Implement completion endpoint for allowance (#55)

Closes #19

Reviewed-on: #55

backend/main.go

@@ -287,6 +287,49 @@ func putUserAllowance(c *gin.Context) {
 	c.IndentedJSON(http.StatusOK, gin.H{"message": "Allowance updated successfully"})
 }
 
+func completeAllowance(c *gin.Context) {
+	userIdStr := c.Param("userId")
+	allowanceIdStr := c.Param("allowanceId")
+
+	userId, err := strconv.Atoi(userIdStr)
+	if err != nil {
+		log.Printf(ErrInvalidUserID+": %v", err)
+		c.JSON(http.StatusBadRequest, gin.H{"error": ErrInvalidUserID})
+		return
+	}
+
+	allowanceId, err := strconv.Atoi(allowanceIdStr)
+	if err != nil {
+		log.Printf("Invalid allowance ID: %v", err)
+		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid allowance ID"})
+		return
+	}
+
+	exists, err := db.UserExists(userId)
+	if err != nil {
+		log.Printf(ErrCheckingUserExist, err)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": ErrInternalServerError})
+		return
+	}
+	if !exists {
+		c.JSON(http.StatusNotFound, gin.H{"error": ErrUserNotFound})
+		return
+	}
+
+	err = db.CompleteAllowance(userId, allowanceId)
+	if errors.Is(err, mysqlite.ErrNoRows) {
+		c.JSON(http.StatusNotFound, gin.H{"error": "Allowance not found"})
+		return
+	}
+	if err != nil {
+		log.Printf("Error completing allowance: %v", err)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": ErrInternalServerError})
+		return
+	}
+
+	c.IndentedJSON(http.StatusOK, gin.H{"message": "Allowance completed successfully"})
+}
+
 func createTask(c *gin.Context) {
 	var taskRequest CreateTaskRequest
 	if err := c.ShouldBindJSON(&taskRequest); err != nil {
@@ -518,6 +561,7 @@ func start(ctx context.Context, config *ServerConfig) {
 	router.GET("/api/user/:userId/allowance/:allowanceId", getUserAllowanceById)
 	router.DELETE("/api/user/:userId/allowance/:allowanceId", deleteUserAllowance)
 	router.PUT("/api/user/:userId/allowance/:allowanceId", putUserAllowance)
+	router.POST("/api/user/:userId/allowance/:allowanceId/complete", completeAllowance)
 	router.POST("/api/tasks", createTask)
 	router.GET("/api/tasks", getTasks)
 	router.GET("/api/task/:taskId", getTask)
@@ -558,5 +602,9 @@ func main() {
 		Datasource: os.Getenv("DB_PATH"),
 		Addr:       ":8080",
 	}
+	if config.Datasource == "" {
+		config.Datasource = "allowance_planner.db3"
+		log.Printf("Warning: No DB_PATH set, using default of %s", config.Datasource)
+	}
 	start(context.Background(), &config)
 }