/**
 * 服务端入口：Express 托管前端静态资源 + Socket.IO 处理对局事件。
 * 单进程内存态，因此部署时必须保持单副本（见 k8s/deployment.yaml）。
 */
import { createServer } from 'node:http'
import { fileURLToPath } from 'node:url'
import path from 'node:path'
import express from 'express'
import { Server } from 'socket.io'
import {
  EV,
  type ActionAck,
  type CreateAck,
  type JoinAck,
  type NoticePayload,
  type Player,
} from '../shared/protocol.js'
import { Room, RoomManager } from './room.js'

const HERE = path.dirname(fileURLToPath(import.meta.url))
const PORT = Number(process.env.PORT ?? 3000)
/**
 * 构建产物布局（因 server/ 与 shared/ 需一同编译，tsc 保留了目录层级）：
 *   dist-server/server/index.js   ← 当前文件
 *   dist-server/shared/protocol.js
 *   dist-web/                     ← 前端静态资源
 */
const WEB_DIR = process.env.WEB_DIR ?? path.resolve(HERE, '../../dist-web')

const app = express()
// 位于 Ingress / 反代之后，需要信任 X-Forwarded-* 才能拿到真实协议与 IP
app.set('trust proxy', true)

app.get('/healthz', (_req, res) => {
  res.json({ ok: true, rooms: manager.size, uptime: Math.round(process.uptime()) })
})

app.use(express.static(WEB_DIR, { index: 'index.html', maxAge: '1h' }))

// SPA 兜底：非 /socket.io、非静态资源的 GET 一律返回 index.html
app.get('*', (req, res, next) => {
  if (req.path.startsWith('/socket.io')) return next()
  res.sendFile(path.join(WEB_DIR, 'index.html'))
})

const httpServer = createServer(app)
const io = new Server(httpServer, {
  serveClient: false,
  pingInterval: 25_000,
  pingTimeout: 20_000,
  maxHttpBufferSize: 1e5,
})

const manager = new RoomManager()

declare module 'socket.io' {
  interface SocketData {
    roomId?: string
    seat?: Player
  }
}

/* ------------------------------------------------------------------ */
/* 工具                                                                */
/* ------------------------------------------------------------------ */

/** 把房间最新状态按各自座位视角分别下发给两端 */
function broadcast(room: Room): void {
  for (const seat of [1, 2] as const) {
    const sid = room.socketIdOf(seat)
    if (sid) io.to(sid).emit(EV.state, room.snapshot(seat))
  }
}

function notice(socketId: string, level: NoticePayload['level'], message: string): void {
  io.to(socketId).emit(EV.notice, { level, message } satisfies NoticePayload)
}

type Ctx = { room: Room; seat: Player } | null

/**
 * 取 Socket.IO 的回调。
 * 不能用可选链直接调用：客户端可能把载荷当 ack 传进来，
 * `ack?.()` 只判空不判可调用，会抛未捕获异常打挂整个进程。
 */
type AnyAck = (r: unknown) => void

function asAck(v: unknown): AnyAck | undefined {
  return typeof v === 'function' ? (v as AnyAck) : undefined
}

/** 取出当前 socket 所处的房间与座位，顺带校验房间是否已被回收 */
function ctxOf(socketId: string, socketData: { roomId?: string; seat?: Player }): Ctx {
  const { roomId, seat } = socketData
  if (!roomId || !seat) return null
  const room = manager.get(roomId)
  if (!room) return null
  if (room.socketIdOf(seat) !== socketId) return null
  return { room, seat }
}

/* ------------------------------------------------------------------ */
/* 事件                                                                */
/* ------------------------------------------------------------------ */

io.on('connection', (socket) => {
  /**
   * 统一包装动作类事件：校验上下文 → 执行 → ack → 广播。
   * 校验不通过时不广播，仅把错误回给发起方。
   */
  function withCtx<T>(
    fn: (ctx: { room: Room; seat: Player }, payload: T) => ActionAck,
  ): (payload: T | undefined, ack?: unknown) => void {
    return (payload, ack) => {
      const reply = asAck(ack)
      const ctx = ctxOf(socket.id, socket.data)
      if (!ctx) {
        reply?.({ ok: false, error: '你已不在对局中，请重新进入房间' })
        return
      }
      const result = fn(ctx, payload as T)
      if (result.ok) broadcast(ctx.room)
      reply?.(result)
    }
  }

  socket.on(EV.create, (_payload: unknown, ack?: unknown) => {
    const reply = asAck(ack)
    const room = manager.create()
    room.bind(1, socket.id)
    socket.data.roomId = room.id
    socket.data.seat = 1
    void socket.join(room.id)
    reply?.({ ok: true, roomId: room.id, seat: 1, resumeToken: room.tokenOf(1) } satisfies CreateAck)
    broadcast(room)
  })

  socket.on(
    EV.join,
    (
      payload: { roomId?: string; resumeToken?: string } | undefined,
      ack?: unknown,
    ) => {
      const reply = asAck(ack)
      const raw = payload?.roomId ?? ''
      const room = manager.get(raw)
      if (!room) {
        reply?.({ ok: false, error: '房间不存在或已过期' })
        return
      }

