package org.bouncycastle.crypto.tls;

import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import org.bouncycastle.asn1.DERBitString;
import org.bouncycastle.asn1.x509.KeyUsage;
import org.bouncycastle.asn1.x509.X509CertificateStructure;
import org.bouncycastle.asn1.x509.X509Extension;
import org.bouncycastle.asn1.x509.X509Extensions;
import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.digests.MD5Digest;
import org.bouncycastle.crypto.digests.SHA1Digest;
import org.bouncycastle.crypto.macs.HMac;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.util.Strings;
import org.bouncycastle.util.io.Streams;

Some helper fuctions for MicroTLS.
/**
 * Some helper fuctions for MicroTLS.
 */
public class TlsUtils
{
    protected static void writeUint8(short i, OutputStream os) throws IOException
    {
        os.write(i);
    }

    protected static void writeUint8(short i, byte[] buf, int offset)
    {
        buf[offset] = (byte)i;
    }

    protected static void writeUint16(int i, OutputStream os) throws IOException
    {
        os.write(i >> 8);
        os.write(i);
    }

    protected static void writeUint16(int i, byte[] buf, int offset)
    {
        buf[offset] = (byte)(i >> 8);
        buf[offset + 1] = (byte)i;
    }

    protected static void writeUint24(int i, OutputStream os) throws IOException
    {
        os.write(i >> 16);
        os.write(i >> 8);
        os.write(i);
    }

    protected static void writeUint24(int i, byte[] buf, int offset)
    {
        buf[offset] = (byte)(i >> 16);
        buf[offset + 1] = (byte)(i >> 8);
        buf[offset + 2] = (byte)(i);
    }

    protected static void writeUint32(long i, OutputStream os) throws IOException
    {
        os.write((int)(i >> 24));
        os.write((int)(i >> 16));
        os.write((int)(i >> 8));
        os.write((int)(i));
    }

    protected static void writeUint32(long i, byte[] buf, int offset)
    {
        buf[offset] = (byte)(i >> 24);
        buf[offset + 1] = (byte)(i >> 16);
        buf[offset + 2] = (byte)(i >> 8);
        buf[offset + 3] = (byte)(i);
    }

    protected static void writeUint64(long i, OutputStream os) throws IOException
    {
        os.write((int)(i >> 56));
        os.write((int)(i >> 48));
        os.write((int)(i >> 40));
        os.write((int)(i >> 32));
        os.write((int)(i >> 24));
        os.write((int)(i >> 16));
        os.write((int)(i >> 8));
        os.write((int)(i));
    }


    protected static void writeUint64(long i, byte[] buf, int offset)
    {
        buf[offset] = (byte)(i >> 56);
        buf[offset + 1] = (byte)(i >> 48);
        buf[offset + 2] = (byte)(i >> 40);
        buf[offset + 3] = (byte)(i >> 32);
        buf[offset + 4] = (byte)(i >> 24);
        buf[offset + 5] = (byte)(i >> 16);
        buf[offset + 6] = (byte)(i >> 8);
        buf[offset + 7] = (byte)(i);
    }

    protected static void writeOpaque8(byte[] buf, OutputStream os) throws IOException
    {
        writeUint8((short)buf.length, os);
        os.write(buf);
    }

    protected static void writeOpaque16(byte[] buf, OutputStream os) throws IOException
    {
        writeUint16(buf.length, os);
        os.write(buf);
    }

    protected static void writeOpaque24(byte[] buf, OutputStream os) throws IOException
    {
        writeUint24(buf.length, os);
        os.write(buf);
    }

    protected static void writeUint8Array(short[] uints, OutputStream os) throws IOException
    {
        for (int i = 0; i < uints.length; ++i)
        {
            writeUint8(uints[i], os);
        }
    }

    protected static void writeUint16Array(int[] uints, OutputStream os) throws IOException
    {
        for (int i = 0; i < uints.length; ++i)
        {
            writeUint16(uints[i], os);
        }
    }

    protected static short readUint8(InputStream is) throws IOException
    {
        int i = is.read();
        if (i == -1)
        {
            throw new EOFException();
        }
        return (short)i;
    }

    protected static int readUint16(InputStream is) throws IOException
    {
        int i1 = is.read();
        int i2 = is.read();
        if ((i1 | i2) < 0)
        {
            throw new EOFException();
        }
        return i1 << 8 | i2;
    }

    protected static int readUint24(InputStream is) throws IOException
    {
        int i1 = is.read();
        int i2 = is.read();
        int i3 = is.read();
        if ((i1 | i2 | i3) < 0)
        {
            throw new EOFException();
        }
        return (i1 << 16) | (i2 << 8) | i3;
    }

