package com.runescape.networking.codec.login;

import java.math.BigInteger;

import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.frame.FrameDecoder;

import com.runescape.game.model.player.Player;
import com.runescape.networking.codec.login.RS2LoginDecoder.Stage;
import com.runescape.utility.BufferUtility;
import com.runescape.utility.Misc;
import com.runescape.utility.game.FileLoader;
import com.runescape.utility.game.LoginResponse;
import com.runescape.utility.game.LoginResponse.Response;
import com.runescape.utility.game.XTEA;

/**
 * An {@link FrameDecoder} implementation used to decode the world login
 * procedure.
 *
 * @author Tyluur
 *
 */
public class RS2LoginDecoder extends StagedFrameDecoder<Stage> {

	/**
	 * The Standard login type.
	 */
	public static final int LOGIN_TYPE = 16;

	/**
	 * The Reconnection login type.
	 */
	public static final int RECONNECTION_TYPE = 18;

	/**
	 * The lobby login type.
	 */
	public static final int LOBBY_TYPE = 19;

	/**
	 * The remaining bytes left in the login block.
	 */
	private int loginSize;

	/**
	 * The login type
	 */
	private int loginType;

	/**
	 * The rsa exponent.
	 */
	public static final BigInteger EXPONENT = new BigInteger("90587072701551327129007891668787349509347630408215045082807628285770049664232156776755654198505412956586289981306433146503308411067358680117206732091608088418458220580479081111360656446804397560752455367862620370537461050334224448167071367743407184852057833323917170323302797356352672118595769338616589092625");

	/**
	 * The rsa modulus.
	 */
	public static final BigInteger MODULUS = new BigInteger("102876637271116124732338500663639643113504464789339249490399312659674772039314875904176809267475033772367707882873773291786014475222178654932442254125731622781524413208523465520758537060408541610254619166907142593731337618490879831401461945679478046811438574041131738117063340726565226753787565780501845348613");

	/**
	 * The different stages of login.
	 *
	 * @author Thomas Le Godais
	 *
	 */
	public enum Stage {

		CONNECTION_TYPE,

		CLIENT_DETAILS,

		WORLD_PAYLOAD;
	}

	/**
	 * Constrcuts a new WorldLoginDecoder.
	 */
	public RS2LoginDecoder() {
		super(Stage.CONNECTION_TYPE);
	}


	@Override
	protected Object decode(ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {
		switch(stage) {
		case CONNECTION_TYPE:
			return decodeConnectionType(channel, buffer);
		case CLIENT_DETAILS:
			return decodeClientDetails(channel, buffer);
		case WORLD_PAYLOAD:
			return decodeWorldPayload(channel, buffer);
		}
		return null;
	}

	/**
	 * Decodes the connection type.
	 *
	 * @param channel The channel.
	 * @param buffer The buffer.
	 * @return The object.
	 */
	private Object decodeConnectionType(Channel channel, ChannelBuffer buffer) {
		if(buffer.readable()) {
			loginType = buffer.readUnsignedByte();
			if(loginType != LOGIN_TYPE && loginType != RECONNECTION_TYPE) {
				sendResponse(channel, 13);
			}
			loginSize = buffer.readUnsignedShort();
			setStage(Stage.CLIENT_DETAILS);
		}
		return null;
	}

	/**
	 * Decodes the client details.
	 *
	 * @param channel The channel.
	 * @param buffer The buffer.
	 * @return The object.
	 */
	private Object decodeClientDetails(Channel channel, ChannelBuffer buffer) {
		if(buffer.readableBytes() >= loginSize) {
			int version = buffer.readInt();
			buffer.readInt();
			if(version != 718) {
				sendResponse(channel, 6);
			}
			if(loginType != LOBBY_TYPE) {
				setStage(Stage.WORLD_PAYLOAD);
			}
		}
		return null;
	}

	/**
	 * Decodes the world login payload.
	 *
	 * @param channel The channel.
	 * @param buffer The buffer.
	 * @return The object.
	 */
	@SuppressWarnings("unused")
	private Object decodeWorldPayload(Channel channel, ChannelBuffer buffer) {
		buffer.readUnsignedByte();

		int blockSize = buffer.readShort() & 0xFFFF;
		if(!(blockSize > buffer.readableBytes())) {

			byte[] rsaData = new byte[blockSize];
			buffer.readBytes(rsaData, 0, blockSize);
			ChannelBuffer rsaPayload = ChannelBuffers.wrappedBuffer(new BigInteger(rsaData).modPow(EXPONENT, MODULUS).toByteArray());

			int rsaBlock = rsaPayload.readByte() & 0xFF;
			if(rsaBlock != 10) {
				sendResponse(channel, 10);
				return null;
			}

			int[] isaacKeys = new int[4];
			for(int i = 0; i < isaacKeys.length; i++) {
				isaacKeys[i] = rsaPayload.readInt();
			}

			long rsaPass = rsaPayload.readLong();
			if(rsaPass != 0L) {
				sendResponse(channel, 10);
				return null;
			}

			String password = BufferUtility.readString(rsaPayload);
			if(password.length() > 30 || password.length() < 3) {
				sendResponse(channel, Response.WEAK_PASSWORD.getOpcode());
				return null;
			}

			String unknown = Misc.longToString(rsaPayload.readLong());
			byte[] block = new byte[buffer.readableBytes()];
			buffer.readBytes(block);
			ChannelBuffer xteaBuffer = ChannelBuffers.wrappedBuffer(XTEA.decipher(isaacKeys, block));

			boolean decodeAsString = (xteaBuffer.readByte() & 0xff) == 1;
			String username = Misc.formatPlayerNameForProtocol(decodeAsString ? BufferUtility.readString(xteaBuffer) : Misc.longToString(xteaBuffer.readLong()));

			int displayMode = xteaBuffer.readByte() & 0xff;
			xteaBuffer.readUnsignedShort();
			xteaBuffer.readUnsignedShort();
			xteaBuffer.readUnsignedByte();

			xteaBuffer.skipBytes(24);
			String clientSettings = BufferUtility.readString(xteaBuffer);

			xteaBuffer.readInt();
			int skipLen = xteaBuffer.readByte() & 0xff;
			xteaBuffer.skipBytes(skipLen);

			xteaBuffer.readInt();
			xteaBuffer.readLong();

			boolean additInfo = (xteaBuffer.readByte() & 0xFF) == 1;
			if(additInfo) {
				BufferUtility.readString(xteaBuffer);
			}
			for(int i = 0; i < 3; i++) {
				xteaBuffer.readUnsignedByte();
			}
			xteaBuffer.readByte();
			xteaBuffer.readInt();

			String unknownString = BufferUtility.readString(xteaBuffer);

			xteaBuffer.readUnsignedByte();

			System.out.println("Login Request [username=" + username + " password=" + password + " displayMode=" + displayMode + "]");
			Player player;
			if (!FileLoader.containsPlayer(username)) {
				player = new Player();
			} else {
				player = FileLoader.loadPlayer(username);
				if (!player.getFeatures().getPassword().equals(password)) {
					sendResponse(channel, Response.INVALID_CREDENTIALS.getOpcode());
					return null;
				}
			}
			player.init(channel, username, password);
			player.start();
		} else {
			channel.close();
		}
		return null;
	}

	/**
	 * Sends a response.
	 *
	 * @param channel The channel to write the response.
	 * @param rOpcode The response opcode.
	 */
	private void sendResponse(Channel channel, int rOpcode) {
		channel.write(new LoginResponse(Response.forId(rOpcode)));
	}
}