(DB/FEAT): Implemented toggle favorite in the backend.

The frontend is half wired up, just need to update the button. I also
want to update the recipe methods to return the favorite status. This
will follow very similar to the way I updated the tags. Another method
which can be called to attach the favorite state.

doc/TechnicalSpecification.md

@@ -299,11 +299,11 @@ found in **OTHER** section.
     - [x] UserId (FK: User.Id)  Serial, optional for not logged in users
     - [x] Created (Required) date/time stamp
 
-- [ ] Likes: **Many-to-many** table to represent a list of recipes liked by a user.
-    - [ ] ID (PK) *Composite key***
-    - [ ] UserId (FK: User.Id, Required)  Serial
-    - [ ] RecipeId (FK: Recipe.Id, Required)  Serial
-    - [ ] Created (Required) date/time stamp
+- [x] Favorites: **Many-to-many** table to represent a list of recipes favorites by a user.
+    - [x] ID (PK) *Composite key***
+    - [x] UserId (FK: User.Id, Required)  Serial
+    - [x] RecipeId (FK: Recipe.Id, Required)  Serial
+    - [x] Created (Required) date/time stamp
 
 - [x] Tags: Represents a single tag that can be had by many recipes.
     - [x] ID (PK) Serial

internal/app/handlers/engagement_handler.go

@@ -33,7 +33,7 @@ func EngagementViewRecipe(ctx *gin.Context) {
 	}
 }
 
-func EngagementLikeRecipe(ctx *gin.Context) {
+func EngagementFavoriteRecipe(ctx *gin.Context) {
 	deps := ctx.MustGet("deps").(*domain.InjectedDependencies)
 
 	if !domain.IsLoggedIn(ctx) {
@@ -46,7 +46,7 @@ func EngagementLikeRecipe(ctx *gin.Context) {
 	recipeId, _ := strconv.Atoi(id)
 	userId := ctx.MustGet("userId").(int)
 
-	if _, err := deps.EngagementService.UserLikeRecipe(userId, recipeId); err != nil {
+	if _, err := deps.EngagementService.UserFavoriteRecipe(userId, recipeId); err != nil {
 		ctx.JSON(http.StatusInternalServerError, gin.H{
 			"status": http.StatusInternalServerError,
 			"message": err.Error(),

internal/app/server/server.go

@@ -188,7 +188,7 @@ func (s *Server) Setup() *Server {
 
 	// Engagement endpoints
 	router_api.POST("/engagement/view/:id", handlers.EngagementViewRecipe)
-	router_api.POST("/engagement/like/:id", handlers.EngagementLikeRecipe)
+	router_api.POST("/engagement/favorite/:id", handlers.EngagementFavoriteRecipe)
 	router_api.POST("/engagement/make/:id", handlers.EngagementMakeRecipe)
 
 	// Catch un-routed URLS

internal/app/service/engagement_service.go

@@ -39,22 +39,35 @@ func (s *EngagementService) UserViewRecipe(userId, recipeId int) (domain.Engagem
 	return s.engagementRepository.AddUserEntityEngagement(userId, recipeId, message, domain.EngagementViewed)
 }
 
-// UserLikeRecipe requires a user ID and a recipe ID to create an engagement record in the database.
+// UserFavoriteRecipe requires a user ID and a recipe ID to create an engagement record in the database.
 // A message will be generated using the recipe data and then used to add a like engagement to the
 // database.
-func (s *EngagementService) UserLikeRecipe(userId, recipeId int) (domain.Engagement, error) {
+func (s *EngagementService) UserFavoriteRecipe(userId, recipeId int) (domain.Engagement, error) {
 	recipe, err := s.recipeRepository.GetRecipe(recipeId)
 	if err != nil {
 		return domain.Engagement{}, err
 	}
 
