siprouter/ts/call/prompt-cache.ts

/**
 * PromptCache — manages named audio prompt WAV files for IVR and voicemail.
 *
 * Generates WAV files via espeak-ng (primary) or Kokoro TTS through the
 * proxy-engine (fallback). Also supports loading pre-existing WAV files
 * and programmatic tone generation.
 *
 * All audio playback happens in Rust (audio_player / start_interaction).
 * This module only manages WAV files on disk.
 */

import { execSync } from 'node:child_process';
import fs from 'node:fs';
import path from 'node:path';
import { Buffer } from 'node:buffer';
import { sendProxyCommand, isProxyReady } from '../proxybridge.ts';

// ---------------------------------------------------------------------------
// Types
// ---------------------------------------------------------------------------

/** A cached prompt — just a WAV file path and metadata. */
export interface ICachedPrompt {
  /** Unique prompt identifier. */
  id: string;
  /** Path to the WAV file on disk. */
  wavPath: string;
  /** Total duration in milliseconds (approximate, from WAV header). */
  durationMs: number;
}

// ---------------------------------------------------------------------------
// TTS helpers
// ---------------------------------------------------------------------------

const TTS_DIR = path.join(process.cwd(), '.nogit', 'tts');

/** Check if espeak-ng is available. */
function isEspeakAvailable(): boolean {
  try {
    execSync('which espeak-ng', { stdio: 'pipe' });
    return true;
  } catch {
    return false;
  }
}

/** Generate WAV via espeak-ng. */
function generateViaEspeak(wavPath: string, text: string): boolean {
  try {
    execSync(
      `espeak-ng -v en-us -s 150 -w "${wavPath}" "${text}"`,
      { timeout: 10000, stdio: 'pipe' },
    );
    return true;
  } catch {
    return false;
  }
}

/** Generate WAV via Kokoro TTS (runs inside proxy-engine). */
async function generateViaKokoro(wavPath: string, text: string, voice: string): Promise<boolean> {
  const modelPath = path.join(TTS_DIR, 'kokoro-v1.0.onnx');
  const voicesPath = path.join(TTS_DIR, 'voices.bin');
  if (!fs.existsSync(modelPath) || !fs.existsSync(voicesPath)) return false;
  if (!isProxyReady()) return false;

  try {
    await sendProxyCommand('generate_tts', {
      model: modelPath,
      voices: voicesPath,
      voice,
      text,
      output: wavPath,
    });
    return true;
  } catch {
    return false;
  }
}

/** Read a WAV file's duration from its header. */
function getWavDurationMs(wavPath: string): number {
  try {
    const wav = fs.readFileSync(wavPath);
    if (wav.length < 44) return 0;
    if (wav.toString('ascii', 0, 4) !== 'RIFF') return 0;

    let sampleRate = 16000;
    let dataSize = 0;
    let bitsPerSample = 16;
    let channels = 1;
    let offset = 12;

    while (offset < wav.length - 8) {
      const chunkId = wav.toString('ascii', offset, offset + 4);
      const chunkSize = wav.readUInt32LE(offset + 4);
      if (chunkId === 'fmt ') {
        channels = wav.readUInt16LE(offset + 10);
        sampleRate = wav.readUInt32LE(offset + 12);
        bitsPerSample = wav.readUInt16LE(offset + 22);
      }
      if (chunkId === 'data') {
        dataSize = chunkSize;
      }
      offset += 8 + chunkSize;
      if (offset % 2 !== 0) offset++;
    }

    const bytesPerSample = (bitsPerSample / 8) * channels;
    const totalSamples = bytesPerSample > 0 ? dataSize / bytesPerSample : 0;
    return sampleRate > 0 ? Math.round((totalSamples / sampleRate) * 1000) : 0;
  } catch {
    return 0;
  }
}

// ---------------------------------------------------------------------------
// PromptCache
// ---------------------------------------------------------------------------

export class PromptCache {
  private prompts = new Map<string, ICachedPrompt>();
  private log: (msg: string) => void;
  private espeakAvailable: boolean | null = null;

  constructor(log: (msg: string) => void) {
    this.log = log;
  }

  // -------------------------------------------------------------------------
  // Public API
  // -------------------------------------------------------------------------

  /** Get a cached prompt by ID. */
  get(id: string): ICachedPrompt | null {
    return this.prompts.get(id) ?? null;
  }

  /** Check if a prompt is cached. */
  has(id: string): boolean {
    return this.prompts.has(id);
  }

  /** List all cached prompt IDs. */
  listIds(): string[] {
    return [...this.prompts.keys()];
  }

