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

/**
 * Automation utility functions for creating and manipulating automation data
 */

import type {
  AutomationLane,
  AutomationPoint,
  AutomationCurveType,
  AutomationMode,
  CreateAutomationPointInput,
} from '@/types/automation';

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

/**
 * Generate unique automation lane ID
 */
export function generateAutomationLaneId(): string {
  return `autolane-${Date.now()}-${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: string,
  parameterName: string,
  valueRange: {
    min: number;
    max: number;
    unit?: string;
    formatter?: (value: number) => string;
  }
): AutomationLane {
  return {
    id: generateAutomationLaneId(),
    trackId,
    parameterId,
    parameterName,
    visible: true,
    height: 80,
    points: [],
    mode: 'read',
    valueRange,
  };
}

/**
 * Linear interpolation between two values
 */
function lerp(a: number, b: number, t: number): number {
  return a + (b - a) * t;
}

/**
 * Evaluate automation value at a specific time using linear interpolation
 */
export function evaluateAutomationLinear(
  points: AutomationPoint[],
  time: number
): number {
  if (points.length === 0) return 0.5; // Default middle value
  if (points.length === 1) return points[0].value;

  // Sort points by time (should already be sorted, but ensure it)
  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 p1 = sortedPoints[i];
    const p2 = sortedPoints[i + 1];

    if (time >= p1.time && time <= p2.time) {
      // Handle step curve
      if (p1.curve === 'step') {
        return p1.value;
      }

      // Linear interpolation
      const t = (time - p1.time) / (p2.time - p1.time);
      return lerp(p1.value, p2.value, t);
    }
  }

  return sortedPoints[sortedPoints.length - 1].value;
}

/**
 * Add an automation point to a lane, maintaining time-sorted order
 */
export function addAutomationPoint(
  lane: AutomationLane,
  point: CreateAutomationPointInput
): AutomationLane {
  const newPoint = createAutomationPoint(point);
  const points = [...lane.points, newPoint].sort((a, b) => a.time - b.time);

  return {
    ...lane,
    points,
  };
}

/**
 * Remove an automation point by ID
 */
export function removeAutomationPoint(
  lane: AutomationLane,
  pointId: string
): AutomationLane {
  return {
    ...lane,
    points: lane.points.filter((p) => p.id !== pointId),
  };
}

/**
 * Update an automation point's time and/or value
 */
export function updateAutomationPoint(
  lane: AutomationLane,
  pointId: string,
  updates: { time?: number; value?: number; curve?: AutomationCurveType }
): AutomationLane {
  const points = lane.points.map((p) =>
    p.id === pointId ? { ...p, ...updates } : p
  );

  // Re-sort by time if time was updated
  if (updates.time !== undefined) {
    points.sort((a, b) => a.time - b.time);
  }

  return {
    ...lane,
    points,
  };
}

/**
 * Remove all automation points in a time range
 */
export function clearAutomationRange(
  lane: AutomationLane,
  startTime: number,
  endTime: number
): AutomationLane {
  return {
    ...lane,
    points: lane.points.filter((p) => p.time < startTime || p.time > endTime),
  };
}

/**
 * Format automation value for display based on lane's value range
 */
export function formatAutomationValue(
  lane: AutomationLane,
  normalizedValue: number
): string {
  const { min, max, unit, formatter } = lane.valueRange;

  if (formatter) {
    const actualValue = lerp(min, max, normalizedValue);
    return formatter(actualValue);
  }

  const actualValue = lerp(min, max, normalizedValue);

  // Format based on unit
  if (unit === 'dB') {
    // Convert to dB scale
    const db = normalizedValue === 0 ? -Infinity : 20 * Math.log10(normalizedValue);
    return db === -Infinity ? '-∞ dB' : `${db.toFixed(1)} dB`;
  }

  if (unit === '%') {
    return `${(actualValue * 100).toFixed(0)}%`;
  }

  if (unit === 'ms') {
    return `${actualValue.toFixed(1)} ms`;
  }

  if (unit === 'Hz') {
    return `${actualValue.toFixed(0)} Hz`;
  }

  // Default: 2 decimal places with unit
  return unit ? `${actualValue.toFixed(2)} ${unit}` : actualValue.toFixed(2);
}

/**
 * Snap value to grid (useful for user input)
 */
export function snapToGrid(value: number, gridSize: number = 0.25): number {
  return Math.round(value / gridSize) * gridSize;
}

/**
 * Clamp value between 0 and 1
 */
export function clampNormalized(value: number): number {
  return Math.max(0, Math.min(1, value));
}