/*
 * Minecraft Forge
 * Copyright (c) 2016-2018.
 *
 * This library 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 version 2.1
 * of the License.
 *
 * 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.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

package net.minecraftforge.fml;

import cpw.mods.modlauncher.TransformingClassLoader;
import net.minecraftforge.api.distmarker.Dist;
import net.minecraftforge.client.event.ModelRegistryEvent;
import net.minecraftforge.common.MinecraftForge;
import net.minecraftforge.common.capabilities.CapabilityManager;
import net.minecraftforge.fml.config.ConfigTracker;
import net.minecraftforge.fml.config.ModConfig;
import net.minecraftforge.fml.loading.FMLPaths;
import net.minecraftforge.forgespi.language.IModInfo;
import net.minecraftforge.fml.loading.FMLLoader;
import net.minecraftforge.fml.loading.LoadingModList;
import net.minecraftforge.fml.loading.moddiscovery.ModFile;
import net.minecraftforge.fml.loading.moddiscovery.ModFileInfo;
import net.minecraftforge.forgespi.language.IModLanguageProvider;
import net.minecraftforge.registries.GameData;
import net.minecraftforge.registries.ObjectHolderRegistry;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import static net.minecraftforge.fml.Logging.CORE;
import static net.minecraftforge.fml.Logging.LOADING;

/**
 * Loads mods.
 *
 * Dispatch cycle is seen in {@link #loadMods()} and {@link #finishMods()}
 *
 * Overall sequence for loadMods is:
 * <dl>
 *     <dt>CONSTRUCT</dt>
 *     <dd>Constructs the mod instance. Mods can typically setup basic environment such as Event listeners
 *     and Configuration specifications here.</dd>
 *     <dt>Automated dispatches</dt>
 *     <dd>Dispatches automated elements : {@link net.minecraftforge.fml.common.Mod.EventBusSubscriber},
 *     {@link net.minecraftforge.event.RegistryEvent}, {@link net.minecraftforge.common.capabilities.CapabilityInject}
 *     and others</dd>
 *     <dt>CONFIG_LOAD</dt>
 *     <dd>Dispatches ConfigLoadEvent to mods</dd>
 *     <dt>COMMON_SETUP</dt>
 *     <dd>Dispatches {@link net.minecraftforge.fml.event.lifecycle.FMLCommonSetupEvent} to mods</dd>
 *     <dt>SIDED_SETUP</dt>
 *     <dd>Dispatches {@link net.minecraftforge.fml.event.lifecycle.FMLClientSetupEvent} or
 *     {@link net.minecraftforge.fml.event.lifecycle.FMLDedicatedServerSetupEvent} to mods</dd>
 * </dl>
 *
 * Overall sequence for finishMods is:
 * <dl>
 *     <dt>ENQUEUE_IMC</dt>
 *     <dd>Dispatches {@link net.minecraftforge.fml.event.lifecycle.InterModEnqueueEvent} to mods,
 *     for enqueuing {@link InterModComms} messages for other mods to receive subsequently</dd>
 *     <dt>PROCESS_IMC</dt>
 *     <dd>Dispatches {@link net.minecraftforge.fml.event.lifecycle.InterModProcessEvent} to mods,
 *     for processing {@link InterModComms} messages received from other mods prior to this event</dd>
 *     <dt>COMPLETE</dt>
 *     <dd>Dispatches {@link net.minecraftforge.fml.event.lifecycle.FMLLoadCompleteEvent} to mods,
 *     and completes the mod loading sequence.</dd>
 * </dl>
 */
public class ModLoader
{
    private static final Logger LOGGER = LogManager.getLogger();
    private static ModLoader INSTANCE;
    private final TransformingClassLoader launchClassLoader;
    private final LoadingModList loadingModList;

    private final List<ModLoadingException> loadingExceptions;
    private ModLoader()
    {
        INSTANCE = this;
        this.launchClassLoader = FMLLoader.getLaunchClassLoader();
        this.loadingModList = FMLLoader.getLoadingModList();
        this.loadingExceptions = FMLLoader.getLoadingModList().
                getErrors().stream().flatMap(ModLoadingException::fromEarlyException).collect(Collectors.toList());
    }

    public static ModLoader get()
    {
        return INSTANCE == null ? INSTANCE = new ModLoader() : INSTANCE;
    }

    private static Runnable fireClientEvents()
    {
        return ()->MinecraftForge.EVENT_BUS.post(new ModelRegistryEvent());
    }

