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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 2008 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.deps;

import static com.google.javascript.jscomp.deps.DefaultDependencyResolver.CLOSURE_BASE;
import static com.google.javascript.jscomp.deps.DefaultDependencyResolver.CLOSURE_BASE_PROVIDE;

import com.google.javascript.jscomp.ErrorManager;
import com.google.javascript.jscomp.LoggerErrorManager;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.logging.Logger;

/**
 * SourceFile containing dependency information.  Delegates file handling to
 * another SourceFile such that a VirtualFile, LocalFile or RemoteFile can be
 * used.
 */
public final class DependencyFile implements SourceFile {

  /** Map of name spaces to their dependency info. */
  private final Map dependencies = new HashMap<>();

  /** A source file to delegate functionality too. */
  private final SourceFile delegate;

  /** Logger for DependencyResolver. */
  private static final Logger logger = Logger.getLogger(DependencyFile.class.getName());

  /** Creates a new dependency file. */
  public DependencyFile(SourceFile delegate) {
    this.delegate = delegate;
  }

  @Override
  public String getName() {
    return delegate.getName();
  }

  @Override
  public String getContent() {
    return delegate.getContent();
  }

  @Override
  public boolean wasModified() {
    return delegate.wasModified();
  }

  /**
   * Ensures that the dependency graph is up to date and reloads the graph if
   * necessary.
   */
  public void ensureUpToDate() throws ServiceException {
    if (dependencies.isEmpty() || wasModified()) {
      loadGraph();
    }
  }

  /**
   * Gets the dependency info for the provided symbol, if contained in this
   * dependency file.
   */
  public DependencyInfo getDependencyInfo(String symbol) {
    return dependencies.get(symbol);
  }

  /** Loads the dependency graph. */
  private void loadGraph() throws ServiceException {
    dependencies.clear();

    logger.info("Loading dependency graph");

    // Parse the deps.js file.
    ErrorManager errorManager = new LoggerErrorManager(logger);
    DepsFileRegexParser parser = new DepsFileRegexParser(errorManager);
    List depInfos =
        parser.parseFile(getName(), getContent());

    // Ensure the parse succeeded.
    if (!parser.didParseSucceed()) {
      throw new ServiceException("Problem parsing " + getName()
          + ". See logs for details.");
    }
    // Incorporate the dependencies into our maps.
    for (DependencyInfo depInfo : depInfos) {
      for (String provide : depInfo.getProvides()) {
        DependencyInfo existing = dependencies.get(provide);
        if (existing != null && !existing.equals(depInfo)) {
          throw new ServiceException("Duplicate provide of " + provide
              + ". Was provided by " + existing.getPathRelativeToClosureBase()
              + " and " + depInfo.getPathRelativeToClosureBase());
        }
        dependencies.put(provide, depInfo);
      }
    }

    List provides = new ArrayList<>();
    provides.add(CLOSURE_BASE_PROVIDE);

    // Add implicit base.js entry.
    dependencies.put(
        CLOSURE_BASE_PROVIDE,
        SimpleDependencyInfo.builder(CLOSURE_BASE, CLOSURE_BASE).setProvides(provides).build());
    errorManager.generateReport();

    logger.info("Dependencies loaded");
  }

}