Initial commit

Signed-off-by: Thomas Klaehn <thomas.klaehn@perinet.io>

internal/client/auth.go

@@ -0,0 +1,90 @@
+package client
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+
+	"golang.org/x/oauth2"
+)
+
+// TokenCache handles token persistence
+type TokenCache struct {
+	filePath string
+}
+
+// NewTokenCache creates a new token cache
+func NewTokenCache(filePath string) *TokenCache {
+	return &TokenCache{filePath: filePath}
+}
+
+// Load loads a token from cache
+func (tc *TokenCache) Load() (*oauth2.Token, error) {
+	// Check if file exists
+	if _, err := os.Stat(tc.filePath); os.IsNotExist(err) {
+		return nil, nil // No cached token
+	}
+
+	// Read file
+	data, err := os.ReadFile(tc.filePath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read token cache: %w", err)
+	}
+
+	// Unmarshal token
+	var token oauth2.Token
+	if err := json.Unmarshal(data, &token); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal token: %w", err)
+	}
+
+	// Check if token is expired
+	if token.Expiry.Before(time.Now()) {
+		return nil, nil // Token expired
+	}
+
+	return &token, nil
+}
+
+// Save saves a token to cache
+func (tc *TokenCache) Save(token *oauth2.Token) error {
+	// Create directory if it doesn't exist
+	dir := filepath.Dir(tc.filePath)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return fmt.Errorf("failed to create token cache directory: %w", err)
+	}
+
+	// Marshal token
+	data, err := json.MarshalIndent(token, "", "  ")
+	if err != nil {
+		return fmt.Errorf("failed to marshal token: %w", err)
+	}
+
+	// Write to file with restricted permissions
+	if err := os.WriteFile(tc.filePath, data, 0600); err != nil {
+		return fmt.Errorf("failed to write token cache: %w", err)
+	}
+
+	return nil
+}
+
+// Authenticate authenticates with Zwift using username and password
+func Authenticate(ctx context.Context, username, password string, tokenCache *TokenCache) (*oauth2.Token, error) {
+	// Try to load cached token first
+	if tokenCache != nil {
+		token, err := tokenCache.Load()
+		if err == nil && token != nil && token.Valid() {
+			return token, nil
+		}
+	}
+
+	// Authenticate with username/password
+	// Note: The gravl library handles the actual OAuth2 flow
+	// We'll use the credentials directly with the client
+
+	// For now, we'll return nil as the gravl client handles authentication
+	// This function serves as a placeholder for explicit token management
+	return nil, fmt.Errorf("authentication handled by gravl client")
+}