */
+@Composable
+fun WPopup(
+    titleBar: @Composable () -> Unit,
+    width: Dp,
+    height: Dp,
+    onDismiss: () -> Unit,
+    modifier: Modifier = Modifier,
+    bottomBar: (@Composable () -> Unit) = {},
+    children: @Composable (PaddingValues) -> Unit = {}
+) {
+    Dialog(
+        onDismissRequest = onDismiss,
+        properties = DialogProperties(usePlatformDefaultWidth = false)
+    ) {
+        Box(
+            contentAlignment = Alignment.Center,
+            modifier = modifier
+                .width(width)
+                .height(height)
+        ) {
+            Scaffold(
+                topBar = titleBar,
+                bottomBar = bottomBar,
+                content = children,
+                modifier = Modifier
+                    .fillMaxSize()
+                    .border(
+                        width = 1.dp,
+                        color = MainGreen,
+                        shape = RoundedCornerShape(10.dp)
+                    )
+                    .clip(RoundedCornerShape(10.dp))
+            )
+        }
+
+    }
+}

app/src/main/java/be/re/writand/screens/editor/EditorScreen.kt

@@ -1,37 +1,60 @@
 package be.re.writand.screens.editor
 
 import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.padding
 import androidx.compose.material3.Scaffold
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.navigation.NavHostController
 import be.re.writand.screens.editor.bottom.BottomEditorBar
 import be.re.writand.screens.editor.editorspace.EditorSpace
 import be.re.writand.screens.editor.top.TopEditorBar
+import be.re.writand.screens.filetree.WFiletree
+import kotlin.io.path.name
 import be.re.writand.screens.settings.SettingsPopup
 
 /**
  * Composable presenting the full screen when IDE is open. This holds all the different composables
  * that come together on the screen.
+ * @param[vm] the viewmodel of this component, used for managing the general state for the entire screen.
  */
 @Composable
 fun EditorScreen(
-    navHostController: NavHostController
+    navHostController: NavHostController,
+    vm: EditorScreenViewModel = hiltViewModel()
 ) {
+    // state for filetree view
+    val (isOpened, setIsOpened) = remember { mutableStateOf(false) }
+
+    // state for currently opened filepath
+    val openedFile by vm.openedFile
 
     Scaffold(
         topBar = {
-            TopEditorBar()
+            TopEditorBar(currentFile = openedFile?.name ?: "") {
+                setIsOpened(!isOpened)
+            }
         },
         bottomBar = {
             BottomEditorBar()
         }
     ) {
-        Row(modifier = Modifier.padding(it)) {
+        Row(modifier = Modifier.padding(it).padding(10.dp)) {
-            // TODO: show filetree when open
+            if(isOpened) {
-            EditorSpace()
+                WFiletree(
-            SettingsPopup()
+                    root = "/storage/emulated/0/Documents/webserver",
+                    modifier = Modifier.weight(1F),
+                    onSelect = { path ->
+                    vm.setOpenedFile(path)
+                })
+            }
+            EditorSpace(fileState = openedFile, modifier = Modifier.weight(2F).fillMaxSize())
         }
     }
 

app/src/main/java/be/re/writand/screens/editor/EditorScreenViewModel.kt

@@ -0,0 +1,20 @@
+package be.re.writand.screens.editor
+
+import androidx.compose.runtime.State
+import androidx.compose.runtime.mutableStateOf
+import be.re.writand.screens.WViewModel
+import java.nio.file.Path
+
+/**
+ * The viewmodel for the editor screen.
+ * This manages the general shared state between all the components of the editor screen.
+ */
+class EditorScreenViewModel : WViewModel() {
+
+    private val _openedFile = mutableStateOf<Path?>(null)
+    val openedFile: State<Path?> = _openedFile
+
+    fun setOpenedFile(path: Path?) {
+        _openedFile.value = path
+    }
+}

app/src/main/java/be/re/writand/screens/editor/editorspace/EditorSpace.kt

@@ -1,5 +1,6 @@
 package be.re.writand.screens.editor.editorspace
 
+import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxHeight
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.width
@@ -12,8 +13,6 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableIntStateOf
-import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.input.key.Key
@@ -26,26 +25,34 @@ import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
 import be.re.writand.screens.components.WLoadingIndicator
 import be.re.writand.screens.components.WText
+import java.nio.file.Path
 
 /**
  * The editor space itself where the user can edit the currently open file.
  * @param[vM] the viewmodel used to handle input changes to the open file.
+ * @param[fileState] the currently opened file in de editor, comes from EditorScreen.
+ * @param[modifier] the modifier for the outer row of this component.
  */
 @Composable
 fun EditorSpace(
+    fileState: Path?,
+    modifier: Modifier = Modifier,
     vM: EditorSpaceViewModel = hiltViewModel()
 ) {
     val uiState by vM.uiState.collectAsState()
+    var linesText by vM.lineCount
 
+    LaunchedEffect(fileState) {
+        vM.readContents(fileState)
+    }
+
+    Row(modifier = modifier) {
         when (val value = uiState) {
             EditorSpaceUiState.Loading -> {
                 WLoadingIndicator()
             }
 
             is EditorSpaceUiState.Success -> {
-            // using a mutable state to store the number of lines
-            var linesText by remember { mutableIntStateOf(value.fileContent.count { it == '\n' } + 1) }
-
                 // the scrolling state of both text fields
                 val linesTextScroll = rememberScrollState()
                 val scriptTextScroll = rememberScrollState()
@@ -93,11 +100,12 @@ fun EditorSpace(
                         vM.onTextChange(textFieldValue)
                     },
                 )
+
             }
 
             is EditorSpaceUiState.Failed -> {
                 WText(text = value.message)
             }
         }
-
+    }
 }

app/src/main/java/be/re/writand/screens/editor/editorspace/EditorSpaceViewModel.kt

