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')
  }

  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)) 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)
  if (!existsSync(outputPath)) {
    throw new Error('Could not extract the first 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
  }
}

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 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 xfadeStitch(part1Path: string, part2Path: string, outputPath: string) {
  const [duration1, duration2, size, audio1, audio2] = await Promise.all([
    probeDuration(part1Path),
    probeDuration(part2Path),
    probeSize(part1Path),
    probeHasAudio(part1Path),
    probeHasAudio(part2Path)
  ])
  const fade = Math.min(XFADE_DURATION, Math.max(0.04, duration1 - 0.08), Math.max(0.04, duration2 - 0.08))
  const offset = Math.max(0, Number((duration1 - fade - 0.04).toFixed(3)))
  const prepare1 = `scale=${size.width}:${size.height}:flags=bicubic,format=yuv420p,setpts=PTS-STARTPTS`
  const prepare2 = `select='gte(n,1)',setpts=PTS-STARTPTS,scale=${size.width}:${size.height}:flags=bicubic,format=yuv420p`
  const videoFilter = `[0:v]${prepare1}[v0];[1:v]${prepare2}[v1];[v0][v1]xfade=transition=fade:duration=${fade.toFixed(3)}:offset=${offset},setpts=PTS-STARTPTS[v]`
  const runVideo = async (withAudio: boolean) => {
    const args = [
      '-y',
      '-i', part1Path,
      '-i', part2Path,
      '-filter_complex', withAudio
        ? `${videoFilter};[0:a]asetpts=PTS-STARTPTS[a0];[1:a]asetpts=PTS-STARTPTS[a1];[a0][a1]acrossfade=d=${fade.toFixed(3)}:c1=tri:c2=tri[a]`
        : videoFilter,
      '-map', '[v]',
      ...(withAudio ? ['-map', '[a]'] : []),
      ...encodeArgs(outputPath, withAudio)
    ]
    await runFfmpeg(args, 300000)
  }
  if (audio1 && audio2) {
    try {
      await runVideo(true)
    } catch {
      await runVideo(false)
    }
  } else {
    await runVideo(false)
  }
  if (!existsSync(outputPath)) {
    throw new Error('FFmpeg did not write the blended video')
  }
  await assertStitchLength(part1Path, part2Path, outputPath, fade)
}

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', outputPath], 180000)
    await assertStitchLength(part1Path, part2Path, outputPath)
  } catch {
    await concatReencode(part1Path, part2Path, outputPath)
  }
}

export async function stitchExtension(params: { part1Path: string; part2: Buffer; tmpDir: 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')
  }
  try {
    await xfadeStitch(params.part1Path, part2Path, finalPath)
  } catch (error) {
    console.error('[stitch] xfade failed, concatenating:', (error as Error).message)
    await concatReencode(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
}