package service

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

	webpush "github.com/SherClockHolmes/webpush-go"
	"github.com/prabhupadasays/spsays-bff/internal/repository"
	"go.uber.org/zap"
)

// PushPayload is the JSON the service worker receives in its `push` event.
type PushPayload struct {
	Title string `json:"title"`
	Body  string `json:"body"`
	URL   string `json:"url,omitempty"`
	Icon  string `json:"icon,omitempty"`
	Tag   string `json:"tag,omitempty"`
}

// PushSender delivers Web Push messages via VAPID. Construct with
// NewPushSender; it returns nil when VAPID isn't configured, and every method
// is nil-safe so callers needn't branch.
type PushSender struct {
	repo    *repository.PushRepo
	pub     string
	priv    string
	subject string
	logger  *zap.Logger
}

// NewPushSender returns nil if the VAPID keys are absent (push disabled).
func NewPushSender(repo *repository.PushRepo, publicKey, privateKey, subject string, logger *zap.Logger) *PushSender {
	if publicKey == "" || privateKey == "" || repo == nil {
		return nil
	}
	return &PushSender{repo: repo, pub: publicKey, priv: privateKey, subject: subject, logger: logger}
}

// PublicKey is the VAPID application server key the browser subscribes with.
func (p *PushSender) PublicKey() string {
	if p == nil {
		return ""
	}
	return p.pub
}

// Enabled reports whether push delivery is configured.
func (p *PushSender) Enabled() bool { return p != nil }

// SendToUser pushes a payload to every subscription the user has, pruning any
// endpoint the push service reports as gone (404/410). Best-effort: failures
// are logged, never returned.
func (p *PushSender) SendToUser(ctx context.Context, userID string, payload PushPayload) {
	if p == nil {
		return
	}
	subs, err := p.repo.ListByUser(ctx, userID)
	if err != nil {
		p.logger.Warn("push: list subscriptions failed", zap.String("user", userID), zap.Error(err))
		return
	}
	if len(subs) == 0 {
		return
	}
	body, err := json.Marshal(payload)
	if err != nil {
		return
	}
	for _, s := range subs {
		sub := &webpush.Subscription{
			Endpoint: s.Endpoint,
			Keys:     webpush.Keys{P256dh: s.P256dh, Auth: s.Auth},
		}
		resp, err := webpush.SendNotification(body, sub, &webpush.Options{
			Subscriber:      p.subject,
			VAPIDPublicKey:  p.pub,
			VAPIDPrivateKey: p.priv,
			TTL:             60,
			Urgency:         webpush.UrgencyNormal,
		})
		if err != nil {
			p.logger.Warn("push: send failed", zap.String("user", userID), zap.Error(err))
			continue
		}
		status := resp.StatusCode
		_ = resp.Body.Close()
		// Subscription expired/gone — drop it so we stop trying.
		if status == http.StatusNotFound || status == http.StatusGone {
			if derr := p.repo.DeleteByEndpoint(ctx, s.Endpoint); derr != nil {
				p.logger.Warn("push: prune failed", zap.Error(derr))
			}
		} else if status >= 400 {
			p.logger.Warn("push: non-2xx", zap.Int("status", status), zap.String("user", userID))
		}
	}
}