audio-ui/lib/audio/automation/playback.ts

/**
 * Automation playback engine
 * Applies automation to track parameters in real-time during playback
 */

import type { Track } from '@/types/track';
import type { AutomationLane, AutomationValue } from '@/types/automation';
import { interpolateAutomationValue, applyAutomationToTrack } from './utils';

/**
 * Get all automation values at a specific time
 */
export function getAutomationValuesAtTime(
  track: Track,
  time: number
): AutomationValue[] {
  if (!track.automation || track.automation.lanes.length === 0) {
    return [];
  }

  const values: AutomationValue[] = [];

  for (const lane of track.automation.lanes) {
    // Skip lanes in write mode (don't apply during playback)
    if (lane.mode === 'write') continue;

    // Skip lanes with no points
    if (lane.points.length === 0) continue;

    const value = interpolateAutomationValue(lane.points, time);

    values.push({
      parameterId: lane.parameterId,
      value,
      time,
    });
  }

  return values;
}

/**
 * Apply automation values to a track
 * Returns a new track object with automated parameters applied
 */
export function applyAutomationValues(
  track: Track,
  values: AutomationValue[]
): Track {
  let updatedTrack = track;

  for (const automation of values) {
    updatedTrack = applyAutomationToTrack(
      updatedTrack,
      automation.parameterId,
      automation.value
    );
  }

  return updatedTrack;
}

/**
 * Apply automation to all tracks at a specific time
 * Returns a new tracks array with automation applied
 */
export function applyAutomationToTracks(
  tracks: Track[],
  time: number
): Track[] {
  return tracks.map((track) => {
    const automationValues = getAutomationValuesAtTime(track, time);

    if (automationValues.length === 0) {
      return track;
    }

    return applyAutomationValues(track, automationValues);
  });
}

/**
 * Record automation point during playback
 */
export function recordAutomationPoint(
  lane: AutomationLane,
  time: number,
  value: number
): AutomationLane {
  // In write mode, replace all existing points in the recorded region
  // For simplicity, just add the point for now
  // TODO: Implement proper write mode that clears existing points

  const newPoint = {
    id: `point-${Date.now()}-${Math.random().toString(36).substr(2, 9)}`,
    time,
    value,
    curve: 'linear' as const,
  };

  return {
    ...lane,
    points: [...lane.points, newPoint],
  };
}

/**
 * Automation playback scheduler
 * Schedules automation updates at regular intervals during playback
 */
export class AutomationPlaybackScheduler {
  private intervalId: number | null = null;
  private updateInterval: number = 50; // Update every 50ms (20 Hz)
  private onUpdate: ((time: number) => void) | null = null;

  /**
   * Start the automation scheduler
   */
  start(onUpdate: (time: number) => void): void {
    if (this.intervalId !== null) {
      this.stop();
    }

    this.onUpdate = onUpdate;
    this.intervalId = window.setInterval(() => {
      // Get current playback time from your audio engine
      // This is a placeholder - you'll need to integrate with your actual playback system
      if (this.onUpdate) {
        // Call update callback with current time
        // The callback should get the time from your actual playback system
        this.onUpdate(0); // Placeholder
      }
    }, this.updateInterval);
  }

  /**
   * Stop the automation scheduler
   */
  stop(): void {
    if (this.intervalId !== null) {
      window.clearInterval(this.intervalId);
      this.intervalId = null;
    }
    this.onUpdate = null;
  }

  /**
   * Set update interval (in milliseconds)
   */
  setUpdateInterval(interval: number): void {
    this.updateInterval = Math.max(10, Math.min(1000, interval));

    // Restart if already running
    if (this.intervalId !== null && this.onUpdate) {
      const callback = this.onUpdate;
      this.stop();
      this.start(callback);
    }
  }

  /**
   * Check if scheduler is running
   */
  isRunning(): boolean {
    return this.intervalId !== null;
  }
}