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/client.go

@@ -0,0 +1,168 @@
+package lastfm
+
+import (
+	"crypto/md5"
+	"encoding/hex"
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"log"
+	"net/http"
+	"net/http/httputil"
+	"net/url"
+	"sort"
+
+	"github.com/andybalholm/cascadia"
+	"golang.org/x/net/html"
+)
+
+const (
+	baseURL = "https://ws.audioscrobbler.com/2.0/"
+)
+
+var (
+	ErrLastFM = errors.New("last.fm error")
+
+	//nolint:gochecknoglobals
+	artistOpenGraphQuery = cascadia.MustCompile(`html > head > meta[property="og:image"]`)
+)
+
+type Client struct {
+	httpClient *http.Client
+}
+
+func NewClient() *Client {
+	return &Client{
+		httpClient: http.DefaultClient,
+	}
+}
+
+func getParamSignature(params url.Values, secret string) string {
+	// the parameters must be in order before hashing
+	paramKeys := make([]string, 0, len(params))
+	for k := range params {
+		paramKeys = append(paramKeys, k)
+	}
+	sort.Strings(paramKeys)
+	toHash := ""
+	for _, k := range paramKeys {
+		toHash += k
+		toHash += params[k][0]
+	}
+	toHash += secret
+	hash := md5.Sum([]byte(toHash))
+	return hex.EncodeToString(hash[:])
+}
+
+func (c *Client) makeRequest(method string, params url.Values) (LastFM, error) {
+	req, _ := http.NewRequest(method, baseURL, nil)
+	req.URL.RawQuery = params.Encode()
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return LastFM{}, fmt.Errorf("get: %w", err)
+	}
+	defer resp.Body.Close()
+	decoder := xml.NewDecoder(resp.Body)
+	lastfm := LastFM{}
+	if err = decoder.Decode(&lastfm); err != nil {
+		respBytes, _ := httputil.DumpResponse(resp, true)
+		log.Printf("received bad lastfm response:\n%s", string(respBytes))
+		return LastFM{}, fmt.Errorf("decoding: %w", err)
+	}
+	if lastfm.Error.Code != 0 {
+		respBytes, _ := httputil.DumpResponse(resp, true)
+		log.Printf("received bad lastfm response:\n%s", string(respBytes))
+		return LastFM{}, fmt.Errorf("%v: %w", lastfm.Error.Value, ErrLastFM)
+	}
+	return lastfm, nil
+}
+
+func (c *Client) ArtistGetInfo(apiKey string, artistName string) (Artist, error) {
+	params := url.Values{}
+	params.Add("method", "artist.getInfo")
+	params.Add("api_key", apiKey)
+	params.Add("artist", artistName)
+	resp, err := c.makeRequest("GET", params)
+	if err != nil {
+		return Artist{}, fmt.Errorf("making artist GET: %w", err)
+	}
+	return resp.Artist, nil
+}
+
+func (c *Client) ArtistGetTopTracks(apiKey, artistName string) (TopTracks, error) {
+	params := url.Values{}
+	params.Add("method", "artist.getTopTracks")
+	params.Add("api_key", apiKey)
+	params.Add("artist", artistName)
+	resp, err := c.makeRequest("GET", params)
+	if err != nil {
+		return TopTracks{}, fmt.Errorf("making track GET: %w", err)
+	}
+	return resp.TopTracks, nil
+}
+
+func (c *Client) TrackGetSimilarTracks(apiKey string, artistName, trackName string) (SimilarTracks, error) {
+	params := url.Values{}
+	params.Add("method", "track.getSimilar")
+	params.Add("api_key", apiKey)
+	params.Add("track", trackName)
+	params.Add("artist", artistName)
+	resp, err := c.makeRequest("GET", params)
+	if err != nil {
+		return SimilarTracks{}, fmt.Errorf("making track GET: %w", err)
+	}
+	return resp.SimilarTracks, nil
+}
+
+func (c *Client) ArtistGetSimilar(apiKey string, artistName string) (SimilarArtists, error) {
+	params := url.Values{}
+	params.Add("method", "artist.getSimilar")
+	params.Add("api_key", apiKey)
+	params.Add("artist", artistName)
+	resp, err := c.makeRequest("GET", params)
+	if err != nil {
+		return SimilarArtists{}, fmt.Errorf("making similar artists GET:  %w", err)
+	}
+	return resp.SimilarArtists, nil
+}
+
+func (c *Client) GetSession(apiKey, secret, token string) (string, error) {
+	params := url.Values{}
+	params.Add("method", "auth.getSession")
+	params.Add("api_key", apiKey)
+	params.Add("token", token)
+	params.Add("api_sig", getParamSignature(params, secret))
+	resp, err := c.makeRequest("GET", params)
+	if err != nil {
+		return "", fmt.Errorf("making session GET: %w", err)
+	}
+	return resp.Session.Key, nil
+}
+
+func (c *Client) StealArtistImage(artistURL string) (string, error) {
+	resp, err := http.Get(artistURL) //nolint:gosec
+	if err != nil {
+		return "", fmt.Errorf("get artist url: %w", err)
+	}
+	defer resp.Body.Close()
+
+	node, err := html.Parse(resp.Body)
+	if err != nil {
+		return "", fmt.Errorf("parse html: %w", err)
+	}
+
+	n := cascadia.Query(node, artistOpenGraphQuery)
+	if n == nil {
+		return "", nil
+	}
+
+	var imageURL string
+	for _, attr := range n.Attr {
+		if attr.Key == "content" {
+			imageURL = attr.Val
+			break
+		}
+	}
+
+	return imageURL, nil
+}