package server.refactor.net.codec.login;

import java.math.BigInteger;
import java.security.SecureRandom;
import java.util.logging.Logger;

import org.apache.mina.common.ByteBuffer;
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 server.RS2Server;
import server.net.ChannelBufferUtils;
import server.refactor.net.NetworkConstants;
import server.refactor.net.codec.StatefulFrameDecoder;
import server.refactor.security.ISAACRandomGenPair;
import server.refactor.security.PlayerCredentials;
import server.util.ISAACRandomGen;
import server.util.Misc;

/**
 * A {@link StatefulFrameDecoder} which decodes the login request frames.
 */
public final class LoginDecoder extends StatefulFrameDecoder<LoginDecoderState> {

	private final Logger logger = Logger.getLogger(LoginDecoder.class.getName());

	/**
	 * The secure random number generator.
	 */
	private static final SecureRandom random = new SecureRandom();

	/**
	 * The username hash.
	 */
	private int usernameHash;

	/**
	 * The server-side session key.
	 */
	private long serverSeed;

	/**
	 * The reconnecting flag.
	 */
	private boolean reconnecting;

	/**
	 * The login packet length.
	 */
	private int loginLength;

	/**
	 * The modifier for encrypted strings
	 */
	private int stringModifier;

	/**
	 * Creates the login decoder with the default initial state.
	 */
	public LoginDecoder() {
		super(LoginDecoderState.LOGIN_HANDSHAKE, true);
	}

	@Override
	protected Object decode(final ChannelHandlerContext ctx, final Channel channel, final ChannelBuffer buffer, final LoginDecoderState state) throws Exception {

		switch (state) {
		case LOGIN_HANDSHAKE:
			return decodeHandshake(ctx, channel, buffer);
		case LOGIN_HEADER:
			return decodeHeader(ctx, channel, buffer);
		case LOGIN_PAYLOAD:
			return decodePayload(ctx, channel, buffer);
		default:
			throw new Exception("Invalid login decoder state");
		}
	}

	/**
	 * Decodes in the handshake state.
	 *
	 * @param ctx
	 *            The channel handler context.
	 * @param channel
	 *            The channel.
	 * @param buffer
	 *            The buffer.
	 * @return The frame, or {@code null}.
	 * @throws Exception
	 *             if an error occurs.
	 */
	private Object decodeHandshake(final ChannelHandlerContext ctx, final Channel channel, final ChannelBuffer buffer) throws Exception {
		if (buffer.readable()) {
			usernameHash = buffer.readUnsignedByte();
			// Delay login process in case server startup is not finished.
			if (!RS2Server.engineStarted) {
				final ChannelBuffer resp = ChannelBuffers.buffer(9);
				resp.writeLong(0);
				resp.writeByte(LoginConstants.STATUS_DELAY);
				channel.write(resp);
				channel.close();
			} else {
				serverSeed = random.nextLong();
				final ChannelBuffer resp = ChannelBuffers.buffer(19);
				resp.writeLong(0);
				resp.writeByte(LoginConstants.STATUS_EXCHANGE_DATA);
				// TODO: Send input order
				resp.writeLong(serverSeed);
				stringModifier = (0xFF + Misc.random(0xFFFF - 0xFF));
//				System.out.println("Sending modifier: " + stringModifier);
				resp.writeShort(stringModifier);
				channel.write(resp);
				setState(LoginDecoderState.LOGIN_HEADER);
			}
		}
		return null;
	}

	/**
	 * Decodes in the header state.
	 *
	 * @param ctx
	 *            The channel handler context.
	 * @param channel
	 *            The channel.
	 * @param buffer
	 *            The buffer.
	 * @return The frame, or {@code null}.
	 * @throws Exception
	 *             if an error occurs.
	 */
	private Object decodeHeader(final ChannelHandlerContext ctx, final Channel channel, final ChannelBuffer buffer) throws Exception {
		if (buffer.readableBytes() >= 2) {
			final int loginType = buffer.readByte();
			if (loginType != LoginConstants.TYPE_STANDARD && loginType != LoginConstants.TYPE_RECONNECTION)
				throw new Exception("Invalid login type");
			reconnecting = loginType == LoginConstants.TYPE_RECONNECTION;
			loginLength = buffer.readUnsignedByte();
			setState(LoginDecoderState.LOGIN_PAYLOAD);
		}
		return null;
	}


