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/*
 * de.unkrig.commons - A general-purpose Java class library
 *
 * Copyright (c) 2014, Arno Unkrig
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
 * following conditions are met:
 *
 *    1. Redistributions of source code must retain the above copyright notice, this list of conditions and the
 *       following disclaimer.
 *    2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
 *       following disclaimer in the documentation and/or other materials provided with the distribution.
 *    3. The name of the author may not be used to endorse or promote products derived from this software without
 *       specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
 * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

package de.unkrig.commons.junit4;

import java.io.File;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogRecord;
import java.util.logging.Logger;

import org.junit.Assert;

import de.unkrig.commons.lang.AssertionUtil;
import de.unkrig.commons.lang.StringUtil;
import de.unkrig.commons.lang.protocol.RunnableWhichThrows;
import de.unkrig.commons.nullanalysis.Nullable;

/**
 * Utility methods related to JUNIT and {@code java.util.logging}.
 */
public final
class AssertLogging {

    static { AssertionUtil.enableAssertionsForThisClass(); }

    private AssertLogging() {}

    /**
     * A representation of the log records produced by {@link AssertLogging#collectLogs(Logger, RunnableWhichThrows)}.
     */
    public
    interface Logs {

        /**
         * Verifies that a log record with the given {@code message} was logged.
         */
        void assertContains(String expected);

        /**
         * Verifies that no log record with the given {@code message} was logged.
         */
        void assertDoesNotContain(String expected);
    }

    /**
     * Temporarily enables logging for the given {@link Logger}, runs the {@code runnable}, and silently collects the
     * log records it produces.
     *
     * @return An object representing the collected log records
     * @see Logs
     */
    public static Logs
    collectLogs(Logger logger, RunnableWhichThrows runnable) throws Exception {
        final List messages = Collections.synchronizedList(new ArrayList());
        Handler            handler  = new Handler() {
            @Override public void flush() {}
            @Override public void close() {}

            @Override public void
            publish(@Nullable LogRecord lr) {
                assert lr != null;

                String   message    = lr.getMessage();
                Object[] parameters = lr.getParameters();
                if (message.contains("{") && parameters != null && parameters.length > 0) {
                    try { message = MessageFormat.format(message, parameters); } catch (Exception e) {}
                }

                messages.add(message.replace(File.separatorChar, '/'));
            }
        };
        Level   originalLevel             = logger.getLevel();
        boolean originalUseParentHandlers = logger.getUseParentHandlers();

        logger.addHandler(handler);
        logger.setLevel(Level.ALL);
        logger.setUseParentHandlers(false);
        try {

            runnable.run();

            return new Logs() {

                @Override public void
                assertContains(String expected) {
                    Assert.assertTrue(
                        "Missing log message '" + expected + "' from\n  " + StringUtil.join(messages, "\n  "),
                        messages.contains(expected)
                    );
                }

                @Override public void
                assertDoesNotContain(String unexpected) {
                    Assert.assertFalse(unexpected, messages.contains(unexpected));
                }

            };
        } finally {
            logger.removeHandler(handler);
            logger.setLevel(originalLevel);
            logger.setUseParentHandlers(originalUseParentHandlers);
        }
    }
}