audio-ui/lib/audio/track-utils.ts

/**
 * Track utility functions
 */

import type { Track, TrackColor } from '@/types/track';
import { DEFAULT_TRACK_HEIGHT, TRACK_COLORS } from '@/types/track';
import { createEffectChain } from '@/lib/audio/effects/chain';
import { createAutomationLane } from '@/lib/audio/automation-utils';

/**
 * Generate a unique track ID
 */
export function generateTrackId(): string {
  return `track-${Date.now()}-${Math.random().toString(36).substr(2, 9)}`;
}

/**
 * Create a new empty track
 */
export function createTrack(name?: string, color?: TrackColor): Track {
  const colors: TrackColor[] = ['blue', 'green', 'purple', 'orange', 'pink', 'indigo', 'yellow', 'red'];
  const randomColor = colors[Math.floor(Math.random() * colors.length)];

  // Ensure name is always a string, handle cases where event objects might be passed
  const trackName = typeof name === 'string' && name.trim() ? name.trim() : 'New Track';

  const trackId = generateTrackId();

  return {
    id: trackId,
    name: trackName,
    color: TRACK_COLORS[color || randomColor],
    height: DEFAULT_TRACK_HEIGHT,
    audioBuffer: null,
    volume: 0.8,
    pan: 0,
    mute: false,
    solo: false,
    recordEnabled: false,
    effectChain: createEffectChain(`${trackName} Effects`),
    automation: {
      lanes: [
        createAutomationLane(trackId, 'volume', 'Volume', {
          min: 0,
          max: 1,
          unit: 'dB',
        }),
        createAutomationLane(trackId, 'pan', 'Pan', {
          min: -1,
          max: 1,
          formatter: (value: number) => {
            if (value === 0) return 'C';
            if (value < 0) return `${Math.abs(value * 100).toFixed(0)}L`;
            return `${(value * 100).toFixed(0)}R`;
          },
        }),
      ],
      showAutomation: false,
    },
    collapsed: false,
    selected: false,
    selection: null,
  };
}

/**
 * Create a track from an audio buffer
 */
export function createTrackFromBuffer(
  buffer: AudioBuffer,
  name?: string,
  color?: TrackColor
): Track {
  // Ensure name is a string before passing to createTrack
  const trackName = typeof name === 'string' && name.trim() ? name.trim() : undefined;
  const track = createTrack(trackName, color);
  track.audioBuffer = buffer;
  return track;
}

/**
 * Mix multiple tracks into a single stereo buffer
 */
export function mixTracks(
  tracks: Track[],
  sampleRate: number,
  duration: number
): AudioBuffer {
  // Determine the length needed
  const length = Math.ceil(duration * sampleRate);

  // Create output buffer (stereo)
  const offlineContext = new OfflineAudioContext(2, length, sampleRate);
  const outputBuffer = offlineContext.createBuffer(2, length, sampleRate);

  const leftChannel = outputBuffer.getChannelData(0);
  const rightChannel = outputBuffer.getChannelData(1);

  // Check if any tracks are soloed
  const soloedTracks = tracks.filter((t) => t.solo && !t.mute);
  const audibleTracks = soloedTracks.length > 0 ? soloedTracks : tracks.filter((t) => !t.mute);

  // Mix each audible track
  for (const track of audibleTracks) {
    if (!track.audioBuffer) continue;

    const buffer = track.audioBuffer;
    const trackLength = Math.min(buffer.length, length);

    // Get source channels (handle mono/stereo)
    const sourceLeft = buffer.getChannelData(0);
    const sourceRight = buffer.numberOfChannels > 1 ? buffer.getChannelData(1) : sourceLeft;

    // Calculate pan gains (constant power panning)
    const panAngle = (track.pan * Math.PI) / 4; // -π/4 to π/4
    const leftGain = Math.cos(panAngle + Math.PI / 4) * track.volume;
    const rightGain = Math.sin(panAngle + Math.PI / 4) * track.volume;

    // Mix into output buffer
    for (let i = 0; i < trackLength; i++) {
      leftChannel[i] += sourceLeft[i] * leftGain;
      rightChannel[i] += sourceRight[i] * rightGain;
    }
  }

  return outputBuffer;
}

/**
 * Get the maximum duration across all tracks
 */
export function getMaxTrackDuration(tracks: Track[]): number {
  let maxDuration = 0;

  for (const track of tracks) {
    if (track.audioBuffer) {
      const duration = track.audioBuffer.duration;
      if (duration > maxDuration) {
        maxDuration = duration;
      }
    }
  }

  return maxDuration;
}

/**
 * Calculate track mix gain (considering solo/mute)
 */
export function getTrackGain(track: Track, allTracks: Track[]): number {
  // If track is muted, gain is 0
  if (track.mute) return 0;

  // Check if any tracks are soloed
  const hasSoloedTracks = allTracks.some((t) => t.solo);

  // If there are soloed tracks and this track is not soloed, gain is 0
  if (hasSoloedTracks && !track.solo) return 0;

  // Otherwise, return the track's volume
  return track.volume;
}