package org.bouncycastle.bcpg;

import java.io.*;

import org.bouncycastle.bcpg.sig.Exportable;
import org.bouncycastle.bcpg.sig.IssuerKeyID;
import org.bouncycastle.bcpg.sig.KeyExpirationTime;
import org.bouncycastle.bcpg.sig.KeyFlags;
import org.bouncycastle.bcpg.sig.PreferredAlgorithms;
import org.bouncycastle.bcpg.sig.PrimaryUserID;
import org.bouncycastle.bcpg.sig.Revocable;
import org.bouncycastle.bcpg.sig.SignatureCreationTime;
import org.bouncycastle.bcpg.sig.SignatureExpirationTime;
import org.bouncycastle.bcpg.sig.SignerUserID;
import org.bouncycastle.bcpg.sig.TrustSignature;

/**
 * reader for signature sub-packets
 */
public class SignatureSubpacketInputStream
    extends InputStream implements SignatureSubpacketTags
{
    InputStream    in;
    
    public SignatureSubpacketInputStream(
        InputStream    in)
    {
        this.in = in;
    }
    
    public int available()
        throws IOException
    {
        return in.available();
    }
    
    public int read()
        throws IOException
    {
        return in.read();
    }
    
    private void readFully(
        byte[]    buf,
        int       off,
        int       len)
        throws IOException
    {
        if (len > 0)
        {
            int    b = this.read();
            
            if (b < 0)
            {
                throw new EOFException();
            }
            
            buf[off] = (byte)b;
            off++;
            len--;
        }
        
        while (len > 0)
        {
            int    l = in.read(buf, off, len);
            
            if (l < 0)
            {
                throw new EOFException();
            }
            
            off += l;
            len -= l;
        }
    }
    
    public SignatureSubpacket readPacket()
        throws IOException
    {
        int            l = this.read();
        int            bodyLen = 0;
        
        if (l < 0)
        {
            return null;
        }

        if (l < 192)
        {
            bodyLen = l;
        }
        else if (l < 223)
        {
            bodyLen = ((l - 192) << 8) + (in.read()) + 192;
        }
        else if (l == 255)
        {
            bodyLen = (in.read() << 24) | (in.read() << 16) |  (in.read() << 8)  | in.read();
        }

       int        tag = in.read();

       if (tag < 0)
       {
               throw new EOFException("unexpected EOF reading signature sub packet");
       }
       
       byte[]    data = new byte[bodyLen - 1];
       
       this.readFully(data, 0, data.length);
       
       boolean   isCritical = ((tag & 0x80) != 0);
       int       type = tag & 0x7f;

       switch (type)
       {
       case CREATION_TIME:
               return new SignatureCreationTime(isCritical, data);
        case KEY_EXPIRE_TIME:
              return new KeyExpirationTime(isCritical, data);
        case EXPIRE_TIME:
              return new SignatureExpirationTime(isCritical, data);
       case REVOCABLE:
               return new Revocable(isCritical, data);
       case EXPORTABLE:
               return new Exportable(isCritical, data);
       case ISSUER_KEY_ID:
               return new IssuerKeyID(isCritical, data);
       case TRUST_SIG:
               return new TrustSignature(isCritical, data);
       case PREFERRED_COMP_ALGS:
       case PREFERRED_HASH_ALGS:
       case PREFERRED_SYM_ALGS:
               return new PreferredAlgorithms(type, isCritical, data);
       case KEY_FLAGS:
               return new KeyFlags(isCritical, data);
       case PRIMARY_USER_ID:
               return new PrimaryUserID(isCritical, data);
       case SIGNER_USER_ID:
           return new SignerUserID(isCritical, data);
       }

       return new SignatureSubpacket(type, isCritical, data);
    }
}
