Move all Spotify and LastFM code into only one folder for each

core/agents/lastfm/client.go

@@ -0,0 +1,113 @@
+package lastfm
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"strconv"
+)
+
+const (
+	apiBaseUrl = "https://ws.audioscrobbler.com/2.0/"
+)
+
+type lastFMError struct {
+	Code    int
+	Message string
+}
+
+func (e *lastFMError) Error() string {
+	return fmt.Sprintf("last.fm error(%d): %s", e.Code, e.Message)
+}
+
+type httpDoer interface {
+	Do(req *http.Request) (*http.Response, error)
+}
+
+func NewClient(apiKey string, lang string, hc httpDoer) *Client {
+	return &Client{apiKey, lang, hc}
+}
+
+type Client struct {
+	apiKey string
+	lang   string
+	hc     httpDoer
+}
+
+func (c *Client) makeRequest(params url.Values) (*Response, error) {
+	params.Add("format", "json")
+	params.Add("api_key", c.apiKey)
+
+	req, _ := http.NewRequest("GET", apiBaseUrl, nil)
+	req.URL.RawQuery = params.Encode()
+
+	resp, err := c.hc.Do(req)
+	if err != nil {
+		return nil, err
+	}
+
+	defer resp.Body.Close()
+	data, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	var response Response
+	jsonErr := json.Unmarshal(data, &response)
+
+	if resp.StatusCode != 200 && jsonErr != nil {
+		return nil, fmt.Errorf("last.fm http status: (%d)", resp.StatusCode)
+	}
+
+	if jsonErr != nil {
+		return nil, jsonErr
+	}
+
+	if response.Error != 0 {
+		return &response, &lastFMError{Code: response.Error, Message: response.Message}
+	}
+
+	return &response, nil
+}
+
+func (c *Client) ArtistGetInfo(ctx context.Context, name string, mbid string) (*Artist, error) {
+	params := url.Values{}
+	params.Add("method", "artist.getInfo")
+	params.Add("artist", name)
+	params.Add("mbid", mbid)
+	params.Add("lang", c.lang)
+	response, err := c.makeRequest(params)
+	if err != nil {
+		return nil, err
+	}
+	return &response.Artist, nil
+}
+
+func (c *Client) ArtistGetSimilar(ctx context.Context, name string, mbid string, limit int) (*SimilarArtists, error) {
+	params := url.Values{}
+	params.Add("method", "artist.getSimilar")
+	params.Add("artist", name)
+	params.Add("mbid", mbid)
+	params.Add("limit", strconv.Itoa(limit))
+	response, err := c.makeRequest(params)
+	if err != nil {
+		return nil, err
+	}
+	return &response.SimilarArtists, nil
+}
+
+func (c *Client) ArtistGetTopTracks(ctx context.Context, name string, mbid string, limit int) (*TopTracks, error) {
+	params := url.Values{}
+	params.Add("method", "artist.getTopTracks")
+	params.Add("artist", name)
+	params.Add("mbid", mbid)
+	params.Add("limit", strconv.Itoa(limit))
+	response, err := c.makeRequest(params)
+	if err != nil {
+		return nil, err
+	}
+	return &response.TopTracks, nil
+}

core/agents/lastfm/client_test.go

@@ -0,0 +1,108 @@
+package lastfm
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"io/ioutil"
+	"net/http"
+	"os"
+
+	"github.com/navidrome/navidrome/tests"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Client", func() {
+	var httpClient *tests.FakeHttpClient
+	var client *Client
+
+	BeforeEach(func() {
+		httpClient = &tests.FakeHttpClient{}
+		client = NewClient("API_KEY", "pt", httpClient)
+	})
+
+	Describe("ArtistGetInfo", func() {
+		It("returns an artist for a successful response", func() {
