<?php

/**
 * A Mustache implementation in PHP.
 *
 * {@link http://defunkt.github.com/mustache}
 *
 * Mustache is a framework-agnostic logic-less templating language. It enforces separation of view
 * logic from template files. In fact, it is not even possible to embed logic in the template.
 *
 * This is very, very rad.
 *
 * @author Justin Hileman {@link http://justinhileman.com}
 */
class Mustache {

	protected $otag = '{{';
	protected $ctag = '}}';
	protected $tagRegEx;

	protected $template;
	protected $view;
	protected $partials;

	/**
	 * Mustache class constructor.
	 *
	 * This method accepts a $template string and a $view object. Optionally, pass an associative
	 * array of partials as well.
	 *
	 * @access public
	 * @param mixed $template (default: null)
	 * @param mixed $view (default: null)
	 * @param mixed $partials (default: null)
	 * @return void
	 */
	public function __construct($template = null, $view = null, $partials = null) {
		$this->template = $template;
		$this->view     = $view;
		$this->partials = $partials;
	}

	/**
	 * Render the given template and view object.
	 *
	 * Defaults to the template and view passed to the class constructor unless a new one is provided.
	 * Optionally, pass an associative array of partials as well.
	 *
	 * @access public
	 * @param string $template (default: null)
	 * @param mixed $view (default: null)
	 * @param mixed $partials (default: null)
	 * @return string Rendered Mustache template.
	 */
	public function render($template = null, $view = null, $partials = null) {
		if ($template === null) $template = $this->template;
		if ($partials !== null) $this->partials = $partials;

		if ($view === null) {
			if ($this->view) {
				$view = $this->view;
			} else {
				$view = $this;
			}
		}

		$template = $this->renderSection($template, $view);
		return $this->renderTags($template, $view);
	}

	/**
	 * Render boolean and enumerable sections.
	 *
	 * @access protected
	 * @param string $template
	 * @param mixed $view
	 * @return string
	 */
	protected function renderSection($template, $view) {
		if (strpos($template, $this->otag . '#') === false) {
			return $template;
		}

		$otag  = $this->prepareRegEx($this->otag);
		$ctag  = $this->prepareRegEx($this->ctag);
		$regex = '/' . $otag . '\\#(.+?)' . $ctag . '\\s*([\\s\\S]+?)' . $otag . '\\/\\1' . $ctag . '\\s*/m';

		$matches = array();
		while (preg_match($regex, $template, $matches, PREG_OFFSET_CAPTURE)) {
			$section  = $matches[0][0];
			$offset   = $matches[0][1];
			$tag_name = trim($matches[1][0]);
			$content  = $matches[2][0];

			$replace = '';
			$val = $this->getVariable($tag_name, $view);
			if (is_array($val)) {
				foreach ($val as $local_view) {
					$replace .= $this->render($content, $local_view);
				}
			} else if ($val) {
				$replace .= $content;
			}

			$template = substr_replace($template, $replace, $offset, strlen($section));
		}

		return $template;
	}

	/**
	 * Loop through and render individual Mustache tags.
	 *
	 * @access protected
	 * @param string $template
	 * @param mixed $view
	 * @return void
	 */
	protected function renderTags($template, $view) {
		if (strpos($template, $this->otag) === false) {
			return $template;
		}

		$otag  = $this->prepareRegEx($this->otag);
		$ctag  = $this->prepareRegEx($this->ctag);
		$this->tagRegEx = '/' . $otag . "(=|!|>|\\{|&)?([^\/#]+?)\\1?" . $ctag . "+/";
		$html = '';
		$matches = array();
		while (preg_match($this->tagRegEx, $template, $matches, PREG_OFFSET_CAPTURE)) {
			$tag      = $matches[0][0];
			$offset   = $matches[0][1];
			$modifier = $matches[1][0];
			$tag_name = trim($matches[2][0]);

