/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You 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
 *
 *      https://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 org.apache.tools.ant.taskdefs.optional.depend;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.function.Predicate;
import java.util.stream.Stream;

import org.apache.tools.ant.AntClassLoader;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.DirectoryScanner;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.taskdefs.MatchingTask;
import org.apache.tools.ant.taskdefs.rmic.DefaultRmicAdapter;
import org.apache.tools.ant.taskdefs.rmic.WLRmic;
import org.apache.tools.ant.types.Path;
import org.apache.tools.ant.types.Reference;
import org.apache.tools.ant.types.Resource;
import org.apache.tools.ant.types.ResourceCollection;
import org.apache.tools.ant.types.resources.FileProvider;
import org.apache.tools.ant.util.FileUtils;
import org.apache.tools.ant.util.depend.DependencyAnalyzer;

Generates a dependency file for a given set of classes.
/**
 * Generates a dependency file for a given set of classes.
 *
 */
public class Depend extends MatchingTask {
    private static final int ONE_SECOND = 1000;

    
A class (struct) user to manage information about a class
/**
     * A class (struct) user to manage information about a class
     *
     */
    private static class ClassFileInfo {
        
The file where the class file is stored in the file system /** The file where the class file is stored in the file system */
        private File absoluteFile;

        
The Java class name of this class /** The Java class name of this class */
        private String className;

        
The source File containing this class /** The source File containing this class */
        private File sourceFile;

        
if user has been warned about this file not having a source file /** if user has been warned about this file not having a source file */
        private boolean isUserWarned = false;
    }

    
The path where source files exist /** The path where source files exist */
    private Path srcPath;

    
The path where compiled class files exist. /** The path where compiled class files exist. */
    private Path destPath;

    
The directory which contains the dependency cache. /** The directory which contains the dependency cache. */
    private File cache;

    
A map which gives for every class a list of the class which it
affects.
/**
     * A map which gives for every class a list of the class which it
     * affects.
     */
    private Map<String, Map<String, ClassFileInfo>> affectedClassMap;

    
A map which gives information about a class /** A map which gives information about a class */
    private Map<String, ClassFileInfo> classFileInfoMap;

    
A map which gives the list of jars and classes from the classpath
that a class depends upon
/**
     * A map which gives the list of jars and classes from the classpath
     * that a class depends upon
     */
    private Map<String, Set<File>> classpathDependencies;

    
The list of classes which are out of date. /** The list of classes which are out of date. */
    private Map<String, String> outOfDateClasses;

    
indicates that the dependency relationships should be extended beyond
direct dependencies to include all classes. So if A directly affects
B and B directly affects C, then A indirectly affects C.
/**
     * indicates that the dependency relationships should be extended beyond
     * direct dependencies to include all classes. So if A directly affects
     * B and B directly affects C, then A indirectly affects C.
     */
    private boolean closure = false;

    
flag to enable warning if we encounter RMI stubs
/**
     * flag to enable warning if we encounter RMI stubs
     */
    private boolean warnOnRmiStubs = true;

    
Flag which controls whether the reversed dependencies should be
dumped to the log
/**
     * Flag which controls whether the reversed dependencies should be
     * dumped to the log
     */
    private boolean dump = false;

    
The classpath to look for additional dependencies /** The classpath to look for additional dependencies */
    private Path dependClasspath;

    
constants used with the cache file /** constants used with the cache file */
    private static final String CACHE_FILE_NAME = "dependencies.txt";
    
String Used to separate classnames in the dependency file /** String Used to separate classnames in the dependency file */
    private static final String CLASSNAME_PREPEND = "||:";

    
Set the classpath to be used for this dependency check.
Params:
classpath – the classpath to be used when checking for
     dependencies on elements in the classpath/**
     * Set the classpath to be used for this dependency check.
     *
     * @param classpath the classpath to be used when checking for
     *      dependencies on elements in the classpath
     */
    public void setClasspath(Path classpath) {
        if (dependClasspath == null) {
            dependClasspath = classpath;
        } else {
            dependClasspath.append(classpath);
        }
    }

