/*
 * Copyright (c) 2016 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.yanglib.impl;

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

import com.google.common.base.Predicate;
import com.google.common.base.Strings;
import com.google.common.collect.Iterables;
import com.google.common.io.ByteStreams;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.MoreExecutors;
import java.io.File;
import java.io.IOException;
import java.nio.charset.Charset;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutionException;
import org.opendaylight.mdsal.binding.api.DataBroker;
import org.opendaylight.mdsal.binding.api.WriteTransaction;
import org.opendaylight.mdsal.common.api.CommitInfo;
import org.opendaylight.mdsal.common.api.LogicalDatastoreType;
import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.inet.types.rev130715.Uri;
import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.yang.library.rev160621.ModulesState;
import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.yang.library.rev160621.ModulesStateBuilder;
import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.yang.library.rev160621.RevisionUtils;
import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.yang.library.rev160621.module.list.Module;
import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.yang.library.rev160621.module.list.ModuleBuilder;
import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.yang.library.rev160621.module.list.ModuleKey;
import org.opendaylight.yang.gen.v1.urn.ietf.params.xml.ns.yang.ietf.yang.types.rev130715.YangIdentifier;
import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.controller.yanglib.impl.rev141210.YanglibConfig;
import org.opendaylight.yanglib.api.YangLibService;
import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
import org.opendaylight.yangtools.yang.common.Revision;
import org.opendaylight.yangtools.yang.model.parser.api.YangParserFactory;
import org.opendaylight.yangtools.yang.model.repo.api.RevisionSourceIdentifier;
import org.opendaylight.yangtools.yang.model.repo.api.SchemaSourceRepresentation;
import org.opendaylight.yangtools.yang.model.repo.api.SourceIdentifier;
import org.opendaylight.yangtools.yang.model.repo.api.YangTextSchemaSource;
import org.opendaylight.yangtools.yang.model.repo.spi.PotentialSchemaSource;
import org.opendaylight.yangtools.yang.model.repo.spi.SchemaListenerRegistration;
import org.opendaylight.yangtools.yang.model.repo.spi.SchemaSourceListener;
import org.opendaylight.yangtools.yang.model.repo.util.FilesystemSchemaSourceCache;
import org.opendaylight.yangtools.yang.parser.repo.SharedSchemaRepository;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Listens on new schema sources registered event. For each new source
 * registered generates URL representing its schema source and write this URL
 * along with source identifier to
 * ietf-netconf-yang-library/modules-state/module list.
 */
public class YangLibProvider implements AutoCloseable, SchemaSourceListener, YangLibService {
    private static final Logger LOG = LoggerFactory.getLogger(YangLibProvider.class);

    private static final Predicate<PotentialSchemaSource<?>> YANG_SCHEMA_SOURCE =
        input -> YangTextSchemaSource.class.isAssignableFrom(input.getRepresentation());

    private final DataBroker dataBroker;
    private final YanglibConfig yanglibConfig;
    private final SharedSchemaRepository schemaRepository;
    private SchemaListenerRegistration schemaListenerRegistration;

    public YangLibProvider(final YanglibConfig yanglibConfig, final DataBroker dataBroker,
            final YangParserFactory parserFactory) {
        this.yanglibConfig = requireNonNull(yanglibConfig);
        this.dataBroker = requireNonNull(dataBroker);
        this.schemaRepository = new SharedSchemaRepository("yang-library", parserFactory);
    }

    @Override
    public void close() {
        if (schemaListenerRegistration != null) {
            schemaListenerRegistration.close();
        }
    }

    public void init() {
        if (Strings.isNullOrEmpty(yanglibConfig.getCacheFolder())) {
            LOG.info("No cache-folder set in yanglib-config - yang library services will not be available");
            return;
        }

        final File cacheFolderFile = new File(yanglibConfig.getCacheFolder());
        checkArgument(cacheFolderFile.exists(), "cache-folder %s does not exist", cacheFolderFile);
        checkArgument(cacheFolderFile.isDirectory(), "cache-folder %s is not a directory", cacheFolderFile);

        final FilesystemSchemaSourceCache<YangTextSchemaSource> cache =
                new FilesystemSchemaSourceCache<>(schemaRepository, YangTextSchemaSource.class, cacheFolderFile);
        schemaRepository.registerSchemaSourceListener(cache);

        schemaListenerRegistration = schemaRepository.registerSchemaSourceListener(this);

