// 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.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableList;
import com.google.devtools.build.lib.actions.Artifact;
import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.collect.nestedset.NestedSet;
import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
import com.google.devtools.build.lib.collect.nestedset.Order;
import com.google.devtools.build.lib.packages.PackageSpecification;
import com.google.devtools.build.lib.packages.Target;
import com.google.devtools.build.lib.syntax.ClassObject;
import com.google.devtools.build.lib.syntax.SkylarkNestedSet;

/**
 * An abstract implementation of ConfiguredTarget in which all properties are
 * assigned trivial default values.
 */
public abstract class AbstractConfiguredTarget
    implements ConfiguredTarget, VisibilityProvider, ClassObject {
  private final Target target;
  private final BuildConfiguration configuration;

  private final NestedSet<PackageSpecification> visibility;

  // Accessors for Skylark
  private static final String DATA_RUNFILES_FIELD = "data_runfiles";
  private static final String DEFAULT_RUNFILES_FIELD = "default_runfiles";
  private static final String LABEL_FIELD = "label";
  private static final String FILES_FIELD = "files";

  AbstractConfiguredTarget(Target target,
                           BuildConfiguration configuration) {
    this.target = target;
    this.configuration = configuration;
    this.visibility = NestedSetBuilder.emptySet(Order.STABLE_ORDER);
  }

  AbstractConfiguredTarget(TargetContext targetContext) {
    this.target = targetContext.getTarget();
    this.configuration = targetContext.getConfiguration();
    this.visibility = targetContext.getVisibility();
  }

  @Override
  public final NestedSet<PackageSpecification> getVisibility() {
    return visibility;
  }

  @Override
  public Target getTarget() {
    return target;
  }

  @Override
  public BuildConfiguration getConfiguration() {
    return configuration;
  }

  @Override
  public Label getLabel() {
    return getTarget().getLabel();
  }

  @Override
  public String toString() {
    return "ConfiguredTarget(" + getTarget().getLabel() + ", " + getConfiguration() + ")";
  }

  @Override
  public <P extends TransitiveInfoProvider> P getProvider(Class<P> provider) {
    AnalysisUtils.checkProvider(provider);
    if (provider.isAssignableFrom(getClass())) {
      return provider.cast(this);
    } else {
      return null;
    }
  }

  @Override
  public Object getValue(String name) {
    switch (name) {
      case LABEL_FIELD:
        return getLabel();
      case FILES_FIELD:
        // A shortcut for files to build in Skylark. FileConfiguredTarget and RuleConfiguredTarget
        // always has FileProvider and Error- and PackageGroupConfiguredTarget-s shouldn't be
        // accessible in Skylark.
        return SkylarkNestedSet.of(
            Artifact.class, getProvider(FileProvider.class).getFilesToBuild());
      case DEFAULT_RUNFILES_FIELD:
        return RunfilesProvider.DEFAULT_RUNFILES.apply(this);
      case DATA_RUNFILES_FIELD:
        return RunfilesProvider.DATA_RUNFILES.apply(this);
      default:
        return get(name);
    }
  }
  
  @Override
  public String errorMessage(String name) {
    return null;
  }

  @Override
  public ImmutableCollection<String> getKeys() {
    return ImmutableList.of(DATA_RUNFILES_FIELD, DEFAULT_RUNFILES_FIELD, LABEL_FIELD, FILES_FIELD);
  }
}