package sse

import (
	"fmt"
	"net/http"
	"sync"
)

// SseMsg SSE 事件消息
type SseMsg struct {
	Type string // 事件名，如表单名 dashboard.*
	Data string // JSON 字符串
}

// Hub SSE 推送中心（支持看板局部刷新）
type Hub struct {
	mu      sync.Mutex
	clients map[chan SseMsg]struct{}
	closed  map[chan SseMsg]bool
}

func NewHub() *Hub {
	return &Hub{clients: make(map[chan SseMsg]struct{})}
}

// Add 新增客户端
func (h *Hub) Add() chan SseMsg {
	ch := make(chan SseMsg, 16)
	h.mu.Lock()
	h.clients[ch] = struct{}{}
	h.mu.Unlock()
	return ch
}

func (h *Hub) Remove(ch chan SseMsg) {
	h.mu.Lock()
	if _, ok := h.clients[ch]; ok {
		delete(h.clients, ch)
		close(ch)
	}
	h.mu.Unlock()
}

// Publish 广播事件
func (h *Hub) Publish(typ string, data string) {
	h.mu.Lock()
	defer h.mu.Unlock()
	for ch := range h.clients {
		select {
		case ch <- SseMsg{Type: typ, Data: data}:
		default:
		}
	}
}

// Handler SSE 长连接端点
func (h *Hub) Handler(w http.ResponseWriter, r *http.Request) {
	fl, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "streaming unsupported", http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	ch := h.Add()
	defer h.Remove(ch)

	h.Publish("dashboard.hello", "{}")
	for {
		select {
		case m := <-ch:
			if _, err := fmt.Fprintf(w, "event: %s\ndata: %s\n\n", m.Type, m.Data); err != nil {
				return
			}
			fl.Flush()
		case <-r.Context().Done():
			return
		}
	}
}