/*

 * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.internal.net.http.hpack;

import jdk.internal.net.http.common.Utils;

import jdk.internal.net.http.hpack.HPACK.Logger.Level;

import java.nio.ByteBuffer;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.Map;

import java.util.ResourceBundle;

import java.util.function.Supplier;

import static java.lang.String.format;

import static java.util.stream.Collectors.joining;

import static jdk.internal.net.http.hpack.HPACK.Logger.Level.EXTRA;

import static jdk.internal.net.http.hpack.HPACK.Logger.Level.NONE;

import static jdk.internal.net.http.hpack.HPACK.Logger.Level.NORMAL;

/**

 * Internal utilities and stuff.

 */

public final class HPACK {

    private static final RootLogger LOGGER;

    private static final Map<String, Level> logLevels =

            Map.of("NORMAL", NORMAL, "EXTRA", EXTRA);

    static {

        String PROPERTY = "jdk.internal.httpclient.hpack.log.level";

        String value = AccessController.doPrivileged(

                (PrivilegedAction<String>) () -> System.getProperty(PROPERTY));

        if (value == null) {

            LOGGER = new RootLogger(NONE);

        } else {

            String upperCasedValue = value.toUpperCase();

            Level l = logLevels.get(upperCasedValue);

            if (l == null) {

                LOGGER = new RootLogger(NONE);

                LOGGER.log(System.Logger.Level.INFO,

                        () -> format("%s value '%s' not recognized (use %s); logging disabled",

                                     PROPERTY, value, logLevels.keySet().stream().collect(joining(", "))));

            } else {

                LOGGER = new RootLogger(l);

                LOGGER.log(System.Logger.Level.DEBUG,

                        () -> format("logging level %s", l));

            }

        }

    }

    public static Logger getLogger() {

        return LOGGER;

    }

    private HPACK() { }

    /**

     * The purpose of this logger is to provide means of diagnosing issues _in

     * the HPACK implementation_. It's not a general purpose logger.

     */

    // implements System.Logger to make it possible to skip this class

    // when looking for the Caller.

    public static class Logger implements System.Logger {

        /**

         * Log detail level.

         */

        public enum Level {

            NONE(0, System.Logger.Level.OFF),

            NORMAL(1, System.Logger.Level.DEBUG),

            EXTRA(2, System.Logger.Level.TRACE);

            private final int level;

            final System.Logger.Level systemLevel;

            Level(int i, System.Logger.Level system) {

                level = i;

                systemLevel = system;

            }

            public final boolean implies(Level other) {

                return this.level >= other.level;

            }

        }

        private final String name;

        private final Level level;

        private final String path;

        private final System.Logger logger;

        private Logger(String path, String name, Level level) {

            this(path, name, level, null);

        }

        private Logger(String p, String name, Level level, System.Logger logger) {

            this.path = p;

            this.name = name;

            this.level = level;

            this.logger = Utils.getHpackLogger(path::toString, level.systemLevel);

        }

        public final String getName() {

            return name;

        }

        @Override

        public boolean isLoggable(System.Logger.Level level) {

            return logger.isLoggable(level);

        }

        @Override

        public void log(System.Logger.Level level, ResourceBundle bundle, String msg, Throwable thrown) {

            logger.log(level, bundle, msg,thrown);

        }

        @Override

        public void log(System.Logger.Level level, ResourceBundle bundle, String format, Object... params) {

            logger.log(level, bundle, format, params);

        }

        /*

         * Usual performance trick for logging, reducing performance overhead in

         * the case where logging with the specified level is a NOP.

