/*
 * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.mdsal.binding.dom.codec.impl;

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import org.opendaylight.mdsal.binding.spec.reflect.BindingReflections;
import org.opendaylight.yangtools.concepts.IllegalArgumentCodec;
import org.opendaylight.yangtools.yang.model.api.TypeDefinition;
import org.opendaylight.yangtools.yang.model.api.type.BitsTypeDefinition;
import org.opendaylight.yangtools.yang.model.api.type.EnumTypeDefinition;

/**
 * Value codec, which serializes / deserializes values from DOM simple values.
 */
// FIXME: IllegalArgumentCodec is perhaps not appropriate here due to null behavior
abstract class ValueTypeCodec implements IllegalArgumentCodec<Object, Object> {
    /*
     * Use identity comparison for keys and allow classes to be GCd themselves.
     *
     * Since codecs can (and typically do) hold a direct or indirect strong reference to the class, they need to be also
     * accessed via reference. Using a weak reference could be problematic, because the codec would quite often be only
     * weakly reachable. We therefore use a soft reference, whose implementation guidance is suitable to our use case:
     *
     *     "Virtual machine implementations are, however, encouraged to bias against clearing recently-created or
     *      recently-used soft references."
     */
    private static final Cache<Class<?>, SchemaUnawareCodec> STATIC_CODECS = CacheBuilder.newBuilder()
            .weakKeys().softValues().build();

    /**
     * Marker interface for codecs, which functionality will not be affected by schema change (introduction of new YANG
     * modules) they may have one static instance generated when first time needed.
     */
    // FIXME: IllegalArgumentCodec is perhaps not appropriate here due to null behavior
    interface SchemaUnawareCodec extends IllegalArgumentCodec<Object, Object> {

    }

    /**
     * No-op Codec, Java YANG Binding uses same types as NormalizedNode model for base YANG types, representing numbers,
     * binary, strings and empty.
     */
    public static final SchemaUnawareCodec NOOP_CODEC = new SchemaUnawareCodec() {
        @Override
        public Object serialize(final Object input) {
            return input;
        }

        @Override
        public Object deserialize(final Object input) {
            return input;
        }
    };

    public static SchemaUnawareCodec getCodecFor(final Class<?> typeClz, final TypeDefinition<?> def) {
        if (BindingReflections.isBindingClass(typeClz)) {
            return getCachedSchemaUnawareCodec(typeClz, getCodecLoader(typeClz, def));
        }
        return NOOP_CODEC;
    }

    private static SchemaUnawareCodec getCachedSchemaUnawareCodec(final Class<?> typeClz,
            final Callable<? extends SchemaUnawareCodec> loader) {
        try {
            return STATIC_CODECS.get(typeClz, loader);
        } catch (ExecutionException e) {
            throw new IllegalStateException(e);
        }
    }

    private static Callable<? extends SchemaUnawareCodec> getCodecLoader(final Class<?> typeClz,
            final TypeDefinition<?> def) {

        TypeDefinition<?> rootType = def;
        while (rootType.getBaseType() != null) {
            rootType = rootType.getBaseType();
        }
        if (rootType instanceof EnumTypeDefinition) {
            return EnumerationCodec.loader(typeClz, (EnumTypeDefinition) rootType);
        } else if (rootType instanceof BitsTypeDefinition) {
            return BitsCodec.loader(typeClz, (BitsTypeDefinition) rootType);
        }
        return EncapsulatedValueCodec.loader(typeClz, def);
    }

    @SuppressWarnings("rawtypes")
    static ValueTypeCodec encapsulatedValueCodecFor(final Class<?> typeClz, final TypeDefinition<?> typeDef,
             final IllegalArgumentCodec delegate) {
        SchemaUnawareCodec extractor = getCachedSchemaUnawareCodec(typeClz,
            EncapsulatedValueCodec.loader(typeClz, typeDef));
        return new CompositeValueCodec(extractor, delegate);
    }
}