// 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.ImmutableSet;
import com.google.common.collect.Sets;
import com.google.common.collect.Sets.SetView;
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 com.google.devtools.build.lib.query2.engine.QueryEnvironment.QueryTaskCallable;
import com.google.devtools.build.lib.query2.engine.QueryEnvironment.QueryTaskFuture;
import com.google.devtools.build.lib.query2.engine.QueryEnvironment.ThreadSafeMutableSet;
import java.util.List;

/**
 * A somepath(x, y) query expression, which computes the set of nodes
 * on some arbitrary path from a target in set x to a target in set y.
 *
 * <pre>expr ::= SOMEPATH '(' expr ',' expr ')'</pre>
 */
class SomePathFunction implements QueryFunction {
  SomePathFunction() {
  }

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

  @Override
  public int getMandatoryArguments() {
    return 2;
  }

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

  @Override
  public <T> QueryTaskFuture<Void> eval(
      final QueryEnvironment<T> env,
      QueryExpressionContext<T> context,
      final QueryExpression expression,
      List<Argument> args,
      final Callback<T> callback) {
    final QueryTaskFuture<ThreadSafeMutableSet<T>> fromValueFuture =
        QueryUtil.evalAll(env, context, args.get(0).getExpression());
    final QueryTaskFuture<ThreadSafeMutableSet<T>> toValueFuture =
        QueryUtil.evalAll(env, context, args.get(1).getExpression());

    return env.whenAllSucceedCall(
        ImmutableList.of(fromValueFuture, toValueFuture),
        new QueryTaskCallable<Void>() {
          @Override
          public Void call() throws QueryException, InterruptedException {
            // Implementation strategy: for each x in "from", compute its forward
            // transitive closure.  If it intersects "to", then do a path search from x
            // to an arbitrary node in the intersection, and return the path.  This
            // avoids computing the full transitive closure of "from" in some cases.

            ThreadSafeMutableSet<T> fromValue = fromValueFuture.getIfSuccessful();
            ThreadSafeMutableSet<T> toValue = toValueFuture.getIfSuccessful();

            env.buildTransitiveClosure(expression, fromValue, Integer.MAX_VALUE);

            // This set contains all nodes whose TC does not intersect "toValue".
            Uniquifier<T> uniquifier = env.createUniquifier();

            for (T x : uniquifier.unique(fromValue)) {
              ThreadSafeMutableSet<T> xSet = env.createThreadSafeMutableSet();
              xSet.add(x);
              ThreadSafeMutableSet<T> xtc = env.getTransitiveClosure(xSet, context);
              SetView<T> result;
              if (xtc.size() > toValue.size()) {
                result = Sets.intersection(toValue, xtc);
              } else {
                result = Sets.intersection(xtc, toValue);
              }
              if (!result.isEmpty()) {
                callback.process(env.getNodesOnPath(x, result.iterator().next(), context));
                return null;
              }
              uniquifier.unique(xtc);
            }
            callback.process(ImmutableSet.<T>of());
            return null;
          }
        });
  }
}

@@ -3280,77 +3280,31 @@
     
-// This set contains all nodes whose TC does not intersect %22to
+for (T x : from
 Value
-%22.
+) %7B
 %0A   
@@ -3316,220 +3316,411 @@
     
-Uniquifier%3CT%3E uniquifier = env.createUniquifier();%0A%0A            for (T x : uniquifier.unique(fromValue)) %7B%0A              ThreadSafeMutableSet%3CT%3E xSet = env.createThreadSafeMutableSet();%0A              xSet.add(x);
+  // TODO(b/122548314): if x was already seen as part of a previous node's tc, we should%0A              // skip it here. That's subsumed by the TODO below.%0A              ThreadSafeMutableSet%3CT%3E xSet = env.createThreadSafeMutableSet();%0A              xSet.add(x);%0A              // TODO(b/122548314): this transitive closure building should stop at any nodes that%0A              // have already been visited.
 %0A   
@@ -4218,46 +4218,8 @@
   %7D%0A
-              uniquifier.unique(xtc);%0A
     

Remove useless Uniquifier#unique call. The return value of #unique is only used once in this method, before any of these unnecessary #unique calls are made, so it is impossible to observe the changed state of the Uniquifier from these calls.