lastfm: authentication

internal/backends/backends.go

@@ -27,6 +27,7 @@ import (
 	"go.uploadedlobster.com/scotty/internal/backends/dump"
 	"go.uploadedlobster.com/scotty/internal/backends/funkwhale"
 	"go.uploadedlobster.com/scotty/internal/backends/jspf"
+	"go.uploadedlobster.com/scotty/internal/backends/lastfm"
 	"go.uploadedlobster.com/scotty/internal/backends/listenbrainz"
 	"go.uploadedlobster.com/scotty/internal/backends/maloja"
 	"go.uploadedlobster.com/scotty/internal/backends/scrobblerlog"
@@ -80,6 +81,7 @@ var knownBackends = map[string]func() models.Backend{
 	"dump":          func() models.Backend { return &dump.DumpBackend{} },
 	"funkwhale":     func() models.Backend { return &funkwhale.FunkwhaleApiBackend{} },
 	"jspf":          func() models.Backend { return &jspf.JSPFBackend{} },
+	"lastfm":        func() models.Backend { return &lastfm.LastfmApiBackend{} },
 	"listenbrainz":  func() models.Backend { return &listenbrainz.ListenBrainzApiBackend{} },
 	"maloja":        func() models.Backend { return &maloja.MalojaApiBackend{} },
 	"scrobbler-log": func() models.Backend { return &scrobblerlog.ScrobblerLogBackend{} },

internal/backends/deezer/auth.go

@@ -33,8 +33,13 @@ func (s deezerStrategy) Config() oauth2.Config {
 	return s.conf
 }
 
-func (s deezerStrategy) AuthCodeURL(verifier string, state string) string {
-	return s.conf.AuthCodeURL(state, oauth2.AccessTypeOffline, oauth2.S256ChallengeOption(verifier))
+func (s deezerStrategy) AuthCodeURL(verifier string, state string) auth.AuthUrl {
+	url := s.conf.AuthCodeURL(state, oauth2.AccessTypeOffline, oauth2.S256ChallengeOption(verifier))
+	return auth.AuthUrl{
+		Url:   url,
+		State: state,
+		Param: "code",
+	}
 }
 
 func (s deezerStrategy) ExchangeToken(code auth.CodeResponse, verifier string) (*oauth2.Token, error) {

internal/backends/lastfm/auth.go

@@ -0,0 +1,51 @@
+/*
+Copyright © 2023 Philipp Wolfer <phw@uploadedlobster.com>
+
+Scotty is free software: you can redistribute it and/or modify it under the
+terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later version.
+
+Scotty is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+Scotty. If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package lastfm
+
+import (
+	"net/url"
+
+	"github.com/shkh/lastfm-go/lastfm"
+	"go.uploadedlobster.com/scotty/internal/auth"
+	"golang.org/x/oauth2"
+)
+
+type lastfmStrategy struct {
+	client      *lastfm.Api
+	redirectUrl *url.URL
+}
+
+func (s lastfmStrategy) Config() oauth2.Config {
+	return oauth2.Config{}
+}
+
+func (s lastfmStrategy) AuthCodeURL(verifier string, state string) auth.AuthUrl {
+	// Last.fm does not use OAuth2, but the provided authorization flow with
+	// callback URL is close enough we can shoehorn it into the existing
+	// authentication strategy.
+	// TODO: Investigate and use callback-less flow with api.GetAuthTokenUrl(token)
+	url := s.client.GetAuthRequestUrl(s.redirectUrl.String())
+	return auth.AuthUrl{
+		Url:   url,
+		State: "", // last.fm does not use state
+		Param: "token",
+	}
+}
+
+func (s lastfmStrategy) ExchangeToken(code auth.CodeResponse, verifier string) (*oauth2.Token, error) {
+	// The token is directly valid
+	return &oauth2.Token{AccessToken: code.Code}, nil
+}

internal/backends/lastfm/lastfm.go

@@ -0,0 +1,54 @@
+/*
+Copyright © 2023 Philipp Wolfer <phw@uploadedlobster.com>
+
+Scotty is free software: you can redistribute it and/or modify it under the
+terms of the GNU General Public License as published by the Free Software
+Foundation, either version 3 of the License, or (at your option) any later version.
+
+Scotty is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+Scotty. If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package lastfm
+
+import (
+	"net/url"
+
+	"github.com/shkh/lastfm-go/lastfm"
+	"github.com/spf13/viper"
+	"go.uploadedlobster.com/scotty/internal/auth"
+	"go.uploadedlobster.com/scotty/internal/models"
+	"golang.org/x/oauth2"
+)
+
+type LastfmApiBackend struct {
+	client *lastfm.Api
+}
+
+func (b *LastfmApiBackend) Name() string { return "lastfm" }
+
+func (b *LastfmApiBackend) FromConfig(config *viper.Viper) models.Backend {
+	clientId := config.GetString("client-id")
+	clientSecret := config.GetString("client-secret")
+	b.client = lastfm.New(clientId, clientSecret)
+	return b
+}
+
+func (b *LastfmApiBackend) OAuth2Strategy(redirectUrl *url.URL) auth.OAuth2Strategy {
+	return lastfmStrategy{
+		client:      b.client,
+		redirectUrl: redirectUrl,
+	}
+}
+
+func (b *LastfmApiBackend) OAuth2Setup(token oauth2.TokenSource) error {
+	t, err := token.Token()
+	if err != nil {
+		return err
+	}
+	return b.client.LoginWithToken(t.AccessToken)
+}