import { Client } from 'pg';

export type Credential = {
  user: string;
  database: string;
  port: number;
  host: string;
  password: string;
};

const defaultCred: Credential = {
  database: process.env.TYPEORM_DATABASE!,
  host: process.env.TYPEORM_HOST!,
  password: process.env.TYPEORM_PASSWORD!,
  port: Number(process.env.TYPEORM_PORT!),
  user: process.env.TYPEORM_USERNAME!,
};

export const getClient = async (): Promise<Client> => {
  const client = new Client({ ...defaultCred });
  await client.connect();
  return client;
};

export async function createDatabase(name: string): Promise<Client> {
  const client = await getClient();
  const existingDb = await client.query(`
      SELECT datname
      FROM pg_catalog.pg_database
      WHERE lower(datname) = lower('${name}');
    `);

  if (existingDb.rowCount > 0) {
    throw Error('DB exists');
  }
  await client.query(`CREATE DATABASE "${name}";`);
  return client;
}

export async function dropDatabase(
  client: Client,
  name: string
): Promise<void> {
  const existingDb = await client.query(`
      SELECT datname
      FROM pg_catalog.pg_database
      WHERE lower(datname) = lower('${name}');
    `);

  if (existingDb.rowCount === 0) {
    throw new Error('no database exists');
  }
  await dropConnections(client, name);

  await client.query(`DROP DATABASE "${name}";`);
}

export async function dropConnections(
  client: Client,
  name: string
): Promise<void> {
  await client.query(`
    SELECT
      pg_terminate_backend(pg_stat_activity.pid)
    FROM
      pg_stat_activity
    WHERE
      pg_stat_activity.datname = '${name}'
      AND pid <> pg_backend_pid();
  `);
}

export async function teardown(client: Client, name: string): Promise<void> {
  await dropDatabase(client, name);
  await client.end();
}