/**
 * Ti-Pote — Play a PCM/WAV file on the ESP32 speaker over USB.
 *
 * Usage:
 *   pnpm esp:play <file.wav|file.raw>
 *
 * Accepts either:
 *   - raw S16 LE mono 16 kHz PCM
 *   - WAV file with a 44-byte RIFF header (header is stripped)
 *
 * Default port: auto-detected, override with ESP_PORT=/dev/cu.usbserial-XXX
 */

import { execFileSync } from 'node:child_process';
import { existsSync, mkdtempSync, readFileSync, readdirSync, rmSync } from 'node:fs';
import { tmpdir } from 'node:os';
import { join, extname } from 'node:path';
import { SerialPort } from 'serialport';

const SAMPLE_RATE = 16000;

function findDefaultPort(): string {
  const envPort = process.env.ESP_PORT;
  if (envPort) return envPort;
  const candidates = readdirSync('/dev').filter(
    (f) =>
      f.startsWith('cu.usbserial') ||
      f.startsWith('cu.SLAB_') ||
      f.startsWith('cu.wchusbserial'),
  );
  if (candidates.length === 0) {
    throw new Error(
      'No ESP32 serial port detected. Plug the board in, or set ESP_PORT=/dev/cu.usbserial-XXX',
    );
  }
  return `/dev/${candidates[0]}`;
}

function stripWav(buf: Buffer): Buffer {
  if (
    buf.length > 44 &&
    buf.toString('ascii', 0, 4) === 'RIFF' &&
    buf.toString('ascii', 8, 12) === 'WAVE'
  ) {
    return buf.subarray(44);
  }
  return buf;
}

/**
 * Convert any audio file macOS can decode (m4a, mp3, ogg, aiff, …) to
 * S16 LE mono 16 kHz WAV using the built-in `afconvert` tool. Returns
 * the path to a new .wav file in a temp dir which the caller is
 * responsible for cleaning up.
 */
function convertToEsp32Wav(inputPath: string): { wavPath: string; cleanup: () => void } {
  const dir = mkdtempSync(join(tmpdir(), 'tipote-'));
  const wavPath = join(dir, 'converted.wav');
  console.log(`→ converting ${inputPath} → 16 kHz mono S16LE WAV`);
  try {
    execFileSync(
      'afconvert',
      [
        '-f', 'WAVE',
        '-d', 'LEI16@16000',
        '-c', '1',
        inputPath,
        wavPath,
      ],
      { stdio: 'inherit' },
    );
  } catch (err) {
    rmSync(dir, { recursive: true, force: true });
    throw new Error(`afconvert failed: ${(err as Error).message}`);
  }
  return {
    wavPath,
    cleanup: () => rmSync(dir, { recursive: true, force: true }),
  };
}

async function main(): Promise<void> {
  const inPath = process.argv[2];
  if (!inPath) {
    console.error('Usage: esp-play.ts <file>  (wav, raw, m4a, mp3, …)');
    process.exit(1);
  }
  if (!existsSync(inPath)) {
    throw new Error(`file not found: ${inPath}`);
  }

  // Convert anything that isn't already a .wav or raw PCM blob. This
  // covers m4a / mp3 / ogg / aiff / opus / flac via the built-in
  // macOS `afconvert` tool.
  const ext = extname(inPath).toLowerCase();
  const needsConversion = ext !== '.wav' && ext !== '.raw' && ext !== '.pcm';

  let cleanup: () => void = () => {};
  let loadPath = inPath;
  if (needsConversion) {
    const converted = convertToEsp32Wav(inPath);
    loadPath = converted.wavPath;
    cleanup = converted.cleanup;
  }

  const raw = readFileSync(loadPath);
  const pcm = stripWav(raw);
  const samples = pcm.length / 2;
  const durationMs = (samples / SAMPLE_RATE) * 1000;
  console.log(
    `→ loaded ${loadPath}: ${pcm.length} bytes (${samples} samples, ${durationMs.toFixed(0)} ms)`,
  );

