/*
 * 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.adapter;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
import static java.util.Objects.requireNonNull;

import com.google.common.util.concurrent.FluentFuture;
import com.google.common.util.concurrent.MoreExecutors;
import java.util.Optional;
import org.eclipse.jdt.annotation.NonNull;
import org.opendaylight.mdsal.binding.api.query.QueryExpression;
import org.opendaylight.mdsal.binding.api.query.QueryResult;
import org.opendaylight.mdsal.binding.dom.adapter.query.DefaultQuery;
import org.opendaylight.mdsal.common.api.LogicalDatastoreType;
import org.opendaylight.mdsal.dom.api.DOMDataTreeQueryOperations;
import org.opendaylight.mdsal.dom.api.DOMDataTreeReadOperations;
import org.opendaylight.mdsal.dom.api.DOMDataTreeTransaction;
import org.opendaylight.mdsal.dom.api.query.DOMQuery;
import org.opendaylight.mdsal.dom.api.query.DOMQueryResult;
import org.opendaylight.mdsal.dom.spi.query.DOMQueryEvaluator;
import org.opendaylight.yangtools.concepts.Delegator;
import org.opendaylight.yangtools.concepts.Identifiable;
import org.opendaylight.yangtools.yang.binding.DataObject;
import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

abstract class AbstractForwardedTransaction<T extends DOMDataTreeTransaction> implements Delegator<T>,
        Identifiable<Object> {
    private static final Logger LOG = LoggerFactory.getLogger(AbstractForwardedTransaction.class);

    private final @NonNull AdapterContext adapterContext;
    private final @NonNull T delegate;

    AbstractForwardedTransaction(final AdapterContext adapterContext, final T delegateTx) {
        this.adapterContext = requireNonNull(adapterContext, "Codec must not be null");
        this.delegate = requireNonNull(delegateTx, "Delegate must not be null");
    }

    @Override
    public final Object getIdentifier() {
        return delegate.getIdentifier();
    }

    @Override
    public final T getDelegate() {
        return delegate;
    }

    protected final <S extends DOMDataTreeTransaction> S getDelegateChecked(final Class<S> txType) {
        checkState(txType.isInstance(delegate));
        return txType.cast(delegate);
    }

    protected final AdapterContext adapterContext() {
        return adapterContext;
    }

    protected final <D extends DataObject> @NonNull FluentFuture<Optional<D>> doRead(
            final DOMDataTreeReadOperations readOps, final LogicalDatastoreType store,
            final InstanceIdentifier<D> path) {
        checkArgument(!path.isWildcarded(), "Invalid read of wildcarded path %s", path);

        final CurrentAdapterSerializer codec = adapterContext.currentSerializer();
        final YangInstanceIdentifier domPath = codec.toYangInstanceIdentifier(path);

        return readOps.read(store, domPath)
                .transform(optData -> optData.map(domData -> (D) codec.fromNormalizedNode(domPath, domData).getValue()),
                    MoreExecutors.directExecutor());
    }

    protected final @NonNull FluentFuture<Boolean> doExists(final DOMDataTreeReadOperations readOps,
            final LogicalDatastoreType store, final InstanceIdentifier<?> path) {
        checkArgument(!path.isWildcarded(), "Invalid exists of wildcarded path %s", path);
        return readOps.exists(store, adapterContext.currentSerializer().toYangInstanceIdentifier(path));
    }

    protected final <T extends @NonNull DataObject> @NonNull FluentFuture<QueryResult<T>> doExecute(
            final DOMDataTreeReadOperations readOps, final @NonNull LogicalDatastoreType store,
            final @NonNull QueryExpression<T> query) {
        checkArgument(query instanceof DefaultQuery, "Unsupported query type %s", query);
        final DefaultQuery<T> defaultQuery = (DefaultQuery<T>) query;

        final FluentFuture<DOMQueryResult> domResult = readOps instanceof DOMDataTreeQueryOperations
            ? ((DOMDataTreeQueryOperations) readOps).execute(store, defaultQuery.asDOMQuery())
                : fallbackExecute(readOps, store, defaultQuery.asDOMQuery());

        return domResult.transform(defaultQuery::toQueryResult, MoreExecutors.directExecutor());
    }

    private static FluentFuture<DOMQueryResult> fallbackExecute(final @NonNull DOMDataTreeReadOperations readOps,
            final @NonNull LogicalDatastoreType store, final @NonNull DOMQuery domQuery) {
        LOG.trace("Fallback evaluation of {} on {}", domQuery, readOps);
        return readOps.read(store, domQuery.getRoot())
            .transform(
                node -> node.map(data -> DOMQueryEvaluator.evaluateOn(domQuery, data)).orElse(DOMQueryResult.of()),
                // TODO: execute on a dedicated thread pool
                MoreExecutors.directExecutor());
    }
}