<?php
/**
 * The Strangecode Codebase - a general application development framework for PHP
 * For details visit the project site: <http://trac.strangecode.com/codebase/>
 * Copyright 2001-2012 Strangecode, LLC
 *
 * This file is part of The Strangecode Codebase.
 *
 * The Strangecode Codebase is free software: you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at your option)
 * any later version.
 *
 * The Strangecode Codebase is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * The Strangecode Codebase. If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * Currency.inc.php
 *
 * Class to convert currency values.
 *
 * @author  Quinn Comendant <quinn@strangecode.com>
 * @version 1.5
 *
 * Example of use:
---------------------------------------------------------------------
$currency = new Currency();
$currency->setParam(array('cache_dir' => COMMON_BASE . '/tmp/xcache'));
echo $currency->getRage('eur', 'usd');
echo $currency->getValue(125.50, 'eur', 'usd');
---------------------------------------------------------------------
 */

class Currency
{
    // Configuration parameters for this object.
    protected $_params = array(
        'cache_result' => true,
        'cache_dir' => '',
        'cache_age' => 86400, // 24 hours.
        'api' => 'ecb', // 'xurrency' or 'ecb'. Add other APIs under the _performAPICall() method.
        'api_key' => '', // Used only by xurrency API.
    );

    // Static runtime cache of values.
    private static $rates = array();

    /**
     * Cart constructor.
     */
    public function __construct($params=array())
    {
        $app =& App::getInstance();

        // Set custom parameters.
        $this->setParam($params);

        // Setup cache directory.
        if ($this->getParam('cache_result')) {
            if ('' == $this->getParam('cache_dir')) {
                // Use a sane default cache directory.
                $this->setParam(array('cache_dir' => '/tmp/xcache_' . md5(COMMON_BASE)));
            }
            if (!is_dir($this->getParam('cache_dir'))) {
                $app->logMsg(sprintf('Creating cache_dir: %s', $this->getParam('cache_dir')), LOG_INFO, __FILE__, __LINE__);
                if (!mkdir($this->getParam('cache_dir'))) {
                    $app->logMsg(sprintf('Could not create cache_dir: %s', $this->getParam('cache_dir')), LOG_WARNING, __FILE__, __LINE__);
                }
            }
        }
    }

    /**
     * Set the params of this object.
     *
     * @param  array $params   Array of param keys and values to set.
     */
    public function setParam($params=null)
    {
        if (isset($params) && is_array($params)) {
            // Merge new parameters with old overriding only those passed.
            $this->_params = array_merge($this->_params, $params);
        }
    }

    /**
     * Return the value of a parameter, if it exists.
     *
     * @access public
     * @param string $param        Which parameter to return.
     * @return mixed               Configured parameter value.
     */
    public function getParam($param)
    {
        $app =& App::getInstance();

        if (array_key_exists($param, $this->_params)) {
            return $this->_params[$param];
        } else {
            $app->logMsg(sprintf('Parameter is not set: %s', $param), LOG_DEBUG, __FILE__, __LINE__);
            return null;
        }
    }

    /*
    * Return the exchange value between the two given currencies for given amount.
    *
    * @access   public
    * @param    float   $amount Base amount to convert from.
    * @param    string  $base   3-letter currency code to convert from.
    * @param    string  $target 3-letter currency code to convert to.
    * @return   mixed   Float converted currency value, or false on error.
    * @author   Quinn Comendant <quinn@strangecode.com>
    * @version  1.0
    * @since    05 May 2008 23:50:59
    */
    public function getValue($amount, $base, $target)
    {
        if (false !== ($rate = $this->getRate($base, $target))) {
            return abs($rate * $amount);
        } else {
            return false;
        }
    }

    /*
    * Return the currency conversion rate as a ratio.
    *
    * @access   public
    * @param    string  $base   3-letter currency code to convert from.
    * @param    string  $target 3-letter currency code to convert to.
    * @return   mixed   Float exchange rate value, or false on error.
    * @author   Quinn Comendant <quinn@strangecode.com>
    * @version  1.0
    * @since    25 May 2011 01:26:24
    */
    public function getRate($base, $target)
    {
        $app =& App::getInstance();

        // If we've looked-up this rate during this run, return it from the runtime cache.
        $rate_key = sprintf('%s-to-%s', $base, $target);
        if (isset(self::$rates[$rate_key])) {
            $app->logMsg(sprintf('Found %s in runtime cache: %s', $rate_key, self::$rates[$rate_key]), LOG_DEBUG, __FILE__, __LINE__);
            return self::$rates[$rate_key];
        }

