<?php

declare(strict_types=1);

/**
 * This file is part of littleredbutton/bigbluebutton-api-php.
 *
 * littleredbutton/bigbluebutton-api-php is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * littleredbutton/bigbluebutton-api-php 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with littleredbutton/bigbluebutton-api-php. If not, see <http://www.gnu.org/licenses/>.
 */

namespace BigBlueButton\Http\Transport;

use BigBlueButton\Exceptions\NetworkException;
use BigBlueButton\Exceptions\RuntimeException;
use BigBlueButton\Util\ArrayHelper;

/**
 * Allows to send requests to the BBB server with the pure PHP cURL implementation.
 */
final class CurlTransport implements TransportInterface
{
    public const DEFAULT_CURL_OPTIONS = [
        \CURLOPT_SSL_VERIFYPEER => 1,
        \CURLOPT_CONNECTTIMEOUT => self::DEFAULT_CONNECT_TIMEOUT,
        \CURLOPT_TIMEOUT => self::DEFAULT_TIMEOUT,
    ];

    /**
     * These options must be always set to the given value to ensure that the transport operates properly.
     */
    private const INTERNAL_CURL_OPTIONS = [
        \CURLOPT_ENCODING => 'UTF-8',
        \CURLOPT_RETURNTRANSFER => 1,
        \CURLOPT_FOLLOWLOCATION => 1,
    ];

    /**
     * Time to connect to BigBlueButton host.
     */
    private const DEFAULT_CONNECT_TIMEOUT = 10;

    /**
     * Time to for the whole request and response flow (inclusive connect, see above).
     */
    private const DEFAULT_TIMEOUT = 30;

    /**
     * Allows to inject custom cURL options used on dispatching request to BBB.
     * Please note that you must ensure on your own that the usage of custom options does not break the transport.
     *
     * @see CurlTransport::createWithDefaultOptions() Please use this factory method to create the CurlTransport with the recommended defaults.
     * @see https://www.php.net/manual/en/function.curl-setopt.php List of known cURL options
     *
     * @param mixed[] $curlOptions A list of cURL options to pass to the cURL handle. Option name as key, option value as value.
     */
    public function __construct(private readonly array $curlOptions = [])
    {
    }

    /**
     * @param string[] $additionalCurlOptions A list of additional cURL options to pass to the cURL handle. Option name as key, option value as value.
     */
    public static function createWithDefaultOptions(array $additionalCurlOptions = []): self
    {
        // @codeCoverageIgnoreStart
        return new self(self::mergeCurlOptions($additionalCurlOptions, self::DEFAULT_CURL_OPTIONS));
        // @codeCoverageIgnoreEnd
    }

    public function request(TransportRequest $request): TransportResponse
    {
        // @codeCoverageIgnoreStart
        if (!\extension_loaded('curl')) {
            throw new RuntimeException('Curl PHP module is not installed or not enabled.');
        }
        // @codeCoverageIgnoreEnd

        $ch = curl_init();
        // @codeCoverageIgnoreStart
        if (!$ch) {
            throw new RuntimeException('Could not create curl instance.');
        }
        // @codeCoverageIgnoreEnd

        $options = self::mergeCurlOptions(
            self::buildUrlOptions($request),
            self::buildPostOptions($request),
            self::INTERNAL_CURL_OPTIONS,
            $this->curlOptions
        );

        foreach ($options as $option => $value) {
            curl_setopt($ch, $option, $value);
        }

        [$headers, $data] = self::getHeadersAndContentFromCurlHandle($ch);

        $httpCode = curl_getinfo($ch, \CURLINFO_HTTP_CODE);
        if ($httpCode < 200 || $httpCode >= 300) {
            throw new NetworkException('Bad response.', $httpCode);
        }

        curl_close($ch);

