build spotify-to-navidrome migrator with recovery flow

internal/session/session.go

@@ -0,0 +1,96 @@
+package session
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+type Data struct {
+	Spotify SpotifyState `json:"spotify"`
+}
+
+type SpotifyState struct {
+	ClientID     string `json:"client_id,omitempty"`
+	AccessToken  string `json:"access_token,omitempty"`
+	RefreshToken string `json:"refresh_token,omitempty"`
+	TokenType    string `json:"token_type,omitempty"`
+	Scope        string `json:"scope,omitempty"`
+	ExpiresAt    string `json:"expires_at,omitempty"`
+}
+
+func Load(path string) (Data, error) {
+	path, err := expandPath(path)
+	if err != nil {
+		return Data{}, err
+	}
+	b, err := os.ReadFile(path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return Data{}, nil
+		}
+		return Data{}, fmt.Errorf("read session file: %w", err)
+	}
+	var d Data
+	if err := json.Unmarshal(b, &d); err != nil {
+		return Data{}, fmt.Errorf("decode session file: %w", err)
+	}
+	return d, nil
+}
+
+func Save(path string, d Data) error {
+	path, err := expandPath(path)
+	if err != nil {
+		return err
+	}
+
+	dir := filepath.Dir(path)
+	if err := os.MkdirAll(dir, 0o700); err != nil {
+		return fmt.Errorf("create session directory: %w", err)
+	}
+
+	b, err := json.MarshalIndent(d, "", "  ")
+	if err != nil {
+		return fmt.Errorf("encode session file: %w", err)
+	}
+
+	tmp := path + ".tmp"
+	if err := os.WriteFile(tmp, b, 0o600); err != nil {
+		return fmt.Errorf("write temp session file: %w", err)
+	}
+	if err := os.Rename(tmp, path); err != nil {
+		return fmt.Errorf("replace session file: %w", err)
+	}
+	return nil
+}
+
+func (s SpotifyState) ExpiresAtTime() time.Time {
+	t, err := time.Parse(time.RFC3339, strings.TrimSpace(s.ExpiresAt))
+	if err != nil {
+		return time.Time{}
+	}
+	return t
+}
+
+func expandPath(path string) (string, error) {
+	path = strings.TrimSpace(path)
+	if path == "" {
+		return "", fmt.Errorf("session path cannot be empty")
+	}
+	if strings.HasPrefix(path, "~/") || path == "~" {
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return "", fmt.Errorf("resolve home directory: %w", err)
+		}
+		if path == "~" {
+			path = home
+		} else {
+			path = filepath.Join(home, strings.TrimPrefix(path, "~/"))
+		}
+	}
+	return filepath.Clean(path), nil
+}

internal/session/session_test.go

@@ -0,0 +1,42 @@
+package session
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+func TestSaveLoadRoundTrip(t *testing.T) {
+	t.Parallel()
+
+	path := filepath.Join(t.TempDir(), "session.json")
+	in := Data{
+		Spotify: SpotifyState{
+			ClientID:     "abc123",
+			AccessToken:  "access-token",
+			RefreshToken: "refresh-token",
+			ExpiresAt:    "2026-01-02T03:04:05Z",
+		},
+	}
+
+	if err := Save(path, in); err != nil {
+		t.Fatalf("Save failed: %v", err)
+	}
+
+	out, err := Load(path)
+	if err != nil {
+		t.Fatalf("Load failed: %v", err)
+	}
+
+	if out.Spotify.ClientID != in.Spotify.ClientID {
+		t.Fatalf("ClientID mismatch: got %q want %q", out.Spotify.ClientID, in.Spotify.ClientID)
+	}
+	if out.Spotify.AccessToken != in.Spotify.AccessToken {
+		t.Fatalf("AccessToken mismatch")
+	}
+	if out.Spotify.RefreshToken != in.Spotify.RefreshToken {
+		t.Fatalf("RefreshToken mismatch")
+	}
+	if out.Spotify.ExpiresAt != in.Spotify.ExpiresAt {
+		t.Fatalf("ExpiresAt mismatch: got %q want %q", out.Spotify.ExpiresAt, in.Spotify.ExpiresAt)
+	}
+}