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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 2018 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.common.base.Preconditions.checkState;

import com.google.javascript.jscomp.ModuleMetadataMap.ModuleMetadata;
import com.google.javascript.jscomp.modules.Binding;
import com.google.javascript.jscomp.modules.Export;
import javax.annotation.Nullable;

/** Centralized location for determining how to rename modules. */
final class ModuleRenaming {

  private ModuleRenaming() {}

  // TODO(johnplaisted): Consolidate this and Es6RewriteModule's constant.
  private static final String DEFAULT_EXPORT_VAR_PREFIX = "$jscompDefaultExport";

  /**
   * @param moduleMetadata the metadata of the module to get the global name of
   * @param googNamespace the Closure namespace that is being referenced fromEsModule this module,
   *     if any
   * @return the global, qualified name to rewrite any references to this module to
   */
  static String getGlobalName(ModuleMetadata moduleMetadata, @Nullable String googNamespace) {
    checkState(googNamespace == null || moduleMetadata.googNamespaces().contains(googNamespace));
    switch (moduleMetadata.moduleType()) {
      case GOOG_MODULE:
        return ClosureRewriteModule.getBinaryModuleNamespace(googNamespace);
      case GOOG_PROVIDE:
      case LEGACY_GOOG_MODULE:
        return googNamespace;
      case ES6_MODULE:
      case COMMON_JS:
        return moduleMetadata.path().toModuleName();
      case SCRIPT:
        // fall through, throw an error
    }
    throw new IllegalStateException("Unexpected module type: " + moduleMetadata.moduleType());
  }

  static String getGlobalName(Export export) {
    if (export.moduleMetadata().isEs6Module()) {
      String prefix = checkNotNull(export.localName());
      if (export.localName().equals(Export.DEFAULT_EXPORT_NAME)) {
        prefix = DEFAULT_EXPORT_VAR_PREFIX;
      }
      return prefix + "$$" + getGlobalName(export.moduleMetadata(), /* googNamespace= */ null);
    }
    return getGlobalName(export.moduleMetadata(), export.closureNamespace())
        + "."
        + export.localName();
  }

  static String getGlobalName(Binding binding) {
    if (binding.isModuleNamespace()) {
      return getGlobalName(binding.metadata(), binding.closureNamespace());
    }
    return getGlobalName(binding.originatingExport());
  }
}