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/*
 * Copyright 2011 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.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;

/**
 * Compiler pass that converts all calls to:
 *   goog.object.create(key1, val1, key2, val2, ...) where all of the keys
 *   are literals into object literals.
 *
 * @author [email protected] (Andrew Grieve)
 */
final class ClosureOptimizePrimitives implements CompilerPass {

  /** Reference to the JS compiler */
  private final AbstractCompiler compiler;

  /**
   * Identifies all calls to goog.object.create.
   */
  private class FindObjectCreateCalls extends AbstractPostOrderCallback {

    @Override
    public void visit(NodeTraversal t, Node n, Node parent) {
      if (n.isCall()) {
        Node fn = n.getFirstChild();
        if (fn.matchesQualifiedName("goog$object$create")
            || fn.matchesQualifiedName("goog.object.create")) {
          processObjectCreateCall(n);
        } else if (fn.matchesQualifiedName("goog$object$createSet")
            || fn.matchesQualifiedName("goog.object.createSet")) {
          processObjectCreateSetCall(n);
        }
      }
    }
  }

  /**
   * @param compiler The AbstractCompiler
   */
  ClosureOptimizePrimitives(AbstractCompiler compiler) {
    this.compiler = compiler;
  }

  @Override
  public void process(Node externs, Node root) {
    FindObjectCreateCalls pass = new FindObjectCreateCalls();
    NodeTraversal.traverseEs6(compiler, root, pass);
  }

  /**
   * Converts all of the given call nodes to object literals that are safe to
   * do so.
   */
  private void processObjectCreateCall(Node callNode) {
    Node curParam = callNode.getSecondChild();
    if (canOptimizeObjectCreate(curParam)) {
      Node objNode = IR.objectlit().srcref(callNode);
      while (curParam != null) {
        Node keyNode = curParam;
        Node valueNode = curParam.getNext();
        curParam = valueNode.getNext();

        callNode.removeChild(keyNode);
        callNode.removeChild(valueNode);

        if (!keyNode.isString()) {
          keyNode = IR.string(NodeUtil.getStringValue(keyNode))
              .srcref(keyNode);
        }
        keyNode.setType(Token.STRING_KEY);
        keyNode.setQuotedString();
        objNode.addChildToBack(IR.propdef(keyNode, valueNode));
      }
      callNode.getParent().replaceChild(callNode, objNode);
      compiler.reportCodeChange();
    }
  }

  /**
   * Returns whether the given call to goog.object.create can be converted to an
   * object literal.
   */
  private static boolean canOptimizeObjectCreate(Node firstParam) {
    Node curParam = firstParam;
    while (curParam != null) {
      // All keys must be strings or numbers.
      if (!curParam.isString() && !curParam.isNumber()) {
        return false;
      }
      curParam = curParam.getNext();

      // Check for an odd number of parameters.
      if (curParam == null) {
        return false;
      }
      curParam = curParam.getNext();
    }
    return true;
  }

  /**
   * Converts all of the given call nodes to object literals that are safe to
   * do so.
   */
  private void processObjectCreateSetCall(Node callNode) {
    Node curParam = callNode.getSecondChild();
    if (canOptimizeObjectCreateSet(curParam)) {
      Node objNode = IR.objectlit().srcref(callNode);
      while (curParam != null) {
        Node keyNode = curParam;
        Node valueNode = IR.trueNode().srcref(keyNode);

        curParam = curParam.getNext();
        callNode.removeChild(keyNode);

        if (!keyNode.isString()) {
          keyNode = IR.string(NodeUtil.getStringValue(keyNode))
              .srcref(keyNode);
        }
        keyNode.setType(Token.STRING_KEY);
        keyNode.setQuotedString();
        objNode.addChildToBack(IR.propdef(keyNode, valueNode));
      }
      callNode.getParent().replaceChild(callNode, objNode);
      compiler.reportCodeChange();
    }
  }

  /**
   * Returns whether the given call to goog.object.create can be converted to an
   * object literal.
   */
  private static boolean canOptimizeObjectCreateSet(Node firstParam) {
    Node curParam = firstParam;
    while (curParam != null) {
      // All keys must be strings or numbers.
      if (!curParam.isString() && !curParam.isNumber()) {
        return false;
      }
      curParam = curParam.getNext();
    }
    return true;
  }
}