    
Gets the classpath to be used for this dependency check.
Returns:
the current dependency classpath/**
     * Gets the classpath to be used for this dependency check.
     *
     * @return the current dependency classpath
     */
    public Path getClasspath() {
        return dependClasspath;
    }

    
Adds a classpath to be used for this dependency check.
Returns:
A path object to be configured by Ant/**
     * Adds a classpath to be used for this dependency check.
     *
     * @return A path object to be configured by Ant
     */
    public Path createClasspath() {
        if (dependClasspath == null) {
            dependClasspath = new Path(getProject());
        }
        return dependClasspath.createPath();
    }

    
Adds a reference to a classpath defined elsewhere.
Params:
r – a reference to a path object to be used as the depend
     classpath/**
     * Adds a reference to a classpath defined elsewhere.
     *
     * @param r a reference to a path object to be used as the depend
     *      classpath
     */
    public void setClasspathRef(Reference r) {
        createClasspath().setRefid(r);
    }

    
Flag to set to true if you want dependency issues with RMI
stubs to appear at warning level.
Params:
warnOnRmiStubs – if true set dependency issues to appear at warning level.
Since:
Ant1.7/**
     * Flag to set to true if you want dependency issues with RMI
     * stubs to appear at warning level.
     * @param warnOnRmiStubs if true set dependency issues to appear at warning level.
     * @since Ant1.7
     */
    public void setWarnOnRmiStubs(boolean warnOnRmiStubs) {
        this.warnOnRmiStubs = warnOnRmiStubs;
    }

    
Read the dependencies from cache file
Throws:
IOException – if the dependency file cannot be read
Returns:
a collection of class dependencies/**
     * Read the dependencies from cache file
     *
     * @return a collection of class dependencies
     * @exception IOException if the dependency file cannot be read
     */
    private Map<String, List<String>> readCachedDependencies(File depFile) throws IOException {
        Map<String, List<String>> dependencyMap = new HashMap<>();

        int prependLength = CLASSNAME_PREPEND.length();

        try (BufferedReader in = new BufferedReader(new FileReader(depFile))) {
            List<String> dependencyList = null;
            String line;
            while ((line = in.readLine()) != null) {
                if (line.startsWith(CLASSNAME_PREPEND)) {
                    String className = line.substring(prependLength);
                    dependencyList = dependencyMap.computeIfAbsent(className,
                        k -> new ArrayList<>());
                } else if (dependencyList != null) {
                    dependencyList.add(line);
                }
            }
        }
        return dependencyMap;
    }

    
Write the dependencies to cache file
Params:
dependencyMap – the map of dependencies to be written out.
Throws:
IOException – if the dependency file cannot be written out./**
     * Write the dependencies to cache file
     *
     * @param dependencyMap the map of dependencies to be written out.
     * @exception IOException if the dependency file cannot be written out.
     */
    private void writeCachedDependencies(Map<String, List<String>> dependencyMap)
        throws IOException {
        if (cache != null) {
            cache.mkdirs();
            File depFile = new File(cache, CACHE_FILE_NAME);
            try (BufferedWriter pw =
                new BufferedWriter(new FileWriter(depFile))) {
                for (Map.Entry<String, List<String>> e : dependencyMap
                    .entrySet()) {
                    pw.write(String.format("%s%s%n", CLASSNAME_PREPEND, e.getKey()));
                    for (String s : e.getValue()) {
                        pw.write(s);
                        pw.newLine();
                    }
                }
            }
        }
    }

    
Get the classpath for dependency checking.
This method removes the dest dirs if it is given from the dependency classpath
/**
     * Get the classpath for dependency checking.
     *
     * This method removes the dest dirs if it is given from the dependency classpath
     */
    private Path getCheckClassPath() {
        if (dependClasspath == null) {
            return null;
        }

        Set<Resource> dependNotInDest = new LinkedHashSet<>();
        dependClasspath.forEach(dependNotInDest::add);
        destPath.forEach(dependNotInDest::remove);

        Path p;
        if (dependNotInDest.isEmpty()) {
            p = null;
        } else {
            p = new Path(getProject());
            dependNotInDest.forEach(p::add);
        }

        log("Classpath without dest dir is " + p, Project.MSG_DEBUG);
        return p;
    }

    
Determine the dependencies between classes. Class dependencies are
determined by examining the class references in a class file to other
classes.
This method sets up the following fields

  
affectedClassMap - the list of classes each class affects
  
classFileInfoMap - information about each class
  
classpathDependencies - the list of jars and classes from the
                            classpath that each class depends upon.

