AssetManager.php

<?php

/**
 * Asset dependencies manager
 * @author: dphamtri
 * @date 20140124
 */
class AssetManager
{
    static $instance = null;

    public $_resources = array(
        'js'  => array(),
        'css' => array()
    );

    public $_output = array(
        'js'  => array(
            'optimized'    => false,
            'items'        => array(),
            'items_footer' => array(),
            'pool'         => array(),
            'echoed'       => false
        ),
        'css' => array(
            'optimized' => false,
            'items'     => array(),
            'pool'      => array(),
            'echoed'       => false
        )
    );

    /**
     * Return AssetManager instance
     * @return AssetManager
     */
    public static function getInstance()
    {
        if (is_null(self::$instance)) {
            self::$instance = new self;
        }
        return self::$instance;
    }

    /**
     * Add a javascript files to AM
     * @param string $id
     * @param string $src
     * @param array $dep
     * @param boolean $footer
     * @return $this
     */
    public function addJs($id, $src = '', $dep = array(), $footer = false)
    {
        $this->add('js', $id, $src, $dep, $footer);
        return $this;
    }

    /**
     * Add a stylesheet file to AM
     * @param string $id
     * @param string $src
     * @param array $dep
     * @param boolean $footer
     * @return $this
     */
    public function addCss($id, $src = '', $dep = array(), $footer = false)
    {
        $this->add('css', $id, $src, $dep, $footer);
        return $this;
    }

    public function add($type, $id, $src, $dep = array(), $footer = false)
    {
        if ( $this->_output[$type]['echoed'] ) {
            $footer = true;
        }
        $this->_resources[$type][$id] = array(
            'id'           => $id,
            'src'          => $src,
            'dependencies' => $dep,
            'footer'       => $footer
        );
        $this->setOutputOption($type, 'optimized', false);
        return $this;
    }

    public function setOutputOption($type, $key, $value = null)
    {
        $this->_output[$type][$key] = $value;
    }

    public function alterDependencies($type, $key, $value, $append = true)
    {
        $itemToAlter = null;
        if ( isset($this->_resources[$type][$key])) {
            $itemToAlter =& $this->_resources[$type][$key];
        }
        if ( ! $itemToAlter ) {
            return false;
        }
        if ($append) {
            $itemToAlter['dependencies'][] = $value;
        } else {
            $itemToAlter['dependencies'] = (array) $value;
        }
        if(isset($this->_output[$type]['pool'][$key])) {
            unset($this->_output[$type]['pool'][$key]);
        }
        return true;
    }

    public function output($type, $footer = false)
    {
        if (!$this->_output[$type]['optimized']) {
            $this->optimize($type);
        }

        $output = null;
        if ($footer) {
            $output = implode("\n", $this->_output[$type]['items_footer']);
            $this->__remove_outputed_resources($type, array_keys($this->_output[$type]['items_footer']));
        } else {
            $output = implode("\n", $this->_output[$type]['items']);
            $this->__remove_outputed_resources($type, array_keys($this->_output[$type]['items']));
        }
        $this->_output[$type]['echoed'] = true;
        return $output;
    }

    /**
     * Optimize assets for outputing
     * @param  string $type Type of asset to optimize
     * @return void
     */
    private function optimize($type)
    {
        $resources =& $this->_resources[$type];
        $output =& $this->_output[$type];
        $output['items'] = array();
        $output['items_footer'] = array();
        do {
            $loop   = false;
            $result = array_filter($resources, array($this, "__filter_{$type}_and_return_matches"));
            if ($result) {
                // new resource added to pool, continue to run check
                $loop = true;
                $this->__merge_output_resources($type, $result);
            }
        } while ($loop);
        $this->_output[$type]['optimized'] = true;
    }

    private function __merge_output_resources($type, $items = array())
    {
        $output   =& $this->_output[$type];
        $template = $type === 'js' ? "<script type='text/javascript' id='%s' src='%s'></script>" : "<link rel='stylesheet' id='%s' href='%s' />";
        foreach ($items as $item) {
            if ($item['footer'] || $this->__filter_dependecies_in_footer($type, $item['dependencies'])) {
                $output['items_footer'][$item['id']] = sprintf($template, $item['id'], $item['src']);
               $output['pool'][$item['id']]         = 1;

            } else {
                $output['items'][]           = sprintf($template, $item['id'], $item['src']);
               $output['pool'][$item['id']] = 0;
            }
        }

    }

    private function __remove_outputed_resources($type, $ids)
    {
        $that =& $this;
        array_walk(
            $this->_resources[$type],
            function ($value, $key) use ($ids, $type, $that) {
                if (in_array($key, $ids)) {
                    unset($that->_resources[$type][$key]);
                }
            }
        );
    }

    private function __filter_dependecies_in_footer($type, $dep)
    {
        $pool =& $this->_output[$type]['pool'];
        foreach ($dep as $d) {
            if ($pool[$d]) {
                return true;
            }
            
        }

        return false;
    }

    /**
     * Filter that return TRUE if all item's dependencies are matched
     * @param  [type] $item [description]
     * @return bool [type]       [description]
     */
    private function __filter_js_and_return_matches($item)
    {
        if (in_array($item['id'], array_keys($this->_output['js']['pool']))
            || ($item['dependencies'] != array_intersect(
                    $item['dependencies'],
                   array_keys($this->_output['js']['pool'])
                    // $this->_output['js']['pool']
                ))
        ) {
            return false;
        }

        return true;
    }

    private function __filter_css_and_return_matches($item)
    {
        if (in_array($item['id'], array_keys($this->_output['css']['pool']))
            || ($item['dependencies'] != array_intersect(
                    $item['dependencies'],
                   array_keys($this->_output['css']['pool'])
                    // $this->_output['js']['pool']
                ))
        ) {
            return false;
        }

        return true;
    }

    /**
     * @param $type
     * @param array $items
     * @return $this
     */
    public function setPool($type, $items = array())
    {
        if (!in_array($type, array('js', 'css'))) {
            $type = 'js';
        }
        $pools =& $this->_output[$type]['pool'];
        foreach ($items as $key => $value) {
            $pools[$key] = $value;
        }
        return $this;
    }
}