package org.litesoft.codec;

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

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();
    }
}