If required, the dependencies are written to the cache.
Throws:
IOException – if either the dependencies cache or the class
     files cannot be read or written/**
     * Determine the dependencies between classes. Class dependencies are
     * determined by examining the class references in a class file to other
     * classes.
     *
     * This method sets up the following fields
     * <ul>
     *   <li>affectedClassMap - the list of classes each class affects</li>
     *   <li>classFileInfoMap - information about each class</li>
     *   <li>classpathDependencies - the list of jars and classes from the
     *                             classpath that each class depends upon.</li>
     * </ul>
     *
     * If required, the dependencies are written to the cache.
     *
     * @exception IOException if either the dependencies cache or the class
     *      files cannot be read or written
     */
    private void determineDependencies() throws IOException {
        affectedClassMap = new HashMap<>();
        classFileInfoMap = new HashMap<>();
        boolean cacheDirty = false;

        Map<String, List<String>> dependencyMap = new HashMap<>();
        File cacheFile = null;
        boolean cacheFileExists = true;
        long cacheLastModified = Long.MAX_VALUE;

        // read the dependency cache from the disk
        if (cache != null) {
            cacheFile = new File(cache, CACHE_FILE_NAME);
            cacheFileExists = cacheFile.exists();
            cacheLastModified = cacheFile.lastModified();
            if (cacheFileExists) {
                dependencyMap = readCachedDependencies(cacheFile);
            }
        }
        for (ClassFileInfo info : getClassFiles()) {
            log("Adding class info for " + info.className, Project.MSG_DEBUG);
            classFileInfoMap.put(info.className, info);

            List<String> dependencyList = null;

            if (cache != null) {
                // try to read the dependency info from the map if it is
                // not out of date
                if (cacheFileExists
                    && cacheLastModified > info.absoluteFile.lastModified()) {
                    // depFile exists and is newer than the class file
                    // need to get dependency list from the map.
                    dependencyList = dependencyMap.get(info.className);
                }
            }

            if (dependencyList == null) {
                // not cached - so need to read directly from the class file
                DependencyAnalyzer analyzer = new AntAnalyzer();
                analyzer.addRootClass(info.className);
                analyzer.addClassPath(destPath);
                analyzer.setClosure(false);
                dependencyList = Collections.list(analyzer.getClassDependencies());
                dependencyList.forEach(o -> log("Class " + info.className + " depends on " + o,
                        Project.MSG_DEBUG));
                cacheDirty = true;
                dependencyMap.put(info.className, dependencyList);
            }

            // This class depends on each class in the dependency list. For each
            // one of those, add this class into their affected classes list
            for (String dependentClass : dependencyList) {
                affectedClassMap
                    .computeIfAbsent(dependentClass, k -> new HashMap<>())
                    .put(info.className, info);
                log(dependentClass + " affects " + info.className,
                    Project.MSG_DEBUG);
            }
        }

        classpathDependencies = null;
        Path checkPath = getCheckClassPath();
        if (checkPath != null) {
            // now determine which jars each class depends upon
            classpathDependencies = new HashMap<>();
            try (AntClassLoader loader = getProject().createClassLoader(checkPath)) {

