import { spawn } from 'node:child_process'
import { promises as fs, createWriteStream, constants as fsConst } from 'node:fs'
import path from 'node:path'
import https from 'node:https'
import http from 'node:http'
import { getMcCustomDir } from '../shared/paths.js'
import { t } from './i18n.js'

export interface YtPlaylistEntry {
  id: string
  title: string
  channel: string
  durationSec: number
  url: string
}

export class YtDlpUnavailableError extends Error {
  constructor(message?: string) {
    super(message || t('youtube.ytdlpUnavailable'))
  }
}

/** 현재 OS/아키텍처에서 GitHub Releases 가 제공하는 yt-dlp 파일 이름. */
function getYtDlpAssetName(): string {
  if (process.platform === 'win32') return 'yt-dlp.exe'
  if (process.platform === 'darwin') return 'yt-dlp_macos'
  if (process.platform === 'linux') {
    if (process.arch === 'arm64') return 'yt-dlp_linux_aarch64'
    if (process.arch === 'arm') return 'yt-dlp_linux_armv7l'
    return 'yt-dlp_linux'
  }
  return 'yt-dlp' // 그 외 OS: 순수 파이썬 zipapp. python3 가 PATH 에 있어야 동작
}

/** 로컬 설치 경로: %appdata%/.mc_custom/<asset> */
export function getYtDlpInstallPath(): string {
  return path.join(getMcCustomDir(), getYtDlpAssetName())
}

/** 한 번에 한 다운로드만 진행하도록 락 (서버 동시 요청 보호). */
let installPromise: Promise<string> | null = null

/**
 * %appdata%/.mc_custom/ 에 yt-dlp 가 준비됐는지 확인하고, 없으면 GitHub Releases 에서
 * 현재 OS/아키텍처용 바이너리를 자동으로 받아 설치한다. 성공 시 실행 경로 반환.
 */
export async function ensureYtDlp(): Promise<string> {
  const target = getYtDlpInstallPath()
  // 이미 설치돼 있고 실행 가능하면 그대로 사용
  if (await canExecute(target)) return target
  if (installPromise) return installPromise
  installPromise = (async () => {
    try {
      const dir = getMcCustomDir()
      await fs.mkdir(dir, { recursive: true })
      const asset = getYtDlpAssetName()
      const url = `https://github.com/yt-dlp/yt-dlp/releases/latest/download/${asset}`
      await downloadToFile(url, target)
      // POSIX 계열은 실행 권한 부여
      if (process.platform !== 'win32') {
        await fs.chmod(target, 0o755)
      }
      // 검증
      const okVersion = await probeVersion(target)
      if (!okVersion) {
        throw new YtDlpUnavailableError(t('youtube.ytdlpVerifyFailed'))
      }
      return target
    } catch (err) {
      // 실패 흔적(부분 다운로드) 삭제
      try { await fs.unlink(target) } catch { /* noop */ }
      throw err instanceof YtDlpUnavailableError
        ? err
        : new YtDlpUnavailableError(
            t('youtube.ytdlpInstallFailed', { message: err instanceof Error ? err.message : String(err) })
          )
    } finally {
      installPromise = null
    }
  })()
  return installPromise
}

async function canExecute(filePath: string): Promise<boolean> {
  try {
    await fs.access(filePath, fsConst.F_OK)
  } catch {
    return false
  }
  // POSIX 면 X 비트도 확인
  if (process.platform !== 'win32') {
    try {
      await fs.access(filePath, fsConst.X_OK)
    } catch {
      return false
    }
  }
  // 실제로 --version 으로 한 번 더 확인
  return probeVersion(filePath)
}

function probeVersion(bin: string): Promise<boolean> {
  return new Promise((resolve) => {
    const child = spawn(bin, ['--version'], { stdio: ['ignore', 'pipe', 'pipe'] })
    let ok = false
    child.stdout.on('data', () => { ok = true })
    child.on('error', () => resolve(false))
    child.on('close', (code) => resolve(ok && code === 0))
  })
}

