use antigravity to rewrite all your code to migrate from flat files to relational database. YOLO

server/fitbit.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"database/sql"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -38,33 +39,26 @@ func InitFitbit() {
 }
 
 func loadTokens(userID string) (*FitbitConfig, error) {
-	configPath := fmt.Sprintf("data/users/%s/fitbit_tokens.json", userID)
-	data, err := os.ReadFile(configPath)
-	if err != nil {
-		return nil, err
-	}
-
 	var config FitbitConfig
-	if err := json.Unmarshal(data, &config); err != nil {
+	err := db.QueryRow("SELECT access_token, refresh_token, expires_at FROM fitbit_tokens WHERE user_id = ?", userID).
+		Scan(&config.AccessToken, &config.RefreshToken, &config.ExpiresAt)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, fmt.Errorf("tokens not found for user %s", userID)
+		}
 		return nil, err
 	}
-
 	return &config, nil
 }
 
 func saveTokens(userID string, config *FitbitConfig) error {
-	userDir := fmt.Sprintf("data/users/%s", userID)
-	if err := os.MkdirAll(userDir, 0755); err != nil {
-		return fmt.Errorf("error creating user directory: %w", err)
-	}
-
-	configPath := fmt.Sprintf("%s/fitbit_tokens.json", userDir)
-	data, err := json.MarshalIndent(config, "", "  ")
-	if err != nil {
-		return err
-	}
-
-	return os.WriteFile(configPath, data, 0600)
+	_, err := db.Exec(`
+		INSERT INTO fitbit_tokens (user_id, access_token, refresh_token, expires_at)
+		VALUES (?, ?, ?, ?)
+		ON DUPLICATE KEY UPDATE access_token = ?, refresh_token = ?, expires_at = ?
+	`, userID, config.AccessToken, config.RefreshToken, config.ExpiresAt,
+		config.AccessToken, config.RefreshToken, config.ExpiresAt)
+	return err
 }
 
 // GetDailySteps fetches step count for a specific date (YYYY-MM-DD) for a specific user
@@ -241,14 +235,9 @@ func HandleFitbitCallback(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
-	// Create or update user in registry
-	fmt.Println("[OAuth Callback] Creating/updating user in registry...")
-	if userRegistry == nil {
-		fmt.Println("[OAuth Callback] ERROR: userRegistry is nil!")
-		http.Error(w, "Server configuration error: user registry not initialized", http.StatusInternalServerError)
-		return
-	}
-	_, err = userRegistry.CreateOrUpdateUser(fitbitUserID, displayName, avatarURL)
+	// Create or update user in database
+	fmt.Println("[OAuth Callback] Creating/updating user in database...")
+	_, err = CreateOrUpdateUser(fitbitUserID, displayName, avatarURL)
 	if err != nil {
 		fmt.Printf("[OAuth Callback] ERROR: Failed to create user: %v\n", err)
 		http.Error(w, fmt.Sprintf("Failed to create user: %v", err), http.StatusInternalServerError)