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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs.

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/*
 * Copyright 2019 The Closure Compiler Authors.
 *
 * 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.javascript.jscomp;

import com.google.common.collect.ImmutableMap;
import com.google.errorprone.annotations.Immutable;
import java.io.Serializable;
import java.util.Map;

/** A strongly typed view of information about getters and setters collected from the AST. */
@Immutable
final class AccessorSummary implements Serializable {

  /** Indicates whether a property has a getter or a setter, or both. */
  public enum PropertyAccessKind {
    // To save space properties without getters or setters won't appear
    // in the maps at all, but NORMAL will be returned by some methods.
    NORMAL(0),
    GETTER_ONLY(1),
    SETTER_ONLY(2),
    GETTER_AND_SETTER(3);

    final byte flags;

    PropertyAccessKind(int flags) {
      this.flags = (byte) flags;
    }

    boolean hasGetter() {
      return (flags & 1) != 0;
    }

    boolean hasSetter() {
      return (flags & 2) != 0;
    }

    boolean hasGetterOrSetter() {
      return (flags & 3) != 0;
    }

    // used to combine information from externs and from sources
    PropertyAccessKind unionWith(PropertyAccessKind other) {
      int combinedFlags = this.flags | other.flags;
      switch (combinedFlags) {
        case 0:
          return NORMAL;
        case 1:
          return GETTER_ONLY;
        case 2:
          return SETTER_ONLY;
        case 3:
          return GETTER_AND_SETTER;
        default:
          throw new IllegalStateException("unexpected value: " + combinedFlags);
      }
    }
  }

  static AccessorSummary create(Map accessors) {
    // TODO(nickreid): Efficiently verify that no entry in `accessor` is `NORMAL`.
    return new AccessorSummary(ImmutableMap.copyOf(accessors));
  }

  private final ImmutableMap accessors;

  private AccessorSummary(ImmutableMap accessors) {
    this.accessors = accessors;
  }

  public ImmutableMap getAccessors() {
    return accessors;
  }

  public PropertyAccessKind getKind(String name) {
    return accessors.getOrDefault(name, PropertyAccessKind.NORMAL);
  }
}