// 评论变更的 SSE 端点：GET /api/comments/stream?post_id=N。
// 事件里只有「这篇文章的评论变了」——不带任何内容，前端收到后
// 自己 refetch。这样未审核的评论内容不会经 SSE 泄给围观者。
package api

import (
	"fmt"
	"net/http"
	"strconv"
	"time"

	"oneblog/internal/httpx"
)

// commentsStream 长连推送。EventSource 断线会自动重连，所以这里
// 只需要：连上即发注释行、25s 心跳防代理掐线、事件触发刷新。
func (a *API) commentsStream(w http.ResponseWriter, r *http.Request) {
	postID, err := strconv.ParseInt(r.URL.Query().Get("post_id"), 10, 64)
	if err != nil || postID <= 0 {
		httpx.BadRequest(w, "post_id required")
		return
	}
	fl, ok := w.(http.Flusher)
	if !ok {
		httpx.Error(w, http.StatusInternalServerError, "streaming unsupported")
		return
	}
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	// 反向代理（nginx 等）默认缓冲会吞掉流式响应
	w.Header().Set("X-Accel-Buffering", "no")

	fmt.Fprint(w, ": connected\n\n")
	fl.Flush()

	ch, off := a.Hub.Subscribe(postID)
	defer off()
	heartbeat := time.NewTicker(25 * time.Second)
	defer heartbeat.Stop()
	for {
		select {
		case <-r.Context().Done():
			return
		case <-heartbeat.C:
			fmt.Fprint(w, ": ping\n\n")
			fl.Flush()
		case <-ch:
			fmt.Fprintf(w, "event: comments\ndata: {\"post_id\":%d}\n\n", postID)
			fl.Flush()
		}
	}
}