/*
 * (C) Copyright 2012-2014 Nuxeo SA (http://nuxeo.com/) and contributors.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser General Public License
 * (LGPL) version 2.1 which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/lgpl-2.1.html
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * Contributors:
 *     Sun Seng David TAN <stan@nuxeo.com>, slacoin, jcarsique
 */
package org.nuxeo.runtime.test.runner;

import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.util.ArrayList;
import java.util.List;

import org.apache.log4j.Appender;
import org.apache.log4j.AppenderSkeleton;
import org.apache.log4j.Logger;
import org.apache.log4j.spi.LoggingEvent;
import org.junit.Assert;
import org.junit.runners.model.FrameworkMethod;

/**
 * Test feature to capture from a log4j appender to check that some log4j calls have been correctly called.</br> On a
 * test class or a test method using this feature, a custom {@link LogCaptureFeature.Filter} class is to be provided
 * with the annotation {@link LogCaptureFeature.FilterWith} to select the log events to capture.</br> A
 * {@link LogCaptureFeature.Result} instance is to be injected with {@link Inject} as an attribute of the test.</br> The
 * method {@link LogCaptureFeature.Result#assertHasEvent()} can then be called from test methods to check that matching
 * log calls (events) have been captured.
 *
 * @since 5.7
 */
public class LogCaptureFeature extends SimpleFeature {

    public class NoLogCaptureFilterException extends Exception {
        private static final long serialVersionUID = 1L;
    }

    @Inherited
    @Retention(RetentionPolicy.RUNTIME)
    @Target({ ElementType.TYPE, ElementType.METHOD })
    public @interface FilterWith {
        /**
         * Custom implementation of a filter to select event to capture.
         */
        Class<? extends LogCaptureFeature.Filter> value();
    }

    public class Result {
        protected final ArrayList<LoggingEvent> caughtEvents = new ArrayList<>();

        protected boolean noFilterFlag = false;

        public void assertHasEvent() throws NoLogCaptureFilterException {
            if (noFilterFlag) {
                throw new LogCaptureFeature.NoLogCaptureFilterException();
            }
            Assert.assertFalse("No log result found", caughtEvents.isEmpty());
        }

        public void clear() {
            caughtEvents.clear();
            noFilterFlag = false;
        }

        public List<LoggingEvent> getCaughtEvents() {
            return caughtEvents;
        }

        protected void setNoFilterFlag(boolean noFilterFlag) {
            this.noFilterFlag = noFilterFlag;
        }
    }

    public interface Filter {
        /**
         * {@link LogCaptureFeature} will capture the event if it does match the implementation condition.
         */
        boolean accept(LoggingEvent event);
    }

    protected Filter logCaptureFilter;

    protected final Result myResult = new Result();

    protected Logger rootLogger = Logger.getRootLogger();

    protected Appender logAppender = new AppenderSkeleton() {
        @Override
        public boolean requiresLayout() {
            return false;
        }

        @Override
        public void close() {
        }

        @Override
        protected void append(LoggingEvent event) {
            if (logCaptureFilter == null) {
                myResult.setNoFilterFlag(true);
                return;
            }
            if (logCaptureFilter.accept(event)) {
                myResult.caughtEvents.add(event);
            }
        }
    };

    private Filter setupCaptureFiler;

    @Override
    public void configure(FeaturesRunner runner, com.google.inject.Binder binder) {
        binder.bind(Result.class).toInstance(myResult);
    };

    @Override
    public void beforeSetup(FeaturesRunner runner) throws Exception {
        super.beforeSetup(runner);
        FilterWith filterProvider = runner.getConfig(FilterWith.class);
        if (filterProvider.value() == null) {
            return;
        }
        Class<? extends Filter> filterClass = filterProvider.value();
        enable(filterClass);
    }

    @Override
    public void afterTeardown(FeaturesRunner runner) throws Exception {
        disable();
    }

    @Override
    public void beforeMethodRun(FeaturesRunner runner, FrameworkMethod method, Object test) throws Exception {
        FilterWith filterProvider = runner.getConfig(method, FilterWith.class);
        if (filterProvider.value() == null) {
            return;
        }
        Class<? extends Filter> filterClass = filterProvider.value();
        enable(filterClass);
    }

    @Override
    public void afterMethodRun(FeaturesRunner runner, FrameworkMethod method, Object test) throws Exception {
        disable();
    }

    /**
     * @since 6.0
     */
    protected void enable(Class<? extends Filter> filterClass) throws InstantiationException, IllegalAccessException {
        if (logCaptureFilter != null) {
            setupCaptureFiler = logCaptureFilter;
        } else {
            rootLogger.addAppender(logAppender);
        }
        logCaptureFilter = filterClass.newInstance();
    }

    /**
     * @since 6.0
     */
    protected void disable() {
        if (setupCaptureFiler != null) {
            logCaptureFilter = setupCaptureFiler;
            setupCaptureFiler = null;
            return;
        }
        if (logCaptureFilter != null) {
            myResult.clear();
            rootLogger.removeAppender(logAppender);
            logCaptureFilter = null;
        }
    }

}