-	message := fmt.Sprintf("Liked \"%s\"", recipe.Title)
+	// Update the favorites DB 
+	liked, err := s.engagementRepository.UserFavoriteRecipeToggle(userId, recipeId)
+	if err != nil {
+		return domain.Engagement{}, err
+	}
+	
+	// Determine if this like is a saving or unsaving
+	var message string
+	if liked {
+		message = fmt.Sprintf("Saved \"%s\"", recipe.Title)
+	} else {
+		message = fmt.Sprintf("Unsaved \"%s\"", recipe.Title)
+	}
 
 	return s.engagementRepository.AddUserEntityEngagement(userId, recipeId, message, domain.EngagementLiked)
+
 }
 
-// UserLikeRecipe requires a user ID and a recipe ID to create an engagement record in the database.
-// A message will be generated using the recipe data and then used to add a like engagement to the
+// UserMakeRecipe requires a user ID and a recipe ID to create an engagement record in the database.
+// A message will be generated using the recipe data and then used to add a make engagement to the
 // database.
 func (s *EngagementService) UserMakeRecipe(userId, recipeId int) (domain.Engagement, error) {
 	recipe, err := s.recipeRepository.GetRecipe(recipeId)

internal/domain/engagement/repository.go

@@ -4,4 +4,5 @@ type EngagementRepository interface {
 	AddUserEngagement(userId int, message string, engagementType EngagementType) (Engagement, error)
 	AddUserEntityEngagement(userId, entityId int, message string, engagementType EngagementType) (Engagement, error)
 	GetUserEngagement(userId, limit int) ([]Engagement, error)
+	UserFavoriteRecipeToggle(userId, recipeId int) (bool, error)
 }

internal/domain/engagement/service.go

@@ -2,7 +2,7 @@ package domain
 
 type EngagementService interface {
 	UserViewRecipe(userId, recipeId int) (Engagement, error)
-	UserLikeRecipe(userId, recipeId int) (Engagement, error)
+	UserFavoriteRecipe(userId, recipeId int) (Engagement, error)
 	UserMakeRecipe(userId, recipeId int) (Engagement, error)
 	GetUserEngagement(userId, limit int) ([]Engagement, error)
 }

internal/domain/server/routes.go

@@ -26,7 +26,7 @@ const API_CREATE_RECIPE = VERSION + API + "/recipe"
 const API_SEARCH_RECIPES = VERSION + API + "/recipe/search"
 
 const API_ENGAGEMENT_VIEW = VERSION + API + "/engagement/view/%d"
-const API_ENGAGEMENT_LIKE = VERSION + API + "/engagement/like/%d"
+const API_ENGAGEMENT_FAVORITE = VERSION + API + "/engagement/favorite/%d"
 const API_ENGAGEMENT_MAKE = VERSION + API + "/engagement/make/%d"
 
 // State prefixed routes

internal/infrastructure/database/migrations/008_create_favorites_table.sql

@@ -0,0 +1,14 @@
+-- Author: Hayden Hargreaves (hhargreaves2006@gmail.com)
+-- Desc:   Create the favorites table.
+-- Date:   07/14/2025
+
+BEGIN;
+
+CREATE TABLE IF NOT EXISTS Favorites (
+  Id SERIAL PRIMARY KEY NOT NULL, 
+  UserId INTEGER NOT NULL REFERENCES users(id),
+  RecipeId INTEGER NOT NULL REFERENCES recipes(id),
+  Created TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+COMMIT;

internal/infrastructure/database/repository/engagement_repository.go

@@ -2,6 +2,7 @@ package repository
 
 import (
 	"database/sql"
+	"errors"
 	"fmt"
 	"time"
 
