<?php namespace Laravel; use FilesystemIterator as fIterator; use Closure;

class Blade {

	/**
	 * All of the compiler functions used by Blade.
	 *
	 * @var array
	 */
	protected static $compilers = array(
		'extensions',
		'layouts',
		'comments',
		'echos',
		'forelse',
		'empty',
		'endforelse',
		'structure_openings',
		'structure_closings',
		'else',
		'unless',
		'endunless',
		'includes',
		'render_each',
		'render',
		'yields',
		'yield_sections',
		'section_start',
		'section_end',
	);

	/**
	 * An array of user defined compilers.
	 *
	 * @var array
	 */
	protected static $extensions = array();

	/**
	 * Register the Blade view engine with Laravel.
	 *
	 * @return void
	 */
	public static function sharpen()
	{
		Event::listen(View::engine, function($view)
		{
			// The Blade view engine should only handle the rendering of views which
			// end with the Blade extension. If the given view does not, we will
			// return false so the View can be rendered as normal.
			if ( ! str_contains($view->path, BLADE_EXT))
			{
				return;
			}

			$compiled = Blade::compiled($view->path);

			// If the view doesn't exist or has been modified since the last time it
			// was compiled, we will recompile the view into pure PHP from it's
			// Blade representation, writing it to cached storage.
			if ( ! file_exists($compiled) or Blade::expired($view->view, $view->path))
			{
				file_put_contents($compiled, Blade::compile($view));
			}

			$view->path = $compiled;

			// Once the view has been compiled, we can simply set the path to the
			// compiled view on the view instance and call the typical "get"
			// method on the view to evaluate the compiled PHP view.
			return ltrim($view->get());
		});
	}

	/**
	 * Register a custom Blade compiler.
	 *
	 * <code>
	 * 		Blade::extend(function($view)
	 *		{
	 * 			return str_replace('foo', 'bar', $view);
	 * 		});
	 * </code>
	 *
	 * @param  Closure  $compiler
	 * @return void
	 */
	public static function extend(Closure $compiler)
	{
		static::$extensions[] = $compiler;
	}

	/**
	 * Determine if a view is "expired" and needs to be re-compiled.
	 *
	 * @param  string  $view
	 * @param  string  $path
	 * @return bool
	 */
	public static function expired($view, $path)
	{
		return filemtime($path) > filemtime(static::compiled($path));
	}

	/**
	 * Compiles the specified file containing Blade pseudo-code into valid PHP.
	 *
	 * @param  string  $path
	 * @return string
	 */
	public static function compile($view)
	{
		return static::compile_string(file_get_contents($view->path), $view);
	}

	/**
	 * Compiles the given string containing Blade pseudo-code into valid PHP.
	 *
	 * @param  string  $value
	 * @param  View    $view
	 * @return string
	 */
	public static function compile_string($value, $view = null)
	{
		foreach (static::$compilers as $compiler)
		{
			$method = "compile_{$compiler}";

			$value = static::$method($value, $view);
		}

		return $value;
	}

	/**
	 * Rewrites Blade "@layout" expressions into valid PHP.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_layouts($value)
	{
		// If the Blade template is not using "layouts", we'll just return it
		// unchanged since there is nothing to do with layouts and we will
		// just let the other Blade compilers handle the rest.
		if ( ! starts_with($value, '@layout'))
		{
			return $value;
		}

		// First we'll split out the lines of the template so we can get the
		// layout from the top of the template. By convention it must be
		// located on the first line of the template contents.
		$lines = preg_split("/(\r?\n)/", $value);

		$pattern = static::matcher('layout');

		$lines[] = preg_replace($pattern, '$1@include$2', $lines[0]);

		// We will add a "render" statement to the end of the templates and
		// then slice off the "@layout" shortcut from the start so the
		// sections register before the parent template renders.
		return implode(CRLF, array_slice($lines, 1));
	}

	/**
	 * Extract a variable value out of a Blade expression.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function extract($value, $expression)
	{
		preg_match('/@layout(\s*\(.*\))(\s*)/', $value, $matches);

		return str_replace(array("('", "')"), '', $matches[1]);
	}

	/**
	 * Rewrites Blade comments into PHP comments.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_comments($value)
	{
		$value = preg_replace('/\{\{--(.+?)(--\}\})?\n/', "<?php // $1 ?>", $value);

		return preg_replace('/\{\{--((.|\s)*?)--\}\}/', "<?php /* $1 */ ?>\n", $value);
	}

	/**
	 * Rewrites Blade echo statements into PHP echo statements.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_echos($value)
	{
		return preg_replace('/\{\{(.+?)\}\}/', '<?php echo $1; ?>', $value);
	}

	/**
	 * Rewrites Blade "for else" statements into valid PHP.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_forelse($value)
	{
		preg_match_all('/(\s*)@forelse(\s*\(.*\))(\s*)/', $value, $matches);

		foreach ($matches[0] as $forelse)
		{
			preg_match('/\s*\(\s*(\S*)\s/', $forelse, $variable);