+			f, _ := os.Open("tests/fixtures/lastfm.artist.getinfo.json")
+			httpClient.Res = http.Response{Body: f, StatusCode: 200}
+
+			artist, err := client.ArtistGetInfo(context.TODO(), "U2", "123")
+			Expect(err).To(BeNil())
+			Expect(artist.Name).To(Equal("U2"))
+			Expect(httpClient.SavedRequest.URL.String()).To(Equal(apiBaseUrl + "?api_key=API_KEY&artist=U2&format=json&lang=pt&mbid=123&method=artist.getInfo"))
+		})
+
+		It("fails if Last.FM returns an http status != 200", func() {
+			httpClient.Res = http.Response{
+				Body:       ioutil.NopCloser(bytes.NewBufferString(`Internal Server Error`)),
+				StatusCode: 500,
+			}
+
+			_, err := client.ArtistGetInfo(context.TODO(), "U2", "123")
+			Expect(err).To(MatchError("last.fm http status: (500)"))
+		})
+
+		It("fails if Last.FM returns an http status != 200", func() {
+			httpClient.Res = http.Response{
+				Body:       ioutil.NopCloser(bytes.NewBufferString(`{"error":3,"message":"Invalid Method - No method with that name in this package"}`)),
+				StatusCode: 400,
+			}
+
+			_, err := client.ArtistGetInfo(context.TODO(), "U2", "123")
+			Expect(err).To(MatchError(&lastFMError{Code: 3, Message: "Invalid Method - No method with that name in this package"}))
+		})
+
+		It("fails if Last.FM returns an error", func() {
+			httpClient.Res = http.Response{
+				Body:       ioutil.NopCloser(bytes.NewBufferString(`{"error":6,"message":"The artist you supplied could not be found"}`)),
+				StatusCode: 200,
+			}
+
+			_, err := client.ArtistGetInfo(context.TODO(), "U2", "123")
+			Expect(err).To(MatchError(&lastFMError{Code: 6, Message: "The artist you supplied could not be found"}))
+		})
+
+		It("fails if HttpClient.Do() returns error", func() {
+			httpClient.Err = errors.New("generic error")
+
+			_, err := client.ArtistGetInfo(context.TODO(), "U2", "123")
+			Expect(err).To(MatchError("generic error"))
+		})
+
+		It("fails if returned body is not a valid JSON", func() {
+			httpClient.Res = http.Response{
+				Body:       ioutil.NopCloser(bytes.NewBufferString(`<xml>NOT_VALID_JSON</xml>`)),
+				StatusCode: 200,
+			}
+
+			_, err := client.ArtistGetInfo(context.TODO(), "U2", "123")
+			Expect(err).To(MatchError("invalid character '<' looking for beginning of value"))
+		})
+
+	})
+
+	Describe("ArtistGetSimilar", func() {
+		It("returns an artist for a successful response", func() {
+			f, _ := os.Open("tests/fixtures/lastfm.artist.getsimilar.json")
+			httpClient.Res = http.Response{Body: f, StatusCode: 200}
+
+			similar, err := client.ArtistGetSimilar(context.TODO(), "U2", "123", 2)
+			Expect(err).To(BeNil())
+			Expect(len(similar.Artists)).To(Equal(2))
+			Expect(httpClient.SavedRequest.URL.String()).To(Equal(apiBaseUrl + "?api_key=API_KEY&artist=U2&format=json&limit=2&mbid=123&method=artist.getSimilar"))
+		})
+	})
+
+	Describe("ArtistGetTopTracks", func() {
+		It("returns top tracks for a successful response", func() {
+			f, _ := os.Open("tests/fixtures/lastfm.artist.gettoptracks.json")
+			httpClient.Res = http.Response{Body: f, StatusCode: 200}
+
+			top, err := client.ArtistGetTopTracks(context.TODO(), "U2", "123", 2)
+			Expect(err).To(BeNil())
+			Expect(len(top.Track)).To(Equal(2))