@@ -153,3 +154,62 @@ func (r *EngagementRepository) GetUserEngagement(userId, limit int) ([]domain.En
 
 	return engagements, err
 }
+
+// UserFavoriteRecipeToggle toggles the status of a users favorite of a recipe. If the user has already
+// favorited the provided recipe, the database entry will be delete, hence removing the favorite. Otherwise,
+// an entry will be created. The NEW status of the users favorite will be returned as the boolean. Any 
+// errors will be bubbled to the caller.
+func (r *EngagementRepository) UserFavoriteRecipeToggle(userId, recipeId int) (bool, error) {
+	tx, err := r.db.Begin()
+	if err != nil {
+		tx.Rollback()
+		return false, err
+	}
+
+	query := `
+		SELECT id 
+		FROM favorites
+		WHERE userid = $1 AND recipeid = $2
+	`
+
+	var id int
+	
+	err = tx.QueryRow(query, userId, recipeId).Scan(&id)
+	if err != nil {
+		if !errors.Is(err, sql.ErrNoRows) {
+			tx.Rollback()
+			return false, fmt.Errorf("Failed to get recipe favorite. %s", err.Error())
+		}
+	}
+
+	// Means we should create
+	var success bool
+	if id == 0 {
+		createQuery := "INSERT INTO favorites (userid, recipeid, created) VALUES ($1, $2, $3);"
+
+		if result, err := tx.Exec(createQuery, userId, recipeId, time.Now()); err != nil {
+			tx.Rollback()
+			return false, fmt.Errorf("Failed to create recipe favorite. %s", err.Error())
+		} else {
+			rows, _ := result.RowsAffected()
+			success = rows == 1
+		}
+	} else {
+		deleteQuery := "DELETE FROM favorites WHERE id = $1;"
+
+		if result, err := tx.Exec(deleteQuery, id); err != nil {
+			tx.Rollback()
+			return false, fmt.Errorf("Failed to remove recipe favorite. %s", err.Error())
+		} else {
+			rows, _ := result.RowsAffected()
+			success = rows == 1
+		}
+	}
+
+	if err := tx.Commit(); err != nil {
+		tx.Rollback()
+		return false, err
+	}
+
+	return success, nil
+}

internal/templates/pages/recipe.templ

@@ -228,7 +228,7 @@ templ madeButton(id int) {
 		hx-trigger="click"
 		hx-swap="none"
 		id="make-button"
-    hx-on:click="makeButtonHandler();"
+		hx-on:click="makeButtonHandler();"
 		class="flex items-center justify-center gap-x-1 rounded-lg border border-gray-300 text-gray-800 px-6 py-3 flex-grow hover:bg-gray-50 hover:border-blue-300 duration-300"
 	>
 		<svg

internal/templates/pages/recipe_templ.go

@@ -1,4 +1,4 @@
-// Code generated by templ - DO NOT EDIT.
+	// Code generated by templ - DO NOT EDIT.
 
 // templ: version: v0.3.865
 package templates
@@ -584,7 +584,7 @@ func favoriteButton(favorited bool, id int) templ.Component {
 				return templ_7745c5c3_Err
 			}
 			var templ_7745c5c3_Var22 string
-			templ_7745c5c3_Var22, templ_7745c5c3_Err = templ.JoinStringErrs(fmt.Sprintf(domainServer.API_ENGAGEMENT_LIKE, id))
+			templ_7745c5c3_Var22, templ_7745c5c3_Err = templ.JoinStringErrs(fmt.Sprintf(domainServer.API_ENGAGEMENT_FAVORITE, id))
 			if templ_7745c5c3_Err != nil {
 				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/templates/pages/recipe.templ`, Line: 189, Col: 62}
 			}
@@ -602,7 +602,7 @@ func favoriteButton(favorited bool, id int) templ.Component {
 				return templ_7745c5c3_Err
 			}
 			var templ_7745c5c3_Var23 string
-			templ_7745c5c3_Var23, templ_7745c5c3_Err = templ.JoinStringErrs(fmt.Sprintf(domainServer.API_ENGAGEMENT_LIKE, id))
+			templ_7745c5c3_Var23, templ_7745c5c3_Err = templ.JoinStringErrs(fmt.Sprintf(domainServer.API_ENGAGEMENT_FAVORITE, id))
 			if templ_7745c5c3_Err != nil {
 				return templ.Error{Err: templ_7745c5c3_Err, FileName: `internal/templates/pages/recipe.templ`, Line: 204, Col: 62}
 			}