                Map<String, Object> classpathFileCache = new HashMap<>();
                Object nullFileMarker = new Object();
                for (Map.Entry<String, List<String>> e : dependencyMap.entrySet()) {
                    String className = e.getKey();
                    log("Determining classpath dependencies for " + className,
                        Project.MSG_DEBUG);
                    List<String> dependencyList = e.getValue();
                    Set<File> dependencies = new HashSet<>();
                    classpathDependencies.put(className, dependencies);
                    for (String dependency : dependencyList) {
                        log("Looking for " + dependency, Project.MSG_DEBUG);
                        Object classpathFileObject
                            = classpathFileCache.get(dependency);
                        if (classpathFileObject == null) {
                            classpathFileObject = nullFileMarker;

                            if (!dependency.startsWith("java.")
                                && !dependency.startsWith("javax.")) {
                                URL classURL
                                    = loader.getResource(dependency.replace('.', '/') + ".class");
                                log("URL is " + classURL, Project.MSG_DEBUG);
                                if (classURL != null) {
                                    if ("jar".equals(classURL.getProtocol())) {
                                        String jarFilePath = classURL.getFile();
                                        int classMarker = jarFilePath.indexOf('!');
                                        jarFilePath = jarFilePath.substring(0, classMarker);
                                        if (jarFilePath.startsWith("file:")) {
                                            classpathFileObject = new File(
                                                FileUtils.getFileUtils()
                                                    .fromURI(jarFilePath));
                                        } else {
                                            throw new IOException(
                                                "Bizarre nested path in jar: protocol: "
                                                    + jarFilePath);
                                        }
                                    } else if ("file".equals(classURL.getProtocol())) {
                                        classpathFileObject = new File(
                                            FileUtils.getFileUtils().fromURI(
                                                classURL.toExternalForm()));
                                    }
                                    log("Class " + className
                                        + " depends on " + classpathFileObject
                                        + " due to " + dependency, Project.MSG_DEBUG);
                                }
                            } else {
                                log("Ignoring base classlib dependency "
                                    + dependency, Project.MSG_DEBUG);
                            }
                            classpathFileCache.put(dependency, classpathFileObject);
                        }
                        if (classpathFileObject != nullFileMarker) {
                            // we need to add this jar to the list for this class.
                            File jarFile = (File) classpathFileObject;
                            log("Adding a classpath dependency on " + jarFile,
                                Project.MSG_DEBUG);
                            dependencies.add(jarFile);
                        }
                    }
                }
            }
        } else {
            log("No classpath to check", Project.MSG_DEBUG);
        }

        // write the dependency cache to the disk
        if (cache != null && cacheDirty) {
            writeCachedDependencies(dependencyMap);
        }
    }

    
Delete all the class files which are out of date, by way of their
dependency on a class which is out of date
Returns:
the number of files deleted./**
     * Delete all the class files which are out of date, by way of their
     * dependency on a class which is out of date
     *
     * @return the number of files deleted.
     */
    private int deleteAllAffectedFiles() {
        int count = 0;
        for (String className : outOfDateClasses.keySet()) {
            count += deleteAffectedFiles(className);
            ClassFileInfo classInfo = classFileInfoMap.get(className);
            if (classInfo != null && classInfo.absoluteFile.exists()) {
                if (classInfo.sourceFile == null) {
                    warnOutOfDateButNotDeleted(classInfo, className, className);
                } else {
                    classInfo.absoluteFile.delete();
                    count++;
                }
            }
        }
        return count;
    }

    
Delete all the class files of classes which depend on the given class
Params:
className – the name of the class whose dependent classes will be
     deleted
Returns:
the number of class files removed/**
     * Delete all the class files of classes which depend on the given class
     *
     * @param className the name of the class whose dependent classes will be
     *      deleted
     * @return the number of class files removed
     */
    private int deleteAffectedFiles(String className) {
        int count = 0;