+			Expect(httpClient.SavedRequest.URL.String()).To(Equal(apiBaseUrl + "?api_key=API_KEY&artist=U2&format=json&limit=2&mbid=123&method=artist.getTopTracks"))
+		})
+	})
+})

core/agents/lastfm/lastfm.go

@@ -0,0 +1,164 @@
+package lastfm
+
+import (
+	"context"
+	"net/http"
+
+	"github.com/navidrome/navidrome/conf"
+	"github.com/navidrome/navidrome/consts"
+	"github.com/navidrome/navidrome/core/agents"
+	"github.com/navidrome/navidrome/log"
+	"github.com/navidrome/navidrome/utils"
+)
+
+const (
+	lastFMAgentName = "lastfm"
+	lastFMAPIKey    = "c2918986bf01b6ba353c0bc1bdd27bea"
+	//lastFMAPISecret = "3ff2aa214a6d8f2242515083bbb70e79" // Will be needed when implementing Scrobbling
+)
+
+type lastfmAgent struct {
+	ctx    context.Context
+	apiKey string
+	lang   string
+	client *Client
+}
+
+func lastFMConstructor(ctx context.Context) agents.Interface {
+	l := &lastfmAgent{
+		ctx:  ctx,
+		lang: conf.Server.LastFM.Language,
+	}
+	if conf.Server.LastFM.ApiKey != "" {
+		l.apiKey = conf.Server.LastFM.ApiKey
+	} else {
+		l.apiKey = lastFMAPIKey
+	}
+	hc := utils.NewCachedHTTPClient(http.DefaultClient, consts.DefaultCachedHttpClientTTL)
+	l.client = NewClient(l.apiKey, l.lang, hc)
+	return l
+}
+
+func (l *lastfmAgent) AgentName() string {
+	return lastFMAgentName
+}
+
+func (l *lastfmAgent) GetMBID(id string, name string) (string, error) {
+	a, err := l.callArtistGetInfo(name, "")
+	if err != nil {
+		return "", err
+	}
+	if a.MBID == "" {
+		return "", agents.ErrNotFound
+	}
+	return a.MBID, nil
+}
+
+func (l *lastfmAgent) GetURL(id, name, mbid string) (string, error) {
+	a, err := l.callArtistGetInfo(name, mbid)
+	if err != nil {
+		return "", err
+	}
+	if a.URL == "" {
+		return "", agents.ErrNotFound
+	}
+	return a.URL, nil
+}
+
+func (l *lastfmAgent) GetBiography(id, name, mbid string) (string, error) {
+	a, err := l.callArtistGetInfo(name, mbid)
+	if err != nil {
+		return "", err
+	}
+	if a.Bio.Summary == "" {
+		return "", agents.ErrNotFound
+	}
+	return a.Bio.Summary, nil
+}
+
+func (l *lastfmAgent) GetSimilar(id, name, mbid string, limit int) ([]agents.Artist, error) {
+	resp, err := l.callArtistGetSimilar(name, mbid, limit)
+	if err != nil {
+		return nil, err
+	}
+	if len(resp) == 0 {
+		return nil, agents.ErrNotFound
+	}
+	var res []agents.Artist
+	for _, a := range resp {
+		res = append(res, agents.Artist{
+			Name: a.Name,
+			MBID: a.MBID,
+		})
+	}
+	return res, nil
+}
+
+func (l *lastfmAgent) GetTopSongs(id, artistName, mbid string, count int) ([]agents.Song, error) {
+	resp, err := l.callArtistGetTopTracks(artistName, mbid, count)
+	if err != nil {
+		return nil, err
+	}
+	if len(resp) == 0 {
+		return nil, agents.ErrNotFound
+	}
+	var res []agents.Song
+	for _, t := range resp {
+		res = append(res, agents.Song{
+			Name: t.Name,
+			MBID: t.MBID,
+		})
+	}
+	return res, nil
+}
+
+func (l *lastfmAgent) callArtistGetInfo(name string, mbid string) (*Artist, error) {
+	a, err := l.client.ArtistGetInfo(l.ctx, name, mbid)
+	lfErr, isLastFMError := err.(*lastFMError)
+	if mbid != "" && ((err == nil && a.Name == "[unknown]") || (isLastFMError && lfErr.Code == 6)) {
