<?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));
        };

        $rx = function ($grammar) use ($arg) {
            list($pattern, $result) = $grammar;
            $body = strtr($pattern, [" " => "\s*", "+" => "\s+", ":v" => "(\w+(\s*\.\s*\w+)*)", ":x" => "(\w+)"]);
            return ["/$body/",
                function ($x) use ($result, $arg) {
                    $body = preg_replace_callback("/#(\d+)/", function ($s) use($x, $arg) {
                        return $arg($x[$s[1]]);
                    }, $result);
                    return "<?php $body ?>";
                }];
        };
        
        $pattern = array_map($rx, [
            ["{% for+:v+in+:v %}", "foreach(\$#3 as \$n => \$#1): \$loop = ['first' => \$n == 0];"],
            ["{% endfor %}", "endforeach;"],
            ["{% if+:v %}", "if(isset(\$#1) && \$#1 ):"],
            ["{% endif %}", "endif;"],
            ["{{ :v }}", "echo \$#1;"],
            ["{{ :v\|:x }}", "echo #3(\$#1);"]
        ]);
   
        $result = file_get_contents($html);
        foreach($pattern as $arg) {
            list($key, $value) = $arg;
            $result = preg_replace_callback($key, $value, $result);
        }
        $this->code = $result;
    }

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