<?php
 
 namespace Illuminate\View\Compilers;
 
 use InvalidArgumentException;
 use Illuminate\Filesystem\Filesystem;
 
 abstract class Compiler
 {
     /**
      * The Filesystem instance.
      *
      * @var \Illuminate\Filesystem\Filesystem
      */
     protected $files;
 
     /**
      * Get the cache path for the compiled views.
      *
      * @var string
      */
     protected $cachePath;
 
     /**
      * Create a new compiler instance.
      *
      * @param  \Illuminate\Filesystem\Filesystem  $files
      * @param  string  $cachePath
      * @return void
      *
      * @throws \InvalidArgumentException
      */
     public function __construct(Filesystem $files, $cachePath)
     {
         if (! $cachePath) {
             throw new InvalidArgumentException('Please provide a valid cache path.');
         }
 
         $this->files = $files;
         $this->cachePath = $cachePath;
     }
 
     /**
      * Get the path to the compiled version of a view.
      *
      * @param  string  $path
      * @return string
      */
     public function getCompiledPath($path)
     {
         return $this->cachePath.'/'.sha1($path).'.php';
     }
 
     /**
      * Determine if the view at the given path is expired.
      *
      * @param  string  $path
      * @return bool
      */
     public function isExpired($path)
     {
         $compiled = $this->getCompiledPath($path);
 
         // If the compiled file doesn't exist we will indicate that the view is expired
         // so that it can be re-compiled. Else, we will verify the last modification
         // of the views is less than the modification times of the compiled views.
         if (! $this->files->exists($compiled)) {
             return true;
         }
 
         return $this->files->lastModified($path) >=
                $this->files->lastModified($compiled);
     }
 }