import { Database } from 'bun:sqlite';
import { normalizeWhatsAppId } from './utils/whatsapp'; // Import the utility

// Function to get a database instance. Defaults to 'tasks.db'
export function getDb(filename: string = 'tasks.db'): Database {
  return new Database(filename);
}

// Default export for the main application database
export const db = getDb();

// Initialize function now accepts a database instance
export function initializeDatabase(instance: Database) {
  // Enable foreign key constraints
  instance.exec(`PRAGMA foreign_keys = ON;`);

  // Create users table first as others depend on it
  // Use TEXT for timestamps to store higher precision ISO8601 format easily
  instance.exec(`
    CREATE TABLE IF NOT EXISTS users (
      id TEXT PRIMARY KEY, -- WhatsApp user ID (normalized)
      first_seen TEXT DEFAULT (strftime('%Y-%m-%d %H:%M:%f', 'now')),
      last_seen TEXT DEFAULT (strftime('%Y-%m-%d %H:%M:%f', 'now'))
    );
  `);

  // Create groups table
  instance.exec(`
    CREATE TABLE IF NOT EXISTS groups (
      id TEXT PRIMARY KEY, -- Group ID (normalized)
      community_id TEXT NOT NULL,
      name TEXT,
      last_verified TEXT DEFAULT (strftime('%Y-%m-%d %H:%M:%f', 'now')),
      active BOOLEAN DEFAULT TRUE
    );
  `);

  // Create tasks table
  instance.exec(`
    CREATE TABLE IF NOT EXISTS tasks (
      id INTEGER PRIMARY KEY AUTOINCREMENT,
      description TEXT NOT NULL,
      created_at TEXT DEFAULT (strftime('%Y-%m-%d %H:%M:%f', 'now')),
      due_date TEXT NULL, -- Store dates as ISO8601 strings or YYYY-MM-DD
      completed BOOLEAN DEFAULT FALSE,
      completed_at TEXT NULL,
      group_id TEXT NULL, -- Normalized group ID
      created_by TEXT NOT NULL, -- Normalized user ID
      FOREIGN KEY (created_by) REFERENCES users(id) ON DELETE CASCADE,
      FOREIGN KEY (group_id) REFERENCES groups(id) ON DELETE SET NULL -- Optional: Link task to group
    );
  `);
    
  // Create task_assignments table
  instance.exec(`
    CREATE TABLE IF NOT EXISTS task_assignments (
      task_id INTEGER NOT NULL,
      user_id TEXT NOT NULL, -- Normalized user ID
      assigned_by TEXT NOT NULL, -- Normalized user ID
      assigned_at TEXT DEFAULT (strftime('%Y-%m-%d %H:%M:%f', 'now')),
      PRIMARY KEY (task_id, user_id),
      FOREIGN KEY (task_id) REFERENCES tasks(id) ON DELETE CASCADE,
      FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE,
      FOREIGN KEY (assigned_by) REFERENCES users(id) ON DELETE CASCADE
    );
  `);
}

/**
 * Ensures a user exists in the database based on their raw WhatsApp ID.
 * If the user exists, updates their last_seen timestamp.
 * If the user does not exist, creates them.
 * Uses the normalizeWhatsAppId utility.
 * Stores timestamps with millisecond precision.
 * 
 * @param rawUserId The raw WhatsApp ID (e.g., '12345@s.whatsapp.net').
 * @param instance The database instance to use (defaults to the main db).
 * @returns The normalized user ID if successful, otherwise null.
 */
export function ensureUserExists(rawUserId: string | null | undefined, instance: Database = db): string | null {
  const normalizedId = normalizeWhatsAppId(rawUserId);

  if (!normalizedId) {
    console.error(`[ensureUserExists] Could not normalize or invalid user ID provided: ${rawUserId}`);
    return null;
  }

  try {
    // Use strftime for millisecond precision timestamps
    const insertStmt = instance.prepare(`
      INSERT INTO users (id, first_seen, last_seen) 
      VALUES (?, strftime('%Y-%m-%d %H:%M:%f', 'now'), strftime('%Y-%m-%d %H:%M:%f', 'now'))
      ON CONFLICT(id) DO NOTHING;
    `);
    
    const updateStmt = instance.prepare(`
      UPDATE users 
      SET last_seen = strftime('%Y-%m-%d %H:%M:%f', 'now')
      WHERE id = ?;
    `);

    // Run as transaction for atomicity
    instance.transaction(() => {
      insertStmt.run(normalizedId);
      // Update last_seen even if the user was just inserted or already existed
      updateStmt.run(normalizedId); 
    })(); // Immediately invoke the transaction

    return normalizedId;

  } catch (error) {
    console.error(`[ensureUserExists] Database error for user ID ${normalizedId}:`, error);
    return null;
  }
}