import { existsSync, writeFileSync, readFileSync, unlinkSync } from 'node:fs'
import { dirname, join } from 'node:path'
import { spawn } from 'node:child_process'

function collectError(stderr: string, fallback: string) {
  const text = stderr.replace(/\r/g, '').trim()
  const lines = text.split('\n').map(line => line.trim()).filter(Boolean)
  return lines.slice(-6).join(' ') || fallback
}

export function runFfmpeg(args: string[], timeoutMs = 120000) {
  return new Promise<void>((resolve, reject) => {
    const proc = spawn('ffmpeg', args, { stdio: ['ignore', 'ignore', 'pipe'] })
    let stderr = ''
    proc.stderr?.on('data', (chunk: Buffer | string) => { stderr += String(chunk) })
    const timer = setTimeout(() => {
      try { proc.kill('SIGKILL') } catch { /* ignore */ }
      reject(new Error(`FFmpeg timed out after ${Math.round(timeoutMs / 1000)}s`))
    }, timeoutMs)
    proc.on('error', (error) => {
      clearTimeout(timer)
      const message = (error as NodeJS.ErrnoException).code === 'ENOENT'
        ? 'FFmpeg is not installed on this server'
        : error.message
      reject(new Error(message))
    })
    proc.on('close', (code) => {
      clearTimeout(timer)
      if (code === 0) resolve()
      else reject(new Error(collectError(stderr, `FFmpeg exited with code ${code}`)))
    })
  })
}

function runFfprobe(args: string[], timeoutMs = 15000) {
  return new Promise<string>((resolve, reject) => {
    const proc = spawn('ffprobe', args, { stdio: ['ignore', 'pipe', 'pipe'] })
    let out = ''
    let err = ''
    proc.stdout?.on('data', (chunk: Buffer | string) => { out += String(chunk) })
    proc.stderr?.on('data', (chunk: Buffer | string) => { err += String(chunk) })
    const timer = setTimeout(() => {
      try { proc.kill('SIGKILL') } catch { /* ignore */ }
      reject(new Error('ffprobe timed out'))
    }, timeoutMs)
    proc.on('error', (error) => {
      clearTimeout(timer)
      reject(error)
    })
    proc.on('close', (code) => {
      clearTimeout(timer)
      if (code === 0) resolve(out.trim())
      else reject(new Error(collectError(err, `ffprobe exited with code ${code}`)))
    })
  })
}

function concatPath(filePath: string) {
  return filePath.replace(/\\/g, '/').replace(/'/g, "'\\''")
}

export async function extractLastFrame(inputPath: string, outputPath: string) {
  if (!existsSync(inputPath)) {
    throw new Error('Source video is missing')
  }
  await runFfmpeg([
    '-y',
    '-sseof', '-1',
    '-i', inputPath,
    '-update', '1',
    '-frames:v', '1',
    '-q:v', '1',
    outputPath
  ], 30000)
  if (!existsSync(outputPath)) {
    throw new Error('FFmpeg did not write the last frame')
  }
}

export async function probeHasAudio(filePath: string) {
  try {
    const out = await runFfprobe([
      '-v', 'error',
      '-select_streams', 'a:0',
      '-show_entries', 'stream=codec_type',
      '-of', 'csv=p=0',
      filePath
    ])
    return out.includes('audio')
  } catch {
    return false
  }
}

export async function concatMp4(part1Path: string, part2Path: string, outputPath: string) {
  const listPath = join(dirname(outputPath), 'concat_list.txt')
  writeFileSync(listPath, `file '${concatPath(part1Path)}'\nfile '${concatPath(part2Path)}'\n`)
  try {
    await runFfmpeg(['-y', '-f', 'concat', '-safe', '0', '-i', listPath, '-c', 'copy', outputPath], 180000)
  } catch (copyError) {
    const audio1 = await probeHasAudio(part1Path)
    const audio2 = await probeHasAudio(part2Path)
    try {
      if (audio1 && audio2) {
        await runFfmpeg([
          '-y',
          '-i', part1Path,
          '-i', part2Path,
          '-filter_complex', '[0:v][0:a][1:v][1:a]concat=n=2:v=1:a=1[v][a]',
          '-map', '[v]',
          '-map', '[a]',
          '-c:v', 'libx264',
          '-preset', 'fast',
          '-crf', '18',
          '-pix_fmt', 'yuv420p',
          '-c:a', 'aac',
          '-movflags', '+faststart',
          outputPath
        ], 300000)
      } else {
        await runFfmpeg([
          '-y',
          '-i', part1Path,
          '-i', part2Path,
          '-filter_complex', '[0:v][1:v]concat=n=2:v=1:a=0[v]',
          '-map', '[v]',
          '-c:v', 'libx264',
          '-preset', 'fast',
          '-crf', '18',
          '-pix_fmt', 'yuv420p',
          '-movflags', '+faststart',
          outputPath
        ], 300000)
      }
    } catch (encodeError) {
      const copyMessage = copyError instanceof Error ? copyError.message : String(copyError)
      const encodeMessage = encodeError instanceof Error ? encodeError.message : String(encodeError)
      throw new Error(`FFmpeg concat failed (${copyMessage}). Re-encode also failed (${encodeMessage}).`)
    }
  }
  if (!existsSync(outputPath)) {
    throw new Error('FFmpeg did not write the stitched video')
  }
}

export async function stitchExtension(params: { part1Path: string; part2: Buffer; tmpDir: string }) {
  const part2Path = join(params.tmpDir, 'part2.mp4')
  const finalPath = join(params.tmpDir, 'final_stitched_video.mp4')
  writeFileSync(part2Path, params.part2)
  await concatMp4(params.part1Path, part2Path, finalPath)
  const stitched = readFileSync(finalPath)
  for (const extra of [part2Path, join(params.tmpDir, 'concat_list.txt'), join(params.tmpDir, 'last_frame.png')]) {
    try { unlinkSync(extra) } catch { /* ignore */ }
  }
  return stitched
}