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<?php
/**
* This file is part of Stud.IP.
*
* This program 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 2 of
* the License, or (at your option) any later version.
*
* @author Moritz Strohm <strohm@data-quest.de>
* @copyright 2020
* @license http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
* @category Stud.IP
* @since 4.6
*/
/**
* This class contains basic methods for querying a library catalog
* using standardised search parameters.
*/
abstract class LibrarySearch
{
//The following constants define the strings for the
//standardised field names for the query method. These can be
//converted to library-specific field names.
const TITLE = 'title';
const AUTHOR = 'author';
const YEAR = 'year';
const NUMBER = 'number';
const ISSN = 'issn';
const ISBN = 'isbn';
const PUBLICATION = 'publication';
const SIGNATURE = 'signature';
//Constants for the ordering of results.
const ORDER_BY_RELEVANCE = 'relevance';
const ORDER_BY_YEAR = 'year';
/**
* The base URL for the HTTP request to retrieve data.
*/
protected $request_base_url = '';
/**
* Additional URL parameters for the HTTP request to retrieve data.
*/
protected $request_url_parameters = [];
/**
* Implementation-specific configuration that can define the behavior
* of the LibrarySearch implementation.
*/
protected $settings = [];
/**
* A basic constructor.
*
* @param array $configuration The configuration for the LibrarySearch
* implementation. It should be an associative array with the following
* keys:
* - base_url: The base URL for retrieving data.
* - additional_url_parameters: Additional URL parameters for the base URL.
* - settings: Implementation-specific configuration. This should also
* be an associative array.
*/
public function __construct(array $configuration = [])
{
if ($configuration['base_url']) {
$this->request_base_url = $configuration['base_url'];
}
if (is_array($configuration['additional_url_parameters'])) {
$this->request_url_parameters = $configuration['additional_url_parameters'];
}
if (is_array($configuration['settings'])) {
$this->settings = $configuration['settings'];
}
}
/**
* This method shall replace the generalised search query fields with the
* implementation specific query fields.
*
* @param array $query_fields An array with query parameters using the
* generalised query fields.
*
* @returns array The translated version of the $query_fields array.
*/
abstract protected function translateQueryFields(array $query_fields = []) : array;
/**
* A common method for the libcurl code to request data from an URL so that
* LibrarySearch implementations don't have to include their own libcurl
* code to get data.
*
* @param string $base_url The base URL to request data from.
*
* @param array $url_parameters URL parameters for the request. The array
* should consist of an associative array with keys representing
* the parameter name and the values representing the parameter values.
*
* @returns string|bool The result of the request. If the base URL is empty
* or no data could be retrieved due to an error, false is returned.
* In case of success, a string with the retrieved data is returned.
*/
protected function requestData(string $base_url = '', array $url_parameters = [])
{
if (!$base_url) {
return false;
}
$full_url = $base_url;
if ($url_parameters) {
$full_url .= '?' . http_build_query($url_parameters);
}
$data = file_get_contents($full_url, false, get_default_http_stream_context($base_url));
return $data;
}
/**
* Starts a query to a library catalogue using the specified
* parameters. If standardised parameters as defined in the FIELD_
* constants of this class are used as keys in the $search_parameters array,
* their keys may be converted to library-specific search keys.
*
* @param array $search_parameters The search parameters to be used.
* The array must be an associative array where the keys represent
* the fields.
*
* @param string $order_by
*
* @param int $limit The maximum amount of items that shall be retrieved
* from the catalog.
*
* @returns LibrarySearchResult[] An array of LibrarySearchResult items
* if entries matching the search could be found in the library.
*/
abstract public function query(
array $search_parameters = [],
string $order_by = self::ORDER_BY_RELEVANCE,
int $limit = 200
) : array;
}
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