import { readFile, realpath, mkdir } from 'node:fs/promises'
import { join } from 'node:path'
import { createHash } from 'node:crypto'
import { request as httpRequest } from 'node:http'
import { request as httpsRequest } from 'node:https'
import { execFile } from 'node:child_process'
import { promisify } from 'node:util'

const exec = promisify(execFile)
const sleep = ms => new Promise(resolve => setTimeout(resolve, ms))
export const dataKey = root => createHash('sha256').update(root).digest('hex')

export function localJSON(url, headers = {}, method = 'GET', timeout = 1500) {
  const target = new URL(url)
  if (!['http:', 'https:'].includes(target.protocol) || !['127.0.0.1', '[::1]'].includes(target.hostname) || target.username || target.password)
    return Promise.reject(new Error('桌面服务必须使用本机回环地址。'))
  return new Promise((resolve, reject) => {
    const req = (target.protocol === 'https:' ? httpsRequest : httpRequest)(target, { method, headers, agent: false }, res => {
      let body = '', bytes = 0
      res.on('data', chunk => {
        bytes += chunk.length
        if (bytes > 64 * 1024) req.destroy(new Error('服务身份响应过大'))
        else body += chunk
      })
      res.on('end', () => {
        if (res.statusCode !== 200) { reject(new Error(`服务返回 HTTP ${res.statusCode}`)); return }
        try { resolve(JSON.parse(body)) } catch { reject(new Error('服务返回了无效响应')) }
      })
    })
    req.setTimeout(timeout, () => req.destroy(new Error('服务连接超时')))
    req.on('error', reject); req.end()
  })
}

function isAlive(pid) {
  if (!Number.isSafeInteger(pid) || pid < 1) return false
  try { process.kill(pid, 0); return true } catch (e) { return e.code !== 'ESRCH' }
}

