/*
 * Copyright 2015-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.
 */

// Copyright 2014 Google Inc. 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.facebook.buck.query;

import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.util.concurrent.ListeningExecutorService;
import java.util.Collection;

/**
 * A set(word, ..., word) expression, which computes the union of zero or more target patterns
 * separated by whitespace. This is intended to support the use-case in which a set of labels
 * written to a file by a previous query expression can be modified externally, then used as input
 * to another query, like so:
 *
 * <pre>
 * % buck query 'allpaths(foo, bar)' | grep ... | sed ... | awk ... >file
 * % buck query "kind(qux_library, set($(<file)))"
 * </pre>
 *
 * <p>The grammar currently restricts the operands of set() to being zero or more words (target
 * patterns), with no intervening punctuation. In principle this could be extended to arbitrary
 * expressions without grammatical ambiguity, but this seems excessively general for now.
 *
 * <pre>expr ::= SET '(' WORD * ')'</pre>
 */
class SetExpression extends QueryExpression {

  private final ImmutableList<TargetLiteral> words;

  SetExpression(ImmutableList<TargetLiteral> words) {
    this.words = words;
  }

  @Override
  public ImmutableSet<QueryTarget> eval(QueryEnvironment env, ListeningExecutorService executor)
      throws QueryException, InterruptedException {
    ImmutableSet.Builder<QueryTarget> result = new ImmutableSet.Builder<>();
    for (TargetLiteral expr : words) {
      result.addAll(expr.eval(env, executor));
    }
    return result.build();
  }

  @Override
  public void collectTargetPatterns(Collection<String> literals) {
    for (TargetLiteral expr : words) {
      expr.collectTargetPatterns(literals);
    }
  }

  @Override
  public String toString() {
    return "set(" + Joiner.on(' ').join(words) + ")";
  }

  @Override
  public boolean equals(Object other) {
    return (other instanceof SetExpression) && words.equals(((SetExpression) other).words);
  }

  @Override
  public int hashCode() {
    return words.hashCode();
  }
}