// 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.config;

import com.google.devtools.build.lib.analysis.BlazeDirectories;
import com.google.devtools.build.lib.analysis.config.BuildConfiguration.Fragment;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.events.EventHandler;
import com.google.devtools.build.lib.packages.NoSuchPackageException;
import com.google.devtools.build.lib.packages.NoSuchTargetException;
import com.google.devtools.build.lib.packages.Package;
import com.google.devtools.build.lib.packages.Target;
import com.google.devtools.build.lib.pkgcache.LoadedPackageProvider;
import com.google.devtools.build.lib.pkgcache.PackageProvider;
import com.google.devtools.build.lib.vfs.Path;
import javax.annotation.Nullable;

/**
 * An environment to support creating BuildConfiguration instances in a hermetic fashion; all
 * accesses to packages or the file system <b>must</b> go through this interface, so that they can
 * be recorded for correct caching.
 */
public interface ConfigurationEnvironment {

  /**
   * Returns an event handler to report errors to. Note that reporting an error does not cause the
   * computation to abort - you also need to throw an exception.
   */
  EventHandler getEventHandler();

  /**
   * Returns a target for the given label, loading it if necessary, and throwing an exception if it
   * does not exist.
   *
   * @see TargetProvider#getTarget
   */
  Target getTarget(Label label)
      throws NoSuchPackageException, NoSuchTargetException, InterruptedException;

  /** Returns a path for the given file within the given package. */
  Path getPath(Package pkg, String fileName) throws InterruptedException;

  /** Returns fragment based on fragment class and build options. */
  <T extends Fragment> T getFragment(BuildOptions buildOptions, Class<T> fragmentType)
      throws InvalidConfigurationException, InterruptedException;

  /** Returns global value of BlazeDirectories. */
  @Nullable
  BlazeDirectories getBlazeDirectories() throws InterruptedException;

  /**
   * An implementation backed by a {@link PackageProvider} instance.
   */
  public static final class TargetProviderEnvironment implements ConfigurationEnvironment {
    private final LoadedPackageProvider packageProvider;
    private final BlazeDirectories blazeDirectories;

    public TargetProviderEnvironment(PackageProvider packageProvider,
        EventHandler eventHandler, BlazeDirectories blazeDirectories) {
      this.packageProvider = new LoadedPackageProvider(packageProvider, eventHandler);
      this.blazeDirectories = blazeDirectories;
    }

    public TargetProviderEnvironment(PackageProvider packageProvider,
        EventHandler eventHandler) {
      this(packageProvider, eventHandler, null);
    }

    @Override
    public EventHandler getEventHandler() {
      return packageProvider.getEventHandler();
    }

    @Override
    public Target getTarget(final Label label)
        throws NoSuchPackageException, NoSuchTargetException, InterruptedException {
      return packageProvider.getLoadedTarget(label);
    }

    @Override
    public Path getPath(Package pkg, String fileName) {
      return pkg.getPackageDirectory().getRelative(fileName);
    }

    @Override
    public <T extends Fragment> T getFragment(BuildOptions buildOptions, Class<T> fragmentType) {
      throw new UnsupportedOperationException();
    }

    @Override
    public BlazeDirectories getBlazeDirectories() {
      return blazeDirectories;
    }
  }
}
