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 * Copyright (c) 2015, 2017, 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
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package jdk.incubator.http.internal.common;

import java.io.PrintStream;
import java.util.Objects;
import java.util.ResourceBundle;
import java.util.function.Supplier;
import java.lang.System.Logger;


A System.Logger that forwards all messages to an underlying System.Logger, after adding some decoration. The logger also has the ability to additionally send the logged messages to System.err or System.out, whether the underlying logger is activated or not. In addition instance of DebugLogger support both String.format(String, Object...) and MessageFormat.format(String, Object...) formatting. String-like formatting is enabled by the presence of "%s" or "%d" in the format string. MessageFormat-like formatting is enabled by the presence of "{0" or "{1". 
 See Utils.getDebugLogger(Supplier<String>, boolean) and Utils.getHpackLogger(Supplier<String>, boolean). 
/**
 * A {@code System.Logger} that forwards all messages to an underlying
 * {@code System.Logger}, after adding some decoration.
 * The logger also has the ability to additionally send the logged messages
 * to System.err or System.out, whether the underlying logger is activated or not.
 * In addition instance of {@code DebugLogger} support both
 * {@link String#format(String, Object...)} and
 * {@link java.text.MessageFormat#format(String, Object...)} formatting.
 * String-like formatting is enabled by the presence of "%s" or "%d" in the format
 * string. MessageFormat-like formatting is enabled by the presence of "{0" or "{1".
 * <p>
 * See {@link Utils#getDebugLogger(Supplier, boolean)} and
 * {@link Utils#getHpackLogger(Supplier, boolean)}.
 */
class DebugLogger implements Logger {
    // deliberately not in the same subtree than standard loggers.
    final static String HTTP_NAME  = "jdk.internal.httpclient.debug";
    final static String HPACK_NAME = "jdk.internal.httpclient.hpack.debug";
    final static Logger HTTP = System.getLogger(HTTP_NAME);
    final static Logger HPACK = System.getLogger(HPACK_NAME);
    final static long START_NANOS = System.nanoTime();

    private final Supplier<String> dbgTag;
    private final Level errLevel;
    private final Level outLevel;
    private final Logger logger;
    private final boolean debugOn;
    private final boolean traceOn;

    
Create a logger for debug traces.The logger should only be used with levels whose severity is <= DEBUG. By default, this logger will forward all messages logged to the supplied logger. But in addition, if the message severity level is >= to the provided errLevel it will print the messages on System.err, and if the message severity level is >= to the provided outLevel it will also print the messages on System.out. 
 The logger will add some decoration to the printed message, in the form of <Level>:[<thread-name>] [<elapsed-time>] <dbgTag>: <formatted message> 
Params:
  • logger – The internal logger to which messages will be forwarded. This should be either HPACK or HTTP;
  • dbgTag – A lambda that returns a string that identifies the caller
              (e.g: "SocketTube(3)", or "Http2Connection(SocketTube(3))")
  • outLevel – The level above which messages will be also printed on
              System.out (in addition to being forwarded to the internal logger).
  • errLevel – The level above which messages will be also printed on
              System.err (in addition to being forwarded to the internal logger).
API Note:To obtain a logger that will always print things on stderr in addition to forwarding to the internal logger, use new DebugLogger(logger, this::dbgTag, Level.OFF, Level.ALL);. To obtain a logger that will only forward to the internal logger, use new DebugLogger(logger, this::dbgTag, Level.OFF, Level.OFF);.
Returns:A logger for HTTP internal debug traces
/**
     * Create a logger for debug traces.The logger should only be used
     * with levels whose severity is {@code <= DEBUG}.
     *
     * By default, this logger will forward all messages logged to the supplied
     * {@code logger}.
     * But in addition, if the message severity level is {@code >=} to
     * the provided {@code errLevel} it will print the messages on System.err,
     * and if the message severity level is {@code >=} to
     * the provided {@code outLevel} it will also print the messages on System.out.
     * <p>
     * The logger will add some decoration to the printed message, in the form of
     * {@code <Level>:[<thread-name>] [<elapsed-time>] <dbgTag>: <formatted message>}
     *
     * @apiNote To obtain a logger that will always print things on stderr in
     *          addition to forwarding to the internal logger, use
     *          {@code new DebugLogger(logger, this::dbgTag, Level.OFF, Level.ALL);}.
     *          To obtain a logger that will only forward to the internal logger,
     *          use {@code new DebugLogger(logger, this::dbgTag, Level.OFF, Level.OFF);}.
     *
     * @param logger The internal logger to which messages will be forwarded.
     *               This should be either {@link #HPACK} or {@link #HTTP};
     *
     * @param dbgTag A lambda that returns a string that identifies the caller
     *               (e.g: "SocketTube(3)", or "Http2Connection(SocketTube(3))")
     * @param outLevel The level above which messages will be also printed on
     *               System.out (in addition to being forwarded to the internal logger).
     * @param errLevel The level above which messages will be also printed on
     *               System.err (in addition to being forwarded to the internal logger).
     *
     * @return A logger for HTTP internal debug traces
     */
    private DebugLogger(Logger logger,
                Supplier<String> dbgTag,
                Level outLevel,
                Level errLevel) {
        this.dbgTag = dbgTag;
        this.errLevel = errLevel;
        this.outLevel = outLevel;
        this.logger = Objects.requireNonNull(logger);
        // support only static configuration.
        this.debugOn = isEnabled(Level.DEBUG);
        this.traceOn = isEnabled(Level.TRACE);
    }

