refactor: inject the database into services via a constructor

Pilot on the categories service: a CategoriesService class holds the Drizzle
handle, and services/index.ts wires the real instance once for the server while
tests build their own on an in-memory database. AppDatabase moves from
groceries.ts to db/types.ts.

11 files changed, 61 insertions, 57 deletions

diff --git a/src/lib/server/db/types.ts b/src/lib/server/db/types.ts
new file mode 100644
index 0000000..d842677
--- /dev/null
+++ b/src/lib/server/db/types.ts
@@ -0,0 +1,5 @@
+import type { LibSQLDatabase } from 'drizzle-orm/libsql';
+import type * as schema from './schema';
+
+/** The Drizzle handle a service is built with. */
+export type AppDatabase = LibSQLDatabase<typeof schema>;
diff --git a/src/lib/server/services/categories.test.ts b/src/lib/server/services/categories.test.ts
index dbb21fb..164d798 100644
--- a/src/lib/server/services/categories.test.ts
+++ b/src/lib/server/services/categories.test.ts
@@ -1,25 +1,26 @@
 import { describe, it, expect, beforeEach } from 'vitest';
 import { groceries, categories } from '$lib/server/db/schema';
-import { eq } from 'drizzle-orm';
 import { createTestDb, type TestDb } from '$lib/server/db/test-helper';
-import { loadAll, add, deleteCategory } from './categories';
+import { CategoriesService } from './categories';
 
 describe('categories service', () => {
 	let db: TestDb['db'];
+	let service: CategoriesService;
 
 	beforeEach(async () => {
 		db = (await createTestDb()).db;
+		service = new CategoriesService(db);
 	});
 
 	it('loadAll returns categories sorted by name', async () => {
 		await db.insert(categories).values([{ name: 'Zebra' }, { name: 'Apple' }]);
 
-		const result = await loadAll(db);
+		const result = await service.loadAll();
 		expect(result.map((c) => c.name)).toEqual(['Apple', 'Zebra']);
 	});
 
 	it('add creates a category', async () => {
-		const cat = await add('Beverages', db);
+		const cat = await service.add('Beverages');
 		expect(cat.name).toBe('Beverages');
 
 		const rows = await db.select().from(categories);
@@ -41,7 +42,7 @@ describe('categories service', () => {
 			categoryId: cat.id,
 		});
 
-		await deleteCategory(cat.id, db);
+		await service.deleteCategory(cat.id);
 
 		const catRows = await db.select().from(categories);
 		expect(catRows).toHaveLength(0);
diff --git a/src/lib/server/services/categories.ts b/src/lib/server/services/categories.ts
index d6fa2c5..2ee6d2b 100644
--- a/src/lib/server/services/categories.ts
+++ b/src/lib/server/services/categories.ts
@@ -1,42 +1,39 @@
-import { db as defaultDb } from '$lib/server/db';
 import { categories } from '$lib/server/db/schema';
 import { eq, asc, sql } from 'drizzle-orm';
-import type { AppDatabase } from './groceries';
+import type { AppDatabase } from '$lib/server/db/types';
 import type { Category } from './types';
 
-export async function loadAll(db = defaultDb): Promise<Category[]> {
-	return db
-		.select()
-		.from(categories)
-		.orderBy(asc(categories.order), asc(categories.name));
-}
+export class CategoriesService {
+	constructor(private readonly db: AppDatabase) {}
 
-export async function add(name: string, db = defaultDb): Promise<Category> {
-	const [{ maxOrder }] = await db
-		.select({ maxOrder: sql<number>`COALESCE(MAX(${categories.order}), 0)` })
-		.from(categories);
-	const [inserted] = await db
-		.insert(categories)
-		.values({ name, order: (maxOrder ?? 0) + 1 })
-		.returning();
-	return inserted;
-}
+	async loadAll(): Promise<Category[]> {
+		return this.db
+			.select()
+			.from(categories)
+			.orderBy(asc(categories.order), asc(categories.name));
+	}
 
