audio-ui/lib/history/commands/multi-track-edit-command.ts

/**
 * Multi-track edit commands for audio operations across tracks
 */

import { BaseCommand } from '../command';
import type { Track } from '@/types/track';
import type { Selection } from '@/types/selection';
import {
  extractBufferSegment,
  deleteBufferSegment,
  insertBufferSegment,
  duplicateBufferSegment,
} from '@/lib/audio/buffer-utils';

export type MultiTrackEditType = 'cut' | 'copy' | 'delete' | 'paste' | 'duplicate';

export interface MultiTrackEditParams {
  type: MultiTrackEditType;
  trackId: string;
  beforeBuffer: AudioBuffer | null;
  afterBuffer: AudioBuffer | null;
  selection?: Selection;
  clipboardData?: AudioBuffer;
  pastePosition?: number;
  onApply: (trackId: string, buffer: AudioBuffer | null, selection: Selection | null) => void;
}

/**
 * Command for multi-track edit operations
 */
export class MultiTrackEditCommand extends BaseCommand {
  private type: MultiTrackEditType;
  private trackId: string;
  private beforeBuffer: AudioBuffer | null;
  private afterBuffer: AudioBuffer | null;
  private selection?: Selection;
  private clipboardData?: AudioBuffer;
  private pastePosition?: number;
  private onApply: (trackId: string, buffer: AudioBuffer | null, selection: Selection | null) => void;

  constructor(params: MultiTrackEditParams) {
    super();
    this.type = params.type;
    this.trackId = params.trackId;
    this.beforeBuffer = params.beforeBuffer;
    this.afterBuffer = params.afterBuffer;
    this.selection = params.selection;
    this.clipboardData = params.clipboardData;
    this.pastePosition = params.pastePosition;
    this.onApply = params.onApply;
  }

  execute(): void {
    // For copy, don't modify the buffer, just update selection
    if (this.type === 'copy') {
      this.onApply(this.trackId, this.beforeBuffer, this.selection || null);
    } else {
      this.onApply(this.trackId, this.afterBuffer, null);
    }
  }

  undo(): void {
    this.onApply(this.trackId, this.beforeBuffer, null);
  }

  getDescription(): string {
    switch (this.type) {
      case 'cut':
        return 'Cut';
      case 'copy':
        return 'Copy';
      case 'delete':
        return 'Delete';
      case 'paste':
        return 'Paste';
      case 'duplicate':
        return 'Duplicate';
      default:
        return 'Edit';
    }
  }
}

/**
 * Factory functions to create multi-track edit commands
 */

export function createMultiTrackCutCommand(
  trackId: string,
  buffer: AudioBuffer,
  selection: Selection,
  onApply: (trackId: string, buffer: AudioBuffer | null, selection: Selection | null) => void
): MultiTrackEditCommand {
  const afterBuffer = deleteBufferSegment(buffer, selection.start, selection.end);

  return new MultiTrackEditCommand({
    type: 'cut',
    trackId,
    beforeBuffer: buffer,
    afterBuffer,
    selection,
    onApply,
  });
}

export function createMultiTrackCopyCommand(
  trackId: string,
  buffer: AudioBuffer,
  selection: Selection,
  onApply: (trackId: string, buffer: AudioBuffer | null, selection: Selection | null) => void
): MultiTrackEditCommand {
  // Copy doesn't modify the buffer
  return new MultiTrackEditCommand({
    type: 'copy',
    trackId,
    beforeBuffer: buffer,
    afterBuffer: buffer,
    selection,
    onApply,
  });
}

export function createMultiTrackDeleteCommand(
  trackId: string,
  buffer: AudioBuffer,
  selection: Selection,
  onApply: (trackId: string, buffer: AudioBuffer | null, selection: Selection | null) => void
): MultiTrackEditCommand {
  const afterBuffer = deleteBufferSegment(buffer, selection.start, selection.end);

  return new MultiTrackEditCommand({
    type: 'delete',
    trackId,
    beforeBuffer: buffer,
    afterBuffer,
    selection,
    onApply,
  });
}

export function createMultiTrackPasteCommand(
  trackId: string,
  buffer: AudioBuffer | null,
  clipboardData: AudioBuffer,
  pastePosition: number,
  onApply: (trackId: string, buffer: AudioBuffer | null, selection: Selection | null) => void
): MultiTrackEditCommand {
  const targetBuffer = buffer || createSilentBuffer(clipboardData.sampleRate, clipboardData.numberOfChannels, pastePosition);
  const afterBuffer = insertBufferSegment(targetBuffer, clipboardData, pastePosition);

  return new MultiTrackEditCommand({
    type: 'paste',
    trackId,
    beforeBuffer: buffer,
    afterBuffer,
    clipboardData,
    pastePosition,
    onApply,
  });
}

export function createMultiTrackDuplicateCommand(
  trackId: string,
  buffer: AudioBuffer,
  selection: Selection,
  onApply: (trackId: string, buffer: AudioBuffer | null, selection: Selection | null) => void
): MultiTrackEditCommand {
  const afterBuffer = duplicateBufferSegment(buffer, selection.start, selection.end);

  return new MultiTrackEditCommand({
    type: 'duplicate',
    trackId,
    beforeBuffer: buffer,
    afterBuffer,
    selection,
    onApply,
  });
}

/**
 * Helper function to create a silent buffer
 */
function createSilentBuffer(sampleRate: number, numberOfChannels: number, duration: number): AudioBuffer {
  const audioContext = new OfflineAudioContext(
    numberOfChannels,
    Math.ceil(duration * sampleRate),
    sampleRate
  );
  return audioContext.createBuffer(numberOfChannels, Math.ceil(duration * sampleRate), sampleRate);
}