@@ -1,30 +1,40 @@
 package be.re.writand.screens.editor.editorspace
 
+import androidx.compose.runtime.State
+import androidx.compose.runtime.mutableIntStateOf
+import be.re.writand.domain.files.ReadFileContentsUseCase
 import be.re.writand.screens.WViewModel
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
+import java.nio.file.Path
 import javax.inject.Inject
 
 /**
  * Viewmodel to be used by EditorSpace to handle file changes and keep the ui state in memory.
+ * File changes include changing to a new file and reading its contents, and editing this file.
+ * @param[readFileContentsUseCase] the use case used to read in the newly selected file.
  */
-class EditorSpaceViewModel : WViewModel() {
+@HiltViewModel
+class EditorSpaceViewModel @Inject constructor(
+    private val readFileContentsUseCase: ReadFileContentsUseCase
+) : WViewModel() {
 
     private val _uiState: MutableStateFlow<EditorSpaceUiState> =
         MutableStateFlow(EditorSpaceUiState.Loading)
     val uiState: StateFlow<EditorSpaceUiState> = _uiState
 
-    init {
+    val lineCount = mutableIntStateOf(1)
+
+    fun readContents(path: Path?) {
+        path?.let {
             launchCatching {
-            // TODO: call use-case that gets the String of the file
+                val contents = readFileContentsUseCase(path)
-            val file: String = "print('Hello World!')\nprint('second line')\n"
+                lineCount.intValue = contents.count { it == '\n' } + 1
-            if (file.isNotEmpty()) {
+                _uiState.value = EditorSpaceUiState.Success(contents)
-                _uiState.value = EditorSpaceUiState.Success(file)
-            } else {
-                _uiState.value = EditorSpaceUiState.Failed("The file could not be loaded.")
             }
         }
+
     }
 
     fun onTextChange(newValue: String) {

app/src/main/java/be/re/writand/screens/editor/top/TopEditorBar.kt

@@ -24,6 +24,7 @@ import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
 import be.re.writand.R
 import be.re.writand.screens.components.WText
+import java.nio.file.Path
 
 /**
  * Composable representing the top bar of the editor.
@@ -31,9 +32,10 @@ import be.re.writand.screens.components.WText
  */
 @Composable
 fun TopEditorBar(
-    vM: TopEditorBarViewModel = hiltViewModel()
+    vM: TopEditorBarViewModel = hiltViewModel(),
+    currentFile: String,
+    onOpenFileTree: () -> Unit
 ) {
-    val openFile = vM.currentFile.collectAsState()
     val isSaved = vM.isSaved.collectAsState()
 
     Row(
@@ -52,7 +54,7 @@ fun TopEditorBar(
         verticalAlignment = Alignment.CenterVertically
     ) {
         IconButton(
-            onClick = { vM.onFileMenuClick() },
+            onClick = onOpenFileTree,
             modifier = Modifier.padding(start = 10.dp),
         ) {
             Icon(
@@ -65,7 +67,8 @@ fun TopEditorBar(
         Row(
             verticalAlignment = Alignment.CenterVertically
         ) {
-            WText(text = openFile.value)
+            if(currentFile.isNotEmpty()) {
+                WText(text = currentFile)
                 IconButton(onClick = { vM.onSaveFile() }) {
                     if (isSaved.value) {
                         Icon(
@@ -82,6 +85,7 @@ fun TopEditorBar(
                     }
                 }
             }
+        }
 
         IconButton(
             onClick = { vM.onTerminalClick() },

app/src/main/java/be/re/writand/screens/editor/top/TopEditorBarViewModel.kt

@@ -13,9 +13,6 @@ class TopEditorBarViewModel : WViewModel() {
     private val _saved = MutableStateFlow(true)
     val isSaved: StateFlow<Boolean> = _saved.asStateFlow()
 
-    private val _file = MutableStateFlow("hello_world.py")
-    var currentFile: StateFlow<String> = _file.asStateFlow()
-
     fun onFileMenuClick() {
         // TODO: Open or close the filetree
     }

