/*
 * Copyright (c) 2020 PANTHEON.tech, s.r.o. 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.restconf.nb.rfc8040.rests.transactions;

import static java.util.Objects.requireNonNull;
import static org.opendaylight.mdsal.common.api.LogicalDatastoreType.CONFIGURATION;
import static org.opendaylight.yangtools.yang.data.impl.schema.ImmutableNodes.fromInstanceId;

import com.google.common.collect.ImmutableList;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.MoreExecutors;
import com.google.common.util.concurrent.SettableFuture;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.StringJoiner;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import org.eclipse.jdt.annotation.NonNull;
import org.eclipse.jdt.annotation.Nullable;
import org.opendaylight.mdsal.common.api.CommitInfo;
import org.opendaylight.mdsal.common.api.TransactionCommitFailedException;
import org.opendaylight.mdsal.dom.api.DOMRpcResult;
import org.opendaylight.mdsal.dom.spi.DefaultDOMRpcResult;
import org.opendaylight.netconf.api.NetconfDocumentedException;
import org.opendaylight.netconf.dom.api.NetconfDataTreeService;
import org.opendaylight.yangtools.yang.common.ErrorSeverity;
import org.opendaylight.yangtools.yang.common.ErrorTag;
import org.opendaylight.yangtools.yang.common.ErrorType;
import org.opendaylight.yangtools.yang.common.RpcError;
import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.NodeIdentifierWithPredicates;
import org.opendaylight.yangtools.yang.data.api.schema.LeafSetNode;
import org.opendaylight.yangtools.yang.data.api.schema.MapNode;
import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNodeContainer;
import org.opendaylight.yangtools.yang.data.util.DataSchemaContext;
import org.opendaylight.yangtools.yang.data.util.DataSchemaContextTree;
import org.opendaylight.yangtools.yang.model.api.DataSchemaNode;
import org.opendaylight.yangtools.yang.model.api.EffectiveModelContext;
import org.opendaylight.yangtools.yang.model.api.LeafListSchemaNode;
import org.opendaylight.yangtools.yang.model.api.ListSchemaNode;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

final class NetconfRestconfTransaction extends RestconfTransaction {
    private static final Logger LOG = LoggerFactory.getLogger(NetconfRestconfTransaction.class);

    private final List<ListenableFuture<? extends DOMRpcResult>> resultsFutures =
        Collections.synchronizedList(new ArrayList<>());
    private final NetconfDataTreeService netconfService;
    private final Map<YangInstanceIdentifier, Collection<? extends NormalizedNode>> readListCache =
        new ConcurrentHashMap<>();

    private volatile boolean isLocked = false;

    NetconfRestconfTransaction(final EffectiveModelContext modelContext, final NetconfDataTreeService netconfService) {
        super(modelContext);
        this.netconfService = requireNonNull(netconfService);

        final var lockResult = netconfService.lock();
        Futures.addCallback(lockResult, new FutureCallback<DOMRpcResult>() {
            @Override
            public void onSuccess(final DOMRpcResult rpcResult) {
                if (rpcResult != null && allWarnings(rpcResult.errors())) {
                    isLocked = true;
                }
            }

            @Override
            public void onFailure(final Throwable throwable) {
                // do nothing
            }
        }, MoreExecutors.directExecutor());
        resultsFutures.add(lockResult);
    }

    @Override
    void cancel() {
        resultsFutures.clear();
        readListCache.clear();
        executeWithLogging(netconfService::discardChanges);
        executeWithLogging(netconfService::unlock);
    }

    @Override
    void deleteImpl(final YangInstanceIdentifier path) {
        if (isListPath(path, modelContext)) {
            final var items = getListItemsForRemove(path);
            if (items.isEmpty()) {
                LOG.debug("Path {} contains no items, delete operation omitted.", path);
            } else {
                items.forEach(item ->
                    enqueueOperation(() -> netconfService.delete(CONFIGURATION, path.node(item.name()))));
            }
        } else {
            enqueueOperation(() -> netconfService.delete(CONFIGURATION, path));
        }
    }

    @Override
    void removeImpl(final YangInstanceIdentifier path) {
        if (isListPath(path, modelContext)) {
            final var items = getListItemsForRemove(path);
            if (items.isEmpty()) {
                LOG.debug("Path {} contains no items, remove operation omitted.", path);
            } else {
                items.forEach(item ->
                    enqueueOperation(() -> netconfService.remove(CONFIGURATION, path.node(item.name()))));
            }
        } else {
            enqueueOperation(() -> netconfService.remove(CONFIGURATION, path));
        }
    }

