Created recipe service.

server/src/main/java/server/database/RecipeRepository.java

@@ -19,4 +19,6 @@ import org.springframework.data.jpa.repository.JpaRepository;
 
 import commons.Recipe;
 
-public interface RecipeRepository extends JpaRepository<Recipe, Long> {}
+public interface RecipeRepository extends JpaRepository<Recipe, Long> {
+    boolean existsByName(String name);
+}

server/src/main/java/service/RecipeService.java

@@ -0,0 +1,87 @@
+package service;
+
+import commons.Recipe;
+import org.springframework.data.domain.PageRequest;
+import org.springframework.stereotype.Service;
+import server.database.IngredientRepository;
+import server.database.RecipeIngredientRepository;
+import server.database.RecipeRepository;
+
+import java.util.List;
+import java.util.Optional;
+
+@Service
+public class RecipeService {
+    RecipeRepository recipeRepository;
+    IngredientRepository ingredientRepository;
+    RecipeIngredientRepository recipeIngredientRepository;
+
+    public RecipeService(RecipeRepository recipeRepository,
+                         IngredientRepository ingredientRepository,
+                         RecipeIngredientRepository recipeIngredientRepository) {
+        this.recipeRepository = recipeRepository;
+        this.ingredientRepository = ingredientRepository;
+        this.recipeIngredientRepository = recipeIngredientRepository;
+    }
+
+    Optional<Recipe> findById(Long id) {
+        return recipeRepository.findById(id);
+    }
+
+    List<Recipe> findAll() {
+        return recipeRepository.findAll();
+    }
+
+    List<Recipe> findAll(int limit) {
+        return recipeRepository.findAll(PageRequest.of(0, limit)).toList();
+    }
+
+    /**
+     * Creates a new recipe. Returns empty if the recipe with the same name already exists.
+     * @param recipe Recipe to be saved in the db.
+     * @return The created recipe (the recipe arg with a new assigned id).
+     */
+    public Optional<Recipe> create(Recipe recipe) {
+        if (recipeRepository.existsByName(recipe.getName())) {
+            return Optional.empty();
+        }
+
+        return Optional.of(saveWithDependencies(recipe));
+    }
+
+    /**
+     * Updates a recipe. The recipe with the provided id will be replaced with the provided recipe.
+     * Automatically updates ingredients and any dependencies of recipe.
+     * @param id id of the recipe to update.
+     * @param recipe Recipe to be saved in the db.
+     * @return The created recipe (the recipe arg with a new assigned id.)
+     */
+    public Optional<Recipe> update(Long id, Recipe recipe) {
+        assert id.equals(recipe.getId()) : "The id of the updated recipe doesn't match the provided recipes id.";
+        if (!recipeRepository.existsById(id)) {
+            return Optional.empty();
+        }
+
+        return Optional.of(saveWithDependencies(recipe));
+    }
+
+    public void delete(Long id) {
+        // TODO: Propagate deletion to ingredients.
+        recipeRepository.deleteById(id);
+    }
+
+    private Recipe saveWithDependencies(Recipe recipe) {
+        // TODO: try to automate this with JFX somehow.
+        recipe.getIngredients()
+                .forEach(recipeIngredient ->
+                        recipeIngredient.setIngredient(
+                                ingredientRepository
+                                        .findByName(recipeIngredient.getIngredient().name)
+                                        .orElseGet(() -> ingredientRepository.save(recipeIngredient.getIngredient())
+                                        ))
+                );
+        recipeIngredientRepository.saveAll(recipe.getIngredients());
+        return recipeRepository.save(recipe);
+    }
+
+}