app/src/main/java/be/re/writand/screens/filetree/Filetree.kt

@@ -0,0 +1,163 @@
+package be.re.writand.screens.filetree
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.border
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Info
+import androidx.compose.material.icons.filled.Settings
+import androidx.compose.material3.Icon
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Scaffold
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.unit.dp
+import androidx.hilt.navigation.compose.hiltViewModel
+import be.re.writand.screens.components.WLoadingIndicator
+import be.re.writand.screens.components.WText
+import be.re.writand.ui.theme.MainGreen
+import java.nio.file.Path
+
+/**
+ * internal variable to set the height
+ */
+private val barHeight = 45.dp
+
+/**
+ * The top bar for the filetree.
+ * @param[title] the title to be shown.
+ */
+@Composable
+fun TopScaffoldBar(title: String) {
+    Row(
+        horizontalArrangement = Arrangement.Center,
+        verticalAlignment = Alignment.CenterVertically,
+        modifier = Modifier
+            .fillMaxWidth()
+            .height(barHeight)
+            .background(MainGreen)
+            .border(
+                width = 1.dp,
+                color = MainGreen,
+                shape = RoundedCornerShape(
+                    topStart = 10.dp, topEnd = 10.dp,
+                    bottomStart = 0.dp, bottomEnd = 0.dp
+                )
+            )
+    ) {
+        WText(text = title)
+    }
+}
+
+/**
+ * Bottom bar for the filetree.
+ * This holds the info and about buttons.
+ */
+@Composable
+fun BottomScaffoldBar() {
+    Row(
+        horizontalArrangement = Arrangement.SpaceBetween,
+        verticalAlignment = Alignment.CenterVertically,
+        modifier = Modifier
+            .fillMaxWidth()
+            .height(barHeight)
+            .background(MainGreen)
+            .border(
+                width = 1.dp,
+                color = MainGreen,
+                shape = RoundedCornerShape(
+                    topStart = 0.dp, topEnd = 0.dp,
+                    bottomStart = 10.dp, bottomEnd = 10.dp
+                )
+            )
+            .padding(horizontal = 10.dp)
+    ) {
+        Icon(
+            imageVector = Icons.Default.Settings,
+            contentDescription = "Open settings",
+            modifier = Modifier.size(24.dp).clickable { /* TODO: link settings popup */ }
+        )
+        Icon(
+            imageVector = Icons.Default.Info,
+            contentDescription = "More information",
+            modifier = Modifier.size(24.dp).clickable { /* TODO: link about popup */ }
+        )
+    }
+}
+
+/**
+ * The main composable for the filetree.
+ * Brings all of the subcomponents together.
+ * @param[vm] the viewmodel for this filetree, manages all of the operations and states.
+ * @param[modifier] the modifier applied to the scaffold.
+ * @param[root] the root path (as a string) for the filetree to start from.
+ * @param[onSelect] a function telling the filetree what to do if the user selects (clicks once) a file.
+ */
+@Composable
+fun WFiletree(
+    root: String,
+    onSelect: (Path?) -> Unit,
+    modifier: Modifier = Modifier,
+    vm: WFiletreeViewModel = hiltViewModel()
+) {
+    val uiState by vm.uiState.collectAsState()
+
+    LaunchedEffect(Unit) {
+        vm.loadDirectory(root)
+    }
+
+    Scaffold(
+        topBar = { TopScaffoldBar("Filetree") },
+        bottomBar = { BottomScaffoldBar() },
+        containerColor = MaterialTheme.colorScheme.primary,
+        modifier = modifier
+            .border(
+                width = 1.dp,
+                color = MainGreen,
+                shape = RoundedCornerShape(10.dp)
+            )
+            .clip(RoundedCornerShape(10.dp))
+    ) {
+
+        when (val s = uiState) {
+            WFiletreeUiState.Loading -> {
+                Column(
+                    verticalArrangement = Arrangement.Center,
+                    horizontalAlignment = Alignment.CenterHorizontally
+                ) {
+                    WLoadingIndicator()
+                }
+            }
+            is WFiletreeUiState.Success -> {
+                WTreeComponent(
+                    root = s.tree.value, // guaranteed not null because the state is set in loading the directory
+                    modifier = Modifier.padding(it),
+                    getFilename = { id -> vm.getFilename(id) },
+                    isDirectory = { id -> vm.isDirectory(id) },
+                    getIsOpened = { id -> vm.getIsOpened(id) },
+                    getPath = { id -> vm.getPath(id) },
+                    toggleIsOpened = { id -> vm.toggleOpen(id) },
+                    onMove = { from, to -> vm.moveFile(from, to) },
+                    onCreate = { node, name, type -> vm.createFile(name, type, node) },
+                    onDelete = { node -> vm.removeFile(node) },
+                    onSelect = onSelect
+                )
+            }
+
+            is WFiletreeUiState.Failed -> WText("Show error pop up to notify the user")
+        }
+    }
+}

app/src/main/java/be/re/writand/screens/filetree/WFiletreeUiState.kt

@@ -0,0 +1,15 @@
+package be.re.writand.screens.filetree
+
+import be.re.writand.utils.WFileTreeAbstraction
+
+/**
+ * The ui state for the filetree.
+ * - [Loading] the content is still loading in.
+ * - [Success] the filetree is ready, given as an object of [WFileTreeAbstraction].
+ * - [Failed] the tree could not be build, TODO: add error handling here.
+ */
+sealed interface WFiletreeUiState {
+    data object Loading: WFiletreeUiState
+    data class Success(val tree: WFileTreeAbstraction): WFiletreeUiState
+    data class Failed(val placeHolder: Int): WFiletreeUiState
+}

