feat: add initial database schema and task service

src/db.ts

@@ -0,0 +1,39 @@
+import { Database } from 'bun:sqlite';
+
+export const db = new Database('tasks.db');
+
+export function initializeDatabase() {
+  db.exec(`
+    CREATE TABLE IF NOT EXISTS tasks (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      description TEXT NOT NULL,
+      created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+      due_date TIMESTAMP NULL,
+      completed BOOLEAN DEFAULT FALSE,
+      completed_at TIMESTAMP NULL,
+      group_id TEXT NOT NULL
+    );
+    
+    CREATE TABLE IF NOT EXISTS task_assignments (
+      task_id INTEGER NOT NULL,
+      user_id TEXT NOT NULL,
+      assigned_by TEXT NOT NULL,
+      assigned_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+      PRIMARY KEY (task_id, user_id),
+      FOREIGN KEY (task_id) REFERENCES tasks(id) ON DELETE CASCADE
+    );
+    
+    CREATE TABLE IF NOT EXISTS users (
+      phone_number TEXT PRIMARY KEY,
+      wa_id TEXT NOT NULL, // WhatsApp's @s.whatsapp.net ID
+      name TEXT,
+      last_seen TIMESTAMP
+    );
+    
+    CREATE TABLE IF NOT EXISTS groups (
+      id TEXT PRIMARY KEY,
+      community_id TEXT NOT NULL,
+      name TEXT
+    );
+  `);
+}

src/tasks/model.ts

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+export interface Task {
+  id: number;
+  description: string;
+  created_at: Date;
+  due_date: Date | null;
+  completed: boolean;
+  completed_at: Date | null;
+  group_id: string; // WhatsApp group ID where task was created
+}
+
+export interface TaskAssignment {
+  task_id: number;
+  user_id: string; // Normalized phone number
+  assigned_by: string; // Who assigned this
+  assigned_at: Date;
+}

src/tasks/service.ts

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+import { db } from '../db';
+import type { Task, TaskAssignment } from './model';
+
+export class TaskService {
+  static createTask(task: Omit<Task, 'id'>, assignments: Omit<TaskAssignment, 'task_id'>[]) {
+    return db.transaction(() => {
+      const insertTask = db.prepare(`
+        INSERT INTO tasks (description, due_date, group_id)
+        VALUES (?, ?, ?)
+        RETURNING id
+      `);
+      
+      const taskResult = insertTask.get(
+        task.description,
+        task.due_date?.toISOString(),
+        task.group_id
+      ) as { id: number };
+      
+      const insertAssignment = db.prepare(`
+        INSERT INTO task_assignments (task_id, user_id, assigned_by)
+        VALUES (?, ?, ?)
+      `);
+      
+      assignments.forEach(assignment => {
+        insertAssignment.run(
+          taskResult.id,
+          assignment.user_id,
+          assignment.assigned_by
+        );
+      });
+      
+      return taskResult.id;
+    });
+  }
+
+  // We'll add more methods here as we progress
+}

tests/unit/db.test.ts

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+import { db, initializeDatabase } from '../../src/db';
+import { describe, test, expect, beforeEach } from 'bun:test';
+
+describe('Database', () => {
+  beforeEach(() => {
+    // Reset database between tests
+    db.exec('DROP TABLE IF EXISTS tasks');
+    db.exec('DROP TABLE IF EXISTS task_assignments');
+    db.exec('DROP TABLE IF EXISTS users');
+    db.exec('DROP TABLE IF EXISTS groups');
+    initializeDatabase();
+  });
+
+  test('should create all required tables', () => {
+    const tables = db
+      .query("SELECT name FROM sqlite_master WHERE type='table'")
+      .all()
+      .map((t: any) => t.name);
+    
+    expect(tables).toContain('tasks');
+    expect(tables).toContain('task_assignments');
+    expect(tables).toContain('users');
+    expect(tables).toContain('groups');
+  });
+});