memby/server/internal/api/radarr_alerts.go

package api

import (
	"crypto/subtle"
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
	"time"
)

// Radarr's import notification arrives as a webhook, which is why this is the one part
// of the gateway something else pushes to. Polling the calendar could only ever notice
// an import a minute or two late and only for titles inside the five-day window;
// "a movie just landed" is an event, so it is delivered as one. The alert itself goes
// into the shared store in alerts.go, like every other event.

// radarrWebhookPayload is the subset of Radarr's webhook body Memby reads. Radarr sends
// considerably more; anything not named here is ignored on purpose, so a Radarr upgrade
// that adds fields cannot break the hook.
type radarrWebhookPayload struct {
	EventType string `json:"eventType"`
	IsUpgrade bool   `json:"isUpgrade"`
	Movie     struct {
		ID     int    `json:"id"`
		Title  string `json:"title"`
		Year   int    `json:"year"`
		TMDBID int    `json:"tmdbId"`
	} `json:"movie"`
	MovieFile struct {
		ID      int    `json:"id"`
		Quality string `json:"quality"`
	} `json:"movieFile"`
}

// handleRadarrWebhook accepts Radarr's "On Import" notification.
//
// It sits outside both the auth middleware (Radarr has no Memby session) and the
// maintenance gate (an event dropped while maintenance is on is lost for good, and
// recording one costs nothing while the client API is off).
func (s *Server) handleRadarrWebhook(w http.ResponseWriter, r *http.Request) {
	// Unconfigured means absent, the same stance /admin takes: a deployment that never
	// set a token must not expose an endpoint that writes to what every TV displays.
	if s.cfg.RadarrWebhookToken == "" {
		http.NotFound(w, r)
		return
	}
	if subtle.ConstantTimeCompare(
		[]byte(webhookToken(r)), []byte(s.cfg.RadarrWebhookToken),
	) != 1 {
		writeError(w, http.StatusUnauthorized, "invalid webhook token")
		return
	}

	var payload radarrWebhookPayload
	if err := json.NewDecoder(http.MaxBytesReader(w, r.Body, 1<<20)).Decode(&payload); err != nil {
		writeError(w, http.StatusBadRequest, "invalid webhook payload")
		return
	}

	// Radarr's "Test" button posts a stub payload. Answering 200 without announcing a
	// film that does not exist is what makes the test button mean "reachable".
	if strings.EqualFold(payload.EventType, "Test") {
		s.loggerFor(r.Context()).Info("radarr webhook test received")
		writeJSON(w, http.StatusOK, map[string]any{"ok": true, "test": true})
		return
	}

	alert, ok := radarrImportAlert(payload, time.Now().UTC())
	if !ok {
		// A grab, a rename, a health check or an upgrade of something already in the
		// library: all real events, none of them "a new film is here".
		writeJSON(w, http.StatusOK, map[string]any{"ok": true, "announced": false})
		return
	}
	if s.cfg.RadarrAlertWindow <= 0 {
		writeJSON(w, http.StatusOK, map[string]any{"ok": true, "announced": false})
		return
	}

	s.publishAlert(r.Context(), alert, s.cfg.RadarrAlertWindow)
	s.loggerFor(r.Context()).Info("radarr import announced",
		"movie", alert.Title, "alert_id", alert.ID, "quality", payload.MovieFile.Quality)
	writeJSON(w, http.StatusOK, map[string]any{"ok": true, "announced": true})
}

// webhookToken accepts the shared secret three ways because Radarr's webhook settings
// differ by version: a header where custom headers exist, basic auth where they do not,
// and a query parameter as the form that always works.
func webhookToken(r *http.Request) string {
	if token := strings.TrimSpace(r.Header.Get("X-Memby-Token")); token != "" {
		return token
	}
	if token := bearerToken(r); token != "" {
		return token
	}
	if _, password, ok := r.BasicAuth(); ok && password != "" {
		return password
	}
	return strings.TrimSpace(r.URL.Query().Get("token"))
}

// radarrImportAlert turns an import notification into the banner a TV shows, or reports
// that this event is not worth announcing.
//
// An upgrade is deliberately silent: the film was already there, and "new movie added"
// would be a lie about a file that was replaced with a better copy.
func radarrImportAlert(payload radarrWebhookPayload, now time.Time) (clientAlert, bool) {
	if !isRadarrImportEvent(payload.EventType) || payload.IsUpgrade {
		return clientAlert{}, false
	}
	title := strings.TrimSpace(payload.Movie.Title)
	if title == "" || payload.Movie.ID <= 0 {
		return clientAlert{}, false
	}

	// Keyed on the file, so a title deleted and re-imported is news again while a
	// repeated delivery of the same import is not. Clients dedupe on this id forever.
	id := fmt.Sprintf("radarr:%d:file:%d", payload.Movie.ID, payload.MovieFile.ID)
	if payload.MovieFile.ID <= 0 {
		id = fmt.Sprintf("radarr:%d:imported:%d", payload.Movie.ID, now.Unix())
	}

	name := title
	if payload.Movie.Year > 0 {
		name = fmt.Sprintf("%s (%d)", title, payload.Movie.Year)
	}
	return clientAlert{
		ID:      id,
		Kind:    alertKindRadarrImport,
		Label:   "NEW MOVIE ADDED",
		Title:   name,
		Message: fmt.Sprintf("%s will be available in Emby shortly.", title),
		// The image proxy already serves Radarr covers under this id and tag, so the
		// banner shows the poster before Emby has finished scanning the film in.
		ItemID:   fmt.Sprintf("radarr:%d", payload.Movie.ID),
		ImageTag: "radarr",
		AiredAt:  now.UTC().Format(time.RFC3339),
	}, true
}

// isRadarrImportEvent matches the event Radarr fires once a downloaded file has been
// imported into the library. The name has moved between versions, so both are accepted.
func isRadarrImportEvent(eventType string) bool {
	switch strings.ToLower(strings.TrimSpace(eventType)) {
	case "download", "moviefileimported":
		return true
	default:
		return false
	}
}