package usecase

import (
	"blockchain/internal/domain/blockchain"
	"blockchain/internal/domain/repository"
	"blockchain/internal/domain/usecase"
	"context"
	"github.com/lxzan/gws"
	"github.com/zeromicro/go-zero/core/logx"
	"sync"
	"time"
)

type BinanceExchangeParam struct {
	Adapter    repository.ExchangeAdapter
	Handler    repository.StreamHandler
	Backoff    time.Duration
	MaxBackoff time.Duration
	Parallel   bool
	ParallelN  int
}

type Connection struct {
	// Adapter：交易所的實作（Binance/Coinbase/OKX ...）
	// 用來決定如何建立連線、訂閱訊息、解析 K 線、補歷史資料等
	Adapter repository.ExchangeAdapter

	// Handler：資料事件回呼，讓上層接收到統一格式的 K 線或錯誤通知
	Handler repository.StreamHandler

	// === 內部連線狀態 ===
	conn   *gws.Conn          // 當前 WebSocket 連線物件
	ctx    context.Context    // 控制心跳、讀取等 goroutine 的生命週期
	cancel context.CancelFunc // 用來結束 ctx

	// === 訂閱管理 ===
	subsMu sync.Mutex                                  // 保護 subs map 的互斥鎖
	subs   map[string]map[blockchain.Interval]struct{} // 已訂閱的主題表，key=symbol，value=set(interval)

	// === 重連控制 ===
	backoff    time.Duration // 當前重連延遲時間（指數退避用）
	maxBackoff time.Duration // 最大重連延遲時間

	// === gws 併發讀取設定 ===
	parallel  bool // 是否開啟 gws 的 ParallelEnabled
	parallelN int  // 平行讀取時允許的最大 goroutine 數
}

func (c *Connection) SubscribeKLine(symbols []string, interval blockchain.Interval) error {
	c.subsMu.Lock()
	defer c.subsMu.Unlock()
	for _, s := range symbols {
		if _, ok := c.subs[s]; !ok {
			c.subs[s] = map[blockchain.Interval]struct{}{}
		}
		c.subs[s][interval] = struct{}{}
	}
	// 若已連線就立即送訂閱訊息
	if c.conn != nil {
		payloads, err := c.Adapter.BuildSubscribe(symbols, interval)
		if err != nil {
			return err
		}
		for _, p := range payloads {
			_ = c.conn.WriteMessage(gws.OpcodeText, p)
		}
	}

	return nil
}

func (c *Connection) RunForever() {
	for {
		h := WebSocket{c}
		conn, _, err := gws.NewClient(&h, &gws.ClientOption{
			Addr:            c.Adapter.URL(),
			ParallelEnabled: c.parallel,
			ParallelGolimit: c.parallelN,
			PermessageDeflate: gws.PermessageDeflate{
				Enabled:               true,
				ServerContextTakeover: true,
				ClientContextTakeover: true,
			},
			RequestHeader: map[string][]string{"User-Agent": {"universal-ws/1.0"}},
		})
		if err != nil {
			c.sleepBackoff()
			continue
		}
		c.conn = conn
		_ = conn.SetReadDeadline(time.Now().Add(c.Adapter.ReadDeadline()))
		conn.ReadLoop()  // 阻塞直到關閉
		c.conn = nil     // 清除
		c.sleepBackoff() // 退避再重連
	}
}

func (c *Connection) sleepBackoff() {
	time.Sleep(c.backoff)
	if c.backoff < c.maxBackoff {
		c.backoff *= 2
		if c.backoff > c.maxBackoff {
			c.backoff = c.maxBackoff
		}
	}
}

func NewConnection(param BinanceExchangeParam) usecase.ExchangeConnect {
	ctx, cancel := context.WithCancel(context.Background())
	return &Connection{
		Adapter:    param.Adapter,
		Handler:    param.Handler,
		ctx:        ctx,
		cancel:     cancel,
		subs:       make(map[string]map[blockchain.Interval]struct{}),
		backoff:    param.Backoff,
		maxBackoff: param.MaxBackoff,
		parallel:   param.Parallel,
		parallelN:  param.ParallelN,
	}
}

// ========================================

type WebSocket struct {
	conn *Connection
}

func (ws *WebSocket) OnClose(socket *gws.Conn, err error) {
	ws.conn.Handler.OnError(err)
}

func (ws *WebSocket) OnPong(socket *gws.Conn, payload []byte) {
	_ = socket.SetReadDeadline(time.Now().Add(ws.conn.Adapter.ReadDeadline()))
}

func (ws *WebSocket) OnOpen(c *gws.Conn) {
	ws.conn.backoff = time.Second // 重置退避
	// 重訂閱所有
	ws.conn.subsMu.Lock()
	for s, set := range ws.conn.subs {
		for itv := range set {
			payloads, err := ws.conn.Adapter.BuildSubscribe([]string{s}, itv)
			if err != nil {
				ws.conn.Handler.OnError(err)
				continue
			}
			for _, p := range payloads {
				_ = c.WriteMessage(gws.OpcodeText, p)
			}
			//// 回補（可平行：這裡示範最近 2 根的缺口；實務上你可記錄 last close 再補）
			//go func(symbol string, iv blockchain.Interval) {
			//	end := time.Now().UnixMilli()
			//	start := end - 2*int64(time.Minute/time.Millisecond) // demo: 補近 2m
			//	kl, err := ws.conn.Adapter.Backfill(symbol, iv, start, end, 500)
			//	if err != nil {
			//		ws.conn.Handler.OnError(err)
			//		return
			//	}
			//	for _, k := range kl {
			//		ws.conn.Handler.OnKline(k)
			//	}
			//}(s, itv)
		}
	}
	ws.conn.subsMu.Unlock()
}

func (ws *WebSocket) OnPing(socket *gws.Conn, payload []byte) {
	_ = socket.WritePong(payload)
	_ = socket.SetReadDeadline(time.Now().Add(ws.conn.Adapter.ReadDeadline()))
}

func (ws *WebSocket) OnMessage(socket *gws.Conn, message *gws.Message) {
	defer message.Close()
	_ = socket.SetReadDeadline(time.Now().Add(ws.conn.Adapter.ReadDeadline()))
	kLines, err := ws.conn.Adapter.ParseKLines(message.Data.Bytes())
	if err != nil {
		ws.conn.Handler.OnError(err)

		return
	}

	for _, k := range kLines {
		ws.conn.Handler.OnKline(k)
	}
}

// ========================================

type PubHandler struct{}

func (h *PubHandler) OnKline(k blockchain.Kline) {
	// 收到之後可以送到 pub/sub  讓其他
	logx.Infof("[PubHandler] Kline:%v", k)
}
func (h *PubHandler) OnError(err error) { logx.Errorf("failed to pub k line %v", err.Error()) }