package api

import (
	"context"
	"encoding/json"
	"net/http"
	"strings"

	"github.com/SherClockHolmes/webpush-go"

	"messenger/internal/realtime"
	"messenger/internal/store"
)

type pushRequest struct {
	Endpoint string `json:"endpoint"`
	Keys     struct {
		P256dh string `json:"p256dh"`
		Auth   string `json:"auth"`
	} `json:"keys"`
}

func (h *apiHandler) subscribePush(w http.ResponseWriter, r *http.Request) {
	userID, _ := userIDFrom(r.Context())
	var req pushRequest
	if !decodeJSON(w, r, &req) {
		return
	}
	if req.Endpoint == "" || req.Keys.P256dh == "" || req.Keys.Auth == "" {
		writeError(w, http.StatusBadRequest, "endpoint, p256dh and auth are required")
		return
	}
	_, err := h.store.CreatePushSubscription(r.Context(), store.PushSubscription{
		UserID:   userID,
		Endpoint: req.Endpoint,
		P256dh:   req.Keys.P256dh,
		Auth:     req.Keys.Auth,
	})
	if err != nil {
		writeError(w, http.StatusInternalServerError, "internal server error")
		return
	}
	writeJSON(w, http.StatusCreated, map[string]string{"status": "ok"})
}

func (h *apiHandler) unsubscribePush(w http.ResponseWriter, r *http.Request) {
	userID, _ := userIDFrom(r.Context())
	var req pushRequest
	if !decodeJSON(w, r, &req) {
		return
	}
	if req.Endpoint == "" {
		writeError(w, http.StatusBadRequest, "endpoint is required")
		return
	}
	if err := h.store.DeletePushSubscription(r.Context(), userID, req.Endpoint); err != nil {
		writeError(w, http.StatusInternalServerError, "internal server error")
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

type pushNotifier struct {
	store   *store.Store
	hub     *realtime.Hub
	public  string
	private string
	subject string
}

func newPushNotifier(st *store.Store, hub *realtime.Hub, public, private, subject string) *pushNotifier {
	if public == "" || private == "" {
		return nil
	}
	return &pushNotifier{store: st, hub: hub, public: public, private: private, subject: subject}
}

// notifyMembers pushes a message notification to offline members.
// Failed or stale endpoints are cleaned up asynchronously.
func (n *pushNotifier) notifyMembers(ctx context.Context, conversationID, senderID, messageID int64, senderName, body string) {
	members, err := n.store.ListMembers(ctx, conversationID)
	if err != nil {
		return
	}
	title := senderName
	text := strings.TrimSpace(body)
	if text == "" {
		text = "📎 Вложение"
	}
	if len(text) > 140 {
		text = text[:140] + "…"
	}
	payload, _ := json.Marshal(map[string]any{
		"title":           title,
		"body":            text,
		"conversation_id": conversationID,
		"message_id":      messageID,
	})

	for _, m := range members {
		if m.User.ID == senderID || n.hub.IsOnline(m.User.ID) {
			continue
		}
		subs, err := n.store.ListPushSubscriptionsForUser(ctx, m.User.ID)
		if err != nil {
			continue
		}
		for _, sub := range subs {
			go n.send(ctx, m.User.ID, sub, payload)
		}
	}
}

func (n *pushNotifier) send(ctx context.Context, userID int64, sub store.PushSubscription, payload []byte) {
	wp := &webpush.Subscription{Endpoint: sub.Endpoint, Keys: webpush.Keys{P256dh: sub.P256dh, Auth: sub.Auth}}
	resp, err := webpush.SendNotificationWithContext(ctx, payload, wp, &webpush.Options{
		VAPIDPublicKey:  n.public,
		VAPIDPrivateKey: n.private,
		Subscriber:      n.subject,
		TTL:             24 * 60 * 60,
	})
	if err != nil {
		return
	}
	defer resp.Body.Close()
	if resp.StatusCode == http.StatusNotFound || resp.StatusCode == http.StatusGone {
		_ = n.store.DeletePushSubscription(context.Background(), userID, sub.Endpoint)
	}
}