task

#!/usr/bin/env php
<?php
$included_files = get_included_files();
if (__FILE__ == $included_files[0]) {
	$runner = new Runner;
	try {
		$runner->run_with_cli_args(array_slice($argv, 1));
	} catch ( Exception $e )  {
		fwrite(STDERR, "Error: " . $e->getMessage() . "\n");
		exit( 1 );
	}
}

function task($id, $callback) {
	$task = new Task($id, $callback);
	$tasks = Tasks::get_instance();
	$tasks->register($task);
}

class Tasks {
	static $instance = null;

	var $tasks = array();

	static function get_instance() {
		if (is_null(self::$instance)) {
			self::$instance = new Tasks;
		}
		return self::$instance;
	}

	static function register($task) {
		$tasks = self::$instance;
		$tasks->tasks[$task->id] = $task;
	}

	function get_task_by_id($id) {
		if (!isset($this->tasks[$id])) {
			throw new TasksException("Task '$id' does not exist.");
		}
		return $this->tasks[$id];
	}

	function get() {
		return $this->tasks;
	}
}

class Task {
	var $id;
	var $callback;

	function __construct($id, $callback) {
		$this->id = $id;
		$this->callback = $callback;
	}

	function run($args) {
		return call_user_func_array($this->callback, $args);
	}
}

class Runner {
	function run_with_cli_args($cli_args) {
		$this->load_tasks();
		$this->validate_cli_args($cli_args);
		$id = $this->get_id_from_cli_args($cli_args);
		$runnable_args = $this->get_runnable_args_from_cli_args($cli_args);
		$this->run_task_by_id($id, $runnable_args);
	}

	function run_task_by_id($id, $args) {
		$task = $this->tasks->get_task_by_id( $id );
		return $task->run($args);
	}

	function load_tasks() {
		if (is_readable('./Tasksfile'))
			require_once './Tasksfile';
		else
			throw new TasksException('Tasksfile is missing');
		$this->tasks = Tasks::get_instance();
	}

	function get_id_from_cli_args($cli_args) {
		return $cli_args[0];
	}

	function get_runnable_args_from_cli_args($cli_args) {
		return array_slice($cli_args, 1);
	}

	function validate_cli_args($args) {
		if (empty($args)) {
			$this->show_usage_and_die();
		}
	}

	function show_usage_and_die() {
		global $argv;
		fwrite(STDERR, basename($argv[0]) . " <task> [<args>]\n");
		foreach($this->tasks->get() as $id => $task) {
			fwrite(STDERR, "     $id\n");
		}
		exit( 1 );
	}
}

class TasksException extends RuntimeException {
}