/*
 * This file is a part of the SteamWar software.
 *
 * Copyright (C) 2020  SteamWar.de-Serverteam
 *
 * This program 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.
 *
 * This program 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

package de.steamwar.bausystem.region;

import de.steamwar.bausystem.BauSystem;
import de.steamwar.bausystem.region.dynamic.DynamicRegion;
import de.steamwar.bausystem.region.dynamic.RegionConstructorData;
import de.steamwar.bausystem.region.dynamic.Tile;
import de.steamwar.bausystem.region.dynamic.global.GlobalRegion;
import lombok.NonNull;
import org.bukkit.Location;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.*;
import java.util.stream.Stream;

public class DynamicRegionSystem implements RegionSystem {

    public static DynamicRegionSystem INSTANCE;

    private static final Map<Long, Region> regionCache = new LinkedHashMap<>(16, 0.75f, true) {
        @Override
        protected boolean removeEldestEntry(Map.Entry<Long, Region> eldest) {
            return size() > 8192; // Tweak this number if needed!
        }
    }; // Will be cleared on region add/delete/remove!
    private static final Map<UUID, Region> regionMap = new HashMap<>();
    private static final Map<RegionType, Set<Region>> regionTypeMap = new EnumMap<>(RegionType.class);

    public void add(DynamicRegion region) {
        regionCache.clear();
        regionMap.put(region.getID(), region);
        regionTypeMap.computeIfAbsent(region.getType(), __ -> new HashSet<>()).add(region);
    }

    public void remove(DynamicRegion region) {
        regionCache.clear();
        regionMap.remove(region.getId());
        regionTypeMap.getOrDefault(region.getType(), Collections.emptySet()).remove(region);
    }

    @Override
    public void load() {
        INSTANCE = this;

        new BufferedReader(new InputStreamReader(BauSystem.getInstance().getClass().getResourceAsStream("/META-INF/annotations/de.steamwar.bausystem.region.dynamic.RegionConstructorData")))
                .lines()
                .map(s -> {
                    try {
                        return Class.forName(s, false, BauSystem.getInstance().getClass().getClassLoader());
                    } catch (ClassNotFoundException | NoClassDefFoundError e) {
                        throw new SecurityException(e.getMessage(), e);
                    }
                })
                .forEach(clazz -> {
                    RegionConstructorData regionConstructorData = clazz.getAnnotation(RegionConstructorData.class);
                    if (regionConstructorData == null) return;
                    // TODO: Save regionConstructorData together with clazz
                });
    }

    @Override
    public @NonNull Location getWorldSpawn() {
        return null;
    }

    @Override
    public @NonNull Region getGlobalRegion() {
        return GlobalRegion.INSTANCE;
    }

    private Region get(int x, int z, boolean fastCache, Collection<Region> regions) {
        Tile tile = Tile.fromXZ(x, z).orElse(null);
        if (tile == null) {
            return getGlobalRegion();
        }
        if (regionCache.containsKey(tile.getId())) {
            Region region = regionCache.get(tile.getId());
            if (fastCache || regions.contains(region)) return region;
        }
        Region region = regions.stream()
                .filter(rg -> rg.getArea().inRegion(x, z, false))
                .findFirst()
                .orElseGet(this::getGlobalRegion);
        regionCache.put(tile.getId(), region);
        return region;
    }

    @Override
    public @NonNull Region get(@NonNull Location location) {
        return get(location.getBlockX(), location.getBlockZ(), true, regionMap.values());
    }

    @Override
    public Optional<Region> getRegion(@NonNull UUID id) {
        return Optional.ofNullable(regionMap.get(id));
    }

    @Override
    public @NonNull Stream<Region> getRegions() {
        return regionMap.values().stream();
    }

    private Stream<Region> getNeighbours(Region region, boolean noCorners, boolean fastCache, Collection<Region> regions) {
        Point minPoint = region.getArea().getMinPoint(false).subtract(18, 0, 18);
        Point maxPoint = region.getArea().getMaxPoint(false).add(19, 0, 19);
        Set<Region> neighbours = new HashSet<>();

        for (int x = minPoint.getX() + (noCorners ? 18 : 0); x <= maxPoint.getX() - (noCorners ? 19 : 0); x += 19) {
            int minZ = minPoint.getZ();
            int maxZ = maxPoint.getZ();
            neighbours.add(get(x, minZ, fastCache, regions));
            neighbours.add(get(x, maxZ, fastCache, regions));
        }

        for (int z = minPoint.getZ() + 18; z <= maxPoint.getZ() - 19; z += 19) {
            int minX = minPoint.getX();
            int maxX = maxPoint.getX();
            neighbours.add(get(minX, z, fastCache, regions));
            neighbours.add(get(maxX, z, fastCache, regions));
        }

        neighbours.remove(getGlobalRegion());
        return neighbours.stream();
    }

    public Stream<Region> getNeighbours(Region region) {
        return getNeighbours(region, false, true, regionMap.values());
    }

    public Stream<Region> getConnectedRegions(Region region) {
        Set<Region> regions = regionTypeMap.get(region.getType());

        Set<Region> connected = new HashSet<>();
        LinkedHashSet<Region> current = new LinkedHashSet<>();
        current.add(region);

        while (!current.isEmpty()) {
            Region r = current.removeFirst();
            if (!connected.add(r)) continue;
            getNeighbours(r, true, false, regions).forEach(current::add);
        }

        return connected.stream();
    }
}