package dashboard

import (
	"bytes"
	"fmt"
	"net/http"
	"strings"
	"time"
)

type pollState struct {
	kpiHash      string
	stationsHash string
	arrivalsHash string
}

func formatSSE(event, html string) string {
	data := strings.ReplaceAll(strings.TrimSpace(html), "\n", " ")
	return fmt.Sprintf("event: %s\ndata: %s\n\n", event, data)
}

func renderPartial(name string, data interface{}) string {
	t := parse("templates/dashboard/partials/" + name + ".html")
	var buf bytes.Buffer
	t.ExecuteTemplate(&buf, name, data)
	return buf.String()
}

func SSEStream(w http.ResponseWriter, r *http.Request) {
	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "streaming 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") // penting untuk nginx reverse proxy

	project, _ := GetProject(activeMcuID(r))
	if project.McuID == 0 {
		return
	}

	availableDates, _ := GetCheckinDates(project.McuID)
	mode, dateFrom, dateTo := activeDateRange(r, project, availableDates)
	isLive := mode == "daily" && dateFrom == time.Now().Format("2006-01-02")
	var prev pollState

	pushKPI := func(force bool) {
		kpi, _ := GetKPI(project.McuID, dateFrom, dateTo)
		key := fmt.Sprintf("%d|%d|%d", kpi.TotalStaff, kpi.CheckedIn, kpi.CheckedOut)
		if force || key != prev.kpiHash {
			fmt.Fprint(w, formatSSE("kpi", renderPartial("kpi", kpi)))
			prev.kpiHash = key
		}
	}

	pushStations := func(force bool) {
		rows, _ := GetStations(project.McuID, dateFrom, dateTo)
		key := fmt.Sprintf("%v", rows)
		if force || key != prev.stationsHash {
			fmt.Fprint(w, formatSSE("stations", renderPartial("stations", StationsPartial{Rows: rows, IsLive: isLive})))
			prev.stationsHash = key
		}
	}

	pushArrivals := func(force bool) {
		rows, _ := GetArrivals(project.McuID, dateFrom, dateTo, 8)
		key := fmt.Sprintf("%v", rows)
		if force || key != prev.arrivalsHash {
			fmt.Fprint(w, formatSSE("arrivals", renderPartial("arrivals", ArrivalsPartial{Rows: rows, IsLive: isLive})))
			prev.arrivalsHash = key
		}
	}

	// Kirim data langsung saat connect (force=true)
	pushKPI(true)
	pushStations(true)
	pushArrivals(true)
	flusher.Flush()

	ticker := time.NewTicker(3 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			pushKPI(false)
			pushStations(false)
			pushArrivals(false)
			flusher.Flush()
		case <-r.Context().Done():
			// Browser disconnect — goroutine ini langsung berhenti
			return
		}
	}
}