// Copyright 2014 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;

import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.packages.RequiredProviders;
import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
import com.google.devtools.build.lib.skylarkinterface.SkylarkModuleCategory;
import com.google.devtools.build.lib.syntax.SkylarkIndexable;
import javax.annotation.Nullable;

/**
 * Multiple {@link TransitiveInfoProvider}s bundled together.
 *
 * <p>Represents the information made available by a {@link ConfiguredTarget} to other ones that
 * depend on it. For more information about the analysis phase, see {@link
 * com.google.devtools.build.lib.analysis.RuleConfiguredTargetFactory}.
 *
 * <p>Implementations of build rules should <b>not</b> hold on to references to the {@link
 * TransitiveInfoCollection}s representing their direct prerequisites in order to reduce their
 * memory footprint (otherwise, the referenced object could refer one of its direct dependencies in
 * turn, thereby making the size of the objects reachable from a single instance unbounded).
 *
 * @see com.google.devtools.build.lib.analysis.RuleConfiguredTargetFactory
 * @see TransitiveInfoProvider
 */
@SkylarkModule(
  name = "Target",
  category = SkylarkModuleCategory.BUILTIN,
  doc =
      "A BUILD target. It is essentially a <code>struct</code> with the following fields:"
          + "<ul>"
          + "<li><h3 id=\"modules.Target.label\">label</h3><code><a class=\"anchor\" "
          + "href=\"Label.html\">Label</a> Target.label</code><br>The identifier of the "
          + "target.</li>"
          + "<li><h3 id=\"modules.Target.files\">files</h3><code><a class=\"anchor\" "
          + "href=\"depset.html\">depset</a> Target.files </code><br>The set of "
          + "<a class=\"anchor\" href=\"File.html\">File</a>s produced directly by this "
          + "target.</li>"
          + "<li><h3 id=\"modules.Target.aspect_ids\">aspect_ids</h3><code><a class=\"anchor\""
          + "href=\"list.html\">list</a> Target.aspect_ids </code><br>The list of "
          + "<a class=\"anchor\" href=\"ctx.html#aspect_id\">aspect_id</a>s applied to this "
          + "target.</li>"
          + "<li><h3 id=\"modules.Target.extraproviders\">Extra providers</h3>For rule targets all "
          + "additional providers provided by this target are accessible as <code>struct</code> "
          + "fields. These extra providers are defined in the <code>struct</code> returned by the "
          + "rule implementation function.</li>"
          + "</ul>"
)
public interface TransitiveInfoCollection extends SkylarkIndexable, SkylarkProviderCollection {

  /**
   * Returns the transitive information provider requested, or null if the provider is not found.
   * The provider has to be a TransitiveInfoProvider Java class.
   */
  @Nullable <P extends TransitiveInfoProvider> P getProvider(Class<P> provider);

  /**
   * Returns the label associated with this prerequisite.
   */
  Label getLabel();

  /**
   * <p>Returns the {@link BuildConfiguration} for which this transitive info collection is defined.
   * Configuration is defined for all configured targets with exception of {@link
   * InputFileConfiguredTarget} and {@link PackageGroupConfiguredTarget} for which it is always
   * <b>null</b>.</p>
   */
  @Nullable BuildConfiguration getConfiguration();

  /**
   * Checks whether this {@link TransitiveInfoCollection} satisfies given {@link RequiredProviders}.
   */
  default boolean satisfies(RequiredProviders providers) {
    return providers.isSatisfiedBy(
        aClass -> getProvider(aClass.asSubclass(TransitiveInfoProvider.class)) != null,
        id -> this.get(id) != null);
  }

  /**
   * Returns providers that this {@link TransitiveInfoCollection} misses from a given {@link
   * RequiredProviders}.
   *
   * <p>If none are missing, returns {@link RequiredProviders} that accept any set of providers.
   */
  default RequiredProviders missingProviders(RequiredProviders providers) {
    return providers.getMissing(
        aClass -> getProvider(aClass.asSubclass(TransitiveInfoProvider.class)) != null,
        id -> this.get(id) != null);
  }
}