import { existsSync, writeFileSync, readFileSync, unlinkSync, statSync, openSync, readSync, closeSync, copyFileSync } 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, "'\\''")
}

function assertFrameFile(path: string, kind: string) {
  if (!existsSync(path) || statSync(path).size < 64) {
    throw new Error(`Could not extract the ${kind}`)
  }
}

export async function extractLastFrame(inputPath: string, outputPath: string) {
  if (!existsSync(inputPath)) {
    throw new Error('Source video is missing')
  }

  const attempts: string[][] = []
  try {
    const duration = await probeDuration(inputPath)
    const seek = Math.max(0, duration - 0.08)
    attempts.push(['-y', '-ss', seek.toFixed(3), '-i', inputPath, '-frames:v', '1', '-an', '-q:v', '1', outputPath])
  } catch {
    // Truncated files often have no duration index; fall through to decode attempts.
  }
  attempts.push(
    ['-y', '-sseof', '-0.04', '-i', inputPath, '-update', '1', '-frames:v', '1', '-an', '-q:v', '1', outputPath],
    ['-y', '-i', inputPath, '-update', '1', '-an', '-q:v', '1', outputPath]
  )

  for (const args of attempts) {
    try {
      await runFfmpeg(args, 60000)
      if (existsSync(outputPath) && statSync(outputPath).size >= 64) return
    } catch {
      // Try the next seek strategy.
    }
  }

  throw new Error('Could not extract the last frame. The video looks incomplete — interrupting Comfy mid-encode usually causes this. Earlier saved parts are still in the library.')
}

export async function extractFirstFrame(inputPath: string, outputPath: string) {
  if (!existsSync(inputPath)) {
    throw new Error('Source video is missing')
  }
  await runFfmpeg([
    '-y',
    '-i', inputPath,
    '-frames:v', '1',
    '-update', '1',
    '-an',
    '-q:v', '4',
    outputPath
  ], 20000)
  assertFrameFile(outputPath, 'first frame')
}

export async function extractFrameAt(inputPath: string, outputPath: string, seconds: number) {
  if (!existsSync(inputPath)) {
    throw new Error('Source video is missing')
  }
  const seek = Math.max(0, seconds)
  await runFfmpeg([
    '-y',
    '-ss', seek.toFixed(3),
    '-i', inputPath,
    '-frames:v', '1',
    '-update', '1',
    '-an',
    '-q:v', '2',
    outputPath
  ], 60000)
  assertFrameFile(outputPath, 'frame')
}

export async function extractFirstFrameFromBuffer(video: Buffer, tmpDir: string) {
  if (!video.length) throw new Error('Could not extract the first frame')
  const input = join(tmpDir, `seg_head_${Date.now()}.mp4`)
  const output = join(tmpDir, `seg_first_${Date.now()}.jpg`)
  writeFileSync(input, video)
  try {
    await extractFirstFrame(input, output)
    return readFileSync(output)
  } finally {
    try { unlinkSync(input) } catch { /* ignore */ }
    try { unlinkSync(output) } catch { /* ignore */ }
  }
}

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
  }
}

const XFADE_DURATION = 0.12

function parseRate(rate: string) {
  const [num, den] = String(rate || '').split('/').map(Number)
  if (den) return num / den
  const value = Number(rate)
  return Number.isFinite(value) && value > 0 ? value : NaN
}

export async function probeDuration(filePath: string) {
  const raw = await runFfprobe([
    '-v', 'error',
    '-select_streams', 'v:0',
    '-show_entries', 'stream=duration,nb_frames,r_frame_rate,avg_frame_rate',
    '-show_entries', 'format=duration',
    '-of', 'json',
    filePath
  ])
  const parsed = JSON.parse(raw) as {
    format?: { duration?: string }
    streams?: Array<{ duration?: string; nb_frames?: string; r_frame_rate?: string; avg_frame_rate?: string }>
  }
  const stream = parsed.streams?.[0] || {}
  const fps = parseRate(stream.avg_frame_rate || '') || parseRate(stream.r_frame_rate || '')
  const frames = Number(stream.nb_frames)
  const fromFrames = Number.isFinite(frames) && frames > 0 && Number.isFinite(fps) ? frames / fps : NaN
  const candidates = [Number(stream.duration), Number(parsed.format?.duration), fromFrames]
    .filter(value => Number.isFinite(value) && value > 0)
  if (!candidates.length) {
    throw new Error('Could not read video duration')
  }
  return Math.min(...candidates)
}

