package org.litesoft.codec;

import org.litesoft.charstreams.*;
import org.litesoft.commonfoundation.annotations.*;

public abstract class AbstractTypedTerminatingCodec<T> implements TypedTerminatingCodec<T>
{
    protected static final char NULL_AS_CHAR = SixBitCodec.NOT_USED_NOT;

    @Override
    public final @NotNull String encode( @Nullable T pValue )
    {
        CharSink zCharSink = new CharSinkToString();
        encode( zCharSink, pValue );
        return zCharSink.toString();
    }

    @Override
    public final void encode( @NotNull CharSink pCharSink, @Nullable T pValue )
    {
        if ( pValue == null )
        {
            pCharSink.add( NULL_AS_CHAR );
        }
        else
        {
            encodeNonNull( pCharSink, pValue );
        }
    }

    @Override
    public final @Nullable T decode( @NotNull CharSequence pValue )
    {
        CharSource zCharSource = new CharSourceFromSequence( pValue );
        return validateConsumed( pValue, zCharSource, decode( zCharSource ) );
    }

    protected T validateConsumed( CharSequence pValue, CharSource pCharSource, T pDecoded )
    {
        if ( pCharSource.anyRemaining() )
        {
            throw new IllegalArgumentException( "Extraneous character(s) starting at " + pCharSource.getNextOffset() + " in: " + pValue );
        }
        return pDecoded;
    }

    @Override
    public final @Nullable T decode( @NotNull CharSource pCharSource )
    {
        return isEscapeWithConsume( pCharSource ) ? null : decodeNonNull( pCharSource );
    }

    protected abstract void encodeNonNull( CharSink pCharSink, T pValue );

    protected abstract @NotNull T decodeNonNull( CharSource pCharSource );

    protected static boolean isEscapeWithConsume( CharSource pCharSource )
    {
        if ( pCharSource.peek() == NULL_AS_CHAR )
        {
            pCharSource.get(); // consume
            return true;
        }
        return !pCharSource.anyRemaining();
    }
}