/*
 * Copyright (c) 2019-2021 GeyserMC. http://geysermc.org
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @author GeyserMC
 * @link https://github.com/GeyserMC/Geyser
 */

package org.geysermc.connector.network;

import com.nukkitx.protocol.bedrock.BedrockPong;
import com.nukkitx.protocol.bedrock.BedrockServerEventHandler;
import com.nukkitx.protocol.bedrock.BedrockServerSession;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.DefaultEventLoopGroup;
import io.netty.channel.socket.DatagramPacket;
import io.netty.util.concurrent.DefaultThreadFactory;
import org.geysermc.connector.GeyserConnector;
import org.geysermc.connector.common.ping.GeyserPingInfo;
import org.geysermc.connector.configuration.GeyserConfiguration;
import org.geysermc.connector.network.session.GeyserSession;
import org.geysermc.connector.network.translators.chat.MessageTranslator;
import org.geysermc.connector.ping.IGeyserPingPassthrough;
import org.geysermc.connector.utils.LanguageUtils;

import javax.annotation.Nonnull;
import java.net.InetSocketAddress;
import java.nio.charset.StandardCharsets;
import java.util.List;

public class ConnectorServerEventHandler implements BedrockServerEventHandler {
    /*
    The following constants are all used to ensure the ping does not reach a length where it is unparsable by the Bedrock client
     */
    private static final int MINECRAFT_VERSION_BYTES_LENGTH = BedrockProtocol.DEFAULT_BEDROCK_CODEC.getMinecraftVersion().getBytes(StandardCharsets.UTF_8).length;
    private static final int BRAND_BYTES_LENGTH = GeyserConnector.NAME.getBytes(StandardCharsets.UTF_8).length;
    /**
     * The MOTD, sub-MOTD and Minecraft version ({@link #MINECRAFT_VERSION_BYTES_LENGTH}) combined cannot reach this length.
     */
    private static final int MAGIC_RAKNET_LENGTH = 338;

    private final GeyserConnector connector;
    // There is a constructor that doesn't require inputting threads, but older Netty versions don't have it
    private final DefaultEventLoopGroup eventLoopGroup = new DefaultEventLoopGroup(0, new DefaultThreadFactory("Geyser player thread"));

    public ConnectorServerEventHandler(GeyserConnector connector) {
        this.connector = connector;
    }

    @Override
    public boolean onConnectionRequest(InetSocketAddress inetSocketAddress) {
        List<String> allowedProxyIPs = connector.getConfig().getBedrock().getProxyProtocolWhitelistedIPs();
        if (connector.getConfig().getBedrock().isEnableProxyProtocol() && !allowedProxyIPs.isEmpty()) {
            boolean isWhitelistedIP = false;
            for (CIDRMatcher matcher : connector.getConfig().getBedrock().getWhitelistedIPsMatchers()) {
                if (matcher.matches(inetSocketAddress.getAddress())) {
                    isWhitelistedIP = true;
                    break;
                }
            }

            if (!isWhitelistedIP) {
                return false;
            }
        }

        connector.getLogger().info(LanguageUtils.getLocaleStringLog("geyser.network.attempt_connect", inetSocketAddress));
        return true;
    }

    @Override
    public BedrockPong onQuery(InetSocketAddress inetSocketAddress) {
        if (connector.getConfig().isDebugMode()) {
            connector.getLogger().debug(LanguageUtils.getLocaleStringLog("geyser.network.pinged", inetSocketAddress));
        }

        GeyserConfiguration config = connector.getConfig();

        GeyserPingInfo pingInfo = null;
        if (config.isPassthroughMotd() || config.isPassthroughPlayerCounts()) {
            IGeyserPingPassthrough pingPassthrough = connector.getBootstrap().getGeyserPingPassthrough();
            pingInfo = pingPassthrough.getPingInformation(inetSocketAddress);
        }