app/src/main/java/be/re/writand/screens/filetree/WFiletreeViewModel.kt

@@ -0,0 +1,115 @@
+package be.re.writand.screens.filetree
+
+import androidx.compose.runtime.mutableStateMapOf
+import be.re.writand.data.local.filemanager.FileType
+import be.re.writand.domain.files.CreateFileUseCase
+import be.re.writand.domain.files.InitFiletreeUseCase
+import be.re.writand.domain.files.MoveFileUseCase
+import be.re.writand.domain.files.RemoveFileUseCase
+import be.re.writand.screens.WViewModel
+import be.re.writand.utils.FileNode
+import be.re.writand.utils.WFileTreeAbstraction
+import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.withContext
+import java.nio.file.Path
+import java.nio.file.Paths
+import javax.inject.Inject
+import kotlin.io.path.isDirectory
+import kotlin.io.path.name
+
+/**
+ * Viewmodel for the filetree.
+ * Manages the states and all operations.
+ * @param[initFiletreeUseCase] the use case to load in the filetree.
+ * @param[moveFileUseCase] use case which is responsible to move a file from a to be.
+ * @param[createFileUseCase] use case to create a new file.
+ * @param[removeFileUseCase] use case to delete a file.
+ */
+@HiltViewModel
+class WFiletreeViewModel @Inject constructor(
+    private val initFiletreeUseCase: InitFiletreeUseCase,
+    private val moveFileUseCase: MoveFileUseCase,
+    private val createFileUseCase: CreateFileUseCase,
+    private val removeFileUseCase: RemoveFileUseCase
+) : WViewModel() {
+    private val _uiState: MutableStateFlow<WFiletreeUiState> =
+        MutableStateFlow(WFiletreeUiState.Loading)
+
+    val uiState: StateFlow<WFiletreeUiState> = _uiState
+
+    private val isOpenedState = mutableStateMapOf<ULong, Boolean>()
+    private lateinit var fileTree: WFileTreeAbstraction
+
+    fun toggleOpen(id: ULong) {
+        isOpenedState[id] = isOpenedState[id]?.not() ?: true
+    }
+
+    fun getIsOpened(id: ULong): Boolean {
+        return isOpenedState[id] == true
+    }
+
+
+    fun getFilename(id: ULong): String? {
+        if (!this::fileTree.isInitialized) return null
+        return fileTree.getPath(id)?.name
+    }
+
+    fun getPath(id: ULong): Path? {
+        return fileTree.getPath(id)
+    }
+
+    fun isDirectory(id: ULong): Boolean {
+        if (!this::fileTree.isInitialized) return false
+        return fileTree.getPath(id)?.isDirectory() ?: false
+    }
+
+    fun loadDirectory(path: String) {
+        launchCatching {
+            withContext(Dispatchers.IO) {
+                fileTree = initFiletreeUseCase(path)
+                _uiState.value = WFiletreeUiState.Success(fileTree)
+            }
+        }
+    }
+
+    fun removeFile(node: FileNode) {
+        if (!this::fileTree.isInitialized) return
+        val path =
+            fileTree.getPath(node.item)!! // TODO: if path does not exist (error is thrown) show error to user
+        fileTree.delete(node)
+        launchCatching {
+            withContext(Dispatchers.IO) {
+                removeFileUseCase(path)
+            }
+        }
+    }
+
+    fun createFile(name: String, fileType: FileType, root: FileNode) {
+        if (name.isBlank()) return
+        if (!this::fileTree.isInitialized) return
+        val path =
+            fileTree.getPath(root.item)!! // TODO: if path does not exist (error is thrown) show error to user
+        launchCatching {
+            withContext(Dispatchers.IO) {
+                val id = createFileUseCase(name, fileType, path)
+                fileTree.create(Paths.get(path.toString(), name), root, id)
+            }
+        }
+    }
+
+    fun moveFile(from: FileNode, to: FileNode) {
+        if (!this::fileTree.isInitialized) return
+        val fromPath = fileTree.getPath(from.item)!!
+        val toPath = fileTree.getPath(to.item)!!
+
+        fileTree.move(from, to)
+        launchCatching {
+            withContext(Dispatchers.IO) {
+                moveFileUseCase(fromPath, toPath)
+            }
+        }
+    }
+}

