package main

import (
	"context"
	"encoding/base64"
	htmltemplate "html/template"
	"log/slog"
	"os"
	"os/signal"
	"strings"
	"syscall"
	"time"

	"github.com/skip2/go-qrcode"

	"github.com/alchemistkay/guestguard/internal/auth"
	"github.com/alchemistkay/guestguard/internal/config"
	"github.com/alchemistkay/guestguard/internal/natspub"
	"github.com/alchemistkay/guestguard/internal/notification"
	"github.com/alchemistkay/guestguard/internal/storage"
)

func main() {
	if err := run(); err != nil {
		slog.Error("fatal", "err", err)
		os.Exit(1)
	}
}

func run() error {
	cfg, err := config.Load()
	if err != nil {
		return err
	}

	logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: levelFor(cfg.Env)}))
	slog.SetDefault(logger)
	logger = logger.With("service", "notifier")

	rootCtx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
	defer stop()

	logger.Info("connecting to database")
	db, err := storage.NewDB(rootCtx, cfg.DatabaseURL)
	if err != nil {
		return err
	}
	defer db.Close()

	logger.Info("connecting to nats", "url", cfg.NATSURL)
	natsClient, err := natspub.Connect(rootCtx, cfg.NATSURL, logger)
	if err != nil {
		return err
	}
	defer natsClient.Close()

	repo := notification.NewRepo(db)
	suppressions := notification.NewSuppressionRepo(db)
	tpls, err := notification.NewTemplates()
	if err != nil {
		return err
	}

	// Email dispatcher: Resend > SMTP > SES > log stub, same picker as cmd/api.
	combinedEmail, backend, err := notification.PickEmailSender(rootCtx, notification.EmailSenderConfig{
		Resend: notification.ResendConfig{
			APIKey:    cfg.ResendAPIKey,
			FromEmail: cfg.ResendFromEmail,
			FromName:  cfg.ResendFromName,
		},
		SMTP: notification.SMTPConfig{
			Host:      cfg.SMTPHost,
			Port:      cfg.SMTPPort,
			Username:  cfg.SMTPUsername,
			Password:  cfg.SMTPPassword,
			FromEmail: cfg.SMTPFromEmail,
			FromName:  cfg.SMTPFromName,
			TLS:       cfg.SMTPTLS,
		},
		SES: notification.SESConfig{
			Region:           cfg.SESRegion,
			FromEmail:        cfg.SESFromEmail,
			FromName:         cfg.SESFromName,
			ConfigurationSet: cfg.SESConfigurationSet,
			PublicBaseURL:    cfg.PublicBaseURL,
		},
	}, tpls, logger)
	if err != nil {
		return err
	}
	logger.Info("email backend selected", "backend", backend)
	emailSender := notification.NewEmailSender(combinedEmail, suppressions)

	// SMS: Twilio when creds are set, otherwise no-op log sender.
	var smsSender notification.Sender
	if cfg.TwilioAccountSID != "" && cfg.TwilioAuthToken != "" && cfg.TwilioFromNumber != "" {
		t, err := notification.NewTwilioSender(notification.TwilioConfig{
			AccountSID: cfg.TwilioAccountSID,
			AuthToken:  cfg.TwilioAuthToken,
			FromNumber: cfg.TwilioFromNumber,
		})
		if err != nil {
			return err
		}
		smsSender = t
		logger.Info("twilio sms sender configured", "from", cfg.TwilioFromNumber)
	} else {
		smsSender = notification.LogSender{}
		logger.Info("twilio not configured — SMS will use the log stub")
	}

	sender := notification.NewRouter(emailSender, smsSender)

	// Tier 2 Block H — QR signer for the confirmation email's door
	// code. Same secret as the API so the same JWT verifies on either
	// service.
	checkInQRSigner, err := auth.NewCheckInQRSigner(cfg.JWTSecret, cfg.JWTIssuer, 6*time.Hour)
	if err != nil {
		return err
	}

	guestRepo := storage.NewGuestRepo(db)
	eventRepo := storage.NewEventRepo(db)

	rsvpSub, err := natspub.NewRSVPConfirmedSubscriber(
		rootCtx, natsClient, "notifier-rsvp-confirmed",
		func(ctx context.Context, evt natspub.RSVPConfirmed) error {
			return handleRSVPConfirmed(ctx, logger, repo, sender,
				guestRepo, eventRepo, checkInQRSigner, cfg.PublicBaseURL, evt)
		},
		logger,
	)
	if err != nil {
		return err
	}
	rsvpCC, err := rsvpSub.Start(rootCtx)
	if err != nil {
		return err
	}
	defer rsvpCC.Stop()

