package weblive

import (
	"encoding/json"
	"strings"
	"sync"
	"time"
	"unicode/utf8"

	"github.com/gin-gonic/gin"
	"github.com/gorilla/websocket"
)

const maxDanmakuRunes = 120

var (
	danmakuClientsMu sync.Mutex
	danmakuClients   = make(map[*websocket.Conn]struct{})
)

// handleDanmakuWS 弹幕：客户端发 JSON {"text":"..."}，服务端立刻向所有连接广播 {"type":"dm","text","ts"}，不落库
func handleDanmakuWS(c *gin.Context) {
	ws, err := upgrader.Upgrade(c.Writer, c.Request, nil)
	if err != nil {
		return
	}
	ws.SetReadLimit(4096)

	danmakuClientsMu.Lock()
	danmakuClients[ws] = struct{}{}
	danmakuClientsMu.Unlock()

	defer func() {
		danmakuClientsMu.Lock()
		delete(danmakuClients, ws)
		danmakuClientsMu.Unlock()
		_ = ws.Close()
	}()

	for {
		mt, payload, err := ws.ReadMessage()
		if err != nil {
			return
		}
		if mt != websocket.TextMessage {
			continue
		}
		text := extractDanmakuText(payload)
		if text == "" {
			continue
		}
		out, err := json.Marshal(map[string]interface{}{
			"type": "dm",
			"text": text,
			"ts":   time.Now().UnixMilli(),
		})
		if err != nil {
			continue
		}
		danmakuBroadcast(out)
	}
}

func extractDanmakuText(payload []byte) string {
	var v struct {
		Text string `json:"text"`
	}
	if err := json.Unmarshal(payload, &v); err != nil {
		return ""
	}
	t := strings.TrimSpace(v.Text)
	if t == "" {
		return ""
	}
	if utf8.RuneCountInString(t) <= maxDanmakuRunes {
		return t
	}
	runes := []rune(t)
	return string(runes[:maxDanmakuRunes])
}

func danmakuBroadcast(b []byte) {
	danmakuClientsMu.Lock()
	defer danmakuClientsMu.Unlock()
	dead := make([]*websocket.Conn, 0)
	for conn := range danmakuClients {
		_ = conn.SetWriteDeadline(time.Now().Add(8 * time.Second))
		if err := conn.WriteMessage(websocket.TextMessage, b); err != nil {
			dead = append(dead, conn)
		}
	}
	for _, conn := range dead {
		delete(danmakuClients, conn)
		_ = conn.Close()
	}
}