    @Override
    @Nullable NormalizedNodeContainer<?> readList(final YangInstanceIdentifier path) {
        // reading list is mainly invoked for subsequent removal,
        // cache data to avoid extra read invocation on delete/remove
        final var result =  TransactionUtil.syncAccess(read(path), path);
        readListCache.put(path, result.map(data -> ((NormalizedNodeContainer<?>) data).body()).orElse(List.of()));
        return (NormalizedNodeContainer<?>) result.orElse(null);
    }

    private @NonNull Collection<? extends NormalizedNode> getListItemsForRemove(final YangInstanceIdentifier path) {
        final var cached = readListCache.remove(path);
        if (cached != null) {
            return cached;
        }
        // check if keys only can be filtered out to minimize amount of data retrieved
        final var keyFields = keyFieldsFrom(path, modelContext);
        final var future =  keyFields.isEmpty() ? netconfService.getConfig(path)
            // using list wildcard as a root path, it's required for proper key field path construction
            // on building get-config filter
            : netconfService.getConfig(
                path.node(NodeIdentifierWithPredicates.of(path.getLastPathArgument().getNodeType())), keyFields);
        final var retrieved = TransactionUtil.syncAccess(future, path);
        return retrieved.map(data -> ((NormalizedNodeContainer<?>) data).body()).orElse(List.of());
    }

    @Override
    void mergeImpl(final YangInstanceIdentifier path, final NormalizedNode data) {
        enqueueOperation(() -> netconfService.merge(CONFIGURATION, path, data, Optional.empty()));
    }

    @Override
    void createImpl(final YangInstanceIdentifier path, final NormalizedNode data) {
        if (data instanceof MapNode || data instanceof LeafSetNode) {
            final var emptySubTree = fromInstanceId(modelContext, path);
            merge(YangInstanceIdentifier.of(emptySubTree.name()), emptySubTree);

            for (var child : ((NormalizedNodeContainer<?>) data).body()) {
                final var childPath = path.node(child.name());
                enqueueOperation(() -> netconfService.create(CONFIGURATION, childPath, child, Optional.empty()));
            }
        } else {
            enqueueOperation(() -> netconfService.create(CONFIGURATION, path, data, Optional.empty()));
        }
    }

    @Override
    void replaceImpl(final YangInstanceIdentifier path, final NormalizedNode data) {
        if (data instanceof MapNode || data instanceof LeafSetNode) {
            final var emptySubTree = fromInstanceId(modelContext, path);
            merge(YangInstanceIdentifier.of(emptySubTree.name()), emptySubTree);

            for (var child : ((NormalizedNodeContainer<?>) data).body()) {
                final var childPath = path.node(child.name());
                enqueueOperation(() -> netconfService.replace(CONFIGURATION, childPath, child, Optional.empty()));
            }
        } else {
            enqueueOperation(() -> netconfService.replace(CONFIGURATION, path, data, Optional.empty()));
        }
    }

    @Override
    ListenableFuture<? extends @NonNull CommitInfo> commit() {
        final SettableFuture<CommitInfo> commitResult = SettableFuture.create();

        // First complete all resultsFutures and merge them ...
        final ListenableFuture<DOMRpcResult> resultErrors = mergeFutures(resultsFutures);

        // ... then evaluate if there are any problems
        Futures.addCallback(resultErrors, new FutureCallback<>() {
            @Override
            public void onSuccess(final DOMRpcResult result) {
                final Collection<? extends RpcError> errors = result.errors();
                if (!allWarnings(errors)) {
                    Futures.whenAllComplete(discardAndUnlock()).run(
                        () -> commitResult.setException(toCommitFailedException(errors)),
                        MoreExecutors.directExecutor());
                    return;
                }

                // ... no problems so far, initiate commit
                Futures.addCallback(netconfService.commit(), new FutureCallback<DOMRpcResult>() {
                    @Override
                    public void onSuccess(final DOMRpcResult rpcResult) {
                        final Collection<? extends RpcError> errors = rpcResult.errors();
                        if (errors.isEmpty()) {
                            Futures.whenAllComplete(netconfService.unlock()).run(
                                () -> commitResult.set(CommitInfo.empty()),
                                MoreExecutors.directExecutor());
                        } else if (allWarnings(errors)) {
                            LOG.info("Commit successful with warnings {}", errors);
                            Futures.whenAllComplete(netconfService.unlock()).run(
                                () -> commitResult.set(CommitInfo.empty()),
                                MoreExecutors.directExecutor());
                        } else {
                            Futures.whenAllComplete(discardAndUnlock()).run(
                                () -> commitResult.setException(toCommitFailedException(errors)),
                                MoreExecutors.directExecutor());
                        }
                    }

                    @Override
                    public void onFailure(final Throwable throwable) {
                        Futures.whenAllComplete(discardAndUnlock()).run(
                            () -> commitResult.setException(throwable),
                            MoreExecutors.directExecutor());
                    }
                }, MoreExecutors.directExecutor());
            }

