import { execFile, execFileSync } from "node:child_process";
import fs from "node:fs";
import path from "node:path";
import { promisify } from "node:util";

const execFileAsync = promisify(execFile);

let sayChecked = false;
let sayAvailable = false;

function hasSay() {
  if (!sayChecked) {
    sayChecked = true;
    try {
      execFileSync("say", ["-v", "?"], { stdio: "ignore" });
      sayAvailable = true;
    } catch {
      console.warn("`say` not found — skipping TTS narration (subtitles still work).");
    }
  }
  return sayAvailable;
}

const cache = new Map<string, Promise<{ path: string; durationMs: number } | null>>();

/** Synthesizes Spanish narration for a caption via macOS `say`. Returns null (never throws) if unavailable. */
export function synthesize(
  text: string,
  outDir: string,
  index: number,
  voice = "Paulina",
): Promise<{ path: string; durationMs: number } | null> {
  const key = `${voice}:${text}`;
  const cached = cache.get(key);
  if (cached) return cached;

  const promise = (async () => {
    if (!hasSay()) return null;
    fs.mkdirSync(outDir, { recursive: true });
    const file = path.join(outDir, `narration-${String(index).padStart(2, "0")}.aiff`);
    try {
      await execFileAsync("say", ["-v", voice, "-o", file, text]);
      const { stdout } = await execFileAsync("ffprobe", [
        "-v", "error",
        "-show_entries", "format=duration",
        "-of", "csv=p=0",
        file,
      ]);
      const durationMs = Math.round(parseFloat(stdout.trim()) * 1000);
      return { path: file, durationMs };
    } catch (err) {
      console.warn(`Narration synthesis failed for "${text.slice(0, 40)}…": ${err}`);
      fs.rmSync(file, { force: true });
      return null;
    }
  })();
  cache.set(key, promise);
  return promise;
}