<?php

class Klein {  
    private $code;

    function compile($html) {
        $arg = function($name) {
            $list = explode(".", $name);
            $first = array_shift($list);
            return "\$$first" . implode("", array_map(function($x) { return "['$x']"; }, $list));
        };

        $var = "(\w+(\s*\.\s*\w+)*)";

        list($for, $endfor, $if, $endif) = array_map(
            function ($args) {
                $body = implode($args, "\s*");
                return "/{%\s*$body\s*%}/";
            },[
                ['for', $var, 'in', $var],
                ['endfor'],
                ['if', $var],
                ['endif']
            ]);

        $pattern = [
            $for => function ($x) use($arg) { 
                return "<?php foreach({$arg($x[3])} as {$arg($x[1])}): ?>"; 
            },
            $endfor => function ($x) { 
                return "<?php endforeach; ?>"; 
            },
            $if => function ($x) use ($arg) { 
                return "<?php if(isset({$arg($x[1])})): ?>"; 
            },
            $endif => function ($x) { 
                return "<?php endif; ?>"; 
            },
            "/{{\s*$var\s*}}/" => function ($x) use ($arg) { 
                return "<?php echo {$arg($x[1])}; ?>"; 
            },
        ];
    
        $result = file_get_contents($html);
        foreach($pattern as $key => $value) {
            $result = preg_replace_callback($key, $value, $result);
        }

        $this->code = $result;
    }

    function render($vars) {    
        extract($vars);        
        ob_start();
        eval(" ?>".$this->code."<?php ");
        return ob_get_clean();
    }
}