import { NextRequest, NextResponse } from "next/server"
import { execFileSync } from "child_process"
import { existsSync, mkdirSync } from "fs"
import { createHash } from "crypto"
import { readFile, mkdir } from "fs/promises"
import { join } from "path"

const CACHE_DIR = join(process.cwd(), "public", "tts-cache")

async function ensureCacheDir() {
  if (!existsSync(CACHE_DIR)) {
    await mkdir(CACHE_DIR, { recursive: true })
  }
}

function getCachePath(text: string): string {
  const hash = createHash("md5").update(text).digest("hex")
  return join(CACHE_DIR, `${hash}.wav`)
}

export async function GET(request: NextRequest) {
  const text = request.nextUrl.searchParams.get("text")
  if (!text || text.length > 200) {
    return NextResponse.json({ error: "text param required (max 200 chars)" }, { status: 400 })
  }

  // Sanitize: only allow alphanumeric, spaces, and common punctuation
  if (!/^[\w\sáéíóúñüÁÉÍÓÚÑÜ.,;:!¿?¡()\-]+$/.test(text)) {
    return NextResponse.json({ error: "Invalid text characters" }, { status: 400 })
  }

  await ensureCacheDir()
  const cachePath = getCachePath(text)

  if (!existsSync(cachePath)) {
    try {
      execFileSync("espeak-ng", [
        "-v", "es-mx",
        "-s", "140",
        "-p", "60",
        "-w", cachePath,
        text,
      ], { timeout: 10000 })
    } catch {
      return NextResponse.json({ error: "TTS generation failed" }, { status: 500 })
    }
  }

  const audioBuffer = await readFile(cachePath)
  return new NextResponse(audioBuffer, {
    headers: {
      "Content-Type": "audio/wav",
      "Content-Length": audioBuffer.length.toString(),
      "Cache-Control": "public, max-age=31536000, immutable",
    },
  })
}