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

/**
 * Automation utility functions
 */

import type {
  AutomationLane,
  AutomationPoint,
  CreateAutomationLaneInput,
  CreateAutomationPointInput,
  AutomationParameterId,
} from '@/types/automation';

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

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

/**
 * Create a new automation point
 */
export function createAutomationPoint(
  input: CreateAutomationPointInput
): AutomationPoint {
  return {
    id: generateAutomationPointId(),
    ...input,
  };
}

/**
 * Create a new automation lane
 */
export function createAutomationLane(
  trackId: string,
  parameterId: AutomationParameterId,
  parameterName: string,
  input?: Partial<CreateAutomationLaneInput>
): AutomationLane {
  return {
    id: generateAutomationLaneId(),
    trackId,
    parameterId,
    parameterName,
    visible: input?.visible ?? true,
    height: input?.height ?? 80,
    points: input?.points ?? [],
    mode: input?.mode ?? 'read',
    color: input?.color,
    valueRange: input?.valueRange ?? {
      min: 0,
      max: 1,
    },
  };
}

/**
 * Create a volume automation lane
 */
export function createVolumeAutomationLane(trackId: string): AutomationLane {
  return createAutomationLane(trackId, 'volume', 'Volume', {
    valueRange: {
      min: 0,
      max: 1,
      formatter: (value) => `${(value * 100).toFixed(0)}%`,
    },
    color: 'rgb(34, 197, 94)', // green
  });
}

/**
 * Create a pan automation lane
 */
export function createPanAutomationLane(trackId: string): AutomationLane {
  return createAutomationLane(trackId, 'pan', 'Pan', {
    valueRange: {
      min: -1,
      max: 1,
      formatter: (value) => {
        const normalized = value * 2 - 1; // Convert 0-1 to -1-1
        if (normalized === 0) return 'C';
        if (normalized < 0) return `L${Math.abs(Math.round(normalized * 100))}`;
        return `R${Math.round(normalized * 100)}`;
      },
    },
    color: 'rgb(59, 130, 246)', // blue
  });
}

/**
 * Interpolate automation value at a specific time
 */
export function interpolateAutomationValue(
  points: AutomationPoint[],
  time: number
): number {
  if (points.length === 0) return 0;

  const sortedPoints = [...points].sort((a, b) => a.time - b.time);

  // Before first point
  if (time <= sortedPoints[0].time) {
    return sortedPoints[0].value;
  }

  // After last point
  if (time >= sortedPoints[sortedPoints.length - 1].time) {
    return sortedPoints[sortedPoints.length - 1].value;
  }

  // Find surrounding points
  for (let i = 0; i < sortedPoints.length - 1; i++) {
    const prevPoint = sortedPoints[i];
    const nextPoint = sortedPoints[i + 1];

    if (time >= prevPoint.time && time <= nextPoint.time) {
      // Handle step curve
      if (prevPoint.curve === 'step') {
        return prevPoint.value;
      }

      // Handle bezier curve
      if (prevPoint.curve === 'bezier') {
        const timeDelta = nextPoint.time - prevPoint.time;
        const t = (time - prevPoint.time) / timeDelta;
        return interpolateBezier(prevPoint, nextPoint, t);
      }

      // Linear interpolation (default)
      const timeDelta = nextPoint.time - prevPoint.time;
      const valueDelta = nextPoint.value - prevPoint.value;
      const progress = (time - prevPoint.time) / timeDelta;

      return prevPoint.value + valueDelta * progress;
    }
  }

  return 0;
}

/**
 * Interpolate value using cubic Bezier curve
 * Uses the control handles from both points to create smooth curves
 */
function interpolateBezier(
  p0: AutomationPoint,
  p1: AutomationPoint,
  t: number
): number {
  // Default handle positions if not specified
  // Out handle defaults to 1/3 towards next point
  // In handle defaults to 1/3 back from current point
  const timeDelta = p1.time - p0.time;

  // Control point 1 (out handle from p0)
  const c1x = p0.handleOut?.x ?? timeDelta / 3;
  const c1y = p0.handleOut?.y ?? 0;