        LOG.info("Started yang library with sources from {}", cacheFolderFile);
    }

    @Override
    public void schemaSourceEncountered(final SchemaSourceRepresentation source) {
        // NOOP
    }

    @Override
    public void schemaSourceRegistered(final Iterable<PotentialSchemaSource<?>> sources) {
        final Map<ModuleKey, Module> newModules = new HashMap<>();

        for (PotentialSchemaSource<?> potentialYangSource : Iterables.filter(sources, YANG_SCHEMA_SOURCE)) {
            final YangIdentifier moduleName = new YangIdentifier(potentialYangSource.getSourceIdentifier().getName());

            final Module newModule = new ModuleBuilder()
                    .setName(moduleName)
                    .setRevision(RevisionUtils.fromYangCommon(potentialYangSource.getSourceIdentifier().getRevision()))
                    .setSchema(getUrlForModule(potentialYangSource.getSourceIdentifier()))
                    .build();

            newModules.put(newModule.key(), newModule);
        }

        if (newModules.isEmpty()) {
            // If no new yang modules then do nothing
            return;
        }

        WriteTransaction tx = dataBroker.newWriteOnlyTransaction();
        tx.merge(LogicalDatastoreType.OPERATIONAL, InstanceIdentifier.create(ModulesState.class),
                new ModulesStateBuilder().setModule(newModules).build());

        tx.commit().addCallback(new FutureCallback<CommitInfo>() {
            @Override
            public void onSuccess(final CommitInfo result) {
                LOG.debug("Modules state successfully populated with new modules");
            }

            @Override
            public void onFailure(final Throwable throwable) {
                LOG.warn("Unable to update modules state", throwable);
            }
        }, MoreExecutors.directExecutor());
    }

    @Override
    public void schemaSourceUnregistered(final PotentialSchemaSource<?> source) {
        if (!YANG_SCHEMA_SOURCE.apply(source)) {
            // if representation of potential schema source is not yang text schema source do nothing
            // we do not want to delete this module entry from module list
            return;
        }

        WriteTransaction tx = dataBroker.newWriteOnlyTransaction();
        tx.delete(LogicalDatastoreType.OPERATIONAL, InstanceIdentifier.create(ModulesState.class)
            .child(Module.class, new ModuleKey(new YangIdentifier(source.getSourceIdentifier().getName()),
                RevisionUtils.fromYangCommon(source.getSourceIdentifier().getRevision()))));

        tx.commit().addCallback(new FutureCallback<CommitInfo>() {
            @Override
            public void onSuccess(final CommitInfo result) {
                LOG.debug("Modules state successfully updated.");
            }

            @Override
            public void onFailure(final Throwable throwable) {
                LOG.warn("Unable to update modules state", throwable);
            }
        }, MoreExecutors.directExecutor());
    }

    @Override
    public String getSchema(final String name, final String revision) {
        LOG.debug("Attempting load for schema source {}:{}", name, revision);
        final SourceIdentifier sourceId = RevisionSourceIdentifier.create(name,
            revision.isEmpty() ? null : Revision.of(revision));

        final ListenableFuture<YangTextSchemaSource> sourceFuture = schemaRepository.getSchemaSource(sourceId,
            YangTextSchemaSource.class);

        try {
            final YangTextSchemaSource source = sourceFuture.get();
            return new String(ByteStreams.toByteArray(source.openStream()), Charset.defaultCharset());
        } catch (InterruptedException | ExecutionException | IOException e) {
            throw new IllegalStateException("Unable to get schema " + sourceId, e);
        }
    }

    private Uri getUrlForModule(final SourceIdentifier sourceIdentifier) {
        return new Uri("http://" + yanglibConfig.getBindingAddr() + ':' + yanglibConfig.getBindingPort()
                + "/yanglib/schemas/" + sourceIdentifier.getName() + '/' + revString(sourceIdentifier));
    }

    private static String revString(final SourceIdentifier id) {
        return id.getRevision().map(Revision::toString).orElse("");
    }
}