			// Once we have extracted the variable being looped against, we can add
			// an if statement to the start of the loop that checks if the count
			// of the variable being looped against is greater than zero.
			$if = "<?php if (count({$variable[1]}) > 0): ?>";

			$search = '/(\s*)@forelse(\s*\(.*\))/';

			$replace = '$1'.$if.'<?php foreach$2: ?>';

			$blade = preg_replace($search, $replace, $forelse);

			// Finally, once we have the check prepended to the loop we'll replace
			// all instances of this forelse syntax in the view content of the
			// view being compiled to Blade syntax with real PHP syntax.
			$value = str_replace($forelse, $blade, $value);
		}

		return $value;
	}

	/**
	 * Rewrites Blade "empty" statements into valid PHP.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_empty($value)
	{
		return str_replace('@empty', '<?php endforeach; ?><?php else: ?>', $value);
	}

	/**
	 * Rewrites Blade "forelse" endings into valid PHP.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_endforelse($value)
	{
		return str_replace('@endforelse', '<?php endif; ?>', $value);
	}

	/**
	 * Rewrites Blade structure openings into PHP structure openings.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_structure_openings($value)
	{
		$pattern = '/(\s*)@(if|elseif|foreach|for|while)(\s*\(.*\))/';

		return preg_replace($pattern, '$1<?php $2$3: ?>', $value);
	}

	/**
	 * Rewrites Blade structure closings into PHP structure closings.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_structure_closings($value)
	{
		$pattern = '/(\s*)@(endif|endforeach|endfor|endwhile)(\s*)/';

		return preg_replace($pattern, '$1<?php $2; ?>$3', $value);
	}

	/**
	 * Rewrites Blade else statements into PHP else statements.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_else($value)
	{
		return preg_replace('/(\s*)@(else)(\s*)/', '$1<?php $2: ?>$3', $value);
	}

	/**
	 * Rewrites Blade "unless" statements into valid PHP.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_unless($value)
	{
		$pattern = '/(\s*)@unless(\s*\(.*\))/';

		return preg_replace($pattern, '$1<?php if( ! ($2)): ?>', $value);
	}

	/**
	 * Rewrites Blade "unless" endings into valid PHP.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_endunless($value)
	{
		return str_replace('@endunless', '<?php endif; ?>', $value);
	}

	/**
	 * Rewrites Blade @include statements into valid PHP.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_includes($value)
	{
		$pattern = static::matcher('include');

		return preg_replace($pattern, '$1<?php echo view$2->with(get_defined_vars())->render(); ?>', $value);
	}

	/**
	 * Rewrites Blade @render statements into valid PHP.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_render($value)
	{
		$pattern = static::matcher('render');

		return preg_replace($pattern, '$1<?php echo render$2; ?>', $value);
	}

	/**
	 * Rewrites Blade @render_each statements into valid PHP.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_render_each($value)
	{
		$pattern = static::matcher('render_each');

		return preg_replace($pattern, '$1<?php echo render_each$2; ?>', $value);
	}

	/**
	 * Rewrites Blade @yield statements into Section statements.
	 *
	 * The Blade @yield statement is a shortcut to the Section::yield method.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_yields($value)
	{
		$pattern = static::matcher('yield');

		return preg_replace($pattern, '$1<?php echo \\Laravel\\Section::yield$2; ?>', $value);
	}

	/**
	 * Rewrites Blade yield section statements into valid PHP.
	 *
	 * @return string
	 */
	protected static function compile_yield_sections($value)
	{
		$replace = '<?php echo \\Laravel\\Section::yield_section(); ?>';

		return str_replace('@yield_section', $replace, $value);
	}

	/**
	 * Rewrites Blade @section statements into Section statements.
	 *
	 * The Blade @section statement is a shortcut to the Section::start method.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_section_start($value)
	{
		$pattern = static::matcher('section');

		return preg_replace($pattern, '$1<?php \\Laravel\\Section::start$2; ?>', $value);
	}

	/**
	 * Rewrites Blade @endsection statements into Section statements.
	 *
	 * The Blade @endsection statement is a shortcut to the Section::stop method.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_section_end($value)
	{
		return preg_replace('/@endsection/', '<?php \\Laravel\\Section::stop(); ?>', $value);
	}

	/**
	 * Execute user defined compilers.
	 *
	 * @param  string  $value
	 * @return string
	 */
	protected static function compile_extensions($value)
	{
		foreach (static::$extensions as $compiler)
		{
			$value = $compiler($value);
		}

		return $value;
	}	

	/**
	 * Get the regular expression for a generic Blade function.
	 *
	 * @param  string  $function
	 * @return string
	 */
	public static function matcher($function)
	{
		return '/(\s*)@'.$function.'(\s*\(.*\))/';
	}

	/**
	 * Get the fully qualified path for a compiled view.
	 *
	 * @param  string  $view
	 * @return string
	 */
	public static function compiled($path)
	{
		return path('storage').'views/'.md5($path);
	}

}