<?php

declare(strict_types=1);

namespace LinkCheckup\Features\Checking;

use LinkCheckup\Shared\Http\PluginUserAgent;

use function implode;
use function in_array;

final class RedirectFollower {

	private const MAXIMUM_REDIRECTS  = 5;
	private const TIMEOUT_SECONDS    = 10;
	private const LOCATION_HEADER    = 'location';
	private const HEADER_SEPARATOR   = ' ';
	private const REDIRECT_CODES     = array( 301, 302, 303, 307, 308 );
	private const TOO_MANY_REDIRECTS = 'Too many redirects.';

	public function __construct(
		private LocationResolver $location_resolver
	) {
	}

	public function follow( string $method, string $url ): HttpAnswer {
		$current_url       = $url;
		$first_status_code = null;

		for ( $hop = 0; $hop <= self::MAXIMUM_REDIRECTS; $hop++ ) {
			$response = wp_remote_request(
				$current_url,
				$this->request_arguments( $method )
			);

			if ( is_wp_error( $response ) ) {
				return new HttpAnswer(
					null,
					$first_status_code,
					$response->get_error_message(),
					$current_url
				);
			}

			$status_code         = (int) wp_remote_retrieve_response_code(
				$response
			);
			$first_status_code ??= $status_code;
			$location            = $this->location_of( $response );

			if ( ! $this->is_redirect( $status_code, $location ) ) {
				return new HttpAnswer(
					$status_code,
					$first_status_code,
					'',
					$current_url
				);
			}

			$current_url = $this->location_resolver->resolve(
				$current_url,
				$location
			);
		}

		return new HttpAnswer(
			null,
			$first_status_code,
			self::TOO_MANY_REDIRECTS,
			$current_url
		);
	}

	/**
	 * @return array{
	 *     method: string,
	 *     timeout: int,
	 *     redirection: int,
	 *     user-agent: string
	 * }
	 */
	private function request_arguments( string $method ): array {
		return array(
			'method'      => $method,
			'timeout'     => self::TIMEOUT_SECONDS,
			'redirection' => 0,
			'user-agent'  => PluginUserAgent::NAME,
		);
	}

	/** @param array<string, mixed> $response */
	private function location_of( array $response ): string {
		$header = wp_remote_retrieve_header(
			$response,
			self::LOCATION_HEADER
		);

		return implode(
			self::HEADER_SEPARATOR,
			array_filter( (array) $header, 'is_string' )
		);
	}

	private function is_redirect( int $status_code, string $location ): bool {
		return in_array( $status_code, self::REDIRECT_CODES, true )
			&& '' !== $location;
	}
}