         */

        public boolean isLoggable(Level level) {

            return this.level.implies(level);

        }

        public void log(Level level, Supplier<String> s) {

            if (this.level.implies(level)) {

                logger.log(level.systemLevel, s);

            }

        }

        public Logger subLogger(String name) {

            return new Logger(path + "/" + name, name, level);

        }

    }

    private static final class RootLogger extends Logger {

        protected RootLogger(Level level) {

            super("hpack", "hpack", level);

        }

    }

    // -- low-level utilities --

    @FunctionalInterface

    interface BufferUpdateConsumer {

        void accept(long data, int len);

    }

    @SuppressWarnings("fallthrough")

    public static int read(ByteBuffer source,

                           long buffer,

                           int bufferLen,

                           BufferUpdateConsumer consumer)

    {

        // read as much as possible (up to 8 bytes)

        int nBytes = Math.min((64 - bufferLen) >> 3, source.remaining());

        switch (nBytes) {

            case 0:

                break;

            case 3:

                buffer |= ((source.get() & 0x00000000000000ffL) << (56 - bufferLen));

                bufferLen += 8;

            case 2:

                buffer |= ((source.get() & 0x00000000000000ffL) << (56 - bufferLen));

                bufferLen += 8;

            case 1:

                buffer |= ((source.get() & 0x00000000000000ffL) << (56 - bufferLen));

                bufferLen += 8;

                consumer.accept(buffer, bufferLen);

                break;

            case 7:

                buffer |= ((source.get() & 0x00000000000000ffL) << (56 - bufferLen));

                bufferLen += 8;

            case 6:

                buffer |= ((source.get() & 0x00000000000000ffL) << (56 - bufferLen));

                bufferLen += 8;

            case 5:

                buffer |= ((source.get() & 0x00000000000000ffL) << (56 - bufferLen));

                bufferLen += 8;

            case 4:

                buffer |= ((source.getInt() & 0x00000000ffffffffL) << (32 - bufferLen));

                bufferLen += 32;

                consumer.accept(buffer, bufferLen);

                break;

            case 8:

                buffer = source.getLong();

                bufferLen = 64;

                consumer.accept(buffer, bufferLen);

                break;

            default:

                throw new InternalError(String.valueOf(nBytes));

        }

        return nBytes;

    }

    // The number of bytes that can be written at once

    // (calculating in bytes, not bits, since

    //  destination.remaining() * 8 might overflow)

    @SuppressWarnings("fallthrough")

    public static int write(long buffer,

                            int bufferLen,

                            BufferUpdateConsumer consumer,

                            ByteBuffer destination)

    {

        int nBytes = Math.min(bufferLen >> 3, destination.remaining());

        switch (nBytes) {

            case 0:

                break;

            case 3:

                destination.put((byte) (buffer >>> 56));

                buffer <<= 8;

                bufferLen -= 8;

            case 2:

                destination.put((byte) (buffer >>> 56));

                buffer <<= 8;

                bufferLen -= 8;

            case 1:

                destination.put((byte) (buffer >>> 56));

                buffer <<= 8;

                bufferLen -= 8;

                consumer.accept(buffer, bufferLen);

                break;

            case 7:

                destination.put((byte) (buffer >>> 56));

                buffer <<= 8;

                bufferLen -= 8;

            case 6:

                destination.put((byte) (buffer >>> 56));

                buffer <<= 8;

                bufferLen -= 8;

            case 5:

                destination.put((byte) (buffer >>> 56));

                buffer <<= 8;

                bufferLen -= 8;

            case 4:

                destination.putInt((int) (buffer >>> 32));

                buffer <<= 32;

                bufferLen -= 32;

                consumer.accept(buffer, bufferLen);

                break;

            case 8:

                destination.putLong(buffer);

                buffer = 0;

                bufferLen = 0;

                consumer.accept(buffer, bufferLen);

                break;

            default:

                throw new InternalError(String.valueOf(nBytes));

        }

        return nBytes;

    }

    /*

     * Returns the number of bytes the given number of bits constitute.

     */

    static int bytesForBits(int n) {

        assert (n / 8 + (n % 8 != 0 ? 1 : 0)) == (n + 7) / 8

                && (n + 7) / 8 == ((n + 7) >> 3) : n;

        return (n + 7) >> 3;

    }

}