// Copyright 2021 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.bazel.bzlmod;

import com.google.auto.value.AutoValue;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.devtools.build.lib.packages.Attribute;
import com.google.devtools.build.lib.starlarkbuildapi.repository.RepositoryModuleApi.TagClassApi;
import java.util.Optional;

/**
 * Represents a tag class, which is a "class" of {@link Tag}s that share the same attribute schema.
 */
@AutoValue
public abstract class TagClass implements TagClassApi {
  /** The list of attributes of this tag class. */
  public abstract ImmutableList<Attribute> getAttributes();

  /** Documentation about this tag class. */
  public abstract Optional<String> getDoc();

  /**
   * A mapping from the <em>public</em> name of an attribute to the position of said attribute in
   * {@link #getAttributes}.
   */
  public abstract ImmutableMap<String, Integer> getAttributeIndices();

  public static TagClass create(ImmutableList<Attribute> attributes, Optional<String> doc) {
    ImmutableMap.Builder<String, Integer> attributeIndicesBuilder =
        ImmutableMap.builderWithExpectedSize(attributes.size());
    for (int i = 0; i < attributes.size(); i++) {
      attributeIndicesBuilder.put(attributes.get(i).getPublicName(), i);
    }
    return new AutoValue_TagClass(attributes, doc, attributeIndicesBuilder.buildOrThrow());
  }
}
