diff --git a/app/src/main/java/be/ugent/sel/studeez/domain/TimerDAO.kt b/app/src/main/java/be/ugent/sel/studeez/domain/TimerDAO.kt
index 5498696..ab3edcb 100644
--- a/app/src/main/java/be/ugent/sel/studeez/domain/TimerDAO.kt
+++ b/app/src/main/java/be/ugent/sel/studeez/domain/TimerDAO.kt
@@ -1,4 +1,19 @@
 package be.ugent.sel.studeez.domain
 
+import be.ugent.sel.studeez.data.local.models.timer_info.TimerInfo
+import be.ugent.sel.studeez.data.local.models.timer_info.TimerJson
+import kotlinx.coroutines.flow.Flow
+
 interface TimerDAO {
+
+    fun getUserTimers(): Flow<List<TimerInfo>>
+
+    fun getAllTimers(): Flow<List<TimerInfo>>
+
+    fun saveTimer(newTimer: TimerInfo)
+
+    fun updateTimer(timerInfo: TimerInfo)
+
+    fun deleteTimer(timerInfo: TimerInfo)
+
 }
\ No newline at end of file
diff --git a/app/src/main/java/be/ugent/sel/studeez/domain/implementation/FirebaseTimerDAO.kt b/app/src/main/java/be/ugent/sel/studeez/domain/implementation/FirebaseTimerDAO.kt
index c0b0a26..a25c37c 100644
--- a/app/src/main/java/be/ugent/sel/studeez/domain/implementation/FirebaseTimerDAO.kt
+++ b/app/src/main/java/be/ugent/sel/studeez/domain/implementation/FirebaseTimerDAO.kt
@@ -1,4 +1,63 @@
 package be.ugent.sel.studeez.domain.implementation
 
-class FirebaseTimerDAO {
+import be.ugent.sel.studeez.data.local.models.timer_info.*
+import be.ugent.sel.studeez.data.local.models.timer_info.TimerType.*
+import be.ugent.sel.studeez.domain.AccountDAO
+import be.ugent.sel.studeez.domain.TimerDAO
+import com.google.firebase.firestore.CollectionReference
+import com.google.firebase.firestore.DocumentSnapshot
+import com.google.firebase.firestore.FirebaseFirestore
+import com.google.firebase.firestore.ktx.snapshots
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.flow.map
+import javax.inject.Inject
+
+class FirebaseTimerDAO @Inject constructor(
+    private val firestore: FirebaseFirestore,
+    private val configurationService: FirebaseConfigurationService,
+    private val auth: AccountDAO
+) : TimerDAO {
+
+    override fun getUserTimers(): Flow<List<TimerInfo>> {
+        return currentUserTimersCollection()
+            .snapshots()
+            .map { it.toObjects(TimerJson::class.java) }
+            .map { ToTimerConverter().convertToTimerInfoList(it) }
+    }
+
+    override fun getAllTimers(): Flow<List<TimerInfo>> {
+        // Wrap default timers in een flow en combineer met de userTimer flow.
+        val defaultTimers: List<TimerInfo> = configurationService.getDefaultTimers()
+        val defaultTimersFlow: Flow<List<TimerInfo>> = flowOf(defaultTimers)
+        val userTimersFlow: Flow<List<TimerInfo>> =  getUserTimers()
+        return defaultTimersFlow.combine(userTimersFlow) { defaultTimersList, userTimersList ->
+            defaultTimersList + userTimersList
+        }
+    }
+
+    override fun saveTimer(newTimer: TimerInfo) {
+        currentUserTimersCollection().add(newTimer.asJson())
+    }
+
+    override fun updateTimer(timerInfo: TimerInfo) {
+        currentUserTimersCollection().document(timerInfo.id).set(timerInfo.asJson())
+    }
+
+    override fun deleteTimer(timerInfo: TimerInfo) {
+        currentUserTimersCollection().document(timerInfo.id).delete()
+    }
+
+    private fun currentUserTimersCollection(): CollectionReference =
+        firestore.collection(USER_COLLECTION)
+            .document(auth.currentUserId)
+            .collection(TIMER_COLLECTION)
+
+
+    companion object {
+        private const val TIMER_COLLECTION = "timers"
+        private const val USER_COLLECTION = "users"
+    }
+
 }
\ No newline at end of file