    @Override
    public String getName() {
        return logger.getName();
    }

    private boolean isEnabled(Level level) {
        if (level == Level.OFF) return false;
        int severity = level.getSeverity();
        return severity >= errLevel.getSeverity()
                || severity >= outLevel.getSeverity()
                || logger.isLoggable(level);
    }

    @Override
    public boolean isLoggable(Level level) {
        // fast path, we assume these guys never change.
        // support only static configuration.
        if (level == Level.DEBUG) return debugOn;
        if (level == Level.TRACE) return traceOn;
        return isEnabled(level);
    }

    @Override
    public void log(Level level, ResourceBundle unused,
                    String format, Object... params) {
        // fast path, we assume these guys never change.
        // support only static configuration.
        if (level == Level.DEBUG && !debugOn) return;
        if (level == Level.TRACE && !traceOn) return;

        int severity = level.getSeverity();
        if (errLevel != Level.OFF
                && errLevel.getSeverity() <= severity) {
            print(System.err, level, format, params, null);
        }
        if (outLevel != Level.OFF
                && outLevel.getSeverity() <= severity) {
            print(System.out, level, format, params, null);
        }
        if (logger.isLoggable(level)) {
            logger.log(level, unused,
                    getFormat(new StringBuilder(), format, params).toString(),
                    params);
        }
    }

    @Override
    public void log(Level level, ResourceBundle unused, String msg,
                    Throwable thrown) {
        // fast path, we assume these guys never change.
        if (level == Level.DEBUG && !debugOn) return;
        if (level == Level.TRACE && !traceOn) return;

        if (errLevel != Level.OFF
                && errLevel.getSeverity() <= level.getSeverity()) {
            print(System.err, level, msg, null, thrown);
        }
        if (outLevel != Level.OFF
                && outLevel.getSeverity() <= level.getSeverity()) {
            print(System.out, level, msg, null, thrown);
        }
        if (logger.isLoggable(level)) {
            logger.log(level, unused,
                    getFormat(new StringBuilder(), msg, null).toString(),
                    thrown);
        }
    }

    private void print(PrintStream out, Level level, String msg,
                       Object[] params, Throwable t) {
        StringBuilder sb = new StringBuilder();
        sb.append(level.name()).append(':').append(' ');
        sb = format(sb, msg, params);
        if (t != null) sb.append(' ').append(t.toString());
        out.println(sb.toString());
        if (t != null) {
            t.printStackTrace(out);
        }
    }

    private StringBuilder decorate(StringBuilder sb, String msg) {
        String tag = dbgTag == null ? null : dbgTag.get();
        String res = msg == null ? "" : msg;
        long elapsed = System.nanoTime() - START_NANOS;
        long millis = elapsed / 1000_000;
        long secs   = millis / 1000;
        sb.append('[').append(Thread.currentThread().getName()).append(']')
                .append(' ').append('[');
        if (secs > 0) {
            sb.append(secs).append('s');
        }
        millis = millis % 1000;
        if (millis > 0) {
            if (secs > 0) sb.append(' ');
            sb.append(millis).append("ms");
        }
        sb.append(']').append(' ');
        if (tag != null) {
            sb.append(tag).append(' ');
        }
        sb.append(res);
        return sb;
    }


    private StringBuilder getFormat(StringBuilder sb, String format, Object[] params) {
        if (format == null || params == null || params.length == 0) {
            return decorate(sb, format);
        } else if (format.contains("{0}") || format.contains("{1}")) {
            return decorate(sb, format);
        } else if (format.contains("%s") || format.contains("%d")) {
            try {
                return decorate(sb, String.format(format, params));
            } catch (Throwable t) {
                return decorate(sb, format);
            }
        } else {
            return decorate(sb, format);
        }
    }

    private StringBuilder format(StringBuilder sb, String format, Object[] params) {
        if (format == null || params == null || params.length == 0) {
            return decorate(sb, format);
        } else if (format.contains("{0}") || format.contains("{1}")) {
            return decorate(sb, java.text.MessageFormat.format(format, params));
        } else if (format.contains("%s") || format.contains("%d")) {
            try {
                return decorate(sb, String.format(format, params));
            } catch (Throwable t) {
                return decorate(sb, format);
            }
        } else {
            return decorate(sb, format);
        }
    }

    public static DebugLogger createHttpLogger(Supplier<String> dbgTag, Level outLevel, Level errLevel) {
        return new DebugLogger(HTTP, dbgTag, outLevel, errLevel);
    }

    public static DebugLogger createHpackLogger(Supplier<String> dbgTag, Level outLevel, Level errLevel) {
        return new DebugLogger(HPACK, dbgTag, outLevel, errLevel);
    }
}