+		log.Warn(l.ctx, "LastFM/artist.getInfo could not find artist by mbid, trying again", "artist", name, "mbid", mbid)
+		return l.callArtistGetInfo(name, "")
+	}
+
+	if err != nil {
+		log.Error(l.ctx, "Error calling LastFM/artist.getInfo", "artist", name, "mbid", mbid, err)
+		return nil, err
+	}
+	return a, nil
+}
+
+func (l *lastfmAgent) callArtistGetSimilar(name string, mbid string, limit int) ([]Artist, error) {
+	s, err := l.client.ArtistGetSimilar(l.ctx, name, mbid, limit)
+	lfErr, isLastFMError := err.(*lastFMError)
+	if mbid != "" && ((err == nil && s.Attr.Artist == "[unknown]") || (isLastFMError && lfErr.Code == 6)) {
+		log.Warn(l.ctx, "LastFM/artist.getSimilar could not find artist by mbid, trying again", "artist", name, "mbid", mbid)
+		return l.callArtistGetSimilar(name, "", limit)
+	}
+	if err != nil {
+		log.Error(l.ctx, "Error calling LastFM/artist.getSimilar", "artist", name, "mbid", mbid, err)
+		return nil, err
+	}
+	return s.Artists, nil
+}
+
+func (l *lastfmAgent) callArtistGetTopTracks(artistName, mbid string, count int) ([]Track, error) {
+	t, err := l.client.ArtistGetTopTracks(l.ctx, artistName, mbid, count)
+	lfErr, isLastFMError := err.(*lastFMError)
+	if mbid != "" && ((err == nil && t.Attr.Artist == "[unknown]") || (isLastFMError && lfErr.Code == 6)) {
+		log.Warn(l.ctx, "LastFM/artist.getTopTracks could not find artist by mbid, trying again", "artist", artistName, "mbid", mbid)
+		return l.callArtistGetTopTracks(artistName, "", count)
+	}
+	if err != nil {
+		log.Error(l.ctx, "Error calling LastFM/artist.getTopTracks", "artist", artistName, "mbid", mbid, err)
+		return nil, err
+	}
+	return t.Track, nil
+}
+
+func init() {
+	conf.AddHook(func() {
+		if conf.Server.LastFM.Enabled {
+			agents.Register(lastFMAgentName, lastFMConstructor)
+		}
+	})
+}

core/agents/lastfm/lastfm_suite_test.go

@@ -0,0 +1,17 @@
+package lastfm
+
+import (
+	"testing"
+
+	"github.com/navidrome/navidrome/log"
+	"github.com/navidrome/navidrome/tests"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+func TestLastFM(t *testing.T) {
+	tests.Init(t, false)
+	log.SetLevel(log.LevelCritical)
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "LastFM Test Suite")
+}

core/agents/lastfm/lastfm_test.go

@@ -0,0 +1,220 @@
+package lastfm
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"io/ioutil"
+	"net/http"
+	"os"
+
+	"github.com/navidrome/navidrome/conf"
+	"github.com/navidrome/navidrome/core/agents"
+	"github.com/navidrome/navidrome/tests"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+const (
+	lastfmError3 = `{"error":3,"message":"Invalid Method - No method with that name in this package","links":[]}`
+	lastfmError6 = `{"error":6,"message":"The artist you supplied could not be found","links":[]}`
+)
+
+var _ = Describe("lastfmAgent", func() {
+	Describe("lastFMConstructor", func() {
+		It("uses default api key and language if not configured", func() {
+			conf.Server.LastFM.ApiKey = ""
+			agent := lastFMConstructor(context.TODO())
+			Expect(agent.(*lastfmAgent).apiKey).To(Equal(lastFMAPIKey))
+			Expect(agent.(*lastfmAgent).lang).To(Equal("en"))
+		})
+
+		It("uses configured api key and language", func() {
+			conf.Server.LastFM.ApiKey = "123"
+			conf.Server.LastFM.Language = "pt"
