package org.eclipse.aether.internal.impl.filter;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

import javax.inject.Inject;
import javax.inject.Named;
import javax.inject.Singleton;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.Collectors;

import org.eclipse.aether.RepositorySystemSession;
import org.eclipse.aether.artifact.Artifact;
import org.eclipse.aether.impl.RemoteRepositoryFilterManager;
import org.eclipse.aether.metadata.Metadata;
import org.eclipse.aether.repository.RemoteRepository;
import org.eclipse.aether.spi.connector.filter.RemoteRepositoryFilter;
import org.eclipse.aether.spi.connector.filter.RemoteRepositoryFilterSource;

import static java.util.Objects.requireNonNull;

/**
 * Default implementation of {@link RemoteRepositoryFilterManager}, it always returns a {@link RemoteRepositoryFilter}
 * instance, even if no filter sources enabled/registered (then "always allow" instance).
 * <p>
 * The created {@link RemoteRepositoryFilter} instance is created once per session and cached.
 *
 * @since 1.9.0
 */
@Singleton
@Named
public final class DefaultRemoteRepositoryFilterManager
        implements RemoteRepositoryFilterManager
{
    private static final String INSTANCE_KEY = DefaultRemoteRepositoryFilterManager.class.getName() + ".instance";

    private final Map<String, RemoteRepositoryFilterSource> sources;

    /**
     * SL enabled ctor.
     *
     * @deprecated for SL and testing purposes only.
     */
    @Deprecated
    public DefaultRemoteRepositoryFilterManager()
    {
        this.sources = new HashMap<>();
    }

    @Inject
    public DefaultRemoteRepositoryFilterManager( Map<String, RemoteRepositoryFilterSource> sources )
    {
        this.sources = requireNonNull( sources );
    }

    @Override
    public RemoteRepositoryFilter getRemoteRepositoryFilter( RepositorySystemSession session )
    {
        return (RemoteRepositoryFilter) session.getData().computeIfAbsent( INSTANCE_KEY, () ->
                {
                    HashMap<String, RemoteRepositoryFilter> filters = new HashMap<>();
                    for ( Map.Entry<String, RemoteRepositoryFilterSource> entry : sources.entrySet() )
                    {
                        RemoteRepositoryFilter filter = entry.getValue().getRemoteRepositoryFilter( session );
                        if ( filter != null )
                        {
                            filters.put( entry.getKey(), filter );
                        }
                    }
                    if ( !filters.isEmpty() )
                    {
                        return new Participants( filters );
                    }
                    else
                    {
                        return null;
                    }
                }
        );
    }

    /**
     * {@link RemoteRepositoryFilter} instance when there are participant filters present. It evaluates into result
     * using {@link Consensus}.
     */
    private static class Participants implements RemoteRepositoryFilter
    {
        private final Map<String, RemoteRepositoryFilter> participants;

        private Participants( Map<String, RemoteRepositoryFilter> participants )
        {
            this.participants = Collections.unmodifiableMap( participants );
        }

        @Override
        public RemoteRepositoryFilter.Result acceptArtifact( RemoteRepository remoteRepository, Artifact artifact )
        {
            return new Consensus( participants.entrySet().stream()
                    .collect( Collectors.toMap(
                            Map.Entry::getKey,
                            e -> e.getValue().acceptArtifact( remoteRepository, artifact ) ) ) );
        }

        @Override
        public RemoteRepositoryFilter.Result acceptMetadata( RemoteRepository remoteRepository, Metadata metadata )
        {
            return new Consensus( participants.entrySet().stream()
                    .collect( Collectors.toMap(
                            Map.Entry::getKey,
                            e -> e.getValue().acceptMetadata( remoteRepository, metadata ) ) ) );
        }
    }

    /**
     * {@link RemoteRepositoryFilter.Result} based on "consensus". All participant have to "accept" to make this
     * instance "accept".
     */
    private static class Consensus implements RemoteRepositoryFilter.Result
    {
        private final boolean accepted;

        private final String reasoning;

        Consensus( Map<String, RemoteRepositoryFilter.Result> results )
        {
            this.accepted = results.values().stream().allMatch( RemoteRepositoryFilter.Result::isAccepted );
            this.reasoning = results.values().stream().filter( r -> !r.isAccepted() ).map(
                    RemoteRepositoryFilter.Result::reasoning ).collect(
                    Collectors.joining( "; " ) );
        }

        @Override
        public boolean isAccepted()
        {
            return accepted;
        }

        @Override
        public String reasoning()
        {
            return reasoning;
        }
    }
}