        Map<String, ClassFileInfo> affectedClasses = affectedClassMap.get(className);
        if (affectedClasses == null) {
            return count;
        }
        for (Map.Entry<String, ClassFileInfo> e : affectedClasses.entrySet()) {
            String affectedClass = e.getKey();
            ClassFileInfo affectedClassInfo = e.getValue();

            if (!affectedClassInfo.absoluteFile.exists()) {
                continue;
            }

            if (affectedClassInfo.sourceFile == null) {
                warnOutOfDateButNotDeleted(affectedClassInfo, affectedClass, className);
                continue;
            }

            log("Deleting file " + affectedClassInfo.absoluteFile.getPath()
                + " since " + className + " out of date", Project.MSG_VERBOSE);

            affectedClassInfo.absoluteFile.delete();
            count++;
            if (closure) {
                count += deleteAffectedFiles(affectedClass);
            } else {
                // without closure we may delete an inner class but not the
                // top level class which would not trigger a recompile.

                if (!affectedClass.contains("$")) {
                    continue;
                }
                // need to delete the main class
                String topLevelClassName = affectedClass.substring(0, affectedClass.indexOf("$"));
                log("Top level class = " + topLevelClassName,
                    Project.MSG_VERBOSE);
                ClassFileInfo topLevelClassInfo
                    = classFileInfoMap.get(topLevelClassName);
                if (topLevelClassInfo != null
                    && topLevelClassInfo.absoluteFile.exists()) {
                    log("Deleting file "
                        + topLevelClassInfo.absoluteFile.getPath()
                        + " since one of its inner classes was removed",
                        Project.MSG_VERBOSE);
                    topLevelClassInfo.absoluteFile.delete();
                    count++;
                    if (closure) {
                        count += deleteAffectedFiles(topLevelClassName);
                    }
                }
            }
        }
        return count;
    }

    
warn when a class is out of date, but not deleted as its source is unknown. MSG_WARN is the normal level, but we downgrade to MSG_VERBOSE for RMI files if is false 
Params:
affectedClassInfo – info about the affected class
affectedClass – the name of the affected .class file
className – the file that is triggering the out of dateness/**
     * warn when a class is out of date, but not deleted as its source is unknown.
     * MSG_WARN is the normal level, but we downgrade to MSG_VERBOSE for RMI files
     * if {@link #warnOnRmiStubs is false}
     * @param affectedClassInfo info about the affected class
     * @param affectedClass the name of the affected .class file
     * @param className the file that is triggering the out of dateness
     */
    private void warnOutOfDateButNotDeleted(
                                            ClassFileInfo affectedClassInfo, String affectedClass,
                                            String className) {
        if (affectedClassInfo.isUserWarned) {
            return;
        }
        int level = Project.MSG_WARN;
        if (!warnOnRmiStubs) {
            //downgrade warnings on RMI stublike classes, as they are generated
            //by rmic, so there is no need to tell the user that their source is
            //missing.
            if (isRmiStub(affectedClass, className)) {
                level = Project.MSG_VERBOSE;
            }
        }
        log("The class " + affectedClass + " in file "
            + affectedClassInfo.absoluteFile.getPath()
            + " is out of date due to " + className
            + " but has not been deleted because its source file could not be determined",
            level);
        affectedClassInfo.isUserWarned = true;
    }

    
test for being an RMI stub
Params:
affectedClass –  class being tested
className –      possible origin of the RMI stub
Returns:
whether the class affectedClass is a RMI stub/**
     * test for being an RMI stub
     * @param affectedClass  class being tested
     * @param className      possible origin of the RMI stub
     * @return whether the class affectedClass is a RMI stub
     */
    private boolean isRmiStub(String affectedClass, String className) {
        return isStub(affectedClass, className, DefaultRmicAdapter.RMI_STUB_SUFFIX)
            || isStub(affectedClass, className, DefaultRmicAdapter.RMI_SKEL_SUFFIX)
            || isStub(affectedClass, className, WLRmic.RMI_STUB_SUFFIX)
            || isStub(affectedClass, className, WLRmic.RMI_SKEL_SUFFIX);
    }

    private boolean isStub(String affectedClass, String baseClass, String suffix) {
        return (baseClass + suffix).equals(affectedClass);
    }