+			agent := lastFMConstructor(context.TODO())
+			Expect(agent.(*lastfmAgent).apiKey).To(Equal("123"))
+			Expect(agent.(*lastfmAgent).lang).To(Equal("pt"))
+		})
+	})
+
+	Describe("GetBiography", func() {
+		var agent *lastfmAgent
+		var httpClient *tests.FakeHttpClient
+		BeforeEach(func() {
+			httpClient = &tests.FakeHttpClient{}
+			client := NewClient("API_KEY", "pt", httpClient)
+			agent = lastFMConstructor(context.TODO()).(*lastfmAgent)
+			agent.client = client
+		})
+
+		It("returns the biography", func() {
+			f, _ := os.Open("tests/fixtures/lastfm.artist.getinfo.json")
+			httpClient.Res = http.Response{Body: f, StatusCode: 200}
+			Expect(agent.GetBiography("123", "U2", "mbid-1234")).To(Equal("U2 é uma das mais importantes bandas de rock de todos os tempos. Formada em 1976 em Dublin, composta por Bono (vocalista  e guitarrista), The Edge (guitarrista, pianista e backing vocal), Adam Clayton (baixista), Larry Mullen, Jr. (baterista e percussionista).\n\nDesde a década de 80, U2 é uma das bandas mais populares no mundo. Seus shows são únicos e um verdadeiro festival de efeitos especiais, além de serem um dos que mais arrecadam anualmente. <a href=\"https://www.last.fm/music/U2\">Read more on Last.fm</a>"))
+			Expect(httpClient.RequestCount).To(Equal(1))
+			Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(Equal("mbid-1234"))
+		})
+
+		It("returns an error if Last.FM call fails", func() {
+			httpClient.Err = errors.New("error")
+			_, err := agent.GetBiography("123", "U2", "mbid-1234")
+			Expect(err).To(HaveOccurred())
+			Expect(httpClient.RequestCount).To(Equal(1))
+			Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(Equal("mbid-1234"))
+		})
+
+		It("returns an error if Last.FM call returns an error", func() {
+			httpClient.Res = http.Response{Body: ioutil.NopCloser(bytes.NewBufferString(lastfmError3)), StatusCode: 200}
+			_, err := agent.GetBiography("123", "U2", "mbid-1234")
+			Expect(err).To(HaveOccurred())
+			Expect(httpClient.RequestCount).To(Equal(1))
+			Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(Equal("mbid-1234"))
+		})
+
+		It("returns an error if Last.FM call returns an error 6 and mbid is empty", func() {
+			httpClient.Res = http.Response{Body: ioutil.NopCloser(bytes.NewBufferString(lastfmError6)), StatusCode: 200}
+			_, err := agent.GetBiography("123", "U2", "")
+			Expect(err).To(HaveOccurred())
+			Expect(httpClient.RequestCount).To(Equal(1))
+		})
+
+		Context("MBID non existent in Last.FM", func() {
+			It("calls again when the response is artist == [unknown]", func() {
+				f, _ := os.Open("tests/fixtures/lastfm.artist.getinfo.unknown.json")
+				httpClient.Res = http.Response{Body: f, StatusCode: 200}
+				_, _ = agent.GetBiography("123", "U2", "mbid-1234")
+				Expect(httpClient.RequestCount).To(Equal(2))
+				Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(BeEmpty())
+			})
+			It("calls again when last.fm returns an error 6", func() {
+				httpClient.Res = http.Response{Body: ioutil.NopCloser(bytes.NewBufferString(lastfmError6)), StatusCode: 200}
+				_, _ = agent.GetBiography("123", "U2", "mbid-1234")
+				Expect(httpClient.RequestCount).To(Equal(2))
