refactor: major project restructure

internal/downloader/options.go

@@ -0,0 +1,33 @@
+package downloader
+
+import (
+	"fmt"
+)
+
+var validQualities = map[string]bool{
+	"mp3_128": true,
+	"mp3_320": true,
+	"flac":    true,
+	"best":    true,
+}
+
+type Options struct {
+	OutputDir string
+	Quality   string
+}
+
+func (o *Options) Validate(appDir string) error {
+	if o.OutputDir == "" {
+		o.OutputDir = appDir
+	}
+
+	if o.Quality == "" {
+		o.Quality = "best"
+	}
+
+	if !validQualities[o.Quality] {
+		return fmt.Errorf("invalid quality option: %s", o.Quality)
+	}
+
+	return nil
+}