    
Dump the dependency information loaded from the classes to the Ant log
/**
     * Dump the dependency information loaded from the classes to the Ant log
     */
    private void dumpDependencies() {
        log("Reverse Dependency Dump for " + affectedClassMap.size()
            + " classes:", Project.MSG_DEBUG);

        affectedClassMap.forEach((className, affectedClasses) -> {
            log(" Class " + className + " affects:", Project.MSG_DEBUG);
            affectedClasses.forEach((affectedClass, info) -> log(
                "    " + affectedClass + " in " + info.absoluteFile.getPath(),
                Project.MSG_DEBUG));
        });

        if (classpathDependencies != null) {
            log("Classpath file dependencies (Forward):", Project.MSG_DEBUG);

            classpathDependencies.forEach((className, dependencies) -> {
                log(" Class " + className + " depends on:", Project.MSG_DEBUG);
                dependencies.forEach(f -> log("    " + f.getPath(), Project.MSG_DEBUG));
            });
        }
    }

    private void determineOutOfDateClasses() {
        outOfDateClasses = new HashMap<>();
        directories(srcPath).forEach(srcDir -> {
            DirectoryScanner ds = this.getDirectoryScanner(srcDir);
            scanDir(srcDir, ds.getIncludedFiles());
        });

        // now check classpath file dependencies
        if (classpathDependencies == null) {
            return;
        }

        for (Map.Entry<String, Set<File>> e : classpathDependencies.entrySet()) {
            String className = e.getKey();
            if (outOfDateClasses.containsKey(className)) {
                continue;
            }
            ClassFileInfo info = classFileInfoMap.get(className);

            // if we have no info about the class - it may have been deleted already and we
            // are using cached info.
            if (info != null) {
                for (File classpathFile : e.getValue()) {
                    if (classpathFile.lastModified() > info.absoluteFile
                        .lastModified()) {
                        log("Class " + className
                            + " is out of date with respect to "
                            + classpathFile, Project.MSG_DEBUG);
                        outOfDateClasses.put(className, className);
                        break;
                    }
                }
            }
        }
    }

    
Does the work.
Throws:
BuildException – Thrown in case of an unrecoverable error./**
     * Does the work.
     *
     * @exception BuildException Thrown in case of an unrecoverable error.
     */
    @Override
    public void execute() throws BuildException {
        try {
            long start = System.currentTimeMillis();
            if (srcPath == null) {
                throw new BuildException("srcdir attribute must be set",
                                         getLocation());
            }

            if (!directories(srcPath).findAny().isPresent()) {
                throw new BuildException("srcdir attribute must be non-empty",
                                         getLocation());
            }

            if (destPath == null) {
                destPath = srcPath;
            }

            if (cache != null && cache.exists() && !cache.isDirectory()) {
                throw new BuildException(
                    "The cache, if specified, must point to a directory");
            }

            if (cache != null && !cache.exists()) {
                cache.mkdirs();
            }

            determineDependencies();
            if (dump) {
                dumpDependencies();
            }
            determineOutOfDateClasses();
            int count = deleteAllAffectedFiles();

            long duration = (System.currentTimeMillis() - start) / ONE_SECOND;

            final int summaryLogLevel;
            if (count > 0) {
                summaryLogLevel = Project.MSG_INFO;
            }  else {
                summaryLogLevel = Project.MSG_DEBUG;
            }

            log("Deleted " + count + " out of date files in "
                + duration + " seconds", summaryLogLevel);
        } catch (Exception e) {
            throw new BuildException(e);
        }
    }

    
Scans the directory looking for source files that are newer than
their class files. The results are returned in the class variable
compileList
Params:
srcDir – the source directory
files – the names of the files in the source dir which are to be
     checked./**
     * Scans the directory looking for source files that are newer than
     * their class files. The results are returned in the class variable
     * compileList
     *
     * @param srcDir the source directory
     * @param files the names of the files in the source dir which are to be
     *      checked.
     */
    protected void scanDir(File srcDir, String[] files) {
        for (String f : files) {
            File srcFile = new File(srcDir, f);
            if (f.endsWith(".java")) {
                String filePath = srcFile.getPath();
                String className
                    = filePath.substring(srcDir.getPath().length() + 1,
                                         filePath.length() - ".java".length());
                className = ClassFileUtils.convertSlashName(className);
                ClassFileInfo info
                    = classFileInfoMap.get(className);
                if (info == null) {
                    // there was no class file. add this class to the list
                    outOfDateClasses.put(className, className);
                } else if (srcFile.lastModified() > info.absoluteFile
                    .lastModified()) {
                    outOfDateClasses.put(className, className);
                }
            }
        }
    }

