package gateway

import (
	"embed"
	"encoding/json"
	"fmt"
	"io/fs"
	"net/http"
	"sort"
	"strings"
	"time"

	"realtime-gateway/internal/model"
)

//go:embed adminui/*
var adminUIFiles embed.FS

type adminOverview struct {
	Status        string         `json:"status"`
	StartedAt     time.Time      `json:"startedAt"`
	Now           time.Time      `json:"now"`
	UptimeSeconds int64          `json:"uptimeSeconds"`
	HTTPListen    string         `json:"httpListen"`
	Anonymous     bool           `json:"anonymousConsumers"`
	Metrics       map[string]any `json:"metrics"`
	Auth          map[string]any `json:"auth"`
	Endpoints     map[string]any `json:"endpoints"`
}

func (s *Server) registerAdminRoutes(mux *http.ServeMux) error {
	sub, err := fs.Sub(adminUIFiles, "adminui")
	if err != nil {
		return err
	}

	fileServer := http.FileServer(http.FS(sub))
	mux.Handle("/assets/", http.StripPrefix("/assets/", noStoreHandler(fileServer)))
	mux.HandleFunc("/", s.handleAdminIndex)
	mux.HandleFunc("/admin", s.handleAdminIndex)
	mux.HandleFunc("/api/admin/overview", s.handleAdminOverview)
	mux.HandleFunc("/api/admin/sessions", s.handleAdminSessions)
	mux.HandleFunc("/api/admin/latest", s.handleAdminLatest)
	mux.HandleFunc("/api/admin/traffic", s.handleAdminTraffic)
	mux.HandleFunc("/api/admin/live", s.handleAdminLive)
	return nil
}

func (s *Server) handleAdminIndex(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/" && r.URL.Path != "/admin" {
		http.NotFound(w, r)
		return
	}

	data, err := adminUIFiles.ReadFile("adminui/index.html")
	if err != nil {
		http.Error(w, "admin ui unavailable", http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	_, _ = w.Write(data)
}

func noStoreHandler(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Cache-Control", "no-store")
		next.ServeHTTP(w, r)
	})
}

func (s *Server) handleAdminOverview(w http.ResponseWriter, _ *http.Request) {
	subscriberCount, latestStateCount := s.hub.Stats()
	traffic := s.hub.TrafficSnapshot()
	now := time.Now()
	writeJSON(w, http.StatusOK, adminOverview{
		Status:        "ok",
		StartedAt:     s.startedAt,
		Now:           now,
		UptimeSeconds: int64(now.Sub(s.startedAt).Seconds()),
		HTTPListen:    s.cfg.Server.HTTPListen,
		Anonymous:     s.cfg.Auth.AllowAnonymousConsumers,
		Metrics: map[string]any{
			"sessions":       s.sessions.Count(),
			"subscribers":    subscriberCount,
			"latestState":    latestStateCount,
			"channels":       len(s.channels.List()),
			"pluginHandlers": s.plugins.HandlerCount(),
			"published":      traffic.Published,
			"dropped":        traffic.Dropped,
			"fanout":         traffic.Fanout,
		},
		Auth: map[string]any{
			"producerTokens":   len(s.cfg.Auth.ProducerTokens),
			"consumerTokens":   len(s.cfg.Auth.ConsumerTokens),
			"controllerTokens": len(s.cfg.Auth.ControllerTokens),
		},
		Endpoints: map[string]any{
			"websocket":     "/ws",
			"health":        "/healthz",
			"metrics":       "/metrics",
			"createChannel": "/api/channel/create",
			"channels":      "/api/admin/channels",
			"traffic":       "/api/admin/traffic",
			"admin":         "/admin",
		},
	})
}

func (s *Server) handleAdminSessions(w http.ResponseWriter, _ *http.Request) {
	snapshots := s.sessions.List()
	sort.Slice(snapshots, func(i int, j int) bool {
		return snapshots[i].CreatedAt.After(snapshots[j].CreatedAt)
	})
	writeJSON(w, http.StatusOK, map[string]any{
		"items": snapshots,
		"count": len(snapshots),
	})
}

func (s *Server) handleAdminLatest(w http.ResponseWriter, r *http.Request) {
	envelopes := s.hub.LatestStates()
	sort.Slice(envelopes, func(i int, j int) bool {
		return envelopes[i].Timestamp > envelopes[j].Timestamp
	})

	query := strings.TrimSpace(r.URL.Query().Get("topic"))
	if query != "" {
		filtered := make([]any, 0, len(envelopes))
		for _, envelope := range envelopes {
			if envelope.Topic != query {
				continue
			}
			filtered = append(filtered, adminLatestItem(envelope))
		}
		writeJSON(w, http.StatusOK, map[string]any{
			"items": filtered,
			"count": len(filtered),
		})
		return
	}

	items := make([]any, 0, len(envelopes))
	for _, envelope := range envelopes {
		items = append(items, adminLatestItem(envelope))
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"items": items,
		"count": len(items),
	})
}

func (s *Server) handleAdminLive(w http.ResponseWriter, r *http.Request) {
	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "streaming unsupported", http.StatusInternalServerError)
		return
	}

	topic := strings.TrimSpace(r.URL.Query().Get("topic"))
	channelID := strings.TrimSpace(r.URL.Query().Get("channelId"))
	deviceID := strings.TrimSpace(r.URL.Query().Get("deviceId"))

	w.Header().Set("Content-Type", "text/event-stream; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	w.Header().Set("Connection", "keep-alive")
	w.Header().Set("X-Accel-Buffering", "no")

	id, stream := s.hub.SubscribeLive(64)
	defer s.hub.UnsubscribeLive(id)

	fmt.Fprint(w, ": live stream ready\n\n")
	flusher.Flush()

	ping := time.NewTicker(15 * time.Second)
	defer ping.Stop()

	ctx := r.Context()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ping.C:
			fmt.Fprint(w, ": ping\n\n")
			flusher.Flush()
		case envelope, ok := <-stream:
			if !ok {
				return
			}
			if topic != "" && envelope.Topic != topic {
				continue
			}
			if channelID != "" && envelope.Target.ChannelID != channelID {
				continue
			}
			if deviceID != "" && envelope.Target.DeviceID != deviceID {
				continue
			}

			data, err := json.Marshal(adminLatestItem(envelope))
			if err != nil {
				continue
			}
			fmt.Fprintf(w, "event: envelope\ndata: %s\n\n", data)
			flusher.Flush()
		}
	}
}

func (s *Server) handleAdminTraffic(w http.ResponseWriter, _ *http.Request) {
	writeJSON(w, http.StatusOK, s.hub.TrafficSnapshot())
}

func adminLatestItem(envelope model.Envelope) map[string]any {
	payload := map[string]any{}
	_ = json.Unmarshal(envelope.Payload, &payload)

	return map[string]any{
		"timestamp": envelope.Timestamp,
		"topic":     envelope.Topic,
		"channelId": envelope.Target.ChannelID,
		"deviceId":  envelope.Target.DeviceID,
		"groupId":   envelope.Target.GroupID,
		"sourceId":  envelope.Source.ID,
		"mode":      envelope.Source.Mode,
		"payload":   payload,
	}
}