+				Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(BeEmpty())
+			})
+		})
+	})
+
+	Describe("GetSimilar", func() {
+		var agent *lastfmAgent
+		var httpClient *tests.FakeHttpClient
+		BeforeEach(func() {
+			httpClient = &tests.FakeHttpClient{}
+			client := NewClient("API_KEY", "pt", httpClient)
+			agent = lastFMConstructor(context.TODO()).(*lastfmAgent)
+			agent.client = client
+		})
+
+		It("returns similar artists", func() {
+			f, _ := os.Open("tests/fixtures/lastfm.artist.getsimilar.json")
+			httpClient.Res = http.Response{Body: f, StatusCode: 200}
+			Expect(agent.GetSimilar("123", "U2", "mbid-1234", 2)).To(Equal([]agents.Artist{
+				{Name: "Passengers", MBID: "e110c11f-1c94-4471-a350-c38f46b29389"},
+				{Name: "INXS", MBID: "481bf5f9-2e7c-4c44-b08a-05b32bc7c00d"},
+			}))
+			Expect(httpClient.RequestCount).To(Equal(1))
+			Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(Equal("mbid-1234"))
+		})
+
+		It("returns an error if Last.FM call fails", func() {
+			httpClient.Err = errors.New("error")
+			_, err := agent.GetSimilar("123", "U2", "mbid-1234", 2)
+			Expect(err).To(HaveOccurred())
+			Expect(httpClient.RequestCount).To(Equal(1))
+			Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(Equal("mbid-1234"))
+		})
+
+		It("returns an error if Last.FM call returns an error", func() {
+			httpClient.Res = http.Response{Body: ioutil.NopCloser(bytes.NewBufferString(lastfmError3)), StatusCode: 200}
+			_, err := agent.GetSimilar("123", "U2", "mbid-1234", 2)
+			Expect(err).To(HaveOccurred())
+			Expect(httpClient.RequestCount).To(Equal(1))
+			Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(Equal("mbid-1234"))
+		})
+
+		It("returns an error if Last.FM call returns an error 6 and mbid is empty", func() {
+			httpClient.Res = http.Response{Body: ioutil.NopCloser(bytes.NewBufferString(lastfmError6)), StatusCode: 200}
+			_, err := agent.GetSimilar("123", "U2", "", 2)
+			Expect(err).To(HaveOccurred())
+			Expect(httpClient.RequestCount).To(Equal(1))
+		})
+
+		Context("MBID non existent in Last.FM", func() {
+			It("calls again when the response is artist == [unknown]", func() {
+				f, _ := os.Open("tests/fixtures/lastfm.artist.getsimilar.unknown.json")
+				httpClient.Res = http.Response{Body: f, StatusCode: 200}
+				_, _ = agent.GetSimilar("123", "U2", "mbid-1234", 2)
+				Expect(httpClient.RequestCount).To(Equal(2))
+				Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(BeEmpty())
+			})
+			It("calls again when last.fm returns an error 6", func() {
+				httpClient.Res = http.Response{Body: ioutil.NopCloser(bytes.NewBufferString(lastfmError6)), StatusCode: 200}
+				_, _ = agent.GetSimilar("123", "U2", "mbid-1234", 2)
+				Expect(httpClient.RequestCount).To(Equal(2))
+				Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(BeEmpty())
+			})
+		})
+	})
+
+	Describe("GetTopSongs", func() {
+		var agent *lastfmAgent
+		var httpClient *tests.FakeHttpClient
+		BeforeEach(func() {
+			httpClient = &tests.FakeHttpClient{}
+			client := NewClient("API_KEY", "pt", httpClient)
+			agent = lastFMConstructor(context.TODO()).(*lastfmAgent)
+			agent.client = client
+		})
+
+		It("returns top songs", func() {
