<?php
namespace Blog\Template;

use Exception;

class Twig {
  private $blocks = [];
  private $viewsPath;
  private $debugMode;

  public function __construct($viewsPath, $debugMode = false) {
    $this->viewsPath = rtrim($viewsPath, '/') . '/';
    $this->debugMode = $debugMode;
  }

  public function render($file, $data = []) {
    try {
      $code = $this->includeFiles($file);
      $code = $this->compileCode($code);
      extract($data, EXTR_SKIP);

      ob_start();
      eval('?>' . $code);
      return ob_get_clean();
    } catch(Exception $e) {
      if($this->debugMode)
        echo "Error rendering template: " . $e->getMessage();
      throw $e;
    }
  }

  private function compileCode($code) {
    $code = $this->compileBlock($code);
    $code = $this->compileYield($code);
    $code = $this->compileEchos($code);
    $code = $this->compilePHP($code);
    return $code;
  }

  private function includeFiles($file) {
    $filePath = $this->viewsPath . preg_replace("/\.twig$/", "", $file) . ".twig";
    
    if(!file_exists($filePath))
      throw new Exception("View file not found: {$filePath}");
    
    $code = file_get_contents($filePath);
    preg_match_all('/{% ?(extends|include) ?\'?(.*?)\'? ?%}/i', $code, $matches, PREG_SET_ORDER);
    
    foreach($matches as $match) {
      $includedCode = $this->includeFiles($match[2]);
      $code = str_replace($match[0], $includedCode, $code);
    }
    return preg_replace('/{% ?(extends|include) ?\'?(.*?)\'? ?%}/i', '', $code);
  }

  private function compilePHP($code) {
    return preg_replace('~\{%\s*(.+?)\s*%}~is', '<?php $1 ?>', $code);
  }

  private function compileEchos($code) {
    $code = preg_replace('~\{\{\s*(.+?)\s*\}\}~is', '<?=$1?>', $code);
    return preg_replace('~\{\{\{\s*(.+?)\s*\}\}\}~is', '<?=htmlspecialchars($1, ENT_QUOTES, "UTF-8")?>', $code);
  }

  private function compileEscapedEchos($code) {
    return preg_replace('~\{{{\s*(.+?)\s*}}}~is', '<?=htmlentities($1, ENT_QUOTES, "UTF-8")?>', $code);
  }

  private function compileBlock($code) {
    preg_match_all('/{% ?block ?(.*?) ?%}(.*?){% ?endblock ?%}/is', $code, $matches, PREG_SET_ORDER);
    foreach($matches as $match) {
      if(!isset($this->blocks[$match[1]]))
        $this->blocks[$match[1]] = '';
      $this->blocks[$match[1]] = str_replace('@parent', $this->blocks[$match[1]], $match[2]);
      $code = str_replace($match[0], '', $code);
    }
    return $code;
  }

  private function compileYield($code) {
    foreach($this->blocks as $block => $value)
      $code = preg_replace('/{% ?yield ?' . $block . ' ?%}/', $value, $code);
    return preg_replace('/{% ?yield ?(.*?) ?%}/i', '', $code);
  }
}