<?php

/**
 * Concrete class for APC caching strategy.
 *
 * @instantiator new
 * @author       Time.ly Network, Inc.
 * @since        2.0
 * @package      Ai1EC
 * @subpackage   Ai1EC.Cache.Strategy
 */
class Ai1ec_Cache_Strategy_Apc extends Ai1ec_Cache_Strategy {

    /**
     * is_available method
     *
     * Checks if APC is available for use.
     * Following pre-requisites are checked: APC functions availability,
     * APC is enabled via configuration and PHP is not running in CGI.
     *
     * @return bool Availability
     */
    static public function is_available() {
        return function_exists( 'apc_store' ) &&
               function_exists( 'apc_fetch' ) &&
               ini_get( 'apc.enabled' ) &&
               ( false === strpos( php_sapi_name(), 'cgi' ) );
    }

    /**
     *
     * @see Ai1ec_Get_Data_From_Cache::get_data()
     *
     */
    public function get_data( $dist_key ) {
        $key  = $this->_key( $dist_key );
        $data = apc_fetch( $key );
        if ( false === $data ) {
            throw new Ai1ec_Cache_Not_Set_Exception( "$dist_key not set" );
        }
        return $data;
    }

    /**
     *
     * @see Ai1ec_Write_Data_To_Cache::write_data()
     *
     */
    public function write_data( $dist_key, $value ) {
        $key          = $this->_key( $dist_key );
        $store_method = 'apc_add';
        if ( false !== ( $existing = apc_fetch( $key ) ) ) {
            if ( $value === $existing ) {

                return true;
            }
            $store_method = 'apc_store';
        } elseif ( false === function_exists( $store_method ) ) {

            $store_method = 'apc_store';
        }
        if ( false === $store_method( $key, $value ) ) {
            try {
                if ( $value !== $this->get_data( $key ) ) {
                    throw new Ai1ec_Cache_Not_Set_Exception( 'Data mis-match' );
                }
            } catch ( Ai1ec_Cache_Not_Set_Exception $excpt ) {

                throw new Ai1ec_Cache_Not_Set_Exception(
                    'Failed to write ' . $dist_key . ' to APC cache'
                );
            }
        }
        return true;
    }

    /**
     * (non-PHPdoc)
     * @see Ai1ec_Write_Data_To_Cache::delete_data()
     */
    public function delete_data( $key ) {
        if ( false === apc_delete( $this->_key( $key ) ) ) {
            return false;
        }
        return true;
    }

    /**
     *
     * @see Ai1ec_Write_Data_To_Cache::delete_matching()
     */
    public function delete_matching( $pattern ) {
        // not implemented - concider flushing APC cache
        return 0;
    }

    /**
     * _key method
     *
     * Make sure we are on the safe side - in case of multi-instances
     * environment some prefix is required.
     *
     * @param string $key Key to be used against APC cache
     *
     * @return string Key with prefix prepended
     */
    protected function _key( $key ) {
        static $prefix = null;
        if ( NULL === $prefix ) {
            $prefix = substr( md5( ai1ec_get_site_url() ), 0, 8 );
        }
        if ( 0 !== strncmp( $key, $prefix, 8 ) ) {
            $key = $prefix . $key;
        }
        return $key;
    }

}