-export async function reorder(
-	orderedIds: number[],
-	db = defaultDb,
-): Promise<void> {
-	for (let i = 0; i < orderedIds.length; i++) {
-		await db
-			.update(categories)
-			.set({ order: i + 1 })
-			.where(eq(categories.id, orderedIds[i]));
+	async add(name: string): Promise<Category> {
+		const [{ maxOrder }] = await this.db
+			.select({ maxOrder: sql<number>`COALESCE(MAX(${categories.order}), 0)` })
+			.from(categories);
+		const [inserted] = await this.db
+			.insert(categories)
+			.values({ name, order: (maxOrder ?? 0) + 1 })
+			.returning();
+		return inserted;
 	}
-}
 
-export async function deleteCategory(
-	id: number,
-	db = defaultDb,
-): Promise<void> {
-	await db.delete(categories).where(eq(categories.id, id));
+	async reorder(orderedIds: number[]): Promise<void> {
+		for (let i = 0; i < orderedIds.length; i++) {
+			await this.db
+				.update(categories)
+				.set({ order: i + 1 })
+				.where(eq(categories.id, orderedIds[i]));
+		}
+	}
+
+	async deleteCategory(id: number): Promise<void> {
+		await this.db.delete(categories).where(eq(categories.id, id));
+	}
 }
diff --git a/src/lib/server/services/groceries.ts b/src/lib/server/services/groceries.ts
index c56599c..092aba0 100644
--- a/src/lib/server/services/groceries.ts
+++ b/src/lib/server/services/groceries.ts
@@ -2,12 +2,8 @@ import { db as defaultDb } from '$lib/server/db';
 import { groceries, categories, references } from '$lib/server/db/schema';
 import { eq, inArray, asc, desc } from 'drizzle-orm';
 import { referenceOrder } from './references';
-import type { LibSQLDatabase } from 'drizzle-orm/libsql';
-import type * as schema from '$lib/server/db/schema';
 import type { Category, Grocery, Reference } from './types';
 
-export type AppDatabase = LibSQLDatabase<typeof schema>;
-
 export interface EnrichedGrocery extends Grocery {
 	categoryName: string | null;
 	bestRef: Reference | null;
diff --git a/src/lib/server/services/grocery-actions.ts b/src/lib/server/services/grocery-actions.ts
index cedb46e..2eff205 100644
--- a/src/lib/server/services/grocery-actions.ts
+++ b/src/lib/server/services/grocery-actions.ts
@@ -1,6 +1,6 @@
 import { fail, redirect, type ActionFailure } from '@sveltejs/kit';
 import { addOrUncheck, loadUnchecked, toggle } from './groceries';
-import { add as addCategory } from './categories';
+import { categoriesService } from '$lib/server/services';
 import { numericId, parseFormString, parseOptionalNumber } from './validation';
 import { isUniqueViolation } from '$lib/server/db/errors';
 
@@ -52,7 +52,7 @@ export async function addCategoryAction(request: Request) {
 	}
 
 	try {
-		await addCategory(name);
+		await categoriesService.add(name);
 	} catch (error) {
 		if (isUniqueViolation(error)) {
 			return fail(400, { error: 'Cette catégorie existe déjà' });
diff --git a/src/lib/server/services/index.ts b/src/lib/server/services/index.ts
new file mode 100644
index 0000000..25a05be
--- /dev/null
+++ b/src/lib/server/services/index.ts
@@ -0,0 +1,8 @@
+import { db } from '$lib/server/db';
+import { CategoriesService } from './categories';
+
+/**
+ * Services wired once for the running server. Tests build their own instances
+ * with a test database instead of importing from here.
+ */
+export const categoriesService = new CategoriesService(db);
diff --git a/src/lib/server/services/projects.ts b/src/lib/server/services/projects.ts
index b58c2f1..443297b 100644
--- a/src/lib/server/services/projects.ts
+++ b/src/lib/server/services/projects.ts
@@ -1,7 +1,7 @@
 import { db as defaultDb } from '$lib/server/db';
 import { projects } from '$lib/server/db/schema';
 import { asc, eq } from 'drizzle-orm';
-import type { AppDatabase } from './groceries';
+import type { AppDatabase } from '$lib/server/db/types';
 import type { Project } from './types';
 
