feat(backend): Basic state save/restore

backend/queueManager.ts

@@ -1,10 +1,13 @@
 import {fetchMetadata} from "./services/metadata";
 import {DEFAULT_LUCIDA_OPTIONS, DownloadResult, LucidaOptions, ProcessingQueue, Queue, QueueItem} from "./types/queue";
 import Lucida from "./services/lucida";
+import * as fs from "node:fs";
 
 const TIMEOUT: number = 120000;
 const RETRIES: number = 5;
 
+const STATE_FILE: string = '/data/state.json';
+
 class QueueManager {
     private readonly queue: Queue;
     private readonly processing: ProcessingQueue;
@@ -20,6 +23,42 @@ class QueueManager {
 
         this.lucida = null;
         this.lucidaOptions = DEFAULT_LUCIDA_OPTIONS;
+
+        this.loadState();
+    }
+
+    private saveState(): void {
+        const state = {
+            queue: this.processing.map(pi => pi.item).concat(this.queue),
+            history: this.history
+        };
+        fs.writeFileSync(STATE_FILE, JSON.stringify(state, null, 4));
+    }
+
+    private loadState(): void {
+        if (!fs.existsSync(STATE_FILE)) {
+            return;
+        }
+
+        const state = JSON.parse(fs.readFileSync(STATE_FILE, 'utf8'));
+
+        console.log('QueueManager: Restoring state:', state);
+
+        this.queue.push(...state.queue);
+
+        state.history.forEach((item: QueueItem) => {
+            if (!this.queue.some(q => q.id === item.id)) {
+                if (item.result?.success) {
+                    // Add successful items to the history
+                    this.history.push(item);
+                } else {
+                    // Add failed items to the queue
+                    this.queue.push(item);
+                }
+            }
+        });
+
+        this.processQueue();
     }
 
     public setLucidaOptions(options: LucidaOptions): void {
@@ -58,6 +97,7 @@ class QueueManager {
             song: await fetchMetadata(song)
         };
         this.queue.push(item);
+        this.saveState();
         this.processQueue();
 
         return item;
@@ -74,6 +114,7 @@ class QueueManager {
             song: await fetchMetadata(song)
         };
         this.queue.splice(index, 0, item);
+        this.saveState();
         this.processQueue();
 
         return item;
@@ -87,11 +128,13 @@ class QueueManager {
 
         const item: QueueItem = this.queue[index];
         this.queue.splice(index, 1);
+        this.saveState();
         return item;
     }
 
     public clear(): void {
         this.queue.length = 0;
+        this.saveState();
     }
 
     public move(song: string, to: number): QueueItem {
@@ -102,6 +145,7 @@ class QueueManager {
 
         const item: QueueItem = this.queue.splice(index, 1)[0];
         this.queue.splice(to, 0, item);
+        this.saveState();
         return item;
     }
 
@@ -114,6 +158,7 @@ class QueueManager {
         const item: QueueItem = this.history.splice(index, 1)[0];
         item.retries = 0;
         this.queue.push(item);
+        this.saveState();
         this.processQueue();
 
         return item;
@@ -149,9 +194,11 @@ class QueueManager {
                     item.timeout = (item.timeout ?? TIMEOUT) * 2;
                     item.result = result;
                     this.queue.push(item);
+                    this.saveState();
                 } else {
                     item.result = result;
                     this.history.push(item);
+                    this.saveState();
                 }
             } catch (err) {
                 item.result = {
@@ -159,6 +206,7 @@ class QueueManager {
                     error: err instanceof Error ? err.message : 'Unknown error'
                 };
                 this.history.push(item);
+                this.saveState();
             }
 
             this.processing.splice(this.processing.indexOf(current), 1);