/** GitHub Releases 의 latest URL 은 302 리다이렉트를 사용하므로 따라가며 받음. */
function downloadToFile(url: string, dest: string, redirects = 0): Promise<void> {
  return new Promise((resolve, reject) => {
    if (redirects > 8) {
      reject(new Error(t('youtube.tooManyRedirects')))
      return
    }
    const lib = url.startsWith('https://') ? https : http
    const req = lib.get(url, {
      headers: { 'user-agent': 'mc-music-quiz-launcher' }
    }, (res) => {
      const code = res.statusCode || 0
      if (code >= 300 && code < 400 && res.headers.location) {
        res.resume()
        downloadToFile(res.headers.location, dest, redirects + 1).then(resolve, reject)
        return
      }
      if (code !== 200) {
        res.resume()
        reject(new Error(`HTTP ${code} (${url})`))
        return
      }
      const out = createWriteStream(dest)
      res.pipe(out)
      out.on('finish', () => out.close((err) => err ? reject(err) : resolve()))
      out.on('error', reject)
      res.on('error', reject)
    })
    req.on('error', reject)
  })
}

/**
 * 단일 영상 URL 의 메타데이터를 가져온다.
 * `--no-playlist` 로 플레이리스트 URL 이 들어와도 단일 영상 정보만 뽑음.
 */
export async function fetchVideoMeta(url: string): Promise<YtPlaylistEntry | null> {
  const bin = await ensureYtDlp()
  return new Promise((resolve, reject) => {
    const child = spawn(bin, [
      '--dump-json',
      '--no-warnings',
      '--no-playlist',
      '--skip-download',
      url
    ], { stdio: ['ignore', 'pipe', 'pipe'] })
    let stdout = ''
    let stderr = ''
    child.stdout.on('data', (chunk: Buffer) => (stdout += chunk.toString('utf8')))
    child.stderr.on('data', (chunk: Buffer) => (stderr += chunk.toString('utf8')))
    child.on('error', (err) => reject(err))
    child.on('close', (code) => {
      if (code !== 0) {
        reject(new Error(t('youtube.ytdlpVideoFailed', { code: String(code), detail: stderr.trim() || stdout.trim() })))
        return
      }
      const line = stdout.trim().split('\n').find((l) => l.trim().length > 0)
      if (!line) { resolve(null); return }
      try {
        const obj = JSON.parse(line) as Record<string, unknown>
        const id = typeof obj.id === 'string' ? obj.id : ''
        if (!id) { resolve(null); return }
        resolve({
          id,
          title: typeof obj.title === 'string' ? obj.title : '',
          channel: typeof obj.channel === 'string'
            ? obj.channel
            : (typeof obj.uploader === 'string' ? obj.uploader : ''),
          durationSec: typeof obj.duration === 'number' ? Math.floor(obj.duration) : 0,
          url: typeof obj.webpage_url === 'string' && obj.webpage_url.length > 0
            ? obj.webpage_url
            : `https://www.youtube.com/watch?v=${id}`
        })
      } catch (err) {
        reject(err)
      }
    })
  })
}

/**
 * 플레이리스트 URL 을 펼쳐 각 영상의 메타데이터를 가져온다.
 * `--flat-playlist --dump-json` 출력은 한 줄당 한 JSON.
 */
export async function fetchPlaylistEntries(url: string): Promise<YtPlaylistEntry[]> {
  const bin = await ensureYtDlp()
  return new Promise((resolve, reject) => {
    const child = spawn(bin, [
      '--flat-playlist',
      '--dump-json',
      '--no-warnings',
      url
    ], { stdio: ['ignore', 'pipe', 'pipe'] })
    let stdout = ''
    let stderr = ''
    child.stdout.on('data', (chunk: Buffer) => (stdout += chunk.toString('utf8')))
    child.stderr.on('data', (chunk: Buffer) => (stderr += chunk.toString('utf8')))
    child.on('error', (err) => reject(err))
    child.on('close', (code) => {
      if (code !== 0) {
        reject(new Error(t('youtube.ytdlpPlaylistFailed', { code: String(code), detail: stderr.trim() || stdout.trim() })))
        return
      }
      const lines = stdout.split('\n').map((l) => l.trim()).filter((l) => l.length > 0)
      const parsed: YtPlaylistEntry[] = []
      for (const line of lines) {
        try {
          const obj = JSON.parse(line) as Record<string, unknown>
          const id = typeof obj.id === 'string' ? obj.id : ''
          if (!id) continue
          parsed.push({
            id,
            title: typeof obj.title === 'string' ? obj.title : '',
            channel: typeof obj.channel === 'string'
              ? obj.channel
              : (typeof obj.uploader === 'string' ? obj.uploader : ''),
            durationSec: typeof obj.duration === 'number' ? Math.floor(obj.duration) : 0,
            url: typeof obj.url === 'string' && obj.url.length > 0
              ? obj.url
              : `https://www.youtube.com/watch?v=${id}`
          })
        } catch {
          // 한 줄이 깨져도 나머지는 살림
        }
      }
      resolve(parsed)
    })
  })
}