SonicForgeStudio/app/static/js/services/ghostNoteExtractor.js

// SonicForge Studio Ghost Note Extractor Service
(function() {
  function extractGhostLayers(activeTracks, targetTrackId, targetItemId, bpm) {
    if (!activeTracks || !targetItemId) return [];

    const secondsPerBeat = 60.0 / (parseInt(bpm) || 120);

    let targetItem = null;
    for (var i = 0; i < activeTracks.length; i++) {
      var t = activeTracks[i];
      var found = (t.midiItems || []).find(function(m) { return m.id === targetItemId; });
      if (found) { targetItem = found; break; }
    }
    if (!targetItem) return [];

    const windowStartBeat = targetItem.startTime / secondsPerBeat;
    const windowEndBeat = (targetItem.startTime + targetItem.duration) / secondsPerBeat;

    const ghostLayers = [];

    for (var i = 0; i < activeTracks.length; i++) {
      var track = activeTracks[i];
      if (!track.midiItems || !track.midiItems.length) continue;
      if (track.muted) continue;

      var trackGhostNotes = [];

      for (var j = 0; j < track.midiItems.length; j++) {
        var item = track.midiItems[j];
        if (item.id === targetItemId) continue;

        var itemStartBeat = item.startTime / secondsPerBeat;
        var itemEndBeat = (item.startTime + item.duration) / secondsPerBeat;

        if (itemStartBeat >= windowEndBeat || itemEndBeat < windowStartBeat) continue;

        var notes = item.notes || [];
        for (var k = 0; k < notes.length; k++) {
          var note = notes[k];
          var noteAbsStart = itemStartBeat + (note.start_beat || 0);
          var noteAbsEnd = noteAbsStart + (note.duration_beats || 1);

          if (noteAbsStart >= windowEndBeat || noteAbsEnd < windowStartBeat) continue;

          var clampedStart = Math.max(noteAbsStart, windowStartBeat);
          var clampedEnd = Math.min(noteAbsEnd, windowEndBeat);
          var clampedDur = clampedEnd - clampedStart;

          trackGhostNotes.push({
            id: 'ghost_' + (note.id || Math.random().toString(36).substr(2, 9)),
            pitch: note.pitch,
            relative_start_beat: clampedStart - windowStartBeat,
            duration_beats: clampedDur,
            velocity: note.velocity,
            original_track_name: track.name,
            original_track_color: track.color || '#888888'
          });
        }
      }

      if (trackGhostNotes.length > 0) {
        ghostLayers.push({
          track_id: track.id,
          track_name: track.name,
          track_color: track.color || '#6b7280',
          notes: trackGhostNotes
        });
      }
    }

    return ghostLayers;
  }

  window.SonicGhost = { extractGhostLayers: extractGhostLayers };
})();