TPS_URL` environment variable is specified or
 * by using the {@see 'wp_direct_update_https_url'} filter. This allows hosts to send users directly to
 * the page where they can update their site to use HTTPS.
 *
 * @since 5.7.0
 *
 * @return string URL for directly updating to HTTPS or empty string.
 */
function wp_get_direct_update_https_url() {
	$direct_update_url = '';

	if ( false !== getenv( 'WP_DIRECT_UPDATE_HTTPS_URL' ) ) {
		$direct_update_url = getenv( 'WP_DIRECT_UPDATE_HTTPS_URL' );
	}

	/**
	 * Filters the URL for directly updating the PHP version the site is running on from the host.
	 *
	 * @since 5.7.0
	 *
	 * @param string $direct_update_url URL for directly updating PHP.
	 */
	$direct_update_url = apply_filters( 'wp_direct_update_https_url', $direct_update_url );

	return $direct_update_url;
}

/**
 * Get the size of a directory.
 *
 * A helper function that is used primarily to check whether
 * a blog has exceeded its allowed upload space.
 *
 * @since MU (3.0.0)
 * @since 5.2.0 $max_execution_time parameter added.
 *
 * @param string $directory Full path of a directory.
 * @param int    $max_execution_time Maximum time to run before giving up. In seconds.
 *                                   The timeout is global and is measured from the moment WordPress started to load.
 * @return int|false|null Size in bytes if a valid directory. False if not. Null if timeout.
 */
function get_dirsize( $directory, $max_execution_time = null ) {

	// Exclude individual site directories from the total when checking the main site of a network,
	// as they are subdirectories and should not be counted.
	if ( is_multisite() && is_main_site() ) {
		$size = recurse_dirsize( $directory, $directory . '/sites', $max_execution_time );
	} else {
		$size = recurse_dirsize( $directory, null, $max_execution_time );
	}

	return $size;
}

/**
 * Get the size of a directory recursively.
 *
 * Used by get_dirsize() to get a directory size when it contains other directories.
 *
 * @since MU (3.0.0)
 * @since 4.3.0 The `$exclude` parameter was added.
 * @since 5.2.0 The `$max_execution_time` parameter was added.
 * @since 5.6.0 The `$directory_cache` parameter was added.
 *
 * @param string       $directory          Full path of a directory.
 * @param string|array $exclude            Optional. Full path of a subdirectory to exclude from the total,
 *                                         or array of paths. Expected without trailing slash(es).
 * @param int          $max_execution_time Maximum time to run before giving up. In seconds. The timeout is global
 *                                         and is measured from the moment WordPress started to load.
 * @param array        $directory_cache    Optional. Array of cached directory paths.
 *
 * @return int|false|null Size in bytes if a valid directory. False if not. Null if timeout.
 */
function recurse_dirsize( $directory, $exclude = null, $max_execution_time = null, &$directory_cache = null ) {
	$directory  = untrailingslashit( $directory );
	$save_cache = false;

	if ( ! isset( $directory_cache ) ) {
		$directory_cache = get_transient( 'dirsize_cache' );
		$save_cache      = true;
	}

	if ( isset( $directory_cache[ $directory ] ) && is_int( $directory_cache[ $directory ] ) ) {
		return $directory_cache[ $directory ];
	}

	if ( ! file_exists( $directory ) || ! is_dir( $directory ) || ! is_readable( $directory ) ) {
		return false;
	}

	if (
		( is_string( $exclude ) && $directory === $exclude ) ||
		( is_array( $exclude ) && in_array( $directory, $exclude, true ) )
	) {
		return false;
	}

	if ( null === $max_execution_time ) {
		// Keep the previous behavior but attempt to prevent fatal errors from timeout if possible.
		if ( function_exists( 'ini_get' ) ) {
			$max_execution_time = ini_get( 'max_execution_time' );
		} else {
			// Disable...
			$max_execution_time = 0;
		}

		// Leave 1 second "buffer" for other operations if $max_execution_time has reasonable value.
		if ( $max_execution_time > 10 ) {
			$max_execution_time -= 1;
		}
	}

	/**
	 * Filters the amount of storage space used by one directory and all its children, in megabytes.
	 *
	 * Return the actual used space to short-circuit the recursive PHP file size calculation
	 * and use something else, like a CDN API or native operating system tools for better performance.
	 *
	 * @since 5.6.0
	 *
	 * @param int|false $space_used The amount of used space, in bytes. Default false.
	 */
	$size = apply_filters( 'pre_recurse_dirsize', false, $directory, $exclude, $max_execution_time, $directory_cache );

	if ( false === $size ) {
		$size = 0;

		$handle = opendir( $directory );
		if ( $handle ) {
			while ( ( $file = readdir( $handle ) ) !== false ) {
				$path = $directory . '/' . $file;
				if ( '.' !== $file && '..' !== $file ) {
					if ( is_file( $path ) ) {
						$size += filesize( $path );
					} elseif ( is_dir( $path ) ) {
						$handlesize = recurse_dirsize( $path, $exclude, $max_execution_time, $directory_cache );
						if ( $handlesize > 0 ) {
							$size += $handlesize;
						}
					}

					if ( $max_execution_time > 0 && microtime( true ) - WP_START_TIMESTAMP > $max_execution_time ) {
						// Time exceeded. Give up instead of risking a fatal timeout.
						$size = null;
						break;
					}
				}
			}
			closedir( $handle );
		}
	}

	$directory_cache[ $directory ] = $size;

	// Only write the transient on the top level call and not on recursive calls.
	if ( $save_cache ) {
		set_transient( 'dirsize_cache', $directory_cache );
	}

	return $size;
}

/**
 * Cleans directory size cache used by recurse_dirsize().
 *
 * Removes the current directory and all parent directories from the `dirsize_cache` transient.
 *
 * @since 5.6.0
 *
 * @param string $path Full path of a directory or file.
 */
function clean_dirsize_cache( $path ) {
	$directory_cache = get_transient( 'dirsize_cache' );

	if ( empty( $directory_cache ) ) {
		return;
	}

	$path = untrailingslashit( $path );
	unset( $directory_cache[ $path ] );

	while ( DIRECTORY_SEPARATOR !== $path && '.' !== $path && '..' !== $path ) {
		$path = dirname( $path );
		unset( $directory_cache[ $path ] );
	}

	set_transient( 'dirsize_cache', $directory_cache );
}

/**
 * Checks compatibility with the current WordPress version.
 *
 * @since 5.2.0
 *
 * @param string $required Minimum required WordPress version.
 * @return bool True if required version is compatible or empty, false if not.
 */
function is_wp_version_compatible( $required ) {
	return empty( $required ) || version_compare( get_bloginfo( 'version' ), $required, '>=' );
}

/**
 * Checks compatibility with the current PHP version.
 *
 * @since 5.2.0
 *
 * @param string $required Minimum required PHP version.
 * @return bool True if required version is compatible or empty, false if not.
 */
function is_php_version_compatible( $required ) {
	return empty( $required ) || version_compare( phpversion(), $required, '>=' );
}

/**
 * Check if two numbers are nearly the same.
 *
 * This is similar to using `round()` but the precision is more fine-grained.
 *
 * @since 5.3.0
 *
 * @param int|float $expected  The expected value.
 * @param int|float $actual    The actual number.
 * @param int|float $precision The allowed variation.
 * @return bool Whether the numbers match whithin the specified precision.
 */
function wp_fuzzy_number_match( $expected, $actual, $precision = 1 ) {
	return abs( (float) $expected - (float) $actual ) <= $precision;
}