    protected static long readUint32(InputStream is) throws IOException
    {
        int i1 = is.read();
        int i2 = is.read();
        int i3 = is.read();
        int i4 = is.read();
        if ((i1 | i2 | i3 | i4) < 0)
        {
            throw new EOFException();
        }
        return (((long)i1) << 24) | (((long)i2) << 16) | (((long)i3) << 8) | ((long)i4);
    }

    protected static void readFully(byte[] buf, InputStream is) throws IOException
    {
        if (Streams.readFully(is, buf) != buf.length)
        {
            throw new EOFException();
        }
    }

    protected static byte[] readOpaque8(InputStream is) throws IOException
    {
        short length = readUint8(is);
        byte[] value = new byte[length];
        readFully(value, is);
        return value;
    }

    protected static byte[] readOpaque16(InputStream is) throws IOException
    {
        int length = readUint16(is);
        byte[] value = new byte[length];
        readFully(value, is);
        return value;
    }

    protected static void checkVersion(byte[] readVersion, TlsProtocolHandler handler)
        throws IOException
    {
        if ((readVersion[0] != 3) || (readVersion[1] != 1))
        {
            throw new TlsFatalAlert(AlertDescription.protocol_version);
        }
    }

    protected static void checkVersion(InputStream is, TlsProtocolHandler handler)
        throws IOException
    {
        int i1 = is.read();
        int i2 = is.read();
        if ((i1 != 3) || (i2 != 1))
        {
            throw new TlsFatalAlert(AlertDescription.protocol_version);
        }
    }

    protected static void writeGMTUnixTime(byte[] buf, int offset)
    {
        int t = (int)(System.currentTimeMillis() / 1000L);
        buf[offset] = (byte)(t >> 24);
        buf[offset + 1] = (byte)(t >> 16);
        buf[offset + 2] = (byte)(t >> 8);
        buf[offset + 3] = (byte)t;
    }

    protected static void writeVersion(OutputStream os) throws IOException
    {
        os.write(3);
        os.write(1);
    }

    protected static void writeVersion(byte[] buf, int offset) throws IOException
    {
        buf[offset] = 3;
        buf[offset + 1] = 1;
    }

    private static void hmac_hash(Digest digest, byte[] secret, byte[] seed, byte[] out)
    {
        HMac mac = new HMac(digest);
        KeyParameter param = new KeyParameter(secret);
        byte[] a = seed;
        int size = digest.getDigestSize();
        int iterations = (out.length + size - 1) / size;
        byte[] buf = new byte[mac.getMacSize()];
        byte[] buf2 = new byte[mac.getMacSize()];
        for (int i = 0; i < iterations; i++)
        {
            mac.init(param);
            mac.update(a, 0, a.length);
            mac.doFinal(buf, 0);
            a = buf;
            mac.init(param);
            mac.update(a, 0, a.length);
            mac.update(seed, 0, seed.length);
            mac.doFinal(buf2, 0);
            System.arraycopy(buf2, 0, out, (size * i), Math.min(size, out.length - (size * i)));
        }
    }

    protected static byte[] PRF(byte[] secret, String asciiLabel, byte[] seed, int size)
    {
        byte[] label = Strings.toByteArray(asciiLabel);

        int s_half = (secret.length + 1) / 2;
        byte[] s1 = new byte[s_half];
        byte[] s2 = new byte[s_half];
        System.arraycopy(secret, 0, s1, 0, s_half);
        System.arraycopy(secret, secret.length - s_half, s2, 0, s_half);

        byte[] ls = concat(label, seed);

        byte[] buf = new byte[size];
        byte[] prf = new byte[size];
        hmac_hash(new MD5Digest(), s1, ls, prf);
        hmac_hash(new SHA1Digest(), s2, ls, buf);
        for (int i = 0; i < size; i++)
        {
            buf[i] ^= prf[i];
        }
        return buf;
    }

    static byte[] concat(byte[] a, byte[] b)
    {
        byte[] c = new byte[a.length + b.length];
        System.arraycopy(a, 0, c, 0, a.length);
        System.arraycopy(b, 0, c, a.length, b.length);
        return c;
    }

    static void validateKeyUsage(X509CertificateStructure c, int keyUsageBits) throws IOException
    {
        X509Extensions exts = c.getTBSCertificate().getExtensions();
        if (exts != null)
        {
            X509Extension ext = exts.getExtension(X509Extension.keyUsage);
            if (ext != null)
            {
                DERBitString ku = KeyUsage.getInstance(ext);
                int bits = ku.getBytes()[0] & 0xff;
                if ((bits & keyUsageBits) != keyUsageBits)
                {
                    throw new TlsFatalAlert(AlertDescription.certificate_unknown);
                }
            }
        }
    }
}