  /**
   * Generate a TTS prompt WAV and cache its path.
   * Uses espeak-ng (primary) or Kokoro (fallback).
   */
  async generatePrompt(id: string, text: string, voice = 'af_bella'): Promise<ICachedPrompt | null> {
    fs.mkdirSync(TTS_DIR, { recursive: true });
    const wavPath = path.join(TTS_DIR, `prompt-${id}.wav`);

    // Check espeak availability once.
    if (this.espeakAvailable === null) {
      this.espeakAvailable = isEspeakAvailable();
    }

    // Generate WAV if not already on disk.
    if (!fs.existsSync(wavPath)) {
      let generated = false;
      if (this.espeakAvailable) {
        generated = generateViaEspeak(wavPath, text);
      }
      if (!generated) {
        generated = await generateViaKokoro(wavPath, text, voice);
      }
      if (!generated) {
        this.log(`[prompt-cache] failed to generate TTS for "${id}"`);
        return null;
      }
      this.log(`[prompt-cache] generated WAV for "${id}"`);
    }

    return this.registerWav(id, wavPath);
  }

  /**
   * Load a pre-existing WAV file as a prompt.
   */
  async loadWavPrompt(id: string, wavPath: string): Promise<ICachedPrompt | null> {
    if (!fs.existsSync(wavPath)) {
      this.log(`[prompt-cache] WAV not found: ${wavPath}`);
      return null;
    }
    return this.registerWav(id, wavPath);
  }

  /**
   * Generate a beep tone WAV and cache it.
   */
  async generateBeep(
    id: string,
    freqHz = 1000,
    durationMs = 500,
    amplitude = 8000,
  ): Promise<ICachedPrompt | null> {
    fs.mkdirSync(TTS_DIR, { recursive: true });
    const wavPath = path.join(TTS_DIR, `prompt-${id}.wav`);

    if (!fs.existsSync(wavPath)) {
      // Generate 16kHz 16-bit mono sine wave WAV.
      const sampleRate = 16000;
      const totalSamples = Math.floor((sampleRate * durationMs) / 1000);
      const pcm = Buffer.alloc(totalSamples * 2);

      for (let i = 0; i < totalSamples; i++) {
        const t = i / sampleRate;
        const fadeLen = Math.floor(sampleRate * 0.01); // 10ms fade
        let envelope = 1.0;
        if (i < fadeLen) envelope = i / fadeLen;
        else if (i > totalSamples - fadeLen) envelope = (totalSamples - i) / fadeLen;

        const sample = Math.round(Math.sin(2 * Math.PI * freqHz * t) * amplitude * envelope);
        pcm.writeInt16LE(Math.max(-32768, Math.min(32767, sample)), i * 2);
      }

      // Write WAV file.
      const headerSize = 44;
      const dataSize = pcm.length;
      const wav = Buffer.alloc(headerSize + dataSize);

      // RIFF header
      wav.write('RIFF', 0);
      wav.writeUInt32LE(36 + dataSize, 4);
      wav.write('WAVE', 8);

      // fmt chunk
      wav.write('fmt ', 12);
      wav.writeUInt32LE(16, 16);        // chunk size
      wav.writeUInt16LE(1, 20);         // PCM format
      wav.writeUInt16LE(1, 22);         // mono
      wav.writeUInt32LE(sampleRate, 24);
      wav.writeUInt32LE(sampleRate * 2, 28); // byte rate
      wav.writeUInt16LE(2, 32);         // block align
      wav.writeUInt16LE(16, 34);        // bits per sample

      // data chunk
      wav.write('data', 36);
      wav.writeUInt32LE(dataSize, 40);
      pcm.copy(wav, 44);

      fs.writeFileSync(wavPath, wav);
      this.log(`[prompt-cache] beep WAV generated for "${id}"`);
    }

    return this.registerWav(id, wavPath);
  }

  /** Remove a prompt from the cache. */
  remove(id: string): void {
    this.prompts.delete(id);
  }

  /** Clear all cached prompts. */
  clear(): void {
    this.prompts.clear();
  }

  // -------------------------------------------------------------------------
  // Internal
  // -------------------------------------------------------------------------

  private registerWav(id: string, wavPath: string): ICachedPrompt {
    const durationMs = getWavDurationMs(wavPath);
    const prompt: ICachedPrompt = { id, wavPath, durationMs };
    this.prompts.set(id, prompt);
    this.log(`[prompt-cache] cached "${id}": ${wavPath} (${(durationMs / 1000).toFixed(1)}s)`);
    return prompt;
  }
}