	fraudSub, err := natspub.NewFraudScoredSubscriber(
		rootCtx, natsClient, "notifier-fraud-scored",
		func(ctx context.Context, evt natspub.FraudScored) error {
			return handleFraudScored(ctx, logger, repo, sender, evt)
		},
		logger,
	)
	if err != nil {
		return err
	}
	fraudCC, err := fraudSub.Start(rootCtx)
	if err != nil {
		return err
	}
	defer fraudCC.Stop()

	invitationSub, err := natspub.NewInvitationSendSubscriber(
		rootCtx, natsClient, "notifier-invitation-send",
		func(ctx context.Context, evt natspub.InvitationSend) error {
			return handleInvitationSend(ctx, logger, repo, sender, evt)
		},
		logger,
	)
	if err != nil {
		return err
	}
	invitationCC, err := invitationSub.Start(rootCtx)
	if err != nil {
		return err
	}
	defer invitationCC.Stop()

	// Block F — scheduled-message worker. Polls scheduled_messages
	// every 30s and dispatches due rows through the same email
	// pipeline as the NATS-driven flows.
	scheduler := newScheduledMessageWorker(logger, db, combinedEmail, cfg.PublicBaseURL)
	go scheduler.Start(rootCtx)

	logger.Info("notifier started")
	<-rootCtx.Done()
	logger.Info("notifier shutting down")
	return nil
}

func handleRSVPConfirmed(
	ctx context.Context,
	logger *slog.Logger,
	repo *notification.Repo,
	sender notification.Sender,
	guests *storage.GuestRepo,
	events *storage.EventRepo,
	qr *auth.CheckInQRSigner,
	publicBaseURL string,
	evt natspub.RSVPConfirmed,
) error {
	// Look up the guest + event so the templated confirmation has real
	// names, venue, and date. The NATS event only carries IDs.
	guest, gerr := guests.Get(ctx, evt.GuestID)
	if gerr != nil {
		logger.Warn("load guest for confirmation email", "err", gerr, "guest_id", evt.GuestID)
	}
	event, eerr := events.Get(ctx, evt.EventID)
	if eerr != nil {
		logger.Warn("load event for confirmation email", "err", eerr, "event_id", evt.EventID)
	}

	if guest == nil || guest.Email == nil || *guest.Email == "" {
		// No email on file: nothing to do here. The host either has
		// SMS wired up (handled separately) or shares the QR via the
		// confirmation page link.
		logger.Info("skip rsvp confirmation email — no guest email",
			"guest_id", evt.GuestID, "event_id", evt.EventID)
		return nil
	}

	// Mint a QR for attending guests so the email carries their door
	// code along with the confirmation. Other responses get the same
	// email minus the QR section.
	//
	// The image is rendered as a data: URL and handed to html/template as
	// a template.URL — without the type wrapper, html/template's
	// contextual-URL escaper treats `data:` as unsafe and substitutes
	// the placeholder `#ZgotmplZ`, which is why the image appeared
	// broken in Mailpit and inbox clients. Marking it template.URL
	// signals "we trust this URL" and lets the data: prefix through.
	var qrImage htmltemplate.URL
	if evt.Response == "attending" && event != nil && qr != nil {
		now := time.Now().UTC()
		raw, _, qerr := qr.Issue(evt.EventID, evt.GuestID, event.EventDate, now)
		if qerr != nil {
			logger.Warn("issue qr for confirmation email", "err", qerr, "guest_id", evt.GuestID)
		} else if png, perr := qrcode.Encode(raw, qrcode.Medium, 320); perr != nil {
			logger.Warn("render qr png for confirmation email", "err", perr)
		} else {
			qrImage = htmltemplate.URL("data:image/png;base64," + base64.StdEncoding.EncodeToString(png))
		}
	}

	eventName := ""
	venue := ""
	eventDate := ""
	if event != nil {
		eventName = event.Name
		venue = event.Venue
		if !event.EventDate.IsZero() {
			eventDate = event.EventDate.Format("Mon, 02 Jan 2006 · 15:04")
		}
	}

	// Prefer the access link carried on the NATS event — that's the
	// guest's actual /rsvp/<token> URL. If we lost it (older event
	// schema, or token was somehow missing), fall back to the bare
	// dashboard origin so the template still renders without a 404.
	rsvpLink := strings.TrimSpace(evt.AccessLink)
	if rsvpLink == "" && publicBaseURL != "" {
		rsvpLink = strings.TrimRight(publicBaseURL, "/")
	}

	subject := "RSVP confirmed"
	if eventName != "" {
		subject = "RSVP confirmed — " + eventName
	}

	msg := notification.OutboundMessage{
		GuestID: evt.GuestID,
		Channel: notification.ChannelEmail,
		Type:    notification.TypeConfirmation,
		Subject: subject,
		Metadata: map[string]any{
			"to":        *guest.Email,
			"GuestName": guest.Name,
			"HostName":  "your host", // notifier doesn't have the host's name handy
			"EventName": eventName,
			"Venue":     venue,
			"EventDate": eventDate,
			"Response":  evt.Response,
			"PlusOnes":  evt.PlusOnes,
			"QRImage":   qrImage,
			"RSVPLink":  rsvpLink,
		},
	}

