tasks.ts

type Task = () => void | Promise<void>;

function wrapTask (name: string, task: Task): Task {
	return async function $ () {
		console.log(`[Starting: ${name}]`);
		const start = Date.now();
		await task();
		const duration = (Date.now() - start) / 1000;
		console.log(`[Done: ${name} (${duration.toFixed(2)}s)]`);
	};
}
function wrapUnnamedTask (task: Task): Task {
	const name = task.name;
	if (!name.startsWith('$')) {
		task = wrapTask(name, task);
	}
	return task;
}

export function series (...tasks: Task[]): Task {
	return async function $ () {
		for (const task of tasks.map(wrapUnnamedTask)) {
			await task();
		}
	};
}
export function parallel (...tasks: Task[]): Task {
	return async function $ () {
		await Promise.all(
			tasks.map(async task => {
				await wrapUnnamedTask(task)();
			})
		);
	};
}

/**
 * Given a record of tasks, it will run the task as dictated by the CLI arguments.
 *
 * To run a specific task, run `node path/to/script.js taskName`.
 */
export function run (tasks: Partial<Record<string, Task>>) {
	const selected = String(process.argv[2]);
	const task = tasks[selected];
	if (!task) {
		console.error(
			`No such task ${selected}. Available tasks: ${Object.keys(tasks).join(', ')}`
		);
	}
	else {
		runTask(task);
	}
}

/**
 * Runs the given task.
 */
export function runTask (tasks: Task) {
	Promise.resolve()
		.then(() => tasks())
		.catch(reason => {
			console.error('Error:');
			console.error(reason);
		});
}