/*
 * Copyright 2014-present Facebook, Inc.
 *
 * 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.facebook.buck.cxx;

import com.facebook.buck.rules.args.Arg;
import com.facebook.buck.rules.coercer.FrameworkPath;
import com.facebook.buck.util.immutables.BuckStyleImmutable;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import java.util.List;
import java.util.Set;
import org.immutables.value.Value;

/**
 * A class containing inputs to be passed to the native linker. Dependencies (e.g. C++ libraries) of
 * a top-level native linkable rule (e.g. C++ binary) can use this to contribute components to the
 * final link.
 */
@Value.Immutable
@BuckStyleImmutable
abstract class AbstractNativeLinkableInput {

  private static final NativeLinkableInput EMPTY =
      NativeLinkableInput.of(ImmutableList.of(), ImmutableSet.of(), ImmutableSet.of());

  // Arguments to pass to the linker.  In the future it'd be nice to make this more aware of
  // the differences between archives, objects, flags, etc.
  @Value.Parameter
  public abstract List<Arg> getArgs();

  // Frameworks that are used by the linkable to link with.
  @Value.Parameter
  public abstract Set<FrameworkPath> getFrameworks();

  // Libraries to link.
  @Value.Parameter
  public abstract Set<FrameworkPath> getLibraries();

  /** Combine, in order, several {@link NativeLinkableInput} objects into a single one. */
  public static NativeLinkableInput concat(Iterable<NativeLinkableInput> items) {
    ImmutableList.Builder<Arg> args = ImmutableList.builder();
    ImmutableSet.Builder<FrameworkPath> frameworks = ImmutableSet.builder();
    ImmutableSet.Builder<FrameworkPath> libraries = ImmutableSet.builder();

    for (NativeLinkableInput item : items) {
      args.addAll(item.getArgs());
      frameworks.addAll(item.getFrameworks());
      libraries.addAll(item.getLibraries());
    }

    return NativeLinkableInput.of(args.build(), frameworks.build(), libraries.build());
  }

  public static NativeLinkableInput of() {
    return EMPTY;
  }
}