	/**
	 * Decodes in the payload state.
	 *
	 * @param ctx
	 *            The channel handler context.
	 * @param channel
	 *            The channel.
	 * @param buffer
	 *            The buffer.
	 * @return The frame, or {@code null}.
	 * @throws Exception
	 *             if an error occurs.
	 */
	private Object decodePayload(final ChannelHandlerContext ctx, final Channel channel, final ChannelBuffer buffer) throws Exception {
		if (buffer.readableBytes() >= loginLength) {
			final ChannelBuffer payload = buffer.readBytes(loginLength);
			if (payload.readUnsignedByte() != 0xFF) {
				channel.close();
				throw new Exception("Invalid magic id");
			}
			int release = payload.readUnsignedShort();

			int memoryStatus = payload.readUnsignedByte();

			final int[] archiveCrcs = new int[9];
			for (int i = 0; i < 9; i++)
				archiveCrcs[i] = payload.readInt();

			int length = payload.readUnsignedByte();
			if (length != loginLength - 41) {
				channel.close();
				logger.warning("FAIL PAYLOAD length " + length + " " +  " login length " + loginLength );
				throw new Exception("Secure payload length mismatch");
			}

			ChannelBuffer rsaBuffer = payload.readBytes(length);
			BigInteger bigInteger = new BigInteger(rsaBuffer.array());
			bigInteger = bigInteger.modPow(NetworkConstants.RSA_EXPONENT, NetworkConstants.RSA_MODULUS);

			rsaBuffer = ChannelBuffers.wrappedBuffer(bigInteger.toByteArray());


			final int securityID = rsaBuffer.readUnsignedByte();
			if (securityID != 10) {
				channel.close();
				logger.warning("FAIL PAYLOAD ID " + securityID);
				throw new Exception("Invalid secure payload id");
			}
			final long clientSeed = rsaBuffer.readLong();
			final long reportedServerSeed = rsaBuffer.readLong();
			if (reportedServerSeed != serverSeed) {
				channel.close();
				throw new Exception("Server seed mismatch");
			}
			int uid = rsaBuffer.readInt(); // The SignLink uid

			final String playerMacAddress = "";

			final String clientSerial = "";

			final String regSerial =  "";


		    String username = readString(rsaBuffer);
		    String password = readString(rsaBuffer);

			final int[] seed = new int[4];
			seed[0] = (int) (clientSeed >> 32);
			seed[1] = (int) clientSeed;
			seed[2] = (int) (serverSeed >> 32);
			seed[3] = (int) serverSeed;
			final ISAACRandomGen decodingRandom = new ISAACRandomGen(seed);
			for (int i = 0; i < seed.length; i++)
				seed[i] += 50;

			final ISAACRandomGen encodingRandom = new ISAACRandomGen(seed);
			final ISAACRandomGenPair randomPair = new ISAACRandomGenPair(encodingRandom, decodingRandom);

			final PlayerCredentials credentials = new PlayerCredentials(username, password, usernameHash, reconnecting, uid, release, playerMacAddress, clientSerial, regSerial, randomPair, ctx.getChannel(), false);

			final LoginRequest req = new LoginRequest(credentials, randomPair, reconnecting, false, release, null);
			//return new Object[] { req, buffer.readBytes(buffer.readableBytes()) };
			if (buffer.readable())
				return new Object[] { req, buffer.readBytes(buffer.readableBytes()) };
			else {
				logger.warning("req");
				return req;
			}
		}
		return null;
	}

	private String decryptString(byte[] buffer, int multiplier) {
		byte[] decrypted = new byte[buffer.length];
		for (int i = 0, modifier = 1; i < buffer.length; i++) {
			decrypted[i] = (byte) ((buffer[i] ^ (modifier * multiplier) & 0xFF));
			 modifier *= (i * 2);
		}
		return new String(decrypted);
	}

	/**
	 * Reads a string from the specified {@link ByteBuffer}.
	 *
	 * @param buffer The buffer.
	 * @return The string.
	 */
	public static String readString(ByteBuffer buffer) {
		StringBuilder bldr = new StringBuilder();
		char character;
		while ((character = (char) buffer.get()) != STRING_TERMINATOR) {
			bldr.append(character);
		}
		return bldr.toString();
	}

	/**
	 * Reads a string from the specified {@link ByteBuf}.
	 *
	 * @param buffer The buffer.
	 * @return The string.
	 */
	public static String readString(ChannelBuffer buffer) {
		StringBuilder builder = new StringBuilder();
		int character;
		while (buffer.readable() && (character = buffer.readUnsignedByte()) != STRING_TERMINATOR) {
			builder.append((char) character);
		}
		return builder.toString();
	}

	/**
	 * The terminator of a string.
	 */
	public static final int STRING_TERMINATOR = 10;
}