  if (pcm.length === 0) {
    cleanup();
    throw new Error('empty PCM buffer');
  }
  if (pcm.length % 2 !== 0) {
    cleanup();
    throw new Error(
      'PCM size must be a multiple of 2 (S16 mono). The source file is probably not 16-bit or not mono. If you passed a raw file, convert it first.',
    );
  }

  const path = findDefaultPort();
  console.log(`→ opening ${path} @ 921600 baud`);

  const port = new SerialPort({ path, baudRate: 921600, autoOpen: false });
  await new Promise<void>((resolve, reject) => {
    port.open((err) => (err ? reject(err) : resolve()));
  });

  const pongWaiters: Array<() => void> = [];

  const finished = new Promise<void>((resolve, reject) => {
    const timeout = setTimeout(
      () => reject(new Error(`timeout waiting for OK after ${durationMs + 8000} ms`)),
      durationMs + 8000,
    );
    let lineBuf = '';
    port.on('data', (data: Buffer) => {
      lineBuf += data.toString('utf8');
      let idx: number;
      while ((idx = lineBuf.indexOf('\n')) >= 0) {
        const line = lineBuf.slice(0, idx).replace(/\r$/, '').trim();
        lineBuf = lineBuf.slice(idx + 1);
        if (!line) continue;
        if (line === 'OK') {
          clearTimeout(timeout);
          resolve();
          return;
        }
        if (line === 'PONG') {
          while (pongWaiters.length) pongWaiters.shift()!();
          continue;
        }
        if (line === 'READY') {
          // Firmware just booted (USB DTR reset). Ignore — the
          // PING/PONG handshake is our real readiness signal.
          continue;
        }
        if (line.startsWith('ERR ')) {
          clearTimeout(timeout);
          reject(new Error(`firmware error: ${line.slice(4)}`));
          return;
        }
        if (line.startsWith('LOG ')) console.log(`[esp] ${line.slice(4)}`);
        else console.log(`[esp] ${line}`);
      }
    });
    port.on('error', reject);
  });

  // PING/PONG handshake — validates the link in both directions
  // regardless of whether the firmware was recently rebooted or not.
  console.log('→ PING');
  port.write('PING\n');
  await new Promise<void>((resolve, reject) => {
    const timer = setTimeout(
      () =>
        reject(
          new Error(
            'no PONG from firmware — check TX/RX wiring (cross!), baud rate, and that the ESP32 is powered',
          ),
        ),
      3000,
    );
    pongWaiters.push(() => {
      clearTimeout(timer);
      resolve();
    });
  });
  console.log('→ PONG received');

  console.log(`→ PLAY ${pcm.length} bytes`);
  port.write(`PLAY ${pcm.length}\n`);

  // Stream the payload paced EXACTLY at the I2S consumption rate so
  // the ESP32 RX buffer stays roughly constant in size regardless of
  // file length. I2S consumes 16 kHz × 2 bytes/sample = 32 KB/s of
  // S16 mono. A 1024-byte burst is 32 ms of audio → sleeping 32 ms
  // between bursts matches playback exactly.
  //
  // We still pad lightly above 32 KB/s (30 ms instead of 32) so the
  // DMA never runs dry. The excess fills the ~16 KB RX buffer on the
  // firmware slowly; even for a 10 s file we stay well under it.
  const CHUNK = 1024;
  const PAUSE_MS = 30;
  for (let off = 0; off < pcm.length; off += CHUNK) {
    const slice = pcm.subarray(off, off + CHUNK);
    await new Promise<void>((resolve, reject) => {
      port.write(slice, (err) => (err ? reject(err) : resolve()));
    });
    await new Promise<void>((resolve) => port.drain(() => resolve()));
    if (off + CHUNK < pcm.length) {
      await new Promise((r) => setTimeout(r, PAUSE_MS));
    }
  }

  await finished;
  await new Promise<void>((resolve) => port.close(() => resolve()));
  cleanup();
  console.log('✅ playback done');
}

main().catch((err) => {
  console.error(err);
  process.exit(1);
});