    public void loadMods() {
        final ModList modList = ModList.of(loadingModList.getModFiles().stream().map(ModFileInfo::getFile).collect(Collectors.toList()), loadingModList.getMods());
        if (!this.loadingExceptions.isEmpty()) {
            throw new LoadingFailedException(loadingExceptions);
        }
        final Stream<ModContainer> modContainerStream = loadingModList.getModFiles().stream().
                map(ModFileInfo::getFile).
                map(mf -> buildMods(mf, launchClassLoader)).
                flatMap(Collection::stream);
        if (!loadingExceptions.isEmpty()) {
            LOGGER.fatal(CORE, "Failed to initialize mod containers");
            throw new LoadingFailedException(loadingExceptions);
        }
        modList.setLoadedMods(modContainerStream.collect(Collectors.toList()));
        dispatchAndHandleError(LifecycleEventProvider.CONSTRUCT);
        GameData.fireCreateRegistryEvents(LifecycleEventProvider.CREATE_REGISTRIES, this::dispatchAndHandleError);
        ObjectHolderRegistry.findObjectHolders();
        CapabilityManager.INSTANCE.injectCapabilities(modList.getAllScanData());
        GameData.fireRegistryEvents(rl->true, LifecycleEventProvider.LOAD_REGISTRIES, this::dispatchAndHandleError);
        DistExecutor.runWhenOn(Dist.CLIENT, ()->()-> ConfigTracker.INSTANCE.loadConfigs(ModConfig.Type.CLIENT, FMLPaths.CONFIGDIR.get()));
        dispatchAndHandleError(LifecycleEventProvider.SETUP);
        DistExecutor.runWhenOn(Dist.CLIENT, ModLoader::fireClientEvents);
        dispatchAndHandleError(LifecycleEventProvider.SIDED_SETUP);
    }

    private void dispatchAndHandleError(LifecycleEventProvider event) {
        if (!loadingExceptions.isEmpty()) {
            LOGGER.error("Skipping lifecycle event {}, {} errors found.", event, loadingExceptions.size());
        } else {
            event.dispatch(this::accumulateErrors);
        }
        if (!loadingExceptions.isEmpty()) {
            LOGGER.fatal("Failed to complete lifecycle event {}, {} errors found", event, loadingExceptions.size());
            throw new LoadingFailedException(loadingExceptions);
        }
    }
    private void accumulateErrors(List<ModLoadingException> errors) {
        loadingExceptions.addAll(errors);
    }

    private List<ModContainer> buildMods(final ModFile modFile, final TransformingClassLoader modClassLoader)
    {
        final Map<String, IModInfo> modInfoMap = modFile.getModFileInfo().getMods().stream().collect(Collectors.toMap(IModInfo::getModId, Function.identity()));

        LOGGER.debug(LOADING, "ModContainer is {}", ModContainer.class.getClassLoader());
        return modFile.getScanResult().getTargets().entrySet().stream().
                map(e-> buildModContainerFromTOML(modFile, modClassLoader, modInfoMap, e)).collect(Collectors.toList());
    }

    private ModContainer buildModContainerFromTOML(final ModFile modFile, final TransformingClassLoader modClassLoader, final Map<String, IModInfo> modInfoMap, final Map.Entry<String, ? extends IModLanguageProvider.IModLanguageLoader> idToProviderEntry) {
        try {
            final String modId = idToProviderEntry.getKey();
            final IModLanguageProvider.IModLanguageLoader languageLoader = idToProviderEntry.getValue();
            IModInfo info = Optional.ofNullable(modInfoMap.get(modId)).
                    // throw a missing metadata error if there is no matching modid in the modInfoMap from the mods.toml file
                    orElseThrow(()->new ModLoadingException(null, ModLoadingStage.CONSTRUCT, "fml.modloading.missingmetadata", null, modId));
            return languageLoader.loadMod(info, modClassLoader, modFile.getScanResult());
        } catch (ModLoadingException mle) {
            // exceptions are caught and added to the error list for later handling. Null is returned here.
            loadingExceptions.add(mle);
            return null;
        }
    }


    public void finishMods()
    {
        dispatchAndHandleError(LifecycleEventProvider.ENQUEUE_IMC);
        dispatchAndHandleError(LifecycleEventProvider.PROCESS_IMC);
        dispatchAndHandleError(LifecycleEventProvider.COMPLETE);
        GameData.freezeData();
    }

}