<?php

declare(strict_types=1);

namespace LinkCheckup\Shared\Urls;

use function html_entity_decode;
use function in_array;
use function is_array;
use function preg_match;
use function rtrim;
use function str_starts_with;
use function strpos;
use function strtolower;
use function substr;
use function trim;

final class AddressRules {

	private const WEB_SCHEMES    = array( 'http', 'https' );
	private const ANY_SCHEME     = '#^[a-z][a-z0-9+.-]*:#i';
	private const WEB_SCHEME     = '#^https?://#i';
	private const SITE_ROOT      = '#^[a-z][a-z0-9+.-]*://[^/?\#]*#i';
	private const DEFAULT_SCHEME = 'https:';

	public function __construct( private string $home_url ) {
	}

	public function normalize( string $raw_address ): string|null {
		$decoded = html_entity_decode( $raw_address, ENT_QUOTES, 'UTF-8' );
		$address = trim( $this->without_fragment( $decoded ) );

		if ( '' === $address ) {
			return null;
		}

		return $this->absolute_web_address( $address );
	}

	public function is_usable_new_url( string $address ): bool {
		$trimmed = trim( $address );

		if ( $this->is_root_relative( $trimmed ) ) {
			return true;
		}

		return 1 === preg_match( self::WEB_SCHEME, $trimmed )
			&& null !== $this->absolute_web_address( $trimmed );
	}

	public function host_of( string $absolute_address ): string {
		$host = (string) wp_parse_url( $absolute_address, PHP_URL_HOST );

		return strtolower( $host );
	}

	public function is_internal( string $absolute_address ): bool {
		$home_host = $this->host_of( $this->home_url );

		return $this->host_of( $absolute_address ) === $home_host;
	}

	private function without_fragment( string $address ): string {
		$fragment_start = strpos( $address, '#' );

		if ( false === $fragment_start ) {
			return $address;
		}

		return substr( $address, 0, $fragment_start );
	}

	private function is_root_relative( string $address ): bool {
		return str_starts_with( $address, '/' )
			&& ! str_starts_with( $address, '//' );
	}

	private function absolute_form( string $address ): string {
		if ( str_starts_with( $address, '//' ) ) {
			return self::DEFAULT_SCHEME . $address;
		}

		if ( 1 === preg_match( self::ANY_SCHEME, $address ) ) {
			return $address;
		}

		if ( $this->is_root_relative( $address ) ) {
			return $this->site_root() . $address;
		}

		return rtrim( $this->home_url, '/' ) . '/' . $address;
	}

	private function site_root(): string {
		$matches = array();

		preg_match( self::SITE_ROOT, $this->home_url, $matches );

		return $matches[0] ?? rtrim( $this->home_url, '/' );
	}

	private function absolute_web_address( string $address ): string|null {
		$parts = wp_parse_url( $this->absolute_form( $address ) );

		if ( ! is_array( $parts ) ) {
			return null;
		}

		$scheme = strtolower( $parts['scheme'] ?? '' );
		$host   = strtolower( $parts['host'] ?? '' );

		if ( ! in_array( $scheme, self::WEB_SCHEMES, true ) || '' === $host ) {
			return null;
		}

		return $scheme . '://' . $this->user_part( $parts ) . $host
			. $this->port_part( $parts ) . ( $parts['path'] ?? '' )
			. $this->query_part( $parts );
	}

	/** @param array{user?: string, pass?: string} $parts */
	private function user_part( array $parts ): string {
		if ( ! isset( $parts['user'] ) ) {
			return '';
		}

		$password = isset( $parts['pass'] ) ? ':' . $parts['pass'] : '';

		return $parts['user'] . $password . '@';
	}

	/** @param array{port?: int} $parts */
	private function port_part( array $parts ): string {
		return isset( $parts['port'] ) ? ':' . $parts['port'] : '';
	}

	/** @param array{query?: string} $parts */
	private function query_part( array $parts ): string {
		return isset( $parts['query'] ) ? '?' . $parts['query'] : '';
	}
}