+			f, _ := os.Open("tests/fixtures/lastfm.artist.gettoptracks.json")
+			httpClient.Res = http.Response{Body: f, StatusCode: 200}
+			Expect(agent.GetTopSongs("123", "U2", "mbid-1234", 2)).To(Equal([]agents.Song{
+				{Name: "Beautiful Day", MBID: "f7f264d0-a89b-4682-9cd7-a4e7c37637af"},
+				{Name: "With or Without You", MBID: "6b9a509f-6907-4a6e-9345-2f12da09ba4b"},
+			}))
+			Expect(httpClient.RequestCount).To(Equal(1))
+			Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(Equal("mbid-1234"))
+		})
+
+		It("returns an error if Last.FM call fails", func() {
+			httpClient.Err = errors.New("error")
+			_, err := agent.GetTopSongs("123", "U2", "mbid-1234", 2)
+			Expect(err).To(HaveOccurred())
+			Expect(httpClient.RequestCount).To(Equal(1))
+			Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(Equal("mbid-1234"))
+		})
+
+		It("returns an error if Last.FM call returns an error", func() {
+			httpClient.Res = http.Response{Body: ioutil.NopCloser(bytes.NewBufferString(lastfmError3)), StatusCode: 200}
+			_, err := agent.GetTopSongs("123", "U2", "mbid-1234", 2)
+			Expect(err).To(HaveOccurred())
+			Expect(httpClient.RequestCount).To(Equal(1))
+			Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(Equal("mbid-1234"))
+		})
+
+		It("returns an error if Last.FM call returns an error 6 and mbid is empty", func() {
+			httpClient.Res = http.Response{Body: ioutil.NopCloser(bytes.NewBufferString(lastfmError6)), StatusCode: 200}
+			_, err := agent.GetTopSongs("123", "U2", "", 2)
+			Expect(err).To(HaveOccurred())
+			Expect(httpClient.RequestCount).To(Equal(1))
+		})
+
+		Context("MBID non existent in Last.FM", func() {
+			It("calls again when the response is artist == [unknown]", func() {
+				f, _ := os.Open("tests/fixtures/lastfm.artist.gettoptracks.unknown.json")
+				httpClient.Res = http.Response{Body: f, StatusCode: 200}
+				_, _ = agent.GetTopSongs("123", "U2", "mbid-1234", 2)
+				Expect(httpClient.RequestCount).To(Equal(2))
+				Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(BeEmpty())
+			})
+			It("calls again when last.fm returns an error 6", func() {
+				httpClient.Res = http.Response{Body: ioutil.NopCloser(bytes.NewBufferString(lastfmError6)), StatusCode: 200}
+				_, _ = agent.GetTopSongs("123", "U2", "mbid-1234", 2)
+				Expect(httpClient.RequestCount).To(Equal(2))
+				Expect(httpClient.SavedRequest.URL.Query().Get("mbid")).To(BeEmpty())
+			})
+		})
+	})
+})

core/agents/lastfm/responses.go

@@ -0,0 +1,61 @@
+package lastfm
+
+type Response struct {
+	Artist         Artist         `json:"artist"`
+	SimilarArtists SimilarArtists `json:"similarartists"`
+	TopTracks      TopTracks      `json:"toptracks"`
+	Error          int            `json:"error"`
+	Message        string         `json:"message"`
+}
+
+type Artist struct {
+	Name       string        `json:"name"`
+	MBID       string        `json:"mbid"`
+	URL        string        `json:"url"`
+	Image      []ArtistImage `json:"image"`
+	Streamable string        `json:"streamable"`
+	Stats      struct {
+		Listeners string `json:"listeners"`
+		Plays     string `json:"plays"`
+	} `json:"stats"`
+	Similar SimilarArtists `json:"similar"`
+	Tags    struct {
+		Tag []ArtistTag `json:"tag"`