  // Control point 2 (in handle from p1)
  const c2x = p1.handleIn?.x ?? -timeDelta / 3;
  const c2y = p1.handleIn?.y ?? 0;

  // Convert handles to absolute positions
  const cp1Value = p0.value + c1y;
  const cp2Value = p1.value + c2y;

  // Cubic Bezier formula: B(t) = (1-t)³P₀ + 3(1-t)²tP₁ + 3(1-t)t²P₂ + t³P₃
  const mt = 1 - t;
  const mt2 = mt * mt;
  const mt3 = mt2 * mt;
  const t2 = t * t;
  const t3 = t2 * t;

  const value =
    mt3 * p0.value +
    3 * mt2 * t * cp1Value +
    3 * mt * t2 * cp2Value +
    t3 * p1.value;

  return value;
}

/**
 * Create smooth bezier handles for a point based on surrounding points
 * This creates an "auto-smooth" effect similar to DAWs
 */
export function createSmoothHandles(
  prevPoint: AutomationPoint | null,
  currentPoint: AutomationPoint,
  nextPoint: AutomationPoint | null
): { handleIn: { x: number; y: number }; handleOut: { x: number; y: number } } {
  // If no surrounding points, return horizontal handles
  if (!prevPoint && !nextPoint) {
    return {
      handleIn: { x: -0.1, y: 0 },
      handleOut: { x: 0.1, y: 0 },
    };
  }

  // Calculate slope from surrounding points
  let slope = 0;

  if (prevPoint && nextPoint) {
    // Use average slope from both neighbors
    const timeDelta = nextPoint.time - prevPoint.time;
    const valueDelta = nextPoint.value - prevPoint.value;
    slope = valueDelta / timeDelta;
  } else if (nextPoint) {
    // Only have next point
    const timeDelta = nextPoint.time - currentPoint.time;
    const valueDelta = nextPoint.value - currentPoint.value;
    slope = valueDelta / timeDelta;
  } else if (prevPoint) {
    // Only have previous point
    const timeDelta = currentPoint.time - prevPoint.time;
    const valueDelta = currentPoint.value - prevPoint.value;
    slope = valueDelta / timeDelta;
  }

  // Create handles with 1/3 distance to neighbors
  const handleDistance = 0.1; // Fixed distance for smooth curves
  const handleY = slope * handleDistance;

  return {
    handleIn: { x: -handleDistance, y: -handleY },
    handleOut: { x: handleDistance, y: handleY },
  };
}

/**
 * Generate points along a bezier curve for rendering
 * Returns array of {time, value} points
 */
export function generateBezierCurvePoints(
  p0: AutomationPoint,
  p1: AutomationPoint,
  numPoints: number = 50
): Array<{ time: number; value: number }> {
  const points: Array<{ time: number; value: number }> = [];
  const timeDelta = p1.time - p0.time;

  for (let i = 0; i <= numPoints; i++) {
    const t = i / numPoints;
    const time = p0.time + t * timeDelta;
    const value = interpolateBezier(p0, p1, t);
    points.push({ time, value });
  }

  return points;
}

/**
 * Apply automation value to track parameter
 */
export function applyAutomationToTrack(
  track: any,
  parameterId: AutomationParameterId,
  value: number
): any {
  if (parameterId === 'volume') {
    return { ...track, volume: value };
  }

  if (parameterId === 'pan') {
    // Convert 0-1 to -1-1
    return { ...track, pan: value * 2 - 1 };
  }

  // Effect parameters (format: "effect.{effectId}.{paramName}")
  if (parameterId.startsWith('effect.')) {
    const parts = parameterId.split('.');
    if (parts.length === 3) {
      const [, effectId, paramName] = parts;
      return {
        ...track,
        effectChain: {
          ...track.effectChain,
          effects: track.effectChain.effects.map((effect: any) =>
            effect.id === effectId
              ? {
                  ...effect,
                  parameters: {
                    ...effect.parameters,
                    [paramName]: value,
                  },
                }
              : effect
          ),
        },
      };
    }
  }

  return track;
}