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/*
 * Copyright 2009 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.javascript.jscomp.parsing.parser.FeatureSet;
import com.google.javascript.rhino.Node;

/**
 * A factory for creating JSCompiler passes based on the Options
 * injected.  Contains all meta-data about compiler passes (like
 * whether it can be run multiple times, a human-readable name for
 * logging, etc.).
 *
 * @author [email protected] (Nick Santos)
 */
public abstract class PassFactory {

  private final String name;
  private final boolean isOneTimePass;

  /**
   * @param name The name of the pass that this factory creates.
   * @param isOneTimePass If true, the pass produced by this factory can
   *     only be run once.
   */
  protected PassFactory(String name, boolean isOneTimePass) {
    this.name = name;
    this.isOneTimePass = isOneTimePass;
  }

  /**
   * @return The name of this pass.
   */
  String getName() {
    return name;
  }

  @Override
  public String toString() {
    return name;
  }

  /**
   * @return Whether the pass produced by this factory can only be run once.
   */
  boolean isOneTimePass() {
    return isOneTimePass;
  }

  /**
   * Creates a new compiler pass to be run.
   */
  protected abstract CompilerPass create(AbstractCompiler compiler);

  /**
   * The set of features that this pass understands. Passes that can handle any code (no-op passes,
   * extremely simple passes that are unlikely to be broken by new features, etc.) should return
   * FeatureSet.latest().
   */
  protected abstract FeatureSet featureSet();

  /**
   * Any factory whose CompilerPass has a corresponding hot-swap version should
   * override this.
   *
   * @param compiler The compiler that can has been used to do the full compile.
   */
  protected HotSwapCompilerPass getHotSwapPass(AbstractCompiler compiler) {
    // TODO(bashir): If in future most of PassFactory's in DefaultPassConfig
    // turns out to be DefaultPassConfig.HotSwapPassFactory, we should probably
    // change the implementation here by the one in HotSwapPassFactory.
    return null;
  }


  /**
   * Create a no-op pass that can only run once. Used to break up loops.
   */
  public static PassFactory createEmptyPass(String name) {
    return new PassFactory(name, true) {
      @Override
      protected CompilerPass create(final AbstractCompiler compiler) {
        return new CompilerPass() {
          @Override
          public void process(Node externs, Node root) {}
        };
      }

      @Override
      protected FeatureSet featureSet() {
        return FeatureSet.latest();
      }
    };
  }

  /**
   * A pass-factory that is good for {@code HotSwapCompilerPass} passes.
   * Every hotswap pass is expected to be a one-time pass.
   */
  public abstract static class HotSwapPassFactory extends PassFactory {

    HotSwapPassFactory(String name) {
      super(name, true);
    }

    @Override
    protected abstract HotSwapCompilerPass create(AbstractCompiler compiler);

    @Override
    protected HotSwapCompilerPass getHotSwapPass(AbstractCompiler compiler) {
      return this.create(compiler);
    }
  }
}