/**
 * Pre-generated notification sounds for the robot.
 *
 * All sounds are raw S16LE mono PCM at 16 kHz, ready to pass to AudioService.play().
 * Generated once at import time — zero runtime cost per playback.
 */

const SAMPLE_RATE = 16_000;

/**
 * Generate a sine wave tone with attack/release envelope to prevent speaker clicks.
 */
function generateTone(freqHz: number, durationMs: number, amplitude = 0.5): Buffer {
  const sampleCount = Math.floor((SAMPLE_RATE * durationMs) / 1000);
  const buf = Buffer.alloc(sampleCount * 2); // 16-bit = 2 bytes per sample
  const amp = Math.max(0, Math.min(1, amplitude)) * 32767;
  const twoPiF = (2 * Math.PI * freqHz) / SAMPLE_RATE;

  // 5ms linear attack/release envelope
  const rampSamples = Math.floor((SAMPLE_RATE * 5) / 1000);

  for (let i = 0; i < sampleCount; i++) {
    let env = 1;
    if (i < rampSamples) env = i / rampSamples;
    else if (i > sampleCount - rampSamples) env = (sampleCount - i) / rampSamples;

    const s = Math.round(Math.sin(i * twoPiF) * amp * env);
    buf.writeInt16LE(Math.max(-32768, Math.min(32767, s)), i * 2);
  }
  return buf;
}

/**
 * Concatenate multiple PCM buffers with silence gaps between them.
 */
function concat(parts: Buffer[], gapMs = 0): Buffer {
  if (gapMs <= 0) return Buffer.concat(parts);

  const gapBytes = Math.floor((SAMPLE_RATE * gapMs) / 1000) * 2;
  const silence = Buffer.alloc(gapBytes);
  const result: Buffer[] = [];

  for (let i = 0; i < parts.length; i++) {
    result.push(parts[i]);
    if (i < parts.length - 1) result.push(silence);
  }

  return Buffer.concat(result);
}

// ── Pre-generated sounds ──────────────────────────────────────────

/**
 * Short rising two-tone chirp: "bi-bip!" (80ms + 80ms)
 * Played when a remote trigger starts a conversation.
 */
export const SOUND_TRIGGER = concat(
  [
    generateTone(660, 80, 0.4),  // E5
    generateTone(880, 80, 0.4),  // A5
  ],
  30, // 30ms gap
);

/**
 * Single soft beep for generic notifications.
 */
export const SOUND_NOTIFY = generateTone(440, 120, 0.3);

/**
 * Three descending tones for errors.
 */
export const SOUND_ERROR = concat(
  [
    generateTone(880, 100, 0.35),
    generateTone(660, 100, 0.35),
    generateTone(440, 150, 0.35),
  ],
  40,
);