feat(db): implement task service logic and database schema with relational tables

db/schema.ts

@@ -1,9 +1,43 @@
 /**
  * @file db/schema.ts
- * @description Defines the PostgreSQL database schema for users using UUIDs, timestamps, and Drizzle ORM.
+ * @description Defines the PostgreSQL database schema for users, tasks, and task assignees using Drizzle ORM, including custom enums and relations.
  */
 
-import { pgTable, text, timestamp, uuid } from "drizzle-orm/pg-core";
+import {
+  pgEnum,
+  pgTable,
+  primaryKey,
+  text,
+  timestamp,
+  uuid,
+} from "drizzle-orm/pg-core";
+
+// ==========================================
+// Enums
+// ==========================================
+
+/**
+ * Enumeration representing the current lifecycle status of a task.
+ */
+export const taskStatusEnum = pgEnum("task_status", [
+  "todo",
+  "in_progress",
+  "await_feedback",
+  "done",
+]);
+
+/**
+ * Enumeration representing the priority level of a task.
+ */
+export const taskPriorityEnum = pgEnum("task_priority", [
+  "low",
+  "medium",
+  "high",
+]);
+
+// ==========================================
+// Tables
+// ==========================================
 
 /**
  * Database table definition for application users.
@@ -16,11 +50,43 @@ export const usersTable = pgTable("users", {
 });
 
 /**
- * Represents a user record selected from the database.
+ * Database table definition for application tasks.
  */
-export type User = typeof usersTable.$inferSelect;
+export const tasksTable = pgTable("tasks", {
+  id: uuid("id").defaultRandom().primaryKey(),
+  userId: uuid("user_id")
+    .notNull()
+    .references(() => usersTable.id, { onDelete: "cascade" }),
+  title: text("title").notNull(),
+  description: text("description").notNull(),
+  status: taskStatusEnum("status").default("todo").notNull(),
+  priority: taskPriorityEnum("priority").default("medium").notNull(),
+  dueDate: timestamp("due_date"),
+  createdAt: timestamp("created_at").defaultNow().notNull(),
+  updatedAt: timestamp("updated_at").defaultNow().notNull(),
+});
 
 /**
- * Represents a new user object required for insertion into the database.
+ * Junction table for assigning multiple users to tasks (Many-to-Many).
  */
-export type NewUser = typeof usersTable.$inferInsert;
+export const taskAssigneesTable = pgTable(
+  "task_assignees",
+  {
+    taskId: uuid("task_id")
+      .notNull()
+      .references(() => tasksTable.id, { onDelete: "cascade" }),
+    userId: uuid("user_id")
+      .notNull()
+      .references(() => usersTable.id, { onDelete: "cascade" }),
+    assignedAt: timestamp("assigned_at").defaultNow().notNull(),
+  },
+  (t) => ({
+    pk: primaryKey({ columns: [t.taskId, t.userId] }),
+  }),
+);
+
+// ==========================================
+// Type Exports
+// ==========================================
+
+export type Task = typeof tasksTable.$inferSelect;

package-lock.json

@@ -2608,7 +2608,7 @@
       "version": "20.19.43",
       "resolved": "https://registry.npmjs.org/@types/node/-/node-20.19.43.tgz",
       "integrity": "sha512-6oYBAi5ikg4Pl+kGsoYtawUMBT2zZMCvPNF7pVLnHZfd1zf38DRiWn/gT01RYCdUqkv7Fhr+C9ot4/tb+2sVvA==",
-      "devOptional": true,
+      "dev": true,
       "license": "MIT",
       "dependencies": {
         "undici-types": "~6.21.0"
@@ -8342,7 +8342,7 @@
       "version": "6.21.0",
       "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-6.21.0.tgz",
       "integrity": "sha512-iwDZqg0QAGrg9Rav5H4n0M64c3mkR59cJ6wQp+7C4nI0gsmExaedaYLNO44eT4AtBBwjbTiGPMlt2Md0T9H9JQ==",
-      "devOptional": true,
+      "dev": true,
       "license": "MIT"
     },
     "node_modules/unrs-resolver": {

services/task.service.ts

@@ -0,0 +1,55 @@
+/**
+ * @file services/task.service.ts
+ * @description Business logic service handling task permissions and database queries.
+ */
+
+import { db } from "@/db";
+import {
+  tasksTable,
+  taskAssigneesTable,
+  type Task as DbTask,
+} from "@/db/schema";
+import { and, eq, or, exists } from "drizzle-orm";
+
+/**
+ * Service class for handling task-related operations and database interactions.
+ */
+export class TaskService {
+  /**
+   * Verifies whether a user has access to a specific task as either the owner or an assignee.
+   *
+   * @async
+   * @param {string} taskId - The unique identifier of the task.
+   * @param {string} userId - The unique identifier of the user.
+   * @returns {Promise<DbTask | undefined>} The task object if access is verified, otherwise undefined.
+   */
+  static async verifyAccess(
+    taskId: string,
+    userId: string,
+  ): Promise<DbTask | undefined> {
+    const [task] = await db
+      .select()
+      .from(tasksTable)
+      .where(
+        and(
+          eq(tasksTable.id, taskId),
+          or(
+            eq(tasksTable.userId, userId),
+            exists(
+              db
+                .select({ taskId: taskAssigneesTable.taskId })
+                .from(taskAssigneesTable)
+                .where(
+                  and(
+                    eq(taskAssigneesTable.taskId, taskId),
+                    eq(taskAssigneesTable.userId, userId),
+                  ),
+                ),
+            ),
+          ),
+        ),
+      );
+
+    return task as DbTask | undefined;
+  }
+}