app/src/main/java/be/re/writand/screens/filetree/WTreeComponent.kt

@@ -0,0 +1,417 @@
+package be.re.writand.screens.filetree
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.border
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.LazyListScope
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.KeyboardArrowRight
+import androidx.compose.material.icons.filled.Add
+import androidx.compose.material.icons.filled.Close
+import androidx.compose.material.icons.filled.Delete
+import androidx.compose.material.icons.filled.KeyboardArrowDown
+import androidx.compose.material3.Icon
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.semantics.Role
+import androidx.compose.ui.unit.dp
+import be.re.writand.data.local.filemanager.FileType
+import be.re.writand.screens.components.WBorderButton
+import be.re.writand.screens.components.WButton
+import be.re.writand.screens.components.WCheckbox
+import be.re.writand.screens.components.WDangerButton
+import be.re.writand.screens.components.WLabelAndTextField
+import be.re.writand.screens.components.WPopup
+import be.re.writand.screens.components.WText
+import be.re.writand.ui.theme.MainGreen
+import be.re.writand.utils.FileNode
+import java.nio.file.Path
+
+// TODO: add drag and drop functionality to move files from 1 place to another
+
+// based on: https://stackoverflow.com/a/71709816
+
+// constant for standard indentation.
+private val defaultSpacing = 10.dp
+
+// constant to fix the icon size.
+private val iconSize = 16.dp
+
+/**
+ * The main component of the filetree itself.
+ * @param[root] the root node of the filetree.
+ * @param[modifier] the modifier applied to the outer column of the component.
+ * @param[getFilename] the function to obtain the filename of a node.
+ * @param[isDirectory] a function to determine if the node stands for a file or a directory.
+ * @param[getIsOpened] a function to access the state for a given node representing a directory.
+ * @param[getPath] a function to retrieve the path of a node.
+ * @param[toggleIsOpened] the state changer function, toggles between opened and closed.
+ * @param[onMove] the action function to move a file / directory from a to b.
+ * @param[onCreate] the action function to create a new file / directory.
+ * @param[onDelete] the action function to delete a file  / directory.
+ * @param[onSelect] the action function to select a file (directory is not supported).
+ */
+@Composable
+fun WTreeComponent(
+    root: FileNode,
+    modifier: Modifier = Modifier,
+    getFilename: (ULong) -> String?,
+    isDirectory: (ULong) -> Boolean,
+    getIsOpened: (ULong) -> Boolean,
+    getPath: (ULong) -> Path?,
+    toggleIsOpened: (ULong) -> Unit,
+    onMove: (FileNode, FileNode) -> Unit,
+    onCreate: (FileNode, String, FileType) -> Unit,
+    onDelete: (FileNode) -> Unit,
+    onSelect: (Path?) -> Unit
+) {
+    LazyColumn(modifier = modifier, contentPadding = PaddingValues(10.dp)) {
+        WTreeItem(
+            root = root,
+            depth = 0,
+            getFilename = getFilename,
+            getPath = getPath,
+            isDirectory = isDirectory,
+            getIsOpened = getIsOpened,
+            toggleIsOpened = toggleIsOpened,
+            onMove = onMove,
+            onCreate = onCreate,
+            onDelete = onDelete,
+            onSelect = onSelect
+        )
+    }
+}
+
+/**
+ * Helper function in the recursive call to loop over a list of nodes and create
+ * LazyColumn items for each of them.
+ * @param[depth] the current depth in the tree, used to calculate the indentation.
+ * @see[WTreeComponent] for the parameters.
+ */
+fun LazyListScope.WTreeItems(
+    root: List<FileNode>,
+    depth: Int,
+    getFilename: (ULong) -> String?,
+    getPath: (ULong) -> Path?,
+    isDirectory: (ULong) -> Boolean,
+    getIsOpened: (ULong) -> Boolean,
+    toggleIsOpened: (ULong) -> Unit,
+    onMove: (FileNode, FileNode) -> Unit,
+    onCreate: (FileNode, String, FileType) -> Unit,
+    onDelete: (FileNode) -> Unit,
+    onSelect: (Path?) -> Unit
+) {
+    root.forEach {
+        WTreeItem(
+            root = it,
+            depth = depth,
+            getFilename = getFilename,
+            getPath = getPath,
+            isDirectory = isDirectory,
+            getIsOpened = getIsOpened,
+            toggleIsOpened = toggleIsOpened,
+            onMove = onMove,
+            onCreate = onCreate,
+            onDelete = onDelete,
+            onSelect = onSelect
+        )
+    }
+}
+
+/**
+ * Helper function to create 1 LazyColumn item.
+ * @param[depth] the current depth in the tree, used to calculate the indentation.
+ * @see[WTreeComponent] for the parameters.
+ */
+fun LazyListScope.WTreeItem(
+    root: FileNode,
+    depth: Int,
+    getFilename: (ULong) -> String?,
+    getPath: (ULong) -> Path?,
+    isDirectory: (ULong) -> Boolean,
+    getIsOpened: (ULong) -> Boolean,
+    toggleIsOpened: (ULong) -> Unit,
+    onMove: (FileNode, FileNode) -> Unit,
+    onCreate: (FileNode, String, FileType) -> Unit,
+    onDelete: (FileNode) -> Unit,
+    onSelect: (Path?) -> Unit
+) {
+    val filename = getFilename(root.item)
+    val isDir = isDirectory(root.item)
+    if (filename != null) {
+        item {
+            val (showAddPopUp, setShowAddPopUp) = remember { mutableStateOf(false) }
+            val (showRemovePopUp, setShowRemovePopUp) = remember { mutableStateOf(false) }
+            Row {
+                Filename(
+                    root = root,
+                    filename = filename,
+                    isDirectory = isDir,
+                    depth = depth,
+                    getIsOpened = getIsOpened,
+                    getPath = getPath,
+                    toggleIsOpened = toggleIsOpened,
+                    onSelect = onSelect
+                )
+                if (isDir) {
+                    Icon(
+                        imageVector = Icons.Default.Add,
+                        contentDescription = "Add a file or directory",
+                        modifier = Modifier
+                            .size(iconSize)
+                            .clickable {
+                                setShowAddPopUp(true)
+                            }
+                    )
+                }
+                Icon(
+                    imageVector = Icons.Default.Delete,
+                    contentDescription = "Delete the current file or directory",
+                    modifier = Modifier
+                        .size(iconSize)
+                        .clickable {
+                            setShowRemovePopUp(true)
+                        }
+                )
+            }
+
+            if (showAddPopUp) CreateFile(
+                hidePopUp = { setShowAddPopUp(false) },
+                onConfirm = { name, type -> onCreate(root, name, type) }
+            )
+
+            if (showRemovePopUp) RemoveFilePopUp(
+                filename = filename,
+                hidePopUp = { setShowRemovePopUp(false) },
+                onConfirm = { onDelete(root) }
+            )
+        }
