// 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.query2.engine;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.devtools.build.lib.collect.CompactHashSet;
import com.google.devtools.build.lib.query2.engine.QueryEnvironment.Argument;
import com.google.devtools.build.lib.query2.engine.QueryEnvironment.ArgumentType;
import com.google.devtools.build.lib.query2.engine.QueryEnvironment.QueryFunction;

import java.util.List;
import java.util.Set;
import java.util.concurrent.ForkJoinPool;

/**
 * A buildfiles(x) query expression, which computes the set of BUILD files and
 * subincluded files for each target in set x.  The result is unordered.  This
 * operator is typically used for determinining what files or packages to check
 * out.
 *
 * <pre>expr ::= BUILDFILES '(' expr ')'</pre>
 */
class BuildFilesFunction implements QueryFunction {
  BuildFilesFunction() {
  }

  @Override
  public String getName() {
    return "buildfiles";
  }

  @Override
  public <T> void eval(
      final QueryEnvironment<T> env,
      VariableContext<T> context,
      final QueryExpression expression,
      List<Argument> args,
      final Callback<T> callback)
      throws QueryException, InterruptedException {
    env.eval(
        args.get(0).getExpression(),
        context,
        new ThreadSafeCallback<T>() {
          @Override
          public void process(Iterable<T> partialResult)
              throws QueryException, InterruptedException {
            Set<T> result = CompactHashSet.create();
            Iterables.addAll(result, partialResult);
            callback.process(
                env.getBuildFiles(
                    expression, result, /* BUILD */ true, /* subinclude */ true, /* load */ true));
          }
        });
  }

  @Override
  public <T> void parEval(
      QueryEnvironment<T> env,
      VariableContext<T> context,
      QueryExpression expression,
      List<Argument> args,
      ThreadSafeCallback<T> callback,
      ForkJoinPool forkJoinPool) throws QueryException, InterruptedException {
    // 'eval' is written in such a way that it enables parallel evaluation of 'expression'.
    eval(env, context, expression, args, callback);
  }

  @Override
  public int getMandatoryArguments() {
    return 1;
  }

  @Override
  public List<ArgumentType> getArgumentTypes() {
    return ImmutableList.of(ArgumentType.EXPRESSION);
  }
}
