package api

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

	"github.com/syncserver/internal/syncengine"
)

type SSEHandler struct {
	engine *syncengine.Engine
}

func NewSSEHandler(engine *syncengine.Engine) *SSEHandler {
	return &SSEHandler{engine: engine}
}

func (h *SSEHandler) Stream(w http.ResponseWriter, r *http.Request) {
	jobIDStr := r.URL.Query().Get("job_id")
	var filterJobID int64
	if jobIDStr != "" {
		filterJobID, _ = strconv.ParseInt(jobIDStr, 10, 64)
	}

	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "SSE not supported", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	w.Header().Set("X-Accel-Buffering", "no")

	flusher.Flush()

	if h.engine == nil {
		return
	}

	events := h.engine.Events()
	for {
		select {
		case evt := <-events:
			if filterJobID != 0 && evt.JobID != filterJobID {
				continue
			}
			data, _ := json.Marshal(evt)
			fmt.Fprintf(w, "event: %s\ndata: %s\n\n", evt.Type, data)
			flusher.Flush()

		case <-r.Context().Done():
			return

		case <-time.After(30 * time.Second):
			fmt.Fprintf(w, ": keepalive\n\n")
			flusher.Flush()
		}
	}
}