async function probeSize(filePath: string) {
  const out = await runFfprobe([
    '-v', 'error',
    '-select_streams', 'v:0',
    '-show_entries', 'stream=width,height',
    '-of', 'csv=p=0',
    filePath
  ])
  const [width, height] = out.split(',').map(Number)
  return {
    width: Number.isFinite(width) && width > 0 ? width : 1344,
    height: Number.isFinite(height) && height > 0 ? height : 768
  }
}

function mp4MoovIsAtStart(filePath: string) {
  const fd = openSync(filePath, 'r')
  try {
    let offset = 0
    const header = Buffer.alloc(16)
    for (let i = 0; i < 12; i++) {
      if (readSync(fd, header, 0, 8, offset) < 8) return false
      let size = header.readUInt32BE(0)
      const type = header.toString('ascii', 4, 8)
      if (size === 1) {
        if (readSync(fd, header, 8, 8, offset + 8) < 8) return false
        size = Number(header.readBigUInt64BE(8))
      }
      if (!size || size < 8) return false
      if (type === 'moov') return true
      if (type === 'mdat') return false
      offset += size
    }
    return false
  } finally {
    closeSync(fd)
  }
}

export async function remuxFaststart(inputPath: string) {
  if (!existsSync(inputPath)) return
  try {
    if (mp4MoovIsAtStart(inputPath)) return
  } catch {
    // Fall through and try a remux anyway.
  }
  const tmp = `${inputPath}.faststart.tmp.mp4`
  try {
    await runFfmpeg([
      '-y',
      '-i', inputPath,
      '-c', 'copy',
      '-map', '0',
      '-movflags', '+faststart',
      tmp
    ], 120000)
    if (!existsSync(tmp) || statSync(tmp).size < 32) {
      try { unlinkSync(tmp) } catch { /* ignore */ }
      return
    }
    copyFileSync(tmp, inputPath)
    try { unlinkSync(tmp) } catch { /* ignore */ }
  } catch {
    try { unlinkSync(tmp) } catch { /* ignore */ }
  }
}

function encodeArgs(outputPath: string, withAudio: boolean) {
  const args = [
    '-c:v', 'libx264',
    '-preset', 'fast',
    '-crf', '17',
    '-pix_fmt', 'yuv420p',
    '-movflags', '+faststart'
  ]
  if (withAudio) args.push('-c:a', 'aac')
  args.push(outputPath)
  return args
}

async function assertStitchLength(part1Path: string, part2Path: string, outputPath: string, fade = 0) {
  const [duration1, duration2, output] = await Promise.all([
    probeDuration(part1Path),
    probeDuration(part2Path),
    probeDuration(outputPath)
  ])
  const expected = duration1 + duration2 - fade
  if (output < expected * 0.75 || output < duration1 + 0.75) {
    throw new Error(`Stitched video was ${output.toFixed(2)}s, expected about ${expected.toFixed(2)}s`)
  }
}

async function concatReencode(part1Path: string, part2Path: string, outputPath: string) {
  const audio1 = await probeHasAudio(part1Path)
  const audio2 = await probeHasAudio(part2Path)
  if (audio1 && audio2) {
    await runFfmpeg([
      '-y',
      '-i', part1Path,
      '-i', part2Path,
      '-filter_complex', '[0:v]setpts=PTS-STARTPTS[v0];[1:v]select=\'gte(n,1)\',setpts=PTS-STARTPTS[v1];[0:a]asetpts=PTS-STARTPTS[a0];[1:a]asetpts=PTS-STARTPTS[a1];[v0][a0][v1][a1]concat=n=2:v=1:a=1[v][a]',
      '-map', '[v]',
      '-map', '[a]',
      ...encodeArgs(outputPath, true)
    ], 300000)
  } else {
    await runFfmpeg([
      '-y',
      '-i', part1Path,
      '-i', part2Path,
      '-filter_complex', '[0:v]setpts=PTS-STARTPTS[v0];[1:v]select=\'gte(n,1)\',setpts=PTS-STARTPTS[v1];[v0][v1]concat=n=2:v=1:a=0[v]',
      '-map', '[v]',
      ...encodeArgs(outputPath, false)
    ], 300000)
  }
  if (!existsSync(outputPath)) {
    throw new Error('FFmpeg did not write the stitched video')
  }
  await assertStitchLength(part1Path, part2Path, outputPath)
}