      // 优先用重连凭证找回原座位，其次占用空位
      let seat: Player | null = null
      if (payload?.resumeToken) seat = room.seatByToken(payload.resumeToken)
      if (seat === null) seat = room.freeSeat()
      if (seat === null) {
        reply?.({ ok: false, error: '房间已满，无法加入' })
        return
      }

      const staleSocketId = room.socketIdOf(seat)
      room.bind(seat, socket.id)
      socket.data.roomId = room.id
      socket.data.seat = seat
      void socket.join(room.id)

      // 顶掉该座位的旧连接（同一玩家在另一台设备/标签页重连）
      if (staleSocketId && staleSocketId !== socket.id) {
        const stale = io.sockets.sockets.get(staleSocketId)
        if (stale) {
          stale.data.roomId = undefined
          stale.data.seat = undefined
          stale.disconnect(true)
        }
      }

      reply?.({
        ok: true,
        roomId: room.id,
        seat,
        resumeToken: room.tokenOf(seat),
        state: room.snapshot(seat),
      } satisfies JoinAck)
      broadcast(room)
    },
  )

  socket.on(
    EV.move,
    withCtx<{ x?: number; y?: number }>(({ room, seat }, p) => {
      if (!Number.isInteger(p?.x) || !Number.isInteger(p?.y)) {
        return { ok: false, error: '非法坐标' }
      }
      return room.place(p.x as number, p.y as number, seat)
    }),
  )

  socket.on(EV.resign, withCtx<void>(({ room, seat }) => room.resign(seat)))
  socket.on(EV.undoRequest, withCtx<void>(({ room, seat }) => room.requestUndo(seat)))
  socket.on(EV.claimOffline, withCtx<void>(({ room, seat }) => room.claimOffline(seat)))

  socket.on(
    EV.undoRespond,
    withCtx<{ accept?: boolean }>(({ room, seat }, p) => room.respondUndo(seat, p?.accept === true)),
  )

  socket.on(
    EV.restart,
    (payload: { swap?: boolean } | undefined, ack?: unknown) => {
      const reply = asAck(ack)
      const ctx = ctxOf(socket.id, socket.data)
      if (!ctx) {
        reply?.({ ok: false, error: '你已不在对局中' })
        return
      }
      const { swapped, mapping } = ctx.room.restart(payload?.swap === true)
      // 交换黑白后必须同步 socket ↔ 座位映射，否则后续落子校验会认错颜色
      if (swapped) {
        for (const [sid, seat] of mapping) {
          const s = io.sockets.sockets.get(sid)
          if (s) s.data.seat = seat
        }
      }
      reply?.({ ok: true })
      broadcast(ctx.room)
    },
  )

  socket.on('disconnect', () => {
    const ctx = ctxOf(socket.id, socket.data)
    if (!ctx) return
    ctx.room.unbind(socket.id)
    broadcast(ctx.room)
  })
})

/* ------------------------------------------------------------------ */
/* 周期任务：悔棋请求超时、房间回收                                      */
/* ------------------------------------------------------------------ */

const ticker = setInterval(() => {
  for (const room of manager.values()) {
    if (room.expireUndo()) {
      broadcast(room)
      for (const seat of [1, 2] as const) {
        const sid = room.socketIdOf(seat)
        if (sid) notice(sid, 'info', '悔棋请求已超时失效')
      }
    }
  }
  const removed = manager.gc()
  if (removed > 0) console.log(`[gc] 回收房间 ${removed} 个，当前 ${manager.size} 个`)
}, 15_000)
ticker.unref()

httpServer.listen(PORT, '0.0.0.0', () => {
  console.log(`[wuziqi] listening on :${PORT}, static dir = ${WEB_DIR}`)
})

for (const sig of ['SIGINT', 'SIGTERM'] as const) {
  process.on(sig, () => {
    console.log(`[wuziqi] ${sig} received, shutting down`)
    io.close(() => httpServer.close(() => process.exit(0)))
    setTimeout(() => process.exit(0), 3000).unref()
  })
}