/*
 * This file is part of Applied Energistics 2.
 * Copyright (c) 2013 - 2015, AlgorithmX2, All rights reserved.
 *
 * Applied Energistics 2 is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Applied Energistics 2 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.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Applied Energistics 2.  If not, see <http://www.gnu.org/licenses/lgpl>.
 */

package appeng.services;


import java.util.Date;

import javax.annotation.Nonnull;

import com.google.common.base.Preconditions;

import net.minecraft.nbt.NBTTagCompound;

import cpw.mods.fml.common.Loader;
import cpw.mods.fml.common.event.FMLInterModComms;

import appeng.core.AEConfig;
import appeng.core.AELog;
import appeng.core.AppEng;
import appeng.services.version.ModVersionFetcher;
import appeng.services.version.Version;
import appeng.services.version.VersionCheckerConfig;
import appeng.services.version.VersionFetcher;
import appeng.services.version.VersionParser;
import appeng.services.version.github.FormattedRelease;
import appeng.services.version.github.ReleaseFetcher;


/**
 * Tries to connect to GitHub to retrieve the most current build.
 * After comparison with the local version, several path can be chosen.
 *
 * If the local version is invalid, somebody might have build that version themselves
 * or it is run in a developer environment, then nothing needs to be done.
 *
 * If GitHub can not be reached, then either is GitHub down
 * or the connection to GitHub disturbed, then nothing needs to be done,
 * since no comparison can be reached
 *
 * If the version was just recently checked, then no need to poll again.
 * Nobody wants to bother to update several times a day.
 *
 * Config enables to fine-tune when a version is considered newer
 *
 * If the local version is newer or equal to the GitHub version,
 * then no update needs to be posted
 *
 * Only after all that cases, if the external version is higher than the local,
 * use Version Checker Mod and post several information needed for it to update the mod.
 */
public final class VersionChecker implements Runnable
{
	private static final int SEC_TO_HOUR = 3600;
	private static final int MS_TO_SEC = 1000;
	private final VersionCheckerConfig config;

	public VersionChecker( @Nonnull final VersionCheckerConfig config )
	{
		Preconditions.checkNotNull( config );

		this.config = config;
	}

	@Override
	public void run()
	{
		try
		{
			Thread.yield();

			// persist the config
			this.config.save();

			// retrieve data
			final String rawLastCheck = this.config.lastCheck();

			// process data
			final long lastCheck = Long.parseLong( rawLastCheck );
			final Date now = new Date();
			final long nowInMs = now.getTime();
			final long intervalInMs = this.config.interval() * SEC_TO_HOUR * MS_TO_SEC;
			final long lastAfterInterval = lastCheck + intervalInMs;

			this.processInterval( nowInMs, lastAfterInterval );
		}
		catch( Exception exception )
		{
			// Log any unhandled exception to prevent the JVM from reporting them as unhandled.
			AELog.error( exception );
		}

		AELog.info( "Stopping AE2 VersionChecker" );
	}

	/**
	 * checks if enough time since last check has expired
	 *
	 * @param nowInMs now in milli seconds
	 * @param lastAfterInterval last version check including the interval defined in the config
	 */
	private void processInterval( final long nowInMs, final long lastAfterInterval )
	{
		if( nowInMs > lastAfterInterval )
		{
			final String rawModVersion = AEConfig.VERSION;
			final VersionParser parser = new VersionParser();
			final VersionFetcher modFetcher = new ModVersionFetcher( rawModVersion, parser );
			final ReleaseFetcher githubFetcher = new ReleaseFetcher( this.config, parser );

			final Version modVersion = modFetcher.get();
			final FormattedRelease githubRelease = githubFetcher.get();

			this.processVersions( modVersion, githubRelease );
		}
		else
		{
			AELog.info( "Last check was just recently." );
		}
	}

	/**
	 * Checks if the retrieved version is newer as the current mod version.
	 * Will notify player if config is enabled.
	 *
	 * @param modVersion version of mod
	 * @param githubRelease release retrieved through github
	 */
	private void processVersions( @Nonnull final Version modVersion, @Nonnull final FormattedRelease githubRelease )
	{
		final Version githubVersion = githubRelease.version();
		final String modFormatted = modVersion.formatted();
		final String ghFormatted = githubVersion.formatted();

		if( githubVersion.isNewerAs( modVersion ) )
		{
			final String changelog = githubRelease.changelog();

			if( this.config.shouldNotifyPlayer() )
			{
				AELog.info( "Newer version is available: " + ghFormatted + " (found) > " + modFormatted + " (current)" );

				if( this.config.shouldPostChangelog() )
				{
					AELog.info( "Changelog: " + changelog );
				}
			}

			this.interactWithVersionCheckerMod( modFormatted, ghFormatted, changelog );
		}
		else
		{
			AELog.info( "No newer version is available: " + ghFormatted + "(found) < " + modFormatted + " (current)" );
		}
	}

	/**
	 * Checks if the version checker mod is installed and handles it depending on that information
	 *
	 * @param modFormatted mod version formatted as rv2-beta-8
	 * @param ghFormatted retrieved github version formatted as rv2-beta-8
	 * @param changelog retrieved github changelog
	 */
	private void interactWithVersionCheckerMod( @Nonnull final String modFormatted, @Nonnull final String ghFormatted, @Nonnull final String changelog )
	{
		if( Loader.isModLoaded( "VersionChecker" ) )
		{
			final NBTTagCompound versionInf = new NBTTagCompound();
			versionInf.setString( "modDisplayName", AppEng.MOD_NAME );
			versionInf.setString( "oldVersion", modFormatted );
			versionInf.setString( "newVersion", ghFormatted );
			versionInf.setString( "updateUrl", "http://ae-mod.info/builds/appliedenergistics2-" + ghFormatted + ".jar" );
			versionInf.setBoolean( "isDirectLink", true );

			if( !changelog.isEmpty() )
			{
				versionInf.setString( "changeLog", changelog );
			}

			versionInf.setString( "newFileName", "appliedenergistics2-" + ghFormatted + ".jar" );
			FMLInterModComms.sendRuntimeMessage( AppEng.instance(), "VersionChecker", "addUpdate", versionInf );

			AELog.info( "Reported new version to VersionChecker mod." );
		}
		else
		{
			AELog.info( "VersionChecker mod is not installed; Proceeding." );
		}
	}
}