+	} `json:"tags"`
+	Bio ArtistBio `json:"bio"`
+}
+
+type SimilarArtists struct {
+	Artists []Artist `json:"artist"`
+	Attr    Attr     `json:"@attr"`
+}
+
+type Attr struct {
+	Artist string `json:"artist"`
+}
+
+type ArtistImage struct {
+	URL  string `json:"#text"`
+	Size string `json:"size"`
+}
+
+type ArtistTag struct {
+	Name string `json:"name"`
+	URL  string `json:"url"`
+}
+
+type ArtistBio struct {
+	Published string `json:"published"`
+	Summary   string `json:"summary"`
+	Content   string `json:"content"`
+}
+
+type Track struct {
+	Name string `json:"name"`
+	MBID string `json:"mbid"`
+}
+
+type TopTracks struct {
+	Track []Track `json:"track"`
+	Attr  Attr    `json:"@attr"`
+}

core/agents/lastfm/responses_test.go

@@ -0,0 +1,70 @@
+package lastfm
+
+import (
+	"encoding/json"
+	"io/ioutil"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("LastFM responses", func() {
+	Describe("Artist", func() {
+		It("parses the response correctly", func() {
+			var resp Response
+			body, _ := ioutil.ReadFile("tests/fixtures/lastfm.artist.getinfo.json")
+			err := json.Unmarshal(body, &resp)
+			Expect(err).To(BeNil())
+
+			Expect(resp.Artist.Name).To(Equal("U2"))
+			Expect(resp.Artist.MBID).To(Equal("a3cb23fc-acd3-4ce0-8f36-1e5aa6a18432"))
+			Expect(resp.Artist.URL).To(Equal("https://www.last.fm/music/U2"))
+			Expect(resp.Artist.Bio.Summary).To(ContainSubstring("U2 é uma das mais importantes bandas de rock de todos os tempos"))
+
+			similarArtists := []string{"Passengers", "INXS", "R.E.M.", "Simple Minds", "Bono"}
+			for i, similar := range similarArtists {
+				Expect(resp.Artist.Similar.Artists[i].Name).To(Equal(similar))
+			}
+		})
+	})
+
+	Describe("SimilarArtists", func() {
+		It("parses the response correctly", func() {
+			var resp Response
+			body, _ := ioutil.ReadFile("tests/fixtures/lastfm.artist.getsimilar.json")
+			err := json.Unmarshal(body, &resp)
+			Expect(err).To(BeNil())
+
+			Expect(resp.SimilarArtists.Artists).To(HaveLen(2))
+			Expect(resp.SimilarArtists.Artists[0].Name).To(Equal("Passengers"))
+			Expect(resp.SimilarArtists.Artists[1].Name).To(Equal("INXS"))
+		})
+	})
+
+	Describe("TopTracks", func() {
+		It("parses the response correctly", func() {
+			var resp Response
+			body, _ := ioutil.ReadFile("tests/fixtures/lastfm.artist.gettoptracks.json")
+			err := json.Unmarshal(body, &resp)
+			Expect(err).To(BeNil())
+
+			Expect(resp.TopTracks.Track).To(HaveLen(2))
+			Expect(resp.TopTracks.Track[0].Name).To(Equal("Beautiful Day"))
+			Expect(resp.TopTracks.Track[0].MBID).To(Equal("f7f264d0-a89b-4682-9cd7-a4e7c37637af"))
+			Expect(resp.TopTracks.Track[1].Name).To(Equal("With or Without You"))
+			Expect(resp.TopTracks.Track[1].MBID).To(Equal("6b9a509f-6907-4a6e-9345-2f12da09ba4b"))
+		})
+	})
+
+	Describe("Error", func() {
+		It("parses the error response correctly", func() {
+			var error Response
+			body := []byte(`{"error":3,"message":"Invalid Method - No method with that name in this package"}`)
+			err := json.Unmarshal(body, &error)
+			Expect(err).To(BeNil())
+
+			Expect(error.Error).To(Equal(3))
+			Expect(error.Message).To(Equal("Invalid Method - No method with that name in this package"))
+		})
+	})
+})