	providerID, sendErr := sender.Send(ctx, msg)
	status := notification.StatusSent
	errStr := ""
	if sendErr != nil {
		status = notification.StatusFailed
		errStr = sendErr.Error()
	}

	id, err := repo.Record(ctx, notification.RecordParams{
		GuestID:    evt.GuestID,
		Channel:    msg.Channel,
		Type:       msg.Type,
		Status:     status,
		ProviderID: providerID,
		Error:      errStr,
	})
	if err != nil {
		return err
	}

	logger.Info("notification dispatched",
		"notification_id", id,
		"guest_id", evt.GuestID,
		"channel", msg.Channel,
		"type", msg.Type,
		"status", status,
		"provider_id", providerID,
	)
	return nil
}

func handleFraudScored(
	ctx context.Context,
	logger *slog.Logger,
	repo *notification.Repo,
	sender notification.Sender,
	evt natspub.FraudScored,
) error {
	// Only alert when the score crosses a meaningful threshold; low/medium
	// scores are noise for the host.
	if evt.Score < 60 {
		return nil
	}

	msg := notification.OutboundMessage{
		GuestID: evt.GuestID,
		Channel: notification.ChannelEmail,
		Type:    notification.TypeReminder, // reusing existing enum; a fraud_alert type would be nicer
		Subject: "Suspicious access attempt detected",
		Body:    "A flagged access attempt occurred for one of your guests.",
		Metadata: map[string]any{
			"event_id": evt.EventID,
			"score":    evt.Score,
			"risk":     evt.Risk,
			"reasons":  evt.Reasons,
		},
	}

	providerID, sendErr := sender.Send(ctx, msg)
	status := notification.StatusSent
	errStr := ""
	if sendErr != nil {
		status = notification.StatusFailed
		errStr = sendErr.Error()
	}

	id, err := repo.Record(ctx, notification.RecordParams{
		GuestID:    evt.GuestID,
		Channel:    msg.Channel,
		Type:       msg.Type,
		Status:     status,
		ProviderID: providerID,
		Error:      errStr,
	})
	if err != nil {
		return err
	}

	logger.Warn("fraud alert dispatched",
		"notification_id", id,
		"guest_id", evt.GuestID,
		"score", evt.Score,
		"risk", evt.Risk,
		"reasons", evt.Reasons,
		"status", status,
		"provider_id", providerID,
	)
	return nil
}

// handleInvitationSend renders the invitation template + sends through
// the configured sender (Resend in prod, Mailpit in dev), then writes a
// notification row so the host can audit the delivery history.
func handleInvitationSend(
	ctx context.Context,
	logger *slog.Logger,
	repo *notification.Repo,
	sender notification.Sender,
	evt natspub.InvitationSend,
) error {
	if evt.GuestEmail == "" {
		// Nothing to do — host-managed delivery.
		return nil
	}

	eventDate := ""
	if !evt.EventDate.IsZero() {
		eventDate = evt.EventDate.Format("Mon, 02 Jan 2006 · 15:04")
	}

	msg := notification.OutboundMessage{
		GuestID: evt.GuestID,
		Channel: notification.ChannelEmail,
		Type:    notification.TypeInvitation,
		Subject: "You're invited — " + evt.EventName,
		Metadata: map[string]any{
			"to":        evt.GuestEmail,
			"GuestName": evt.GuestName,
			"HostName":  evt.HostName,
			"EventName": evt.EventName,
			"Venue":     evt.Venue,
			"EventDate": eventDate,
			"Link":      evt.Link,
		},
	}

	providerID, sendErr := sender.Send(ctx, msg)
	status := notification.StatusSent
	errStr := ""
	if sendErr != nil {
		status = notification.StatusFailed
		errStr = sendErr.Error()
	}

	id, err := repo.Record(ctx, notification.RecordParams{
		GuestID:           evt.GuestID,
		Channel:           msg.Channel,
		Type:              msg.Type,
		Status:            status,
		ProviderMessageID: providerID,
		Error:             errStr,
	})
	if err != nil {
		return err
	}

	logger.Info("invitation dispatched",
		"notification_id", id,
		"guest_id", evt.GuestID,
		"event_id", evt.EventID,
		"to", evt.GuestEmail,
		"status", status,
		"provider_message_id", providerID,
	)
	if sendErr != nil {
		return sendErr
	}
	return nil
}

func levelFor(env string) slog.Level {
	if env == "development" {
		return slog.LevelDebug
	}
	return slog.LevelInfo
}