/** One owner for a packaged service child. Existing services are connected to,
 * never stopped. All callbacks are fenced to their exact child generation. */
export class DesktopServiceManager {
  constructor(options) {
    this.options = options
    this.state = { phase: 'stopped', message: '本地服务尚未启动' }
    this.child = null
    this.generation = 0
    this.stopping = false
    this.restarts = []
  }
  publish(value) { this.state = value; this.options.onState?.(value) }
  async readRecord() {
    try {
      const r = JSON.parse(await readFile(join(this.root, 'service-instance.json'), 'utf8'))
      return r.protocol === 1 && r.dataKey === dataKey(this.root) && isAlive(r.pid) ? r : null
    } catch { return null }
  }
  async verify(record) {
    if (!record.url) throw new Error('服务尚未监听')
    const url = new URL(record.url)
    if (url.hostname === '0.0.0.0') url.hostname = '127.0.0.1'
    const actual = await localJSON(new URL('/desktop/service', url), { 'x-yaoyao-desktop-token': record.token })
    if (actual.protocol !== 1 || actual.instanceId !== record.instanceId || actual.pid !== record.pid || actual.dataKey !== dataKey(this.root))
      throw new Error('服务身份与本地数据不匹配')
    return { ...actual, url: url.origin }
  }
  async legacyService() {
    // Old CLI/LaunchAgent builds lack the new descriptor. Prove the listener
    // actually holds this directory's SQLite file before reusing its own UI.
    if (process.platform !== 'darwin') return null
    const pids = async args => {
      try { return new Set((await exec('/usr/sbin/lsof', args, { timeout: 3000 })).stdout.trim().split(/\s+/).filter(Boolean)) }
      catch { return new Set() }
    }
    const [holders, listeners] = await Promise.all([
      pids(['-t', join(this.root, 'workspace.sqlite3')]),
      pids(['-nP', `-iTCP:${this.options.port}`, '-sTCP:LISTEN', '-t']),
    ])
    if (!holders.size) return null
    if (holders.size !== 1 || !listeners.has([...holders][0])) throw new Error('数据目录正在被另一个服务使用，请先确认已有服务。')
    const url = `http://127.0.0.1:${this.options.port}`
    const status = await localJSON(new URL('/api/status', url))
    if (status.server_kind !== 'yaoyao-web') throw new Error('已有端口不是夭夭服务。')
    return { url, pid: Number([...holders][0]), external: true, legacy: true, version: '已有服务' }
  }
  async start() {
    if (this.starting) return this.starting
    if (this.state.phase === 'ready') return this.state
    this.stopping = false
    this.starting = this.boot().finally(() => { this.starting = null })
    return this.starting
  }
  async boot() {
    const generation = ++this.generation
    this.publish({ phase: 'starting', message: '正在启动本地服务…' })
    try {
      await mkdir(this.options.home, { recursive: true, mode: 0o700 })
      this.root = await realpath(this.options.home)
      let record = await this.readRecord()
      if (generation !== this.generation || this.stopping) return
      if (record?.url) {
        const service = await this.verify(record)
        if (generation !== this.generation || this.stopping) return
        this.publish({ phase: 'ready', message: '已连接已有服务', ...service, external: !this.child })
        return this.state
      }
      const legacy = !record ? await this.legacyService() : null
      if (generation !== this.generation || this.stopping) return
      if (legacy) { this.publish({ phase: 'ready', message: '已连接已有后台服务', ...legacy }); return this.state }
      if (!record) {
        const child = this.options.fork({ home: this.root, port: this.options.port })
        child.desktopExited = false
        this.child = child
        child.stdout?.on('data', b => this.options.log?.(String(b)))
        child.stderr?.on('data', b => this.options.log?.(String(b)))
        child.once('exit', code => {
          child.desktopExited = true
          if (this.child !== child) return
          this.child = null
          if (this.stopping || this.state.phase === 'starting') return
          this.options.log?.(`服务进程退出：${code}`)
          this.scheduleRestart(this.generation)
        })
      }
      const deadline = Date.now() + (this.options.timeoutMs ?? 30_000)
      let lastError
      while (Date.now() < deadline && !this.stopping && generation === this.generation) {
        record = await this.readRecord()
        if (record?.url) {
          try {
            const service = await this.verify(record)
            if (this.child && service.pid !== this.child.pid) throw new Error('服务启动期间归属发生变化')
            if (generation !== this.generation || this.stopping) return
            this.publish({ phase: 'ready', message: '本地服务已就绪', ...service, external: !this.child })
            return this.state
          } catch (e) { lastError = e }
        }
        if (!this.child && !record) throw new Error('服务进程未能启动，请查看日志后重试。')
        await sleep(100)
      }
      if (!this.stopping) throw new Error(lastError?.message || '服务启动超时，请查看日志后重试。')
    } catch (error) {
      if (generation !== this.generation || this.stopping) return
      await this.stopChild()
      this.publish({ phase: 'error', message: error.message })
      throw error
    }
  }
  scheduleRestart(generation) {
    const now = Date.now()
    this.restarts = this.restarts.filter(time => now - time < 5 * 60_000)
    if (this.restarts.length >= 3) { this.publish({ phase: 'error', message: '服务多次退出，已停止自动重启。请查看日志后重试。' }); return }
    this.restarts.push(now)
    this.publish({ phase: 'restarting', message: '服务已断开，正在恢复…' })
    this.restartTimer = setTimeout(() => {
      if (this.stopping || generation !== this.generation) return
      void this.start().catch(() => {})
    }, 500 * this.restarts.length)
  }
  async check() {
    if (this.state.phase !== 'ready') return
    try {
      if (this.state.legacy) {
        if (!isAlive(this.state.pid)) throw new Error('已有服务已停止')
        await localJSON(new URL('/api/status', this.state.url))
      } else {
        const record = await this.readRecord()
        if (!record) throw new Error('服务已停止')
        await this.verify(record)
      }
    } catch {
      this.publish({ phase: 'error', message: '本地服务连接已断开，请重试。' })
    }
  }
  async stopChild() {
    const child = this.child
    if (!child || child.desktopExited) return
    const exited = new Promise(resolve => child.once('exit', resolve))
    const record = await this.readRecord()
    if (record?.pid === child.pid && record.desktopOwned) {
      try { await localJSON(new URL('/desktop/service', record.url), { 'x-yaoyao-desktop-token': record.token }, 'DELETE') }
      catch { /* Owned process handle remains authoritative for cleanup. */ }
    } else child.kill()
    let timer
    await Promise.race([exited, new Promise(resolve => { timer = setTimeout(() => { child.kill(); resolve() }, 5000) })])
    clearTimeout(timer)
    if (!child.desktopExited) {
      await Promise.race([exited, sleep(2000)])
      if (!child.desktopExited && child.pid) {
        try { process.kill(child.pid, 'SIGKILL') } catch (error) { if (error.code !== 'ESRCH') throw error }
        await Promise.race([exited, sleep(2000)])
      }
      if (!child.desktopExited) throw new Error('旧服务进程尚未确认退出，暂不启动替代进程。')
    }
    if (this.child === child) this.child = null
  }
  async stop() {
    this.stopping = true
    clearTimeout(this.restartTimer)
    ++this.generation
    await this.starting?.catch(() => {})
    await this.stopChild()
    this.publish({ phase: 'stopped', message: '本地服务已停止' })
  }
}