+        if (getIsOpened(root.item)) {
+            WTreeItems(
+                root = root.children,
+                depth = depth + 1,
+                getFilename = getFilename,
+                getPath = getPath,
+                isDirectory = isDirectory,
+                getIsOpened = getIsOpened,
+                toggleIsOpened = toggleIsOpened,
+                onMove = onMove,
+                onCreate = onCreate,
+                onDelete = onDelete,
+                onSelect = onSelect
+            )
+        }
+    }
+}
+
+/**
+ * The composable for a filename.
+ * This shows the filename and the necessary buttons for this node (add, open, ...).
+ * @see[WTreeComponent] for the parameters.
+ */
+@Composable
+fun Filename(
+    root: FileNode,
+    filename: String,
+    isDirectory: Boolean,
+    depth: Int,
+    getIsOpened: (ULong) -> Boolean,
+    getPath: (ULong) -> Path?,
+    toggleIsOpened: (ULong) -> Unit,
+    onSelect: (Path?) -> Unit
+) {
+    Row {
+        if (isDirectory) {
+            Icon(
+                imageVector = if (getIsOpened(root.item)) {
+                    Icons.Default.KeyboardArrowDown
+                } else {
+                    Icons.AutoMirrored.Default.KeyboardArrowRight
+                },
+                modifier = Modifier
+                    .padding(start = defaultSpacing * depth)
+                    .size(iconSize)
+                    .clickable(
+                        onClick = { toggleIsOpened(root.item) },
+                        role = Role.Switch
+                    ),
+                contentDescription = "Open/close the directory"
+            )
+            Text(text = filename)
+        } else {
+            Text(
+                text = filename,
+                modifier = Modifier
+                    .padding(start = defaultSpacing * depth + iconSize)
+                    .clickable {
+                        onSelect(getPath(root.item))
+                    }
+            )
+        }
+    }
+}
+
+/**
+ * Pop up screen to create a file / directory.
+ * @param[hidePopUp] a function telling this component what to do when closing this pop up is requested.
+ * @param[onConfirm] a function performing the action when the user confirms the creation of a new file / directory.
+ */
+@Composable
+fun CreateFile(hidePopUp: () -> Unit, onConfirm: (String, FileType) -> Unit) {
+    val (fileName, setFileName) = remember { mutableStateOf("") }
+    WPopup(
+        titleBar = { TopPopUpBar(title = "Create a new file / directory", onDismiss = hidePopUp) },
+        bottomBar = {
+            Row(
+                horizontalArrangement = Arrangement.SpaceBetween,
+                verticalAlignment = Alignment.CenterVertically,
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(10.dp)
+            ) {
+                val (isDirectory, setIsDirectory) = remember { mutableStateOf(false) }
+
+                WCheckbox(text = "make directory", checked = isDirectory) {
+                    setIsDirectory(!isDirectory)
+                }
+
+                WButton(text = "Create", onClick = {
+                    val type = if (isDirectory) FileType.DIRECTORY else FileType.FILE
+                    hidePopUp() // TODO: show error if field is empty
+                    onConfirm(fileName, type)
+                })
+            }
+        },
+        width = 500.dp,
+        height = 200.dp,
+        onDismiss = hidePopUp
+    ) { padding ->
+        Column(
+            verticalArrangement = Arrangement.Center,
+            modifier = Modifier
+                .padding(padding)
+                .fillMaxSize()
+        ) {
+            Row(
+                modifier = Modifier.padding(10.dp),
+                horizontalArrangement = Arrangement.Center,
+                verticalAlignment = Alignment.CenterVertically
+            ) {
+                WLabelAndTextField(
+                    title = "Filename",
+                    value = fileName,
+                    onTextChange = { setFileName(it) }
+                )
+            }
+        }
+    }
+}
+
+/**
+ * The pop up asking for confirmation when about to delete a file / directory.
+ * @param[filename] the name of the file / directory which is about to be deleted.
+ * @param[hidePopUp] a function implementing the logic to hide this pop up.
+ * @param[onConfirm] a function implementing the logic to actually delete this file / directory.
+ */
+@Composable
+fun RemoveFilePopUp(filename: String, hidePopUp: () -> Unit, onConfirm: () -> Unit) {
+    WPopup(
+        titleBar = {
+            TopPopUpBar(
+                title = "Are you sure?",
+                showExit = false
+            )
+        },
+        bottomBar = {
+            Row(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(10.dp),
+                horizontalArrangement = Arrangement.SpaceBetween,
+                verticalAlignment = Alignment.CenterVertically
+            ) {
+                WBorderButton(
+                    text = "Cancel",
+                    onClick = hidePopUp
+                )
+
+                WDangerButton(
+                    text = "Delete",
+                    onClick = {
+                        onConfirm()
+                        hidePopUp()
+                    }
+                )
+            }
+        },
+        height = 200.dp,
+        width = 500.dp,
+        onDismiss = hidePopUp
+    ) { padding ->
+        Box(
+            contentAlignment = Alignment.Center,
+            modifier = Modifier
+                .padding(padding)
+                .fillMaxSize()
+        ) {
+            WText("Do you really want to delete $filename?")
+        }
+    }
+}
+
+/**
+ * The top bar used in the pop ups.
+ * @see[RemoveFilePopUp]
+ * @see[CreateFile] for the actual pop ups.
+ * @param[title] the title of the pop up.
+ * @param[showExit] a boolean (default to true) whether or not the exit button needs to be shown.
+ * @param[onDismiss] a function belonging to the exit button if it needs to be shown (default is the empty function).
+ */
+@Composable
+private fun TopPopUpBar(title: String, showExit: Boolean = true, onDismiss: () -> Unit = {}) {
+    Row(
+        horizontalArrangement = Arrangement.SpaceBetween,
+        verticalAlignment = Alignment.CenterVertically,
+        modifier = Modifier
+            .fillMaxWidth()
+            .height(45.dp)
+            .background(MainGreen)
+            .border(
+                width = 1.dp,
+                color = MainGreen,
+                shape = RoundedCornerShape(
+                    topStart = 10.dp, topEnd = 10.dp,
+                    bottomStart = 0.dp, bottomEnd = 0.dp
+                )
+            )
+            .padding(5.dp)
+    ) {
+        Spacer(modifier = Modifier.width(0.dp))
+        WText(text = title)
+        if (showExit) {
+            Icon(imageVector = Icons.Default.Close, contentDescription = "", modifier = Modifier.clickable {
+                onDismiss()
+            })
+        } else {
+            Spacer(modifier = Modifier.width(0.dp))
+        }
+    }
+}