    
Get the list of class files we are going to analyse.
Returns:
a vector containing the classes to analyse./**
     * Get the list of class files we are going to analyse.
     *
     * @return a vector containing the classes to analyse.
     */
    private List<ClassFileInfo> getClassFiles() {
        // break the classLocations into its components.
        List<ClassFileInfo> classFileList = new ArrayList<>();

        directories(destPath)
            .forEach(dir -> addClassFiles(classFileList, dir, dir));

        return classFileList;
    }

    
Find the source file for a given class
Params:
classname – the classname in slash format.
sourceFileKnownToExist – if not null, a file already known to exist
                              (saves call to .exists())/**
     * Find the source file for a given class
     *
     * @param classname the classname in slash format.
     * @param sourceFileKnownToExist if not null, a file already known to exist
     *                               (saves call to .exists())
     */
    private File findSourceFile(String classname, File sourceFileKnownToExist) {
        String sourceFilename;
        int innerIndex = classname.indexOf('$');
        if (innerIndex != -1) {
            sourceFilename = classname.substring(0, innerIndex) + ".java";
        } else {
            sourceFilename = classname + ".java";
        }
        // search the various source path entries
        return directories(srcPath)
            .map(d -> new File(d, sourceFilename)).filter(Predicate
                .<File> isEqual(sourceFileKnownToExist).or(File::exists))
            .findFirst().orElse(null);
    }

    
Add the list of class files from the given directory to the class
file vector, including any subdirectories.
Params:
classFileList – a list of ClassFileInfo objects for all the
     files in the directory tree
dir – the directory tree to be searched, recursively, for class
     files
root – the root of the source tree. This is used to determine
     the absolute class name from the relative position in the
     source tree/**
     * Add the list of class files from the given directory to the class
     * file vector, including any subdirectories.
     *
     * @param classFileList a list of ClassFileInfo objects for all the
     *      files in the directory tree
     * @param dir the directory tree to be searched, recursively, for class
     *      files
     * @param root the root of the source tree. This is used to determine
     *      the absolute class name from the relative position in the
     *      source tree
     */
    private void addClassFiles(List<ClassFileInfo> classFileList, File dir, File root) {
        File[] children = dir.listFiles();

        if (children == null) {
            return;
        }

        int rootLength = root.getPath().length();
        File sourceFileKnownToExist = null; // speed optimization
        for (File file : children) {
            if (file.getName().endsWith(".class")) {
                ClassFileInfo info = new ClassFileInfo();
                info.absoluteFile = file;

                String relativeName = file.getPath().substring(rootLength + 1,
                    file.getPath().length() - ".class".length());

                info.className
                    = ClassFileUtils.convertSlashName(relativeName);
                info.sourceFile = sourceFileKnownToExist =
                    findSourceFile(relativeName, sourceFileKnownToExist);
                classFileList.add(info);
            } else {
                addClassFiles(classFileList, file, root);
            }
        }
    }

    
Set the directories path to find the Java source files.
Params:
srcPath – the source path/**
     * Set the directories path to find the Java source files.
     *
     * @param srcPath the source path
     */
    public void setSrcdir(Path srcPath) {
        this.srcPath = srcPath;
    }

    
Set the destination directory where the compiled Java files exist.
Params:
destPath – the destination areas where build files are written/**
     * Set the destination directory where the compiled Java files exist.
     *
     * @param destPath the destination areas where build files are written
     */
    public void setDestDir(Path destPath) {
        this.destPath = destPath;
    }

    
Sets the dependency cache file.
Params:
cