More core audio work

angular.json

@@ -2,7 +2,8 @@
   "$schema": "./node_modules/@angular/cli/lib/config/schema.json",
   "version": 1,
   "cli": {
-    "packageManager": "npm"
+    "packageManager": "npm",
+    "analytics": false
   },
   "newProjectRoot": "projects",
   "projects": {

src/app/lib/IndexedArray.ts

@@ -0,0 +1,73 @@
+import {computed, effect, Signal, signal, WritableSignal} from '@angular/core';
+
+export class IndexedArray<T> {
+  protected list: WritableSignal<T[]> = signal([]);
+  protected currentIndex: WritableSignal<number> = signal(0);
+
+  public playlist: Signal<T[]> = this.list.asReadonly();
+  public index: Signal<number> = this.currentIndex.asReadonly();
+  public current: Signal<T|null>;
+
+  constructor() {
+    this.current = computed(() : T | null => {
+      if (this.currentIndex() > -1 && this.list().length === 0) return null;
+      return this.list()[this.currentIndex()];
+    });
+  }
+
+  next(): T | null {
+    const length = this.list().length;
+    if (length === 0) return null;
+    if (length === 1) return this.list()[0];
+
+    if (this.currentIndex() === length - 1) {
+      this.currentIndex.set(0);
+    } else {
+      this.currentIndex.set(this.currentIndex() + 1);
+    }
+
+    return this.current();
+  }
+
+  prev(): T | null {
+    const length = this.list().length;
+    if (length === 0) return null;
+    if (length === 1) return this.list()[0];
+
+    if (this.currentIndex() === 0) {
+      this.currentIndex.set(length - 1);
+    } else {
+      this.currentIndex.set(this.currentIndex() - 1);
+    }
+
+    return this.current();
+  }
+
+  add(item: T) {
+    this.list.update((list: T[]) => {
+      return [...list, item];
+    });
+  }
+
+  remove(item: T) {
+    // Check item is actually in the list, and find its index
+    const index = this.list().indexOf(item);
+    if (index > -1) {
+      // If we deleted an item before the current index pointer, then shift the index back one to maintain current item
+      if (index < this.currentIndex()) {
+        this.currentIndex.update((index) => index - 1);
+      }
+
+      // If we are at the end of the list (and the list won't become empty) shift index back to maintain pointer at end of list
+      if (index === this.list().length - 1 && index > 0) {
+        this.currentIndex.update((index) => index - 1);
+      }
+
+      // Remove the item
+      this.list.update((list: T[]) => {
+        list.splice(index, 1);
+        return [...list];
+      });
+    }
+  }
+}

src/app/lib/index.ts

@@ -0,0 +1 @@
+export * from './IndexedArray';

src/app/models/FileSystemFile.ts

@@ -1,4 +1,4 @@
-export class File {
+export class FileSystemFile {
   constructor(
     public filename: string,
     public filepath: string,

src/app/models/PlaylistItem.ts

@@ -0,0 +1,58 @@
+import {Track} from './Track';
+
+enum STATE {
+  Playing,
+  Paused,
+  Stopped
+}
+
+export class PlaylistItem {
+  protected element: HTMLAudioElement;
+  protected state: STATE = STATE.Stopped;
+
+  constructor(
+    public track: Track,
+    protected context: AudioContext
+  ) {
+    this.element = this.createElement(this.track.file.filepath, this.track.getMimeType())
+    context.createMediaElementSource(this.element).connect(context.destination);
+  }
+
+  private createElement(filename: string, type: string) {
+    const element = document.createElement('audio');
+    const source = document.createElement('source');
+    source.src = filename;
+    source.type = type;
+    element.appendChild(source);
+    return element;
+  }
+
+  public async play() {
+    if (this.state === STATE.Stopped || this.state === STATE.Paused) {
+      await this.element.play();
+      this.state = STATE.Playing;
+      return;
+    }
+  }
+
+  public async stop() {
+    this.element.currentTime = 0;
+    this.element.pause();
+    this.state = STATE.Stopped;
+  }
+
+  public async pause() {
+    if (this.state === STATE.Paused) {
+      return this.play();
+    }
+    if (this.state === STATE.Playing) {
+      this.element.pause();
+      this.state = STATE.Paused;
+      return;
+    }
+  }
+
+  public isPlaying() {
+    return this.state === STATE.Playing;
+  }
+}

src/app/models/Track.ts

@@ -0,0 +1,21 @@
+import {TrackMeta} from './TrackMeta';
+import {FileSystemFile} from './FileSystemFile';
+
+export class Track {
+  constructor(
+    public file: FileSystemFile,
+    public meta: TrackMeta,
+    public length: number,
+    public format: string,
+    public bitrate: number,
+  ) {
+  }
+
+  getMimeType() {
+    switch (this.format) {
+      case 'mp3':
+      default:
+        return 'audio/mp3';
+    }
+  }
+}

src/app/models/TrackMeta.ts

@@ -0,0 +1,11 @@
+export class TrackMeta {
+
+  constructor(
+    public title: string = '',
+    public artist: string = '',
+    public album: string = '',
+    public genre: string = '',
+    public trackNumber: number = 0,
+  ) {
+  }
+}

src/app/models/index.ts

@@ -0,0 +1,4 @@
+export * from './Track';
+export * from './TrackMeta';
+export * from './PlaylistItem';
+export * from './FileSystemFile';

src/app/models/track.ts

@@ -1,12 +0,0 @@
-import {TrackMeta} from './trackmeta';
-
-export class Track {
-  constructor(
-    public file: File,
-    public meta: TrackMeta,
-    public length: number,
-    public format: string,
-    public bitrate: number,
-  ) {
-  }
-}

src/app/models/trackmeta.ts

@@ -1,10 +0,0 @@
-export class TrackMeta {
-  constructor(
-    public title: string,
-    public artist: string,
-    public album: string,
-    public genre: string,
-    public trackNumber: number,
-  ) {
-  }
-}

src/app/pages/homepage/homepage.html

@@ -1,3 +1,18 @@
 Home
 
-<button id="play" (click)="play($event)">Play</button>
+<button (click)="play($event)">Play</button>
+<button (click)="stop($event)">Stop</button>
+<button (click)="next($event)">Next</button>
+<button (click)="prev($event)">Prev</button>
+<button (click)="pause($event)">Pause/Resume</button>
+<button (click)="add($event)">Add</button>
+<button (click)="remove($event)">Remove</button>
+
+@for (item of audio.list(); track item) {
+  <div>
+  @if ($index === audio.index()) {
+    *
+  }
+  {{ item.track.file.filename }}
+  </div>
+}

src/app/pages/homepage/homepage.ts

@@ -1,5 +1,6 @@
 import {Component, OnInit, viewChild} from '@angular/core';
 import {AudioService} from '../../services/audio.service';
+import {FileSystemFile, Track, TrackMeta} from '../../models';
 
 @Component({
   selector: 'app-home',
@@ -15,4 +16,36 @@ export class HomePage{
   play(event: Event): void {
     this.audio.play();
   }
+
+  stop(event: Event): void {
+    this.audio.stop();
+  }
+
+  next(event: Event): void {
+    this.audio.next();
+  }
+  prev(event: Event): void {
+    this.audio.prev();
+  }
+
+  pause(event: Event): void {
+    this.audio.pause();
+  }
+
+  add(event: Event): void {
+    this.audio.addItem(new Track(
+      new FileSystemFile('3.mp3', 'audio/3.mp3', 0),
+      new TrackMeta(),
+      0,
+      'mp3',
+      128
+    ));
+  }
+
+  remove(event: Event): void {
+    const item = this.audio.current();
+    if (item) {
+      this.audio.removeItem(item);
+    }
+  }
 }

src/app/services/audio.service.ts

@@ -1,30 +1,88 @@
-import {HttpClient} from '@angular/common/http';
+import {FileSystemFile, Track, TrackMeta, PlaylistItem} from '../models';
+import {Signal} from '@angular/core';
+import {IndexedArray} from '../lib';
 
 export class AudioService {
   protected context: AudioContext;
-  protected track?: MediaElementAudioSourceNode;
+  protected playlist: IndexedArray<PlaylistItem> = new IndexedArray();
+  public list: Signal<PlaylistItem[]> = this.playlist.playlist;
+  public current: Signal<PlaylistItem|null> = this.playlist.current;
+  public index: Signal<number> = this.playlist.index;
 
   constructor() {
     this.context = new AudioContext();
+
+    this.addItem(new Track(
+      new FileSystemFile('1.mp3', 'audio/1.mp3', 0),
+      new TrackMeta(),
+      0,
+      'mp3',
+      128
+    ));
+    this.addItem(new Track(
+      new FileSystemFile('2.mp3', 'audio/2.mp3', 0),
+      new TrackMeta(),
+      0,
+      'mp3',
+      128
+    ));
+    this.addItem(new Track(
+      new FileSystemFile('3.mp3', 'audio/3.mp3', 0),
+      new TrackMeta(),
+      0,
+      'mp3',
+      128
+    ));
   }
 
-  createElement(filename: string) {
-    const element = document.createElement('audio');
-    const source = document.createElement('source');
-    source.src = filename;
-    source.type = 'audio/mp3';
-    element.appendChild(source);
-    return element;
+  addItem(track: Track) {
+    this.playlist.add(new PlaylistItem(track, this.context));
+  }
+
+  removeItem(item: PlaylistItem) {
+    if (item.isPlaying() && item === this.current()) {
+      this.current()?.stop();
+      this.playlist.remove(item);
+      this.current()?.play();
+      return;
+    }
+
+    this.playlist.remove(item);
   }
 
   async play(): Promise<void> {
     if (this.context.state === 'suspended') {
       await this.context.resume();
     }
-    const element = this.createElement('audio/1.mp3');
-    this.track = this.context.createMediaElementSource(element);
-    this.track.connect(this.context.destination);
 
-    await element.play();
+    await this.current()?.play();
+  }
+
+  async stop(): Promise<void> {
+    await this.current()?.stop();
+  }
+
+  async next(): Promise<void> {
+    if (this.current()?.isPlaying()) {
+      await this.current()?.stop();
+      this.playlist.next();
+      await this.current()?.play();
+    } else {
+      this.playlist.next();
+    }
+  }
+
+  async prev(): Promise<void> {
+    if (this.current()?.isPlaying()) {
+      await this.current()?.stop();
+      this.playlist.prev();
+      await this.current()?.play();
+    } else {
+      this.playlist.prev();
+    }
+  }
+
+  async pause(): Promise<void> {
+    await this.current()?.pause();
   }
 }