 export async function loadAll(db = defaultDb): Promise<Project[]> {
diff --git a/src/lib/server/services/references.ts b/src/lib/server/services/references.ts
index d48fb9b..accf1ba 100644
--- a/src/lib/server/services/references.ts
+++ b/src/lib/server/services/references.ts
@@ -1,7 +1,7 @@
 import { db as defaultDb } from '$lib/server/db';
 import { references } from '$lib/server/db/schema';
 import { eq, ne, and, desc, asc } from 'drizzle-orm';
-import type { AppDatabase } from './groceries';
+import type { AppDatabase } from '$lib/server/db/types';
 import type { Reference } from './types';
 
 /** Primary refs first, then best score, then insertion order. */
diff --git a/src/lib/server/services/routines.ts b/src/lib/server/services/routines.ts
index b1e210b..809d3f3 100644
--- a/src/lib/server/services/routines.ts
+++ b/src/lib/server/services/routines.ts
@@ -1,7 +1,7 @@
 import { db as defaultDb } from '$lib/server/db';
 import { routines, routineCompletions, projects } from '$lib/server/db/schema';
 import { eq, inArray, desc, sql } from 'drizzle-orm';
-import type { AppDatabase } from './groceries';
+import type { AppDatabase } from '$lib/server/db/types';
 import type { Routine, RoutineCompletion } from './types';
 import {
 	computeRoutineState,
diff --git a/src/routes/groceries/categories/+page.server.ts b/src/routes/groceries/categories/+page.server.ts
index 6e0e3b7..e8794fa 100644
--- a/src/routes/groceries/categories/+page.server.ts
+++ b/src/routes/groceries/categories/+page.server.ts
@@ -1,9 +1,5 @@
 import { fail } from '@sveltejs/kit';
-import {
-	loadAll,
-	deleteCategory,
-	reorder,
-} from '$lib/server/services/categories';
+import { categoriesService } from '$lib/server/services';
 import {
 	addCategoryAction,
 	idAction,
@@ -17,13 +13,14 @@ export interface CategoriesOutput {
 }
 
 export const load: PageServerLoad = async () => {
-	return { categories: await loadAll() };
+	return { categories: await categoriesService.loadAll() };
 };
 
 export const actions: Actions = {
 	add: ({ request }) => addCategoryAction(request),
 
-	delete: ({ request }) => idAction(request, deleteCategory),
+	delete: ({ request }) =>
+		idAction(request, (id) => categoriesService.deleteCategory(id)),
 
 	reorder: async ({ request }) => {
 		const data = await request.formData();
@@ -31,7 +28,7 @@ export const actions: Actions = {
 		if (ids.length === 0) {
 			return fail(400, { error: 'Aucune catégorie' });
 		}
-		await reorder(ids);
+		await categoriesService.reorder(ids);
 		return { success: true };
 	},
 };
diff --git a/src/routes/grocery/[id]/+page.server.ts b/src/routes/grocery/[id]/+page.server.ts
index 232568c..0f386f3 100644
--- a/src/routes/grocery/[id]/+page.server.ts
+++ b/src/routes/grocery/[id]/+page.server.ts
@@ -2,7 +2,7 @@ import { error, fail, redirect } from '@sveltejs/kit';
 import { db } from '$lib/server/db';
 import { groceries, categories } from '$lib/server/db/schema';
 import { eq } from 'drizzle-orm';
-import { loadAll as loadCategories } from '$lib/server/services/categories';
+import { categoriesService } from '$lib/server/services';
 import {
 	loadForGrocery,
 	add as addRef,
@@ -40,7 +40,7 @@ export const load: PageServerLoad = async ({ params, url }) => {
 		: [null];
 
 	const refs = await loadForGrocery(id);
-	const cats = await loadCategories();
+	const cats = await categoriesService.loadAll();
 	const from = url.searchParams.get('from') || '/';
 
 	return {