refactor: fold auth and crypto into deezer domain

internal/deezer/login.go

@@ -0,0 +1,48 @@
+package deezer
+
+import (
+	"context"
+	"fmt"
+)
+
+func resolveARL(ctx context.Context, validate func(ctx context.Context, arl string) error) (string, error) {
+	creds, err := LoadCredentials()
+	if err != nil {
+		return "", err
+	}
+
+	if creds != nil && creds.ARL != "" {
+		if verr := validate(ctx, creds.ARL); verr == nil {
+			return creds.ARL, nil
+		}
+	}
+
+	if creds != nil && creds.Email != "" && creds.Password != "" {
+		arl, _, err := Login(ctx, creds.Email, creds.Password)
+		if err != nil {
+			return "", fmt.Errorf("stored session expired and could not be renewed automatically: %w", err)
+		}
+
+		return arl, nil
+	}
+
+	return "", fmt.Errorf("run 'godeez login' or export DEEZER_ARL environment variable")
+}
+
+func Login(ctx context.Context, email, password string) (string, string, error) {
+	client, err := newMobileClient()
+	if err != nil {
+		return "", "", err
+	}
+
+	creds, username, err := client.login(ctx, email, password)
+	if err != nil {
+		return "", "", err
+	}
+
+	if err := SaveCredentials(creds); err != nil {
+		return "", "", err
+	}
+
+	return creds.ARL, username, nil
+}