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', '-movflags', '+faststart', outputPath], 180000)
    await assertStitchLength(part1Path, part2Path, outputPath)
  } catch {
    await concatReencode(part1Path, part2Path, outputPath)
  }
}

export function buildSourceAssembly(durations: number[], width: number, height: number, fps: number, audio: boolean, blend: boolean) {
  const filters: string[] = []
  durations.forEach((_, index) => {
    filters.push(`[${index}:v]${index ? "select='gte(n,1)'," : ''}setpts=PTS-STARTPTS,scale=${width}:${height}:flags=lanczos,fps=${fps},format=yuv420p,settb=AVTB[v${index}]`)
    if (audio) filters.push(`[${index}:a]aresample=48000,asetpts=PTS-STARTPTS[a${index}]`)
  })
  let duration = durations[0]
  let video = 'v0', sound = 'a0'
  for (let index = 1; index < durations.length; index++) {
    const fade = blend ? Math.min(XFADE_DURATION, Math.max(0.04, duration - 0.08), Math.max(0.04, durations[index] - 0.08)) : 0
    const nextVideo = `joinv${index}`, nextAudio = `joina${index}`
    const offset = Math.max(0, duration - fade)
    filters.push(`[${video}][v${index}]` + (blend
      ? `xfade=transition=fade:duration=${fade.toFixed(6)}:offset=${offset.toFixed(6)}`
      : 'concat=n=2:v=1:a=0') + `[${nextVideo}]`)
    if (audio) filters.push(`[${sound}][a${index}]` + (blend
      ? `acrossfade=d=${fade.toFixed(6)}:c1=tri:c2=tri`
      : 'concat=n=2:v=0:a=1') + `[${nextAudio}]`)
    duration += durations[index] - 1 / fps - fade
    video = nextVideo; sound = nextAudio
  }
  return { filter: filters.join(';'), video, sound, duration }
}

async function assembleOriginalSources(paths: string[], outputPath: string, blend: boolean) {
  const [durations, size, audioFlags, frameRate] = await Promise.all([
    Promise.all(paths.map(probeDuration)), probeSize(paths[0]),
    Promise.all(paths.map(probeHasAudio)),
    runFfprobe(['-v', 'error', '-select_streams', 'v:0', '-show_entries', 'stream=r_frame_rate', '-of', 'default=noprint_wrappers=1:nokey=1', paths[0]])
  ])
  const [numerator, denominator = 1] = frameRate.split('/').map(Number)
  const fps = numerator / denominator
  if (!Number.isFinite(fps) || fps <= 0) throw new Error('Cannot read the source video frame rate')
  const audio = audioFlags.every(Boolean)
  const graph = buildSourceAssembly(durations, size.width, size.height, fps, audio, blend)
  await runFfmpeg(['-y', ...paths.flatMap(path => ['-i', path]), '-filter_complex_threads', '1',
    '-filter_complex', graph.filter, '-map', `[${graph.video}]`, ...(audio ? ['-map', `[${graph.sound}]`] : []),
    ...encodeArgs(outputPath, audio)], 600000)
  const actual = await probeDuration(outputPath)
  if (Math.abs(actual - graph.duration) > Math.max(0.5, graph.duration * 0.02)) throw new Error('Assembled video length does not match the original segments')
}

export async function stitchExtension(params: { part1Path: string; part2: Buffer; tmpDir: string; sourcePaths?: string[] }) {
  const part2Path = join(params.tmpDir, `part2_${Date.now()}.mp4`)
  const finalPath = join(params.tmpDir, 'final_stitched_video.mp4')
  writeFileSync(part2Path, params.part2)
  if (!existsSync(part2Path) || !params.part2.length) {
    throw new Error('Extension segment was missing before stitch')
  }
  const sources = [...(params.sourcePaths?.length ? params.sourcePaths : [params.part1Path]), part2Path]
  try {
    await assembleOriginalSources(sources, finalPath, true)
  } catch (error) {
    console.error('[stitch] source crossfade failed; joining the same original sources:', (error as Error).message)
    await assembleOriginalSources(sources, finalPath, false)
  }
  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
}