add initial Last.FM tests (#329)

* Move model into separate file

* Separate Last.FM client and scrobbler

* Use separate Last.FM client and scrobbler

* Fix playcount attribute name

* Add initial test for Last.FM client

scrobble/lastfm/scrobbler.go

@@ -0,0 +1,67 @@
+package lastfm
+
+import (
+	"fmt"
+	"net/url"
+	"strconv"
+	"time"
+
+	"github.com/google/uuid"
+	"go.senan.xyz/gonic/db"
+	"go.senan.xyz/gonic/scrobble"
+)
+
+type Scrobbler struct {
+	db     *db.DB
+	client *Client
+}
+
+var _ scrobble.Scrobbler = (*Scrobbler)(nil)
+
+func NewScrobbler(db *db.DB, client *Client) *Scrobbler {
+	return &Scrobbler{
+		db:     db,
+		client: client,
+	}
+}
+
+func (s *Scrobbler) Scrobble(user *db.User, track *db.Track, stamp time.Time, submission bool) error {
+	if user.LastFMSession == "" {
+		return nil
+	}
+	apiKey, err := s.db.GetSetting("lastfm_api_key")
+	if err != nil {
+		return fmt.Errorf("get api key: %w", err)
+	}
+	secret, err := s.db.GetSetting("lastfm_secret")
+	if err != nil {
+		return fmt.Errorf("get secret: %w", err)
+	}
+
+	params := url.Values{}
+	if submission {
+		params.Add("method", "track.Scrobble")
+		// last.fm wants the timestamp in seconds
+		params.Add("timestamp", strconv.Itoa(int(stamp.Unix())))
+	} else {
+		params.Add("method", "track.updateNowPlaying")
+	}
+	params.Add("api_key", apiKey)
+	params.Add("sk", user.LastFMSession)
+	params.Add("artist", track.TagTrackArtist)
+	params.Add("track", track.TagTitle)
+	params.Add("trackNumber", strconv.Itoa(track.TagTrackNumber))
+	params.Add("album", track.Album.TagTitle)
+	params.Add("albumArtist", track.Artist.Name)
+	params.Add("duration", strconv.Itoa(track.Length))
+
+	// make sure we provide a valid uuid, since some users may have an incorrect mbid in their tags
+	if _, err := uuid.Parse(track.TagBrainzID); err == nil {
+		params.Add("mbid", track.TagBrainzID)
+	}
+
+	params.Add("api_sig", getParamSignature(params, secret))
+
+	_, err = s.client.makeRequest("POST", params)
+	return err
+}