feat(plugin):Background Music plugin

Added a plugin so users can upload and play a .wav audio file as background music. added volume setting, made sure the file is stored across version updates/downdates, made the music stop when the tab is unfocussed, and registered the plugin as official.

src/plugins/built-in/backgroundMusic/index.ts

@@ -0,0 +1,171 @@
+import type { Plugin } from "@/plugins/core/types";
+import { defineSettings, componentSetting, numberSetting } from "@/plugins/core/settingsHelpers";
+import styles from "./styles.css?inline";
+import BackgroundMusicSetting from "./BackgroundMusicSetting.svelte";
+import localforage from "localforage";
+
+const settings = defineSettings({
+  uploader: componentSetting({
+    title: "Background Music",
+    description: "Upload a .wav audio file to play in the background.",
+    component: BackgroundMusicSetting,
+  }),
+  volume: numberSetting({
+    title: "Volume",
+    description: "Set background music volume",
+    default: 0.5,
+    min: 0,
+    max: 1,
+    step: 0.05,
+  }),
+});
+
+const store = localforage.createInstance({
+  name: "background-music-store",
+  storeName: "music",
+});
+
+let currentAudio: HTMLAudioElement | null = null;
+let currentObjectUrl: string | null = null;
+let cleanupRegistered = false;
+let pendingGestureCancel: (() => void) | null = null;
+let visibilityResumeTimeout: number | null = null;
+
+async function loadAudioBlob(): Promise<Blob | null> {
+  const blob = await store.getItem<Blob>("audio-blob");
+  return blob && blob instanceof Blob ? blob : null;
+}
+
+function stopAndCleanupAudio(): void {
+  if (currentAudio) {
+    currentAudio.pause();
+    currentAudio.src = "";
+    currentAudio.remove();
+    currentAudio = null;
+  }
+  if (currentObjectUrl) {
+    URL.revokeObjectURL(currentObjectUrl);
+    currentObjectUrl = null;
+  }
+}
+
+function ensureGestureStart(handler: () => void): () => void {
+  const eventTypes = ["pointerdown", "keydown", "touchstart"]; // broad user gesture coverage
+  const listener = () => {
+    handler();
+    for (const type of eventTypes) {
+      window.removeEventListener(type, listener);
+    }
+  };
+  for (const type of eventTypes) {
+    window.addEventListener(type, listener, { once: true, passive: true });
+  }
+  return () => {
+    for (const type of eventTypes) {
+      window.removeEventListener(type, listener);
+    }
+  };
+}
+
+async function startPlayback(volume: number): Promise<void> {
+  const blob = await loadAudioBlob();
+  if (!blob) return;
+
+  stopAndCleanupAudio();
+
+  currentObjectUrl = URL.createObjectURL(blob);
+  const audio = new Audio(currentObjectUrl);
+  audio.loop = true;
+  audio.volume = Math.max(0, Math.min(1, volume));
+  audio.preload = "auto";
+  audio.crossOrigin = "anonymous";
+  audio.style.display = "none";
+  document.body.appendChild(audio);
+  currentAudio = audio;
+
+  try {
+    // Attempt immediate play; may be blocked until gesture
+    await audio.play();
+  } catch {
+    // Ignore; will be started after gesture if enabled
+  }
+}
+
+const backgroundMusicPlugin: Plugin<typeof settings> = {
+  id: "background-music",
+  name: "Background Music",
+  description: "Play your own music in the background while SEQTA is open.",
+  version: "1.0.0",
+  settings,
+  styles,
+  disableToggle: true,
+  defaultEnabled: false,
+
+  run: async (api) => {
+    await api.storage.loaded;
+
+    // react to specific setting changes
+    api.settings.onChange("volume" as any, (value: any) => {
+      const vol = (typeof value === "number" ? value : 0.5) as number;
+      if (currentAudio) currentAudio.volume = Math.max(0, Math.min(1, vol));
+    });
+
+    // Note: Stop button/event removed by user; no stop handling needed
+
+    // Start if we have audio and autoplay is enabled
+    const tryStart = async () => {
+      const vol = (api.settings as any).volume ?? 0.5;
+      await startPlayback(vol);
+    };
+
+    // Always arm gesture start and attempt immediate start
+    const cancel = ensureGestureStart(() => { tryStart(); });
+    cleanupRegistered = true;
+    (window as any).__betterseqta_bg_music_cancel__ = cancel;
+    tryStart();
+
+    // Pause on tab hide, resume on show with a small delay
+    const visHandler = () => {
+      if (!currentAudio) return;
+      if (document.visibilityState === "hidden") {
+        if (visibilityResumeTimeout !== null) {
+          clearTimeout(visibilityResumeTimeout);
+          visibilityResumeTimeout = null;
+        }
+        currentAudio.pause();
+      } else if (document.visibilityState === "visible") {
+        if (visibilityResumeTimeout !== null) {
+          clearTimeout(visibilityResumeTimeout);
+        }
+        visibilityResumeTimeout = window.setTimeout(() => {
+          visibilityResumeTimeout = null;
+          currentAudio?.play().catch(() => {});
+        }, 200);
+      }
+    };
+    document.addEventListener("visibilitychange", visHandler);
+
+    // Allow uploads to trigger refresh
+    const uploadedHandler = () => {
+      const vol = (api.settings as any).volume ?? 0.5;
+      startPlayback(vol);
+    };
+    window.addEventListener("betterseqta-background-music-updated", uploadedHandler);
+
+    return () => {
+      document.removeEventListener("visibilitychange", visHandler);
+      window.removeEventListener("betterseqta-background-music-updated", uploadedHandler);
+      if (cleanupRegistered && (window as any).__betterseqta_bg_music_cancel__) {
+        (window as any).__betterseqta_bg_music_cancel__();
+        (window as any).__betterseqta_bg_music_cancel__ = undefined;
+      }
+      if (pendingGestureCancel) { pendingGestureCancel(); pendingGestureCancel = null; }
+      if (visibilityResumeTimeout !== null) { clearTimeout(visibilityResumeTimeout); visibilityResumeTimeout = null; }
+      stopAndCleanupAudio();
+    };
+  },
+};
+
+export default backgroundMusicPlugin;
+
+