// Author: Dr Hamid MADANI <drmdh@msn.com>
//
// POST /api/record/audio — append an audio chunk to the per-session file.
//
// Headers expected :
//   X-Session-Id   : opaque id grouping all chunks of one record
//   X-Chunk-Idx    : monotonic chunk index (informational only)
//   Content-Type   : MIME of the chunk (e.g. audio/webm;codecs=opus)
//
// Storage : ./data/records/<sessionId>.webm  (relative to the studio cwd).

import { NextRequest, NextResponse } from 'next/server'
import { promises as fs } from 'fs'
import path from 'path'

export const runtime = 'nodejs'      // Node fs append needs Node runtime
export const dynamic = 'force-dynamic'

const ROOT = path.join(process.cwd(), 'data', 'records')

const SAFE = /^[a-zA-Z0-9_-]{1,128}$/

export async function POST(req: NextRequest) {
  const sessionId = req.headers.get('x-session-id')
  if (!sessionId || !SAFE.test(sessionId)) {
    return NextResponse.json({ error: 'invalid X-Session-Id' }, { status: 400 })
  }
  const mime = req.headers.get('content-type') ?? 'audio/webm'
  const ext = mime.includes('ogg') ? 'ogg' : 'webm'

  await fs.mkdir(ROOT, { recursive: true })
  const filePath = path.join(ROOT, `${sessionId}.${ext}`)

  const body = await req.arrayBuffer()
  if (body.byteLength === 0) {
    return NextResponse.json({ ok: true, bytes: 0 })
  }
  await fs.appendFile(filePath, Buffer.from(body))
  return NextResponse.json({ ok: true, bytes: body.byteLength })
}