refactor: consolidate download domain into download package

internal/download/metadata.go

@@ -0,0 +1,79 @@
+package download
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+
+	"github.com/mathismqn/godeez/internal/deezer"
+)
+
+type bpmKey struct {
+	BPM string
+	Key string
+}
+
+type metadataResult struct {
+	bpmKey   bpmKey
+	genre    string
+	warnings []string
+}
+
+func fetchMetadata(httpClient *http.Client, ctx context.Context, track *deezer.Track, opts Options) metadataResult {
+	if !opts.BPM && !opts.Genre {
+		return metadataResult{}
+	}
+
+	type bpmResult struct {
+		value bpmKey
+		err   error
+	}
+	type genreResult struct {
+		value string
+		err   error
+	}
+
+	bpmChan := make(chan bpmResult, 1)
+	genreChan := make(chan genreResult, 1)
+
+	if opts.BPM {
+		go func() {
+			result, err := fetchBPM(ctx, httpClient, track.Artist, track.Title, track.Duration)
+			bpmChan <- bpmResult{value: result, err: err}
+		}()
+	}
+
+	if opts.Genre {
+		go func() {
+			genre, err := fetchGenre(ctx, httpClient, track.Artist, track.GetTitle())
+			genreChan <- genreResult{value: genre, err: err}
+		}()
+	}
+
+	var result metadataResult
+
+	if opts.BPM {
+		r := <-bpmChan
+		if r.err != nil {
+			if !errors.Is(r.err, context.Canceled) {
+				result.warnings = append(result.warnings, fmt.Sprintf("failed to fetch BPM and key: %v", r.err))
+			}
+		} else {
+			result.bpmKey = r.value
+		}
+	}
+
+	if opts.Genre {
+		r := <-genreChan
+		if r.err != nil {
+			if !errors.Is(r.err, context.Canceled) {
+				result.warnings = append(result.warnings, fmt.Sprintf("failed to fetch genre: %v", r.err))
+			}
+		} else {
+			result.genre = r.value
+		}
+	}
+
+	return result
+}