oai-pmh2/src/Response.php

<?php

/**
 * OAI-PMH 2.0 Data Provider
 * Copyright (C) 2024 Sebastian Meyer <sebastian.meyer@opencultureconsulting.com>
 *
 * 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 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
 */

declare(strict_types=1);

namespace OCC\OaiPmh2;

use DOMDocument;
use DOMElement;
use DOMException;
use DOMNode;
use GuzzleHttp\Psr7\Uri;
use Psr\Http\Message\ServerRequestInterface;

/**
 * An OAI-PMH XML response object.
 *
 * @author Sebastian Meyer <sebastian.meyer@opencultureconsulting.com>
 * @package OAIPMH2
 */
final class Response
{
    /**
     * This holds the DOMDocument of the OAI-PMH XML response.
     */
    private DOMDocument $dom;

    /**
     * This holds the root node of the OAI-PMH XML response.
     */
    private DOMElement $rootNode;

    /**
     * Add XSL processing instructions to XML response document.
     *
     * @return void
     */
    protected function addProcessingInstructions(): void
    {
        $uri = $this->serverRequest->getUri();
        $basePath = $uri->getPath();
        if (str_ends_with(haystack: $basePath, needle: 'index.php')) {
            $basePath = pathinfo(path: $basePath, flags: PATHINFO_DIRNAME);
        }
        $stylesheet = Uri::composeComponents(
            scheme: $uri->getScheme(),
            authority: $uri->getAuthority(),
            path: rtrim(string: $basePath, characters: '/') . '/resources/stylesheet.xsl',
            query: null,
            fragment: null
        );
        $xslt = $this->dom->createProcessingInstruction(
            target: 'xml-stylesheet',
            data: sprintf(
                format: 'type="text/xsl" href="%s"',
                values: $stylesheet
            )
        );
        $this->dom->appendChild(node: $xslt);
    }

    /**
     * Create and append request element.
     *
     * @return void
     */
    protected function appendRequest(): void
    {
        $uri = $this->serverRequest->getUri();
        $baseUrl = Uri::composeComponents(
            scheme: $uri->getScheme(),
            authority: $uri->getAuthority(),
            path: $uri->getPath(),
            query: null,
            fragment: null
        );
        $request = $this->createElement(
            localName: 'request',
            value: $baseUrl,
            appendToRoot: true
        );
        /** @var array<string, string> */
        $params = $this->serverRequest->getAttributes();
        foreach ($params as $param => $value) {
            $request->setAttribute(
                qualifiedName: $param,
                value: htmlspecialchars(
                    string: $value,
                    flags: ENT_XML1 | ENT_COMPAT,
                    encoding: 'UTF-8'
                )
            );
        }
    }

    /**
     * Create and append response date element.
     *
     * @return void
     */
    protected function appendResponseDate(): void
    {
        $this->createElement(
            localName: 'responseDate',
            value: gmdate(format: 'Y-m-d\TH:i:s\Z'),
            appendToRoot: true
        );
    }

    /**
     * Create and append root element.
     *
     * @return void
     */
    protected function appendRootElement(): void
    {
        $this->rootNode = $this->dom->createElement(localName: 'OAI-PMH');
        $this->rootNode->setAttribute(
            qualifiedName: 'xmlns',
            value: 'http://www.openarchives.org/OAI/2.0/'
        );
        $this->rootNode->setAttribute(
            qualifiedName: 'xmlns:xsi',
            value: 'http://www.w3.org/2001/XMLSchema-instance'
        );
        $this->rootNode->setAttribute(
            qualifiedName: 'xsi:schemaLocation',
            value: 'http://www.openarchives.org/OAI/2.0/ https://www.openarchives.org/OAI/2.0/OAI-PMH.xsd'
        );
        $this->dom->appendChild(node: $this->rootNode);
    }

    /**
     * Create the DOM document.
     *
     * @return void
     */
    protected function createDocument(): void
    {
        $this->dom = new DOMDocument(version: '1.0', encoding: 'UTF-8');
        $this->dom->preserveWhiteSpace = false;
        $this->addProcessingInstructions();
    }

    /**
     * Create a new XML element.
     *
     * @param string $localName The local name for the element
     * @param string $value The optional value for the element
     * @param bool $appendToRoot Append the new element to the root node?
     *
     * @return DOMElement The newly created element
     */
    public function createElement(string $localName, string $value = '', bool $appendToRoot = false): DOMElement
    {
        $node = $this->dom->createElement(
            localName: $localName,
            value: htmlspecialchars(
                string: $value,
                flags: ENT_XML1,
                encoding: 'UTF-8'
            )
        );
        if ($appendToRoot) {
            $this->rootNode->appendChild(node: $node);
        }
        return $node;
    }

    /**
     * Import XML data into response document.
     *
     * @param string $data The XML data
     *
     * @return DOMNode The imported XML node
     *
     * @throws DOMException if the data cannot be imported
     */
    public function importData(string $data): DOMNode
    {
        $document = new DOMDocument(version: '1.0', encoding: 'UTF-8');
        $document->preserveWhiteSpace = false;
        if ($document->loadXML(source: $data) === true) {
            /** @var DOMElement */
            $rootNode = $document->documentElement;
            $node = $this->dom->importNode(node: $rootNode, deep: true);
            return $node;
        } else {
            throw new DOMException(
                message: 'Could not import the XML data. Most likely it is not well-formed.',
                code: 500
            );
        }
    }

    /**
     * Create an OAI-PMH XML response.
     *
     * @param ServerRequestInterface $serverRequest The PSR-7 HTTP Server Request
     */
    public function __construct(private ServerRequestInterface $serverRequest)
    {
        $this->createDocument();
        $this->appendRootElement();
        $this->appendResponseDate();
        $this->appendRequest();
    }

    /**
     * Serialize the OAI-PMH XML response.
     *
     * @return string The XML output
     */
    public function __toString(): string
    {
        $this->dom->formatOutput = true;
        return (string) $this->dom->saveXML();
    }
}