feat: refactor inventory and recipe services for improved error handling and code reuse; add systematic backend review plan

backend/src/recipes/recipes.service.ts

@@ -31,6 +31,31 @@ export class RecipesService {
 
   constructor(private readonly prisma: PrismaService) {}
 
+  private throwRecipeNotFound(id: number): never {
+    throw new NotFoundException(`Recipe with id ${id} not found`);
+  }
+
+  private async findRecipeByIdOrThrow(id: number) {
+    const recipe = await this.prisma.recipe.findUnique({ where: { id } });
+    if (!recipe) {
+      this.throwRecipeNotFound(id);
+    }
+    return recipe;
+  }
+
+  private assertRecipeEditableByUser(recipe: { ownerId: number | null }, userId: number, id: number) {
+    // Legacy behavior: ownerless recipes are editable to preserve existing semantics.
+    if (recipe.ownerId !== null && recipe.ownerId !== userId) {
+      this.throwRecipeNotFound(id);
+    }
+  }
+
+  private assertRecipeOwnedByUser(recipe: { ownerId: number | null }, userId: number, id: number) {
+    if (recipe.ownerId !== userId) {
+      this.throwRecipeNotFound(id);
+    }
+  }
+
   async getInventoryPreview(id: number, userId: number) {
     const recipe = await this.prisma.recipe.findFirst({
       where: {
@@ -218,19 +243,8 @@ export class RecipesService {
   }
 
   async update(id: number, updateRecipeDto: CreateRecipeDto, userId: number) {
-    // Verifiera att receptet finns och att användaren äger det
-    const existingRecipe = await this.prisma.recipe.findUnique({
-      where: { id },
-    });
-
-    if (!existingRecipe) {
-      throw new NotFoundException(`Recipe with id ${id} not found`);
-    }
-
-    // Tillåt uppdatering om användaren är ägare ELLER om receptet är publikt utan ägare
-    if (existingRecipe.ownerId !== null && existingRecipe.ownerId !== userId) {
-      throw new NotFoundException(`Recipe with id ${id} not found`);
-    }
+    const existingRecipe = await this.findRecipeByIdOrThrow(id);
+    this.assertRecipeEditableByUser(existingRecipe, userId, id);
 
     // Ta bort gamla ingredienser
     await this.prisma.recipeIngredient.deleteMany({
@@ -269,17 +283,8 @@ export class RecipesService {
   }
 
   async remove(id: number, userId: number) {
-    const existingRecipe = await this.prisma.recipe.findUnique({
-      where: { id },
-    });
-
-    if (!existingRecipe) {
-      throw new NotFoundException(`Recipe with id ${id} not found`);
-    }
-
-    if (existingRecipe.ownerId !== null && existingRecipe.ownerId !== userId) {
-      throw new NotFoundException(`Recipe with id ${id} not found`);
-    }
+    const existingRecipe = await this.findRecipeByIdOrThrow(id);
+    this.assertRecipeEditableByUser(existingRecipe, userId, id);
 
     await this.prisma.recipeIngredient.deleteMany({ where: { recipeId: id } });
     await this.prisma.recipe.delete({ where: { id } });
@@ -295,13 +300,8 @@ export class RecipesService {
   }
 
   async updateImage(id: number, sourceUrl: string, userId: number) {
-    const existingRecipe = await this.prisma.recipe.findUnique({ where: { id } });
-    if (!existingRecipe) {
-      throw new NotFoundException(`Recipe with id ${id} not found`);
-    }
-    if (existingRecipe.ownerId !== userId) {
-      throw new NotFoundException(`Recipe with id ${id} not found`);
-    }
+    const existingRecipe = await this.findRecipeByIdOrThrow(id);
+    this.assertRecipeOwnedByUser(existingRecipe, userId, id);
 
     const imageUrl = await downloadAndOptimizeImage(sourceUrl, IMAGE_DEST_DIR);
 
@@ -317,10 +317,8 @@ export class RecipesService {
   }
 
   async setVisibility(id: number, userId: number, isPublic: boolean) {
-    const existingRecipe = await this.prisma.recipe.findUnique({ where: { id } });
-    if (!existingRecipe || existingRecipe.ownerId !== userId) {
-      throw new NotFoundException(`Recipe with id ${id} not found`);
-    }
+    const existingRecipe = await this.findRecipeByIdOrThrow(id);
+    this.assertRecipeOwnedByUser(existingRecipe, userId, id);
 
     if (isPublic) {
       const owner = await this.prisma.user.findUnique({
@@ -344,13 +342,8 @@ export class RecipesService {
   }
 
   async shareWithUser(id: number, ownerId: number, username: string) {
-    const recipe = await this.prisma.recipe.findUnique({
-      where: { id },
-      select: { id: true, ownerId: true },
-    });
-    if (!recipe || recipe.ownerId !== ownerId) {
-      throw new NotFoundException(`Recipe with id ${id} not found`);
-    }
+    const recipe = await this.findRecipeByIdOrThrow(id);
+    this.assertRecipeOwnedByUser(recipe, ownerId, id);
 
     const owner = await this.prisma.user.findUnique({
       where: { id: ownerId },
@@ -381,13 +374,8 @@ export class RecipesService {
   }
 
   async unshareWithUser(id: number, ownerId: number, username: string) {
-    const recipe = await this.prisma.recipe.findUnique({
-      where: { id },
-      select: { id: true, ownerId: true },
-    });
-    if (!recipe || recipe.ownerId !== ownerId) {
-      throw new NotFoundException(`Recipe with id ${id} not found`);
-    }
+    const recipe = await this.findRecipeByIdOrThrow(id);
+    this.assertRecipeOwnedByUser(recipe, ownerId, id);
 
     const targetUser = await this.prisma.user.findUnique({
       where: { username },