        $sessionId = null;
        if (isset($headers['set-cookie'])) {
            $sessionId = Cookie::extractJsessionId($headers['set-cookie']);
        }

        return new TransportResponse($data, $sessionId);
    }

    /** @return array<int,mixed> */
    private static function buildPostOptions(TransportRequest $request): array
    {
        $options = [];

        if ('' !== $payload = $request->getPayload()) {
            $options[\CURLOPT_CUSTOMREQUEST] = 'POST';
            $options[\CURLOPT_POST] = 1;
            $options[\CURLOPT_POSTFIELDS] = $payload;
            $options[\CURLOPT_HTTPHEADER] = [
                'Content-type: '.$request->getContentType(),
                'Content-length: '.mb_strlen((string) $payload),
            ];
        }

        return $options;
    }

    /** @return array<int,string> */
    private static function buildUrlOptions(TransportRequest $request): array
    {
        return [
            \CURLOPT_URL => $request->getUrl(),
        ];
    }

    /**
     * @param array<int,mixed> ...$options The first set value of an option will be preserved.
     *                                     Any later options the same key will be discarded.
     *                                     The CURLOPT_HTTPHEADER will be treated in a special
     *                                     way and merged instead, but on values with same header name
     *                                     only the header from the first option set will be preserved.
     *
     * @return array<int,mixed>
     */
    private static function mergeCurlOptions(array ...$options): array
    {
        // headers need special treatment regarding merging them to avoid duplicate fields
        $headerSets = [];
        foreach (array_reverse($options, true) as $setKey => $optionSet) {
            foreach ($optionSet as $key => $option) {
                switch ($key) {
                    case \CURLOPT_HTTPHEADER:
                        unset($options[$setKey][$key]);
                        $headerSets[] = $option;

                        break;
                }
            }
        }
        $headerOptions = [
            \CURLOPT_HTTPHEADER => Header::mergeCurlHeaders(...$headerSets),
        ];

        return ArrayHelper::mergeRecursive(true, $headerOptions, ...$options);
    }

    /**
     * A raw response as returned from cURL will contain the headers followed by "\r\n\r\n" and the content.
     *
     * @return (string|string[][])[] First key headers, second key is content
     *
     * @throws NetworkException
     *
     * @see https://stackoverflow.com/questions/10589889/returning-header-as-array-using-curl
     *
     * @psalm-return array{0: array<string, non-empty-list<string>>, 1: string}
     */
    private static function getHeadersAndContentFromCurlHandle(\CurlHandle $curlHandle): array
    {
        $headers = [];

        curl_setopt($curlHandle, \CURLOPT_HEADER, 1);
        $responseContent = curl_exec($curlHandle);

        // @codeCoverageIgnoreStart
        if (false === $responseContent) {
            throw new NetworkException('Error during curl_exec. Error: '.curl_error($curlHandle));
        }
        // @codeCoverageIgnoreEnd

        $headerSize = curl_getinfo($curlHandle, \CURLINFO_HEADER_SIZE);
        $headerContent = substr($responseContent, 0, $headerSize);

        // Split the string on every "double" new line.
        $headerParts = explode("\r\n\r\n", $headerContent, 2); // only split once to mitigate scrapping content if it contains newlines with carriage return

        // Loop of response headers. The "count() -1" is to avoid an empty row for the extra line break before the body of the response.
        for ($index = 0; $index < \count($headerParts) - 1; $index++) {
            foreach (explode("\r\n", $headerParts[$index]) as $i => $line) {
                if (0 === $i) {
                    // HTTP code
                    continue;
                }

                $splitHeader = explode(': ', $line, 2);
                // @codeCoverageIgnoreStart
                if (!isset($splitHeader[0], $splitHeader[1])) {
                    throw new \InvalidArgumentException(\sprintf('Header value "%s" is invalid. Expected format is "Header-Name: value".', $line));
                }
                // @codeCoverageIgnoreEnd

                [$header, $value] = $splitHeader;
                // Use lower case to have an always predictable result
                $headers[strtolower($header)][] = $value;
            }
        }

        return [$headers, substr($responseContent, $headerSize)];
    }
}
