// Copyright 2015 The Bazel Authors. All rights reserved.
//
// Licensed 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.

package com.google.devtools.build.lib.analysis.constraints;

import com.google.auto.value.AutoValue;
import com.google.common.base.MoreObjects;
import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.collect.ImmutableSet;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
import com.google.devtools.build.lib.packages.EnvironmentLabels;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.SerializationConstant;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

/** Contains a set of {@link Environment} labels and their associated groups. */
@Immutable
public class EnvironmentCollection {
  private final ImmutableMultimap<EnvironmentLabels, Label> map;

  private EnvironmentCollection(ImmutableMultimap<EnvironmentLabels, Label> map) {
    this.map = map;
  }

  /**
   * Stores an environment's build label along with the group it belongs to.
   */
  @AutoValue
  abstract static class EnvironmentWithGroup {
    static EnvironmentWithGroup create(Label environment, EnvironmentLabels group) {
      return new AutoValue_EnvironmentCollection_EnvironmentWithGroup(environment, group);
    }
    abstract Label environment();

    abstract EnvironmentLabels group();
  }

  /**
   * Returns the build labels of each environment in this collection, ordered by their insertion
   * order in {@link Builder}.
   */
  public ImmutableCollection<Label> getEnvironments() {
    return map.values();
  }

  /**
   * Returns the environments in this collection that belong to the given group, ordered by their
   * insertion order in {@link Builder}. If no environments belong to the given group, returns an
   * empty collection.
   */
  ImmutableCollection<Label> getEnvironments(EnvironmentLabels group) {
    return map.get(group);
  }

  /**
   * Returns the set of groups the environments in this collection belong to, ordered by their
   * insertion order in {@link Builder}
   */
  ImmutableSet<EnvironmentLabels> getGroups() {
    return map.keySet();
  }

  /**
   * Returns the build labels of each environment in this collection paired with the
   * group each environment belongs to, ordered by their insertion order in {@link Builder}.
   */
  ImmutableCollection<EnvironmentWithGroup> getGroupedEnvironments() {
    ImmutableSet.Builder<EnvironmentWithGroup> builder = ImmutableSet.builder();
    for (Map.Entry<EnvironmentLabels, Label> entry : map.entries()) {
      builder.add(EnvironmentWithGroup.create(entry.getValue(), entry.getKey()));
    }
    return builder.build();
  }

  /** An empty collection. */
  @SerializationConstant
  static final EnvironmentCollection EMPTY = new EnvironmentCollection(ImmutableMultimap.of());

  @Override
  public String toString() {
    return MoreObjects.toStringHelper(this)
        .add("size", map.size())
        .add("hashCode", map.hashCode())
        .add("map", map)
        .toString();
  }

  /**
   * Builder for {@link EnvironmentCollection}.
   */
  public static class Builder {
    // ImmutableMultiMap.Builder appears to allow duplicate values, which we don't want.
    private final Set<Label> addedLabels = new HashSet<>();
    private final ImmutableMultimap.Builder<EnvironmentLabels, Label> mapBuilder =
        ImmutableMultimap.builder();

    /** Inserts the given environment / owning group pair. */
    @CanIgnoreReturnValue
    public Builder put(EnvironmentLabels group, Label environment) {
      if (addedLabels.add(environment)) {
        mapBuilder.put(group, environment);
      }
      return this;
    }

    /** Inserts the given set of environments, all belonging to the specified group. */
    @CanIgnoreReturnValue
    public Builder putAll(EnvironmentLabels group, Iterable<Label> environments) {
      for (Label env : environments) {
        if (addedLabels.add(env)) {
          mapBuilder.put(group, env);
        }
      }
      return this;
    }

    /** Inserts the contents of another {@link EnvironmentCollection} into this one. */
    @CanIgnoreReturnValue
    public Builder putAll(EnvironmentCollection other) {
      for (Map.Entry<EnvironmentLabels, Label> entry : other.map.entries()) {
        if (addedLabels.add(entry.getValue())) {
          mapBuilder.put(entry);
        }
      }
      return this;
    }

    public EnvironmentCollection build() {
      return new EnvironmentCollection(mapBuilder.build());
    }
  }
}