audio-ui/lib/hooks/useMultiTrack.ts

import { useState, useCallback, useEffect } from 'react';
import type { Track } from '@/types/track';
import { createTrack, createTrackFromBuffer } from '@/lib/audio/track-utils';

const STORAGE_KEY = 'audio-ui-multi-track';

export function useMultiTrack() {
  const [tracks, setTracks] = useState<Track[]>(() => {
    if (typeof window === 'undefined') return [];

    try {
      const saved = localStorage.getItem(STORAGE_KEY);
      if (saved) {
        const parsed = JSON.parse(saved);
        // Note: AudioBuffers can't be serialized, so we only restore track metadata
        return parsed.map((t: any) => ({
          ...t,
          audioBuffer: null, // Will need to be reloaded
        }));
      }
    } catch (error) {
      console.error('Failed to load tracks from localStorage:', error);
    }

    return [];
  });

  // Save tracks to localStorage (without audio buffers)
  useEffect(() => {
    if (typeof window === 'undefined') return;

    try {
      const trackData = tracks.map(({ audioBuffer, ...track }) => track);
      localStorage.setItem(STORAGE_KEY, JSON.stringify(trackData));
    } catch (error) {
      console.error('Failed to save tracks to localStorage:', error);
    }
  }, [tracks]);

  const addTrack = useCallback((name?: string) => {
    const track = createTrack(name);
    setTracks((prev) => [...prev, track]);
    return track;
  }, []);

  const addTrackFromBuffer = useCallback((buffer: AudioBuffer, name?: string) => {
    const track = createTrackFromBuffer(buffer, name);
    setTracks((prev) => [...prev, track]);
    return track;
  }, []);

  const removeTrack = useCallback((trackId: string) => {
    setTracks((prev) => prev.filter((t) => t.id !== trackId));
  }, []);

  const updateTrack = useCallback((trackId: string, updates: Partial<Track>) => {
    setTracks((prev) =>
      prev.map((track) =>
        track.id === trackId ? { ...track, ...updates } : track
      )
    );
  }, []);

  const clearTracks = useCallback(() => {
    setTracks([]);
  }, []);

  const reorderTracks = useCallback((fromIndex: number, toIndex: number) => {
    setTracks((prev) => {
      const newTracks = [...prev];
      const [movedTrack] = newTracks.splice(fromIndex, 1);
      newTracks.splice(toIndex, 0, movedTrack);
      return newTracks;
    });
  }, []);

  const setTrackBuffer = useCallback((trackId: string, buffer: AudioBuffer) => {
    setTracks((prev) =>
      prev.map((track) =>
        track.id === trackId ? { ...track, audioBuffer: buffer } : track
      )
    );
  }, []);

  return {
    tracks,
    addTrack,
    addTrackFromBuffer,
    removeTrack,
    updateTrack,
    clearTracks,
    reorderTracks,
    setTrackBuffer,
  };
}