<?php
/**
 * HTTP API: WP_Http_Encoding class
 *
 * @package WordPress
 * @subpackage HTTP
 * @since 4.4.0
 */

/**
 * Core class used to implement deflate and gzip transfer encoding support for HTTP requests.
 *
 * Includes RFC 1950, RFC 1951, and RFC 1952.
 *
 * @since 2.8.0
 */
#[AllowDynamicProperties]
class WP_Http_Encoding {

    /**
     * Compress raw string using the deflate format.
     *
     * Supports the RFC 1951 standard.
     *
     * @since 2.8.0
     *
     * @param string $raw      String to compress.
     * @param int    $level    Optional. Compression level, 9 is highest. Default 9.
     * @param string $supports Optional, not used. When implemented it will choose
     *                         the right compression based on what the server supports.
     * @return string|false Compressed string on success, false on failure.
     */
    public static function compress( $raw, $level = 9, $supports = null ) {
        return gzdeflate( $raw, $level );
    }

    /**
     * Decompression of deflated string.
     *
     * Will attempt to decompress using the RFC 1950 standard, and if that fails
     * then the RFC 1951 standard deflate will be attempted. Finally, the RFC
     * 1952 standard gzip decode will be attempted. If all fail, then the
     * original compressed string will be returned.
     *
     * @since 2.8.0
     *
     * @param string $compressed String to decompress.
     * @param int    $length     The optional length of the compressed data.
     * @return string|false Decompressed string on success, false on failure.
     */
    public static function decompress( $compressed, $length = null ) {

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

        $decompressed = @gzinflate( $compressed );
        if ( false !== $decompressed ) {
            return $decompressed;
        }

        $decompressed = self::compatible_gzinflate( $compressed );
        if ( false !== $decompressed ) {
            return $decompressed;
        }

        $decompressed = @gzuncompress( $compressed );
        if ( false !== $decompressed ) {
            return $decompressed;
        }

        if ( function_exists( 'gzdecode' ) ) {
            $decompressed = @gzdecode( $compressed );

            if ( false !== $decompressed ) {
                return $decompressed;
            }
        }

        return $compressed;
    }

    /**
     * Decompression of deflated string while staying compatible with the majority of servers.
     *
     * Certain Servers will return deflated data with headers which PHP's gzinflate()
     * function cannot handle out of the box. The following function has been created from
     * various snippets on the gzinflate() PHP documentation.
     *
     * Warning: Magic numbers within. Due to the potential different formats that the compressed
     * data may be returned in, some "magic offsets" are needed to ensure proper decompression
     * takes place. For a simple pragmatic way to determine the magic offset in use, see:
     * https://core.trac.wordpress.org/ticket/18273
     *
     * @since 2.8.1
     *
     * @link https://core.trac.wordpress.org/ticket/18273
     * @link https://www.php.net/manual/en/function.gzinflate.php#70875
     * @link https://www.php.net/manual/en/function.gzinflate.php#77336
     *
     * @param string $gz_data String to decompress.
     * @return string|false Decompressed string on success, false on failure.
     */
    public static function compatible_gzinflate( $gz_data ) {

        // Compressed data might contain a full header, if so strip it for gzinflate().
        if ( str_starts_with( $gz_data, "\x1f\x8b\x08" ) ) {
            $i   = 10;
            $flg = ord( substr( $gz_data, 3, 1 ) );
            if ( $flg > 0 ) {
                if ( $flg & 4 ) {
                    list($xlen) = unpack( 'v', substr( $gz_data, $i, 2 ) );
                    $i          = $i + 2 + $xlen;
                }
                if ( $flg & 8 ) {
                    $i = strpos( $gz_data, "\0", $i ) + 1;
                }
                if ( $flg & 16 ) {
                    $i = strpos( $gz_data, "\0", $i ) + 1;
                }
                if ( $flg & 2 ) {
                    $i = $i + 2;
                }
            }
            $decompressed = @gzinflate( substr( $gz_data, $i, -8 ) );
            if ( false !== $decompressed ) {
                return $decompressed;
            }
        }

        // Compressed data from java.util.zip.Deflater amongst others.
        $decompressed = @gzinflate( substr( $gz_data, 2 ) );
        if ( false !== $decompressed ) {
            return $decompressed;
        }

        return false;
    }

    /**
     * What encoding types to accept and their priority values.
     *
     * @since 2.8.0
     *
     * @param string $url
     * @param array  $args
     * @return string Types of encoding to accept.
     */
    public static function accept_encoding( $url, $args ) {
        $type                = array();
        $compression_enabled = self::is_available();

        if ( ! $args['decompress'] ) { // Decompression specifically disabled.
            $compression_enabled = false;
        } elseif ( $args['stream'] ) { // Disable when streaming to file.
            $compression_enabled = false;
        } elseif ( isset( $args['limit_response_size'] ) ) { // If only partial content is being requested, we won't be able to decompress it.
            $compression_enabled = false;
        }

        if ( $compression_enabled ) {
            if ( function_exists( 'gzinflate' ) ) {
                $type[] = 'deflate;q=1.0';
            }

            if ( function_exists( 'gzuncompress' ) ) {
                $type[] = 'compress;q=0.5';
            }

            if ( function_exists( 'gzdecode' ) ) {
                $type[] = 'gzip;q=0.5';
            }
        }

        /**
         * Filters the allowed encoding types.
         *
         * @since 3.6.0
         *
         * @param string[] $type Array of what encoding types to accept and their priority values.
         * @param string   $url  URL of the HTTP request.
         * @param array    $args HTTP request arguments.
         */
        $type = apply_filters( 'wp_http_accept_encoding', $type, $url, $args );

        return implode( ', ', $type );
    }

    /**
     * What encoding the content used when it was compressed to send in the headers.
     *
     * @since 2.8.0
     *
     * @return string Content-Encoding string to send in the header.
     */
    public static function content_encoding() {
        return 'deflate';
    }

    /**
     * Whether the content be decoded based on the headers.
     *
     * @since 2.8.0
     *
     * @param array|string $headers All of the available headers.
     * @return bool
     */
    public static function should_decode( $headers ) {
        if ( is_array( $headers ) ) {
            if ( array_key_exists( 'content-encoding', $headers ) && ! empty( $headers['content-encoding'] ) ) {
                return true;
            }
        } elseif ( is_string( $headers ) ) {
            return ( stripos( $headers, 'content-encoding:' ) !== false );
        }

        return false;
    }

    /**
     * Whether decompression and compression are supported by the PHP version.
     *
     * Each function is tested instead of checking for the zlib extension, to
     * ensure that the functions all exist in the PHP version and aren't
     * disabled.
     *
     * @since 2.8.0
     *
     * @return bool
     */
    public static function is_available() {
        return ( function_exists( 'gzuncompress' ) || function_exists( 'gzdeflate' ) || function_exists( 'gzinflate' ) );
    }
}