<?php

/**
 * Class works with Amazon Product Advertising REST API.
 *
 * @author gugas <darius.lenkauskis@yahoo.com>
 */
class Amazon {

    /**
     * Class version
     * @var string component version 
     */
    public $version = '1.0';

    /**
     * Suported Amazon Product Advertising API version
     * @var string 
     */
    private $api_version = '2011-08-01';

    /**
     * API_KEY
     * @var string
     */
    private $api = '';

    /**
     * SECRET_CODE
     * @var string 
     */
    private $secret;

    /**
     * ASSOCIATE_TAG
     * @var string 
     */
    private $tag;
    
    /**
     * 
     * @param array $params
     * @throws Exception if API_KEY is not provided
     * @throws Exception if SECRET_CODE is not provided
     * @throws Exception if ASSOCIATE_TAG is not provided
     */
    public function __construct($params = array()) {

        if (!isset($params['api'])) {
            throw new Exception('Parameter API_KEY is not set.');
        }

        $this->api = $params['api'];

        if (!isset($params['secret'])) {
            throw new Exception('Parameter SECRET_CODE is not set.');
        }

        $this->secret = $params['secret'];

        if (!isset($params['tag'])) {
            throw new Exception('Parameter ASSOCIATE_TAG is not set');
        }

        $this->tag = $params['tag'];
    }

    /**
     * Search items in Amazon Store by keywords and category
     * @param string $keywords
     * @param string $searchIndex
     * @param string $locale
     * @param array $params
     * @return SimpleXMLElement
     */
    public function ItemSearch($keywords, $section = 'All', $locale = 'US', $params = array()) {
        $params += array(
            'Keywords' => $keywords,
            'SearchIndex' => $section,
        );

        $request = $this->form_http_query('ItemSearch', $params, $locale);
        $response = simplexml_load_string(file_get_contents($request));
        if ($response->Items->Request->IsValid != 'True') {
            return $response->Items->Request;
        }
        return $response;
    }

    /**
     * Method forms request url and to Amazon Product Advertising API
     * 
     * @see http://docs.amazonwebservices.com/AWSECommerceService/latest/DG/rest-signature.html
     * 
     * @param string $operation 
     * @param array $parameters
     * @param string $locale 
     * @return string 
     */
    public function form_http_query($operation, $parameters = array(), $locale = 'US') {

        $parameters += array(
            'Service' => 'AWSECommerceService',
            'Version' => $this->api_version,
            'AWSAccessKeyId' => $this->api,
            'Operation' => $operation,
            'AssociateTag' => $this->tag,
            'Timestamp' => gmdate("Y-m-d\TH:i:s") . 'Z',
        );

        ksort($parameters);

        $params = array();

        //encode params
        foreach ($parameters as $key => $value) {
            if (is_array($value)) {
                $value = implode(',', $value);
            }
            $param = str_replace("%7E", "~", rawurlencode($key));
            $value = str_replace("%7E", "~", rawurlencode($value));
            $params[] = $param . '=' . $value;
        }

        //Sign Request
        $query_string = implode('&', $params);
        $parsed_url = parse_url($this->getLocale($locale));
        $host = strtolower($parsed_url['host']);
        $string_to_sign = "GET\n$host\n{$parsed_url['path']}\n$query_string";

        $signature = base64_encode(hash_hmac('sha256', $string_to_sign, $this->secret, TRUE));
        $signature = str_replace("%7E", "~", rawurlencode($signature));
        $query_string .= "&Signature=$signature";

        $url = $this->getLocale($locale) . '?' . $query_string;

        return $url;
    }
    
    /**
     * Method from country code returns api url.
     * @param string $locale
     * @return string
     * @throws UnexpectedValueException 
     */
    function getLocale($locale = 'US') {
        
        switch (strtoupper($locale)) {
            case 'US':
                return 'http://ecs.amazonaws.com/onca/xml';
            case 'UK':
                return 'http://ecs.amazonaws.co.uk/onca/xml';
            case 'JP':
                return 'http://ecs.amazonaws.jp/onca/xml';
            case 'FR':
                return 'http://ecs.amazonaws.fr/onca/xml';
            case 'DE':
                return 'http://ecs.amazonaws.de/onca/xml';
            case 'CA':
                return 'http://ecs.amazonaws.ca/onca/xml';
            case 'default':
                throw new UnexpectedValueException(sprintf('Locale \'%s\' is not suported', $locale));
        }
        
    }
    
}