package moe.ymc.acron.net;

import com.google.gson.JsonParseException;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.websocketx.*;
import moe.ymc.acron.MinecraftServerHolder;
import moe.ymc.acron.auth.Action;
import moe.ymc.acron.auth.PolicyChecker;
import moe.ymc.acron.c2s.ReqCmd;
import moe.ymc.acron.c2s.ReqSetConfig;
import moe.ymc.acron.c2s.Request;
import moe.ymc.acron.cmd.CmdQueue;
import moe.ymc.acron.jvav.Pair;
import moe.ymc.acron.s2c.Event;
import moe.ymc.acron.s2c.EventQueue;
import moe.ymc.acron.s2c.response.EventError;
import moe.ymc.acron.s2c.response.EventOk;
import moe.ymc.acron.serialization.Serializer;
import net.minecraft.server.world.ServerWorld;
import net.minecraft.util.math.Vec2f;
import net.minecraft.util.math.Vec3d;
import net.minecraft.world.World;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.jetbrains.annotations.NotNull;

/**
 * The handler for WebSocket requests.
 */
public class WSFrameHandler extends SimpleChannelInboundHandler<WebSocketFrame> {
    private static final Logger LOGGER = LogManager.getLogger();

    @Override
    public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
        super.handlerAdded(ctx);
    }

    @Override
    protected void channelRead0(ChannelHandlerContext ctx, WebSocketFrame msg) throws Exception {
        LOGGER.debug("channelRead0: {} {}",
                this,
                ctx.channel());
        final WebSocketServerHandshaker handshaker =
                ctx.channel().attr(Attributes.HANDSHAKER).get();
        if (msg instanceof CloseWebSocketFrame) {
            handshaker.close(ctx.channel(), (CloseWebSocketFrame) msg.retain());
            return;
        }
        if (msg instanceof PingWebSocketFrame) {
            ctx.write(new PongWebSocketFrame(msg.content().retain()));
            return;
        }
        if (msg instanceof BinaryWebSocketFrame) {
            throw new UnsupportedOperationException("Only text frames are accepted.");
        }
        final TextWebSocketFrame frame = (TextWebSocketFrame) msg;

        final ClientIdentification identification = ctx.channel().attr(Attributes.ID).get();
        final ClientConfiguration configuration = ctx.channel().attr(Attributes.CONFIGURATION).get();
        int id;
        final Request request;
        try {
            request = Serializer.deserialize(frame);
            id = request.getId();
        } catch (JsonParseException | IllegalArgumentException | IllegalStateException e) {
            ctx.channel().writeAndFlush(
                    Serializer.serialize(new EventError(-2, EventError.Code.BAD_REQUEST.value, e.getMessage()))
            );
            return;
        }
        try {
            ctx.channel().writeAndFlush(Serializer.serialize(handle(request,
                    identification,
                    configuration,
                    ctx.channel())));
        } catch (Throwable e) {
            LOGGER.info("An error occurred while processing the request. " +
                            "This may just be a malformed request. " +
                            "It is reported to the client.",
                    e);
            ctx.channel().writeAndFlush(
                    Serializer.serialize(new EventError(id, EventError.Code.SERVER_ERROR.value, e.getMessage()))
            );
        }
    }

    @NotNull
    private Event handle(@NotNull Request request,
                         @NotNull ClientIdentification identification,
                         @NotNull ClientConfiguration configuration,
                         @NotNull Channel channel) throws Throwable {
        if (request instanceof final ReqCmd reqCmd) {
            LOGGER.info("Client {} executed a command: `{}`.",
                    identification.client().id(),
                    reqCmd.cmd());
            final Pair<Action, Boolean> res = PolicyChecker.check(identification.client(),
                    reqCmd.cmd());
            if (res.l() == Action.DENY) {
                return new EventError(reqCmd.id(),
                        EventError.Code.FORBIDDEN.value, "This client is not allowed to " +
                        "execute this command.");
            }
            // TODO: Ok event may be sent after executing the command.
            CmdQueue.enqueue(reqCmd.id(),
                    res.r(),
                    channel,
                    reqCmd.config() == null ?
                            configuration :
                            convertConfiguration(reqCmd.config()),
                    reqCmd.cmd());
            return new EventOk(request.getId());
        } else if (request instanceof final ReqSetConfig reqSetConfig) {
            channel.attr(Attributes.CONFIGURATION).set(convertConfiguration(reqSetConfig));
            return new EventOk(request.getId());
        }
        // This should not occur.
        throw new IllegalStateException("This should not occur.");
    }

    private ClientConfiguration convertConfiguration(@NotNull ReqSetConfig request) {
        final ServerWorld world;
        if (request.world() != null) {
            switch (request.world()) {
                case OVERWORLD -> world = MinecraftServerHolder.getServer().getWorld(World.OVERWORLD);
                case NETHER -> world = MinecraftServerHolder.getServer().getWorld(World.NETHER);
                case END -> world = MinecraftServerHolder.getServer().getWorld(World.END);
                default -> throw new IllegalArgumentException();
            }
        } else {
            world = MinecraftServerHolder.getServer().getOverworld();
        }
        if (world == null) {
            throw new IllegalStateException(String.format("The requested world %s is not available at this time.",
                    request.world()));
        }
        return new ClientConfiguration(
                request.pos() == null ?
                        Vec3d.of(world.getSpawnPos()) :
                        new Vec3d(request.pos().x(), request.pos().y(), request.pos().z()),
                request.rot() == null ?
                        Vec2f.ZERO :
                        new Vec2f(request.rot().x(), request.rot().y()),
                world,
                request.name() == null ? this.toString() : request.name()
        );
    }

    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
        LOGGER.debug("handshakeComplete: {} {}",
                this,
                ctx.channel());
        if (evt instanceof HandshakeComplete) {
            final ClientIdentification identification = ctx.channel().attr(Attributes.ID).get();
            LOGGER.info("Client {} connected. It has {} rules with {} policy mode.",
                    identification.client().id(),
                    identification.client().rules().length,
                    identification.client().policyMode());
            final ServerWorld defaultWorld = MinecraftServerHolder.getServer().getOverworld();
            if (defaultWorld == null) {
                throw new IllegalStateException("The default world is not available at this time.");
            }
            final ClientConfiguration configuration =
                    new ClientConfiguration(defaultWorld,
                            identification.client().id());
            ctx.channel().attr(Attributes.CONFIGURATION).set(configuration);
            EventQueue.registerMessageRecipient(ctx.channel());
        } else {
            ctx.fireUserEventTriggered(evt);
        }
    }
}