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/*
 * Copyright 2014 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.HashBasedTable;
import com.google.common.collect.Table;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.jscomp.parsing.parser.FeatureSet;
import com.google.javascript.jscomp.parsing.parser.FeatureSet.Feature;
import com.google.javascript.rhino.Node;
import java.util.HashSet;
import java.util.Set;

/**
 * Renames declarations and references in function bodies to avoid shadowing
 * names referenced in the parameter list, in default values or computed properties.
 */
public final class Es6RenameVariablesInParamLists extends AbstractPostOrderCallback
    implements HotSwapCompilerPass {

  private final AbstractCompiler compiler;
  private static final FeatureSet transpiledFeatures =
      FeatureSet.BARE_MINIMUM.with(Feature.DEFAULT_PARAMETERS, Feature.COMPUTED_PROPERTIES);

  public Es6RenameVariablesInParamLists(AbstractCompiler compiler) {
    this.compiler = compiler;
  }

  @Override
  public void visit(NodeTraversal t, Node n, Node parent) {
    // Arrow functions without blocked body cannot have declarations in the body
    if (!n.isFunction() || !n.getLastChild().isBlock()) {
      return;
    }

    Node paramList = n.getSecondChild();
    final CollectReferences collector = new CollectReferences();
    NodeTraversal.traverse(compiler, paramList, new NodeTraversal.AbstractPreOrderCallback() {
      @Override
      public final boolean shouldTraverse(NodeTraversal t, Node n, Node parent) {
        if (parent == null) {
          return true;
        }

        if ((parent.isDefaultValue() && n == parent.getLastChild())
            || (parent.isComputedProp() && n == parent.getFirstChild())) {
          NodeTraversal.traverse(compiler, n, collector);
          return false;
        }
        return true;
      }
    });

    Node block = paramList.getNext();
    SyntacticScopeCreator creator = new SyntacticScopeCreator(compiler);
    Scope fScope = creator.createScope(n, t.getScope());
    Scope fBlockScope = creator.createScope(block, fScope);
    Table renameTable = HashBasedTable.create();
    for (Var var : fBlockScope.getVarIterable()) {
      String oldName = var.getName();
      if (collector.currFuncReferences.contains(oldName)
          && !renameTable.contains(fBlockScope.getRootNode(), oldName)) {
        renameTable.put(fBlockScope.getRootNode(),
            oldName, oldName + "$" + compiler.getUniqueNameIdSupplier().get());
      }
    }
    new NodeTraversal(
            compiler, new Es6RenameReferences(renameTable), new SyntacticScopeCreator(compiler))
        .traverseInnerNode(block, block.getParent(), fScope);
  }

  @Override
  public void process(Node externs, Node root) {
    TranspilationPasses.processTranspile(compiler, root, transpiledFeatures, this);
  }

  @Override
  public void hotSwapScript(Node scriptRoot, Node originalRoot) {
    TranspilationPasses.hotSwapTranspile(compiler, scriptRoot, transpiledFeatures, this);
  }

  /**
   * Collects all references in a naive way.
   */
  private static class CollectReferences extends NodeTraversal.AbstractPostOrderCallback {

    private final Set currFuncReferences = new HashSet<>();

    @Override
    public void visit(NodeTraversal t, Node n, Node parent) {
      if (!NodeUtil.isReferenceName(n)) {
        return;
      }
      currFuncReferences.add(n.getString());
    }
  }
}