/*
 * This file is part of the Illarion project.
 *
 * Copyright © 2015 - Illarion e.V.
 *
 * Illarion is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Illarion 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 for more details.
 */
package illarion.client.crash;

import illarion.client.IllaClient;
import illarion.client.util.Lang;
import illarion.common.bug.CrashData;
import illarion.common.bug.CrashReporter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.Nonnull;
import java.lang.Thread.UncaughtExceptionHandler;

/**
 * This abstract class takes care for fetching uncaught exceptions and tries to
 * keep the client alive just in the way it supposed to be.
 *
 * @author Martin Karing <nitram@illarion.org>
 */
abstract class AbstractCrashHandler implements UncaughtExceptionHandler {
    /**
     * The logger instance that takes care for the logging output of this class.
     */
    @Nonnull
    private static final Logger LOGGER = LoggerFactory.getLogger(AbstractCrashHandler.class);

    /**
     * The time since the last crash in milliseconds that need to have passed to
     * trigger a restart attempt. In case the time since the last crash is
     * shorter then this, the client will be shut down.
     */
    private static final int TIME_SINCE_LAST_CRASH = 60000;

    /**
     * This stores if there is currently a crash handled. In this case all other
     * crashes are ignored for now.
     */
    private boolean currentlyCrashing;

    /**
     * The time stored when this crash occurred last time. In case the same part
     * of the client crashes too frequent the entire client is shutdown.
     */
    private long lastCrash;

    /**
     * Fetch a uncaught exception that was thrown and try restart the crashed
     * part of the client correctly.
     *
     * @param t the thread that crashed
     * @param e the error message it crashed with
     */
    @Override
    public final void uncaughtException(@Nonnull Thread t, @Nonnull Throwable e) {
        LOGGER.error("Fetched uncaught exception: {}", getCrashMessage(t, e), e);
        if (currentlyCrashing) {
            return;
        }
        currentlyCrashing = true;

        if (isUnsolvableError(t, e)) {
            crashClient(t, e, false);
        }

        long oldLastCrash = lastCrash;
        lastCrash = System.currentTimeMillis();
        if (isUnsolvableError(t, e) || ((lastCrash - oldLastCrash) < TIME_SINCE_LAST_CRASH)) {
            crashClient(t, e);
            return;
        }

        reportError(t, e);
        restart(t, e);
        currentlyCrashing = false;
    }

    protected boolean isUnsolvableError(@Nonnull Thread t, @Nonnull Throwable e) {
        return false;
    }

    /**
     * Calling this function results in crashing the entire client. Call it only
     * in case there is no chance in keeping the client running.
     */
    protected final void crashClient(@Nonnull Thread t, @Nonnull Throwable e) {
        crashClient(t, e, true);
    }

    protected final void crashClient(@Nonnull Thread t, @Nonnull Throwable e, boolean showFixFailed) {
        String message = getCrashMessage(t, e);
        if (showFixFailed) {
            message += '\n' + Lang.getMsg("crash.fixfailed");
        }
        IllaClient.errorExit(message);

        currentlyCrashing = false;
    }

    /**
     * Get the message that describes the problem that caused this crash
     * readable for a common player.
     *
     * @return the error message for this problem
     */
    @Nonnull
    protected abstract String getCrashMessage(@Nonnull Thread t, @Nonnull Throwable e);

    /**
     * Restart the crashed thread and try to keep the client alive this way.
     * After this function is called the CrashHandler requests a reconnect.
     */
    protected abstract void restart(@Nonnull Thread t, @Nonnull Throwable e);

    /**
     * Send the data about a crash to the Illarion server so some developer is
     * able to look over it.
     *
     * @param t the thread that crashed
     * @param e the reason of the crash
     */
    private void reportError(@Nonnull Thread t, @Nonnull Throwable e) {
        CrashReporter.getInstance()
                .reportCrash(new CrashData(IllaClient.APPLICATION, "Client", getCrashMessage(t, e), t, e));
    }
}