refactor: consolidate download domain into download package

internal/download/genre.go

@@ -0,0 +1,124 @@
+package download
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/PuerkitoBio/goquery"
+)
+
+var electronicKeywords = toLower([]string{
+	"Ambient", "Bass", "Big Room", "Breakbeat", "Dance", "Disco", "Downtempo",
+	"Drum And Bass", "Dub", "Dubstep", "EDM", "Electro", "Electronic", "Electronica",
+	"Eurodance", "Gabber", "Garage", "Hardcore", "Hardstyle", "House", "Industrial",
+	"Jungle", "Moombahton", "Synthpop", "Synthwave", "Techno", "Trance", "Trap",
+	"Trip Hop", "Vaporwave",
+})
+
+var nonElectronicKeywords = toLower([]string{
+	"Blues", "Chillout", "Classical", "Country", "Folk", "Funk", "Hip Hop", "Jazz",
+	"Latin", "Metal", "Pop", "R&B", "Rap", "Reggae", "Rock", "Soul",
+})
+
+func toLower(ss []string) []string {
+	out := make([]string, len(ss))
+	for i, s := range ss {
+		out[i] = strings.ToLower(s)
+	}
+	return out
+}
+
+func fetchGenre(ctx context.Context, httpClient *http.Client, artist, title string) (string, error) {
+	reqURL := fmt.Sprintf("https://www.last.fm/music/%s/%s/+tags", artist, title)
+
+	doc, err := fetchGenrePage(ctx, httpClient, reqURL)
+	if err != nil {
+		return "", err
+	}
+
+	tags := parseGenreTags(doc)
+	if len(tags) > 2 {
+		tags = tags[:2]
+	}
+
+	filtered := filterTags(tags)
+	if len(filtered) == 0 {
+		return "", fmt.Errorf("no data found")
+	}
+
+	return formatTags(filtered), nil
+}
+
+func fetchGenrePage(ctx context.Context, httpClient *http.Client, url string) (*goquery.Document, error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := httpClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("unexpected status code: %d", resp.StatusCode)
+	}
+
+	return goquery.NewDocumentFromReader(resp.Body)
+}
+
+func parseGenreTags(doc *goquery.Document) []string {
+	var tags []string
+	doc.Find("ol.big-tags .big-tags-item-name a").Each(func(_ int, s *goquery.Selection) {
+		if tag := strings.TrimSpace(s.Text()); tag != "" {
+			tags = append(tags, tag)
+		}
+	})
+	return tags
+}
+
+func matchesKeyword(tag string, keywords []string) bool {
+	tagLower := strings.ToLower(tag)
+	for _, kw := range keywords {
+		if strings.Contains(tagLower, kw) {
+			return true
+		}
+	}
+	return false
+}
+
+func filterTags(tags []string) []string {
+	var electronic, nonElectronic []string
+
+	for _, tag := range tags {
+		if matchesKeyword(tag, electronicKeywords) {
+			electronic = append(electronic, tag)
+		} else if matchesKeyword(tag, nonElectronicKeywords) {
+			nonElectronic = append(nonElectronic, tag)
+		}
+	}
+
+	if len(electronic) > 0 {
+		return append(electronic, nonElectronic...)
+	}
+	return electronic
+}
+
+func formatTags(tags []string) string {
+	formatted := make([]string, 0, len(tags))
+	for _, tag := range tags {
+		tag = strings.TrimSpace(tag)
+		if tag == "" {
+			continue
+		}
+		words := strings.Fields(tag)
+		for i, w := range words {
+			words[i] = strings.ToUpper(w[:1]) + strings.ToLower(w[1:])
+		}
+		formatted = append(formatted, strings.Join(words, " "))
+	}
+	return strings.Join(formatted, " / ")
+}