            @Override
            public void onFailure(final Throwable throwable) {
                Futures.whenAllComplete(discardAndUnlock()).run(() -> commitResult.setException(throwable),
                    MoreExecutors.directExecutor());
            }
        }, MoreExecutors.directExecutor());

        return commitResult;
    }

    @Override
    ListenableFuture<Optional<NormalizedNode>> read(final YangInstanceIdentifier path) {
        return netconfService.getConfig(path);
    }

    private List<ListenableFuture<?>> discardAndUnlock() {
        readListCache.clear();
        // execute discard & unlock operations only if lock operation was completed successfully
        if (isLocked) {
            return List.of(netconfService.discardChanges(), netconfService.unlock());
        } else {
            return List.of();
        }
    }

    private void enqueueOperation(final Supplier<ListenableFuture<? extends DOMRpcResult>> operation) {
        final ListenableFuture<? extends DOMRpcResult> operationFuture;
        synchronized (resultsFutures) {
            // if we only have result for the lock operation ...
            if (resultsFutures.size() == 1) {
                operationFuture = Futures.transformAsync(resultsFutures.get(0),
                    result -> {
                        // ... then add new operation to the chain if lock was successful
                        if (result != null && (result.errors().isEmpty() || allWarnings(result.errors()))) {
                            return operation.get();
                        } else {
                            return Futures.immediateFailedFuture(new NetconfDocumentedException("Lock operation failed",
                                ErrorType.APPLICATION, ErrorTag.LOCK_DENIED, ErrorSeverity.ERROR));
                        }
                    },
                    MoreExecutors.directExecutor());
            } else {
                // ... otherwise just add operation to the execution chain
                operationFuture = Futures.transformAsync(resultsFutures.get(resultsFutures.size() - 1),
                    future -> operation.get(),
                    MoreExecutors.directExecutor());
            }
            // ... finally save operation related future to the list
            resultsFutures.add(operationFuture);
        }
    }

    // Transform list of futures related to RPC operation into a single Future
    private static ListenableFuture<DOMRpcResult> mergeFutures(
            final List<ListenableFuture<? extends DOMRpcResult>> futures) {
        return Futures.whenAllComplete(futures).call(() -> {
            if (futures.size() == 1) {
                // Fast path
                return Futures.getDone(futures.get(0));
            }

            final var builder = ImmutableList.<RpcError>builder();
            for (ListenableFuture<? extends DOMRpcResult> future : futures) {
                builder.addAll(Futures.getDone(future).errors());
            }
            return new DefaultDOMRpcResult(null, builder.build());
        }, MoreExecutors.directExecutor());
    }

    private static TransactionCommitFailedException toCommitFailedException(
            final Collection<? extends RpcError> errors) {
        ErrorType errType = ErrorType.APPLICATION;
        ErrorSeverity errSeverity = ErrorSeverity.ERROR;
        StringJoiner msgBuilder = new StringJoiner(" ");
        ErrorTag errorTag = ErrorTag.OPERATION_FAILED;
        for (final RpcError error : errors) {
            errType = error.getErrorType();
            errSeverity = error.getSeverity();
            msgBuilder.add(error.getMessage());
            msgBuilder.add(error.getInfo());
            errorTag = error.getTag();
        }

        return new TransactionCommitFailedException("Netconf transaction commit failed",
            new NetconfDocumentedException("RPC during tx failed. " + msgBuilder.toString(), errType, errorTag,
                errSeverity));
    }

    private static void executeWithLogging(final Supplier<ListenableFuture<? extends DOMRpcResult>> operation) {
        final ListenableFuture<? extends DOMRpcResult> operationResult = operation.get();
        Futures.addCallback(operationResult, new FutureCallback<DOMRpcResult>() {
            @Override
            public void onSuccess(final DOMRpcResult rpcResult) {
                if (rpcResult != null && !rpcResult.errors().isEmpty()) {
                    LOG.error("Errors occurred during processing of the RPC operation: {}",
                        rpcResult.errors().stream().map(Object::toString).collect(Collectors.joining(",")));
                }
            }

            @Override
            public void onFailure(final Throwable throwable) {
                LOG.error("Error processing operation", throwable);
            }
        }, MoreExecutors.directExecutor());
    }

    private static boolean allWarnings(final Collection<? extends @NonNull RpcError> errors) {
        return errors.stream().allMatch(error -> error.getSeverity() == ErrorSeverity.WARNING);
    }

    private static boolean isListPath(final YangInstanceIdentifier path, final EffectiveModelContext modelContext) {
        if (path.getLastPathArgument() instanceof YangInstanceIdentifier.NodeIdentifier) {
            // list can be referenced by NodeIdentifier only, prevent list item do be identified as list
            final var schemaNode = schemaNodeFrom(path, modelContext);
            return schemaNode instanceof ListSchemaNode || schemaNode instanceof LeafListSchemaNode;
        }
        return false;
    }

    private static List<YangInstanceIdentifier> keyFieldsFrom(final YangInstanceIdentifier path,
            final EffectiveModelContext modelContext) {
        final var schemaNode = schemaNodeFrom(path, modelContext);
        return schemaNode instanceof ListSchemaNode listSchemaNode
            ? listSchemaNode.getKeyDefinition().stream().map(YangInstanceIdentifier::of).toList() : List.of();
    }

    private static DataSchemaNode schemaNodeFrom(final YangInstanceIdentifier path,
            final EffectiveModelContext modelContext) {
        return DataSchemaContextTree.from(modelContext).findChild(path)
            .map(DataSchemaContext::dataSchemaNode).orElse(null);
    }
}