			$html .= substr($template, 0, $offset);
			$html .= $this->renderTag($modifier, $tag_name, $view);
			$template = substr($template, $offset + strlen($tag));
		}

		return $html . $template;
	}

	/**
	 * Render the named tag, given the specified modifier.
	 *
	 * Accepted modifiers are `=` (change delimiter), `!` (comment), `>` (partial)
	 * `{` or `&` (don't escape output), or none (render escaped output).
	 *
	 * @access protected
	 * @param string $modifier
	 * @param string $tag_name
	 * @param mixed $view
	 * @return string
	 */
	protected function renderTag($modifier, $tag_name, $view) {
		switch ($modifier) {
			case '=':
				return $this->changeDelimiter($tag_name, $view);
				break;
			case '!':
				return $this->renderComment($tag_name, $view);
				break;
			case '>':
				return $this->renderPartial($tag_name, $view);
				break;
			case '{':
			case '&':
				return $this->renderUnescaped($tag_name, $view);
				break;
			case '':
			default:
				return $this->renderEscaped($tag_name, $view);
				break;
		}
	}

	/**
	 * Escape and return the requested tag.
	 *
	 * @access protected
	 * @param string $tag_name
	 * @param mixed $view
	 * @return string
	 */
	protected function renderEscaped($tag_name, $view) {
		return htmlentities($this->getVariable($tag_name, $view));
	}

	/**
	 * Render a comment (i.e. return an empty string).
	 *
	 * @access protected
	 * @param string $tag_name
	 * @param mixed $view
	 * @return string
	 */
	protected function renderComment($tag_name, $view) {
		return '';
	}

	/**
	 * Return the requested tag unescaped.
	 *
	 * @access protected
	 * @param string $tag_name
	 * @param mixed $view
	 * @return string
	 */
	protected function renderUnescaped($tag_name, $view) {
		return $this->getVariable($tag_name, $view);
	}

	/**
	 * Render the requested partial.
	 *
	 * @access protected
	 * @param string $tag_name
	 * @param mixed $view
	 * @return string
	 */
	protected function renderPartial($tag_name, $view) {
		$view = new self($this->getPartial($tag_name), $view);
		return $view->render();
	}

	/**
	 * Change the Mustache tag delimiter. This method also replaces this object's current
	 * tag RegEx with one using the new delimiters.
	 *
	 * @access protected
	 * @param string $tag_name
	 * @param mixed $view
	 * @return string
	 */
	protected function changeDelimiter($tag_name, $view) {
		$tags = explode(' ', $tag_name);
		$this->otag = $tags[0];
		$this->ctag = $tags[1];

		$otag  = $this->prepareRegEx($this->otag);
		$ctag  = $this->prepareRegEx($this->ctag);
		$this->tagRegEx = '/' . $otag . "(=|!|>|\\{|%)?([^\/#]+?)\\1?" . $ctag . "+/";
		return '';
	}

	/**
	 * Get a variable from the view object.
	 *
	 * If the view is an array, returns the value with array key $tag_name.
	 * If the view is an object, this will check for a public member variable
	 * named $tag_name. If none is available, this method will execute and return
	 * any class method named $tag_name. Failing all of the above, this method will
	 * return an empty string.
	 *
	 * @access protected
	 * @param string $tag_name
	 * @param mixed $view
	 * @return string
	 */
	protected function getVariable($tag_name, $view) {
		if (is_object($view)) {
			if (isset($view->$tag_name)) {
				return $view->$tag_name;
			} else if (method_exists($view, $tag_name)) {
				return $view->$tag_name();
			}
		} else if (isset($view[$tag_name])) {
			return $view[$tag_name];
		}
		return '';
	}

	/**
	 * Retrieve the partial corresponding to the requested tag name.
	 *
	 * Silently fails (i.e. returns '') when the requested partial is not found.
	 *
	 * @access protected
	 * @param string $tag_name
	 * @return string
	 */
	protected function getPartial($tag_name) {
		if (is_array($this->partials) && isset($this->partials[$tag_name])) {
			return $this->partials[$tag_name];
		}
		return '';
	}

	/**
	 * Prepare a string to be used in a regular expression.
	 *
	 * @access protected
	 * @param string $str
	 * @return string
	 */
	protected function prepareRegEx($str) {
		$replace = array(
			'\\' => '\\\\', '^' => '\^', '.' => '\.', '$' => '\$', '|' => '\|', '(' => '\(',
			')' => '\)', '[' => '\[', ']' => '\]', '*' => '\*', '+' => '\+', '?' => '\?',
			'{' => '\{', '}' => '\}', ',' => '\,'
		);
		return strtr($str, $replace);
	}
}