app/src/main/java/be/re/writand/utils/GenerateId.kt

@@ -0,0 +1,49 @@
+package be.re.writand.utils
+
+import java.time.LocalDateTime
+import java.time.ZoneOffset
+import kotlin.random.Random
+import kotlin.random.nextULong
+
+class GenerateId {
+    private val CHARACTERS: List<Char> = initChars()
+    private val characterMap = HashMap<Char, UByte>(CHARACTERS.size)
+    private val random = Random(LocalDateTime.now().toEpochSecond(ZoneOffset.UTC))
+
+    init {
+        for ((i, c) in CHARACTERS.withIndex()) {
+            characterMap[c] = i.toUByte()
+        }
+    }
+
+    private fun initChars(): List<Char> {
+        val alphaNumeric = (('a'..'z') + ('A'..'Z') + ('0'..'9')).toMutableList()
+        val specialChars = listOf(
+            '.', '!', ',', '&', '%', '^', '#', '@',
+            '[', ']', '{', '}', '(', ')', '-', '+',
+            '$', '=', '_', ';'
+        )
+
+        alphaNumeric.addAll(specialChars)
+
+        return alphaNumeric
+    }
+
+    /**
+     * Generates a random UUID corresponding to following scheme:
+     * - the first 2 digits of the ID correspond to the first letter of the filename.
+     * - the rest of the ID is random.
+     * @param[filename] the filename of the current file needing an ID.
+     * @return[ULong] the 8 byte ID.
+     */
+    fun generateUUID(filename: String): ULong {
+        var code = random.nextULong()
+        val charCode = characterMap[filename[0]]
+
+        // code &= 111...111 00000000: set last byte to 0 to or in the code for this specific letter
+        code = code and (255UL).inv()
+        return charCode?.let {
+            code or it.toULong()
+        } ?: 0UL
+    }
+}

app/src/main/java/be/re/writand/utils/Node.kt

@@ -0,0 +1,16 @@
+package be.re.writand.utils
+
+/**
+ * Describe an abstract node of type T used for a tree.
+ * @param[item] the item in this node of the tree.
+ * @param[children] a list of the children of this node.
+ */
+data class FileNode(
+    var item: ULong,
+    var parent: FileNode?,
+    var children: MutableList<FileNode> = mutableListOf()
+) {
+    override fun toString(): String {
+        return "FileNode(item = $item, parent = ${parent?.item}, children = $children)"
+    }
+}

app/src/main/java/be/re/writand/utils/WFileTreeAbstraction.kt

@@ -0,0 +1,109 @@
+package be.re.writand.utils
+
+import androidx.compose.runtime.MutableState
+import androidx.compose.runtime.State
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.neverEqualPolicy
+import androidx.compose.runtime.snapshots.MutableSnapshot
+import java.nio.file.Path
+import java.nio.file.Paths
+import java.util.AbstractQueue
+import java.util.LinkedList
+import java.util.PriorityQueue
+import java.util.Queue
+import javax.inject.Inject
+import kotlin.io.path.isDirectory
+import kotlin.io.path.name
+
+
+/**
+ * Abstract representation of the filetree starting at the root of the project.
+ * All operations performed here are also performed on disk.
+ *
+ * @param[index] a hashmap containing the mappings between an id and its path.
+ * @param[root] the root of the filetree.
+ */
+class WFileTreeAbstraction @Inject constructor(
+    private val index: HashMap<ULong, Path>,
+    root: FileNode,
+) : MutableState<FileNode> {
+    private val _root = mutableStateOf(root, neverEqualPolicy())
+
+    private fun triggerRerender() {
+        _root.value = _root.value
+    }
+
+    private val comparator = compareBy<FileNode> { index[it.item]?.isDirectory() }
+        .reversed()
+        .thenBy { index[it.item]?.name }
+
+    fun getPath(id: ULong): Path? {
+        return index[id]
+    }
+
+    /**
+     * Deletes a node in the filetree, also calling to the manager to delete the file on disk.
+     * @param[node] the node to delete.
+     * @throws IllegalArgumentException if the node points to a non-existent file / directory.
+     */
+    fun delete(node: FileNode) {
+        // if the node is not the root node, remove the node from the children list
+        node.parent?.children?.remove(node)
+
+        val queue = LinkedList<FileNode>()
+        queue.add(node)
+
+        while(!queue.isEmpty()) {
+            val top = queue.poll()!!
+            queue.addAll(top.children)
+            index.remove(top.item)
+        }
+
+        triggerRerender()
+    }
+
+    /**
+     * Create a new file / directory in the current directory.
+     * @param[path] the path of the file.
+     * @param[relativeRoot] the current directory.
+     * @throws IllegalArgumentException if the node points to a non-existent file / directory.
+     */
+    fun create(path: Path, relativeRoot: FileNode, id: ULong) {
+        index[id] = path
+        relativeRoot.children.add(FileNode(id, relativeRoot))
+        relativeRoot.children.sortWith(comparator)
+
+        triggerRerender()
+    }
+
+    /**
+     * Move a file from 1 location to another.
+     * @param[from] the source location to be moved.
+     * @param[to] the destination directory.
+     */
+    fun move(from: FileNode, to: FileNode) {
+        from.parent?.children?.remove(from)
+        to.children.add(from)
+        from.parent = to
+        to.children.sortWith(comparator)
+
+        // update the path stored in the index
+        val parentPath = index[to.item] ?: throw IllegalArgumentException()
+        val fromPath = index[from.item] ?: throw IllegalArgumentException()
+        index[from.item] = Paths.get(parentPath.toString(), fromPath.name)
+
+        triggerRerender()
+    }
+
+    override var value: FileNode
+        get() = _root.value
+        set(value) {_root.value = value}
+
+    override fun component1(): FileNode {
+        return _root.value
+    }
+
+    override fun component2(): (FileNode) -> Unit {
+        return { _root.value = it }
+    }
+}

app/src/main/java/be/re/writand/utils/directorypicker/DirectoryPicker.kt

@@ -0,0 +1,44 @@
+package be.re.writand.utils.directorypicker
+
+import android.content.Intent
+import android.net.Uri
+import android.util.Log
+import androidx.activity.ComponentActivity
+import androidx.activity.result.ActivityResultLauncher
+import androidx.activity.result.contract.ActivityResultContracts
+
+// TODO: make this class a builder-pattern
+class DirectoryPicker(private var activity: ComponentActivity) {
+    private lateinit var listener: IDirectoryPickerListener
+    private var launcher = registerActivityResult()
+
+    private fun registerActivityResult(): ActivityResultLauncher<Uri?> {
+        return activity.registerForActivityResult(
+            contract = ActivityResultContracts.OpenDocumentTree(),
+            callback = { handleResult(it) }
+        )
+    }
+
+    fun setActivity(activity: ComponentActivity) {
+        this.activity = activity
+        launcher = registerActivityResult()
+    }
+
+    fun setListener(listener: IDirectoryPickerListener) {
+        this.listener = listener
+    }
+
+    fun openPicker() {
+        launcher.launch(null)
+    }
+
+    private fun handleResult(data: Uri?) {
+        Log.d("Filetree", "data = ${data.toString()}")
+        data?.let {
+            val flags =
+                Intent.FLAG_GRANT_READ_URI_PERMISSION or Intent.FLAG_GRANT_WRITE_URI_PERMISSION
+            activity.contentResolver.takePersistableUriPermission(data, flags)
+            if(this::listener.isInitialized) listener.notify(data)
+        }
+    }
+}

app/src/main/java/be/re/writand/utils/directorypicker/IDirectoryPickerListener.kt

@@ -0,0 +1,7 @@
+package be.re.writand.utils.directorypicker
+
+import android.net.Uri
+
+interface IDirectoryPickerListener {
+    fun notify(uri: Uri)
+}

app/src/test/java/be/re/writand/FileManagerLocalTest.kt

@@ -1,7 +1,7 @@
 package be.re.writand
 
 import android.annotation.SuppressLint
-import be.re.writand.data.local.FileManagerLocal
+import be.re.writand.data.local.filemanager.FileManagerLocal
 import org.junit.jupiter.api.Assertions.assertFalse
 import org.junit.jupiter.api.Assertions.assertTrue
 import org.junit.jupiter.api.BeforeAll

build.gradle

@@ -5,8 +5,8 @@ buildscript {
     }
 }// Top-level build file where you can add configuration options common to all sub-projects/modules.
 plugins {
-    id 'com.android.application' version '8.5.1' apply false
+    id 'com.android.application' version '8.6.0' apply false
-    id 'com.android.library' version '8.5.1' apply false
+    id 'com.android.library' version '8.6.0' apply false
     id 'org.jetbrains.kotlin.android' version '1.9.0' apply false
     id 'com.google.dagger.hilt.android' version '2.49' apply false
     id 'org.jetbrains.kotlin.plugin.serialization' version '1.6.21'

docs/permissions.md

@@ -0,0 +1,28 @@
+# Documentation for permissions
+This file explains how to request permissions and how to check if the app has them.
+
+## Manage all files
+This permission allows the application to work with the shared storage (normal user storage) without
+general limitations except for sdcard/android/ and storage/android/ and all subdirectories. All other
+directories can be accessed using normal file paths using the java.io.file classes and related.
+
+### Invoking the request
+we need:
+```kotlin
+ACTION_MANAGE_ALL_APP_FILES_ACCESS_PERMISSION // (String)
+```
+to invoke the intent. We can invoke it as follows:
+
+```kotlin
+fun requestStoragePermission() {
+    val launcher = registerForActivityResult(ActivityResultContracts.StartActivityForResult()) {
+        val result = Environment.isExternalStorageManager()
+    }
+    
+    val intent = Intent(EXTERNAL_STORAGE_PERMISSION, Uri.parse("package:$packageName"))
+    launcher.launch(intent)
+}
+```
+
+The result received from this activity is useless. It's only needed to know when the user has exited
+the activity.