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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 2012 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 static com.google.common.base.Preconditions.checkNotNull;
import static com.google.javascript.jscomp.AstFactory.type;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Ordering;
import com.google.javascript.jscomp.colors.StandardColors;
import com.google.javascript.rhino.IR;
import com.google.javascript.rhino.Node;
import java.util.List;

/**
 * Replaces user-visible messages with appropriate calls to chrome.i18n.getMessage. The first
 * argument to getMessage is the id of the message, as a string. If the message contains
 * placeholders, the second argument is an array of the values being used for the placeholders,
 * sorted by placeholder name.
 */
@GwtIncompatible("JsMessage")
class ReplaceMessagesForChrome extends JsMessageVisitor {

  static final DiagnosticType DECLARE_ICU_TEMPLATE_NOT_SUPPORTED =
      DiagnosticType.error(
          "JSC_DECLARE_ICU_TEMPLATE",
          "goog.i18n.messages.declareIcuTemplate() is not supported for Chrome i18n.");

  private final AstFactory astFactory;

  ReplaceMessagesForChrome(AbstractCompiler compiler, JsMessage.IdGenerator idGenerator) {
    super(compiler, idGenerator);
    this.astFactory = compiler.createAstFactory();
  }

  private Node getChromeI18nGetMessageNode(String messageId) {
    Node getMessage = astFactory.createQNameWithUnknownType("chrome.i18n.getMessage");
    return astFactory.createCall(
        getMessage, type(StandardColors.STRING), astFactory.createString(messageId));
  }

  @Override
  protected void processIcuTemplateDefinition(IcuTemplateDefinition definition) {
    // TODO(bradfordcsmith): Add support for this.
    compiler.report(JSError.make(definition.getMessageNode(), DECLARE_ICU_TEMPLATE_NOT_SUPPORTED));
  }

  @Override
  protected void processJsMessageDefinition(JsMessageDefinition definition) {
    Node newValue = getNewValueNode(definition.getMessage(), definition);
    definition.getMessageNode().replaceWith(newValue);
    compiler.reportChangeToEnclosingScope(newValue);
  }

  private Node getNewValueNode(JsMessage message, JsMessageDefinition definition) {
    Node newValueNode = getChromeI18nGetMessageNode(message.getId());

    boolean isHtml = definition.shouldEscapeLessThan();
    if (!message.jsPlaceholderNames().isEmpty() || isHtml) {
      // Output the placeholders, sorted alphabetically by placeholder name,
      // regardless of what order they appear in the original message.
      List placeholderNames = Ordering.natural().sortedCopy(message.jsPlaceholderNames());

      Node placeholderValueArray = astFactory.createArraylit();
      ImmutableMap placeholderValueMap = definition.getPlaceholderValueMap();
      for (String name : placeholderNames) {
        // JsMessageVisitor ensures that every placeholder name appearing in the message string
        // has a corresponding value node. It will report an error and avoid passing any messages
        // violating this invariant to processMessage().
        Node value = checkNotNull(placeholderValueMap.get(name)).cloneTree();
        placeholderValueArray.addChildToBack(value);
      }
      if (isHtml) {
        Node args =
            astFactory.createArraylit(
                astFactory.createString(message.getId()), placeholderValueArray);
        Node options =
            astFactory.createArraylit(
                astFactory.createObjectLit(
                    astFactory.createStringKey("escapeLt", astFactory.createBoolean(true))));
        Node regexp =
            IR.regexp(astFactory.createString("Chrome\\/(\\d+)")).setColor(StandardColors.UNKNOWN);
        Node userAgent = astFactory.createQNameWithUnknownType("navigator.userAgent");
        Node version =
            astFactory.createGetElem(
                astFactory.createOr(
                    astFactory.createCall(
                        astFactory.createGetPropWithUnknownType(regexp, "exec"),
                        type(StandardColors.ARRAY_ID),
                        userAgent),
                    astFactory.createArraylit()),
                astFactory.createNumber(1));
        Node condition =
            IR.ge(version, astFactory.createNumber(79)).setColor(StandardColors.BOOLEAN);
        args =
            astFactory.createCall(
                astFactory.createGetPropWithUnknownType(args, "concat"),
                type(StandardColors.ARRAY_ID),
                astFactory.createHook(condition, options, astFactory.createArraylit()));
        newValueNode =
            astFactory.createCallWithUnknownType(
                astFactory.createQNameWithUnknownType("chrome.i18n.getMessage.apply"),
                astFactory.createNull(),
                args);
      } else {
        newValueNode.addChildToBack(placeholderValueArray);
      }
    }

    newValueNode.srcrefTreeIfMissing(definition.getMessageNode());
    return newValueNode;
  }
}