        BedrockPong pong = new BedrockPong();
        pong.setEdition("MCPE");
        pong.setGameType("Survival"); // Can only be Survival or Creative as of 1.16.210.59
        pong.setNintendoLimited(false);
        pong.setProtocolVersion(BedrockProtocol.DEFAULT_BEDROCK_CODEC.getProtocolVersion());
        pong.setVersion(BedrockProtocol.DEFAULT_BEDROCK_CODEC.getMinecraftVersion()); // Required to not be empty as of 1.16.210.59. Can only contain . and numbers.
        pong.setIpv4Port(config.getBedrock().getPort());

        if (config.isPassthroughMotd() && pingInfo != null && pingInfo.getDescription() != null) {
            String[] motd = MessageTranslator.convertMessageLenient(pingInfo.getDescription()).split("\n");
            String mainMotd = motd[0]; // First line of the motd.
            String subMotd = (motd.length != 1) ? motd[1] : GeyserConnector.NAME; // Second line of the motd if present, otherwise default.

            pong.setMotd(mainMotd.trim());
            pong.setSubMotd(subMotd.trim()); // Trimmed to shift it to the left, prevents the universe from collapsing on us just because we went 2 characters over the text box's limit.
        } else {
            pong.setMotd(config.getBedrock().getMotd1());
            pong.setSubMotd(config.getBedrock().getMotd2());
        }

        if (config.isPassthroughPlayerCounts() && pingInfo != null) {
            pong.setPlayerCount(pingInfo.getPlayers().getOnline());
            pong.setMaximumPlayerCount(pingInfo.getPlayers().getMax());
        } else {
            pong.setPlayerCount(connector.getPlayers().size());
            pong.setMaximumPlayerCount(config.getMaxPlayers());
        }

        // Fallbacks to prevent errors and allow Bedrock to see the server
        if (pong.getMotd() == null || pong.getMotd().isBlank()) {
            pong.setMotd(GeyserConnector.NAME);
        }
        if (pong.getSubMotd() == null || pong.getSubMotd().isBlank()) {
            // Sub-MOTD cannot be empty as of 1.16.210.59
            pong.setSubMotd(GeyserConnector.NAME);
        }

        // The ping will not appear if the MOTD + sub-MOTD is of a certain length.
        // We don't know why, though
        byte[] motdArray = pong.getMotd().getBytes(StandardCharsets.UTF_8);
        int subMotdLength = pong.getSubMotd().getBytes(StandardCharsets.UTF_8).length;
        if (motdArray.length + subMotdLength > (MAGIC_RAKNET_LENGTH - MINECRAFT_VERSION_BYTES_LENGTH)) {
            // Shorten the sub-MOTD first since that only appears locally
            if (subMotdLength > BRAND_BYTES_LENGTH) {
                pong.setSubMotd(GeyserConnector.NAME);
                subMotdLength = BRAND_BYTES_LENGTH;
            }
            if (motdArray.length > (MAGIC_RAKNET_LENGTH - MINECRAFT_VERSION_BYTES_LENGTH - subMotdLength)) {
                // If the top MOTD is still too long, we chop it down
                byte[] newMotdArray = new byte[MAGIC_RAKNET_LENGTH - MINECRAFT_VERSION_BYTES_LENGTH - subMotdLength];
                System.arraycopy(motdArray, 0, newMotdArray, 0, newMotdArray.length);
                pong.setMotd(new String(newMotdArray, StandardCharsets.UTF_8));
            }
        }

        //Bedrock will not even attempt a connection if the client thinks the server is full
        //so we have to fake it not being full
        if (pong.getPlayerCount() >= pong.getMaximumPlayerCount()) {
            pong.setMaximumPlayerCount(pong.getPlayerCount() + 1);
        }

        return pong;
    }

    @Override
    public void onSessionCreation(BedrockServerSession bedrockServerSession) {
        bedrockServerSession.setLogging(true);
        bedrockServerSession.setCompressionLevel(connector.getConfig().getBedrock().getCompressionLevel());
        bedrockServerSession.setPacketHandler(new UpstreamPacketHandler(connector, new GeyserSession(connector, bedrockServerSession, eventLoopGroup.next())));
        // Set the packet codec to default just in case we need to send disconnect packets.
        bedrockServerSession.setPacketCodec(BedrockProtocol.DEFAULT_BEDROCK_CODEC);
    }

    @Override
    public void onUnhandledDatagram(@Nonnull ChannelHandlerContext ctx, DatagramPacket packet) {
        ByteBuf content = packet.content();
        if (QueryPacketHandler.isQueryPacket(content)) {
            new QueryPacketHandler(connector, packet.sender(), content);
        }
    }
}