Add delete goal endpoint (#27)

Closes #18

Reviewed-on: #27

backend/main.go

@@ -16,6 +16,13 @@ import (
 var migrations embed.FS
 var db *Db
 
+const (
+	ErrInternalServerError = "Internal Server Error"
+	ErrInvalidUserID       = "Invalid user ID"
+	ErrUserNotFound        = "User not found"
+	ErrCheckingUserExist   = "Error checking user existence: %v"
+)
+
 // ServerConfig holds configuration for the server.
 type ServerConfig struct {
 	// The datasource to the SQLite database.
@@ -34,7 +41,7 @@ func getUsers(c *gin.Context) {
 	users, err := db.GetUsers()
 	if err != nil {
 		log.Printf("Error getting users: %v", err)
-		c.JSON(http.StatusInternalServerError, gin.H{"error": "Internal Server Error"})
+		c.JSON(http.StatusInternalServerError, gin.H{"error": ErrInternalServerError})
 		return
 	}
 	c.IndentedJSON(http.StatusOK, users)
@@ -44,19 +51,19 @@ func getUser(c *gin.Context) {
 	userIdStr := c.Param("userId")
 	userId, err := strconv.Atoi(userIdStr)
 	if err != nil {
-		log.Printf("Invalid user ID: %v", err)
-		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid user ID"})
+		log.Printf(ErrInvalidUserID+": %v", err)
+		c.JSON(http.StatusBadRequest, gin.H{"error": ErrInvalidUserID})
 		return
 	}
 
 	user, err := db.GetUser(userId)
 	if err != nil {
 		log.Printf("Error getting user: %v", err)
-		c.JSON(http.StatusInternalServerError, gin.H{"error": "Internal Server Error"})
+		c.JSON(http.StatusInternalServerError, gin.H{"error": ErrInternalServerError})
 		return
 	}
 	if user == nil {
-		c.JSON(http.StatusNotFound, gin.H{"error": "User not found"})
+		c.JSON(http.StatusNotFound, gin.H{"error": ErrUserNotFound})
 		return
 	}
 
@@ -67,27 +74,27 @@ func getUserGoals(c *gin.Context) {
 	userIdStr := c.Param("userId")
 	userId, err := strconv.Atoi(userIdStr)
 	if err != nil {
-		log.Printf("Invalid user ID: %v", err)
-		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid user ID"})
+		log.Printf(ErrInvalidUserID+": %v", err)
+		c.JSON(http.StatusBadRequest, gin.H{"error": ErrInvalidUserID})
 		return
 	}
 
 	exists, err := db.UserExists(userId)
 	if err != nil {
-		log.Printf("Error checking user existence: %v", err)
-		c.JSON(http.StatusInternalServerError, gin.H{"error": "Internal Server Error"})
+		log.Printf(ErrCheckingUserExist, err)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": ErrInternalServerError})
 		return
 	}
 	if !exists {
-		log.Printf("Error checking user existence: %v", err)
-		c.JSON(http.StatusNotFound, gin.H{"error": "User not found"})
+		log.Printf(ErrCheckingUserExist, err)
+		c.JSON(http.StatusNotFound, gin.H{"error": ErrUserNotFound})
 		return
 	}
 
 	goals, err := db.GetUserGoals(userId)
 	if err != nil {
 		log.Printf("Error getting user goals: %v", err)
-		c.JSON(http.StatusInternalServerError, gin.H{"error": "Internal Server Error"})
+		c.JSON(http.StatusInternalServerError, gin.H{"error": ErrInternalServerError})
 		return
 	}
 	c.IndentedJSON(http.StatusOK, goals)
@@ -97,8 +104,8 @@ func createUserGoal(c *gin.Context) {
 	userIdStr := c.Param("userId")
 	userId, err := strconv.Atoi(userIdStr)
 	if err != nil {
-		log.Printf("Invalid user ID: %v", err)
-		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid user ID"})
+		log.Printf(ErrInvalidUserID+": %v", err)
+		c.JSON(http.StatusBadRequest, gin.H{"error": ErrInvalidUserID})
 		return
 	}
 
@@ -121,7 +128,7 @@ func createUserGoal(c *gin.Context) {
 	if err != nil {
 		log.Printf("Error creating goal: %v", err)
 		if err.Error() == "user does not exist" {
-			c.JSON(http.StatusNotFound, gin.H{"error": "User not found"})
+			c.JSON(http.StatusNotFound, gin.H{"error": ErrUserNotFound})
 		} else {
 			c.JSON(http.StatusBadRequest, gin.H{"error": "Could not create goal"})
 		}
@@ -133,6 +140,49 @@ func createUserGoal(c *gin.Context) {
 	c.IndentedJSON(http.StatusCreated, response)
 }
 
+func deleteUserGoal(c *gin.Context) {
+	userIdStr := c.Param("userId")
+	goalIdStr := c.Param("goalId")
+
+	userId, err := strconv.Atoi(userIdStr)
+	if err != nil {
+		log.Printf(ErrInvalidUserID+": %v", err)
+		c.JSON(http.StatusBadRequest, gin.H{"error": ErrInvalidUserID})
+		return
+	}
+
+	goalId, err := strconv.Atoi(goalIdStr)
+	if err != nil {
+		log.Printf("Invalid goal ID: %v", err)
+		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid goal 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.DeleteGoal(userId, goalId)
+	if err != nil {
+		if err.Error() == "goal not found" {
+			c.JSON(http.StatusNotFound, gin.H{"error": "Goal not found"})
+		} else {
+			log.Printf("Error deleting goal: %v", err)
+			c.JSON(http.StatusInternalServerError, gin.H{"error": ErrInternalServerError})
+		}
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{"message": "Goal deleted successfully"})
+}
+
 /*
 *
 Initialises the database, and then starts the server.
@@ -147,6 +197,7 @@ func start(ctx context.Context, config *ServerConfig) {
 	router.GET("/api/user/:userId", getUser)
 	router.GET("/api/user/:userId/goals", getUserGoals)
 	router.POST("/api/user/:userId/goals", createUserGoal)
+	router.DELETE("/api/user/:userId/goal/:goalId", deleteUserGoal)
 
 	srv := &http.Server{
 		Addr:    ":" + config.Port,