<?php

// This is a static var just to state where your cache dir will be
Import::$cache_dir = dirname(__FILE__).'/import_cache/';

// Usage of imports ex: $math = import('math.php'); echo $math->square(3);

class ImportCacheError extends Exception {}
class ImportFileError extends Exception {}
class ImportAttributeError extends Exception {}

function import($file) {
	static $imported = array();
	if (!isset($imported[$file])) {
		try {
			$imported[$file] = new Import($file);
		}
		catch (ImportFileError $e) {
			return false;
		}
	}
	return $imported[$file];
}

class Import {

	static $cache_dir;

	public $__variables__,
	$__functions__,
	$__classes__,
	$__file__,
	$__cache_file__,
	$__cached__,
	$__cached_filemtime__,
	$__filemtime__;

	function __construct($file) {
		$this->__file__ = $file;
		if (!is_file($file)) {
			throw new ImportFileError('File "'.$file.'" not found for import.');
		}
		if (!is_writeable(Import::$cache_dir)) {
			throw new ImportCacheError('Cannot write to "'.Import::$cache_dir.'"');
		}
		$this->__filemtime__ = filemtime($file);
		$this->__cache_file__ = Import::$cache_dir.md5($file).'.php';
		$this->__cached__ = is_file($this->__cache_file__) ? true : false;
		if ($this->__cached__) {
			$this->__loadCache__();
			if ($this->__cached_filemtime__ != $this->__filemtime__) {
				$this->__reloadImport__();
				$this->__saveCache__();
			}
			else {
				$this->__loadImport__();
			}
		}
		else {
			$this->__reloadImport__();
			$this->__saveCache__();
		}
	}

	public function __call($attr, $args) {
		$attr = strtolower($attr);
		if (in_array($attr, $this->__functions__)) {
			return call_user_func_array($attr, $args);
		}
		elseif (in_array($attr, $this->__classes__)) {
			return $attr;
		}
		else {
			throw new ImportAttributeError('Import has no "'.$attr.'" attribute.');
		}
	}

	public function __get($attr) {
		if (isset($this->__variables__[$attr])) {
			return $this->__variables__[$attr];
		}
		elseif (in_array(strtolower($attr), $this->__classes__)) {
			return $attr;
		}
		else {
			throw new ImportAttributeError('Import has no "'.$attr.'" attribute.');
		}
	}

	private function __reloadImport__() {
		$this->pre_vars = get_defined_vars();
		$this->pre_funcs = get_defined_functions();
		$this->pre_funcs = $this->pre_funcs['user'];
		$this->pre_classes = get_declared_classes();
		include $this->__file__;
		$this->__variables__ = array_slice(get_defined_vars(), count($this->pre_vars));
		$this->post_funcs = get_defined_functions();
		$this->post_funcs = $this->post_funcs['user'];
		$this->__functions__ = array_slice($this->post_funcs, count($this->pre_funcs));
		$this->__classes__ = array_slice(get_declared_classes(), count($this->pre_classes));
		unset($this->pre_vars, $this->pre_funcs, $this->pre_classes, $this->post_funcs);
	}

	private function __loadCache__() {
		$cache = include $this->__cache_file__;
		$this->__classes__ = $cache['classes'];
		$this->__functions__ = $cache['functions'];
		$this->__cached_filemtime__ = $cache['filemtime'];
	}

	private function __loadImport__() {
		$this->pre_vars = get_defined_vars();
		include $this->__file__;
		$this->__variables__ = array_slice(get_defined_vars(), count($this->pre_vars) - 1);
		unset($this->pre_vars);
	}

	private function __saveCache__() {
		$cache = '<?php return array(\'functions\' => '.
				var_export($this->__functions__, true).','.
				'\'classes\' => '.var_export($this->__classes__, true).',
				\'filemtime\' => '.filemtime($this->__file__).'); ?>';
		file_put_contents($this->__cache_file__, $cache);
	}
}
?>