        $cache_file_path = sprintf('%s/%s-to-%s', $this->getParam('cache_dir'), $base, $target);
        if (!is_dir(dirname($cache_file_path))) {
            mkdir(dirname($cache_file_path));
        }
        $cache_file_mtime = @filemtime($cache_file_path);
        if (!$this->getParam('cache_result') || !$cache_file_mtime || $cache_file_mtime < time() - $this->getParam('cache_age')) {
            // Get fresh data and create cached file if missing or expired.
            $app->logMsg(sprintf('Getting fresh currency exchange rate: %s-to-%s', $base, $target), LOG_DEBUG, __FILE__, __LINE__);
            $value = $this->_performAPICall(array(
                'amount' => '1',
                'base' => $base,
                'target' => $target
            ));
            if (false === $value || !is_numeric($value)) {
                // Failed retrieving value. Use cached copy for now.
                $app->logMsg(sprintf('Failed getting currency exchange rate: %s-to-%s, using cached copy', $base, $target), LOG_NOTICE, __FILE__, __LINE__);
                if (!$value = @file_get_contents($cache_file_path)) {
                    $app->logMsg(sprintf('Failed reading cached exchange rate file: %s', $cache_file_path), LOG_ERR, __FILE__, __LINE__);
                    return false;
                }
            } else if ($this->getParam('cache_result') && !filePutContents($cache_file_path, $value)) {
                $app->logMsg(sprintf('Failed writing to target rate file: %s', $cache_file_path), LOG_ERR, __FILE__, __LINE__);
                return false;
            }
        } else {
            $app->logMsg(sprintf('Getting cached currency exchange rate: %s-to-%s', $base, $target), LOG_DEBUG, __FILE__, __LINE__);
            if (!$value = file_get_contents($cache_file_path)) {
                $app->logMsg(sprintf('Failed reading target rate file: %s', $cache_file_path), LOG_ERR, __FILE__, __LINE__);
                return false;
            }
        }
        $app->logMsg(sprintf('Found currency exchange rate: %s-to-%s = %s', $base, $target, $value), LOG_DEBUG, __FILE__, __LINE__);

        // Store the value in the runtime cache.
        self::$rates[$rate_key] = trim($value);

        return trim($value);
    }

    /**
     * @param  string
     * @param  array
     * @return mixed
     * @access private
     */
    protected function _performAPICall($parameters=null)
    {
        $app =& App::getInstance();

        switch ($this->getParam('api')) {
        case 'xurrency' :
            $api_url = 'http://xurrency.com/api/%s/%s/%s';
            if ('' != $this->getParam('api_key')) {
                $api_url .= '?key=' . $this->getParam('api_key');
            }
            $json_response = file_get_contents(sprintf($api_url, $parameters['base'], $parameters['target'], $parameters['amount']));
            $json = json_decode($json_response);
            if (null === $json) {
                $app->logMsg(sprintf('Could not decode JSON response: %s', getDump($json_response)), LOG_WARNING, __FILE__, __LINE__);
                return false;
            } else if ($json->status === 'fail') {
                if ($json->code == 3) {
                    $app->logMsg(sprintf('Xurrency error LimitReachedException: %s', $json->message), LOG_WARNING, __FILE__, __LINE__);
                } elseif ($json->code == 2) {
                    $app->logMsg(sprintf('Xurrency error InvalidCurrencies: %s', $json->message), LOG_WARNING, __FILE__, __LINE__);
                } elseif ($json->code == 4 || $json->code == 5) {
                    $app->logMsg(sprintf('Xurrency error InvalidKey: %s', $json->message), LOG_WARNING, __FILE__, __LINE__);
                } else {
                    $app->logMsg(sprintf('Xurrency unknown error: %s', $json->message), LOG_WARNING, __FILE__, __LINE__);
                }
                return false;
            } else {
                return $json->result->value;
            }
            break;

        case 'ecb' :
            // Fetch XML from ECB <http://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml>
            $api_url = 'http://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml';
            if (false === ($sXML = file_get_contents($api_url))) {
                $app->logMsg(sprintf('Failed to load ECB XML data from: %s', $api_url), LOG_WARNING, __FILE__, __LINE__);
                return false;
            }
            if (false === ($oXML = simplexml_load_string($sXML))) {
                $app->logMsg(sprintf('Failed to decode ECB XML data: %s', truncate($sXML, 200, 'end')), LOG_WARNING, __FILE__, __LINE__);
                return false;
            }
            // Populate Array
            foreach ($oXML->Cube->Cube->Cube as $oRate) {
                foreach ($oRate->attributes() as $sKey => $sAttribute) {
                    if ($sKey == 'currency') {
                        $sCurrency = strtolower((string) $sAttribute);
                    } else if ($sKey == 'rate') {
                        $nRate = (string) $sAttribute;
                    }
                }
                $aCurrencies['eur'][$sCurrency] = $nRate;
                $aCurrencies[$sCurrency]['eur'] = 1 / $nRate;
            }
            // Check if requested rates are available.
            if (isset($aCurrencies[$parameters['base']][$parameters['target']])) {
                return (float) $aCurrencies[$parameters['base']][$parameters['target']];
            } else {
                $app->logMsg(sprintf('API %s does not have base %s or target %s', $this->getParam('api'), $parameters['base'], $parameters['target']), LOG_ALERT, __FILE__, __LINE__);
                return false;
            }

        default :
            $app->logMsg(sprintf('Unknown currency API: %s', $this->getParam('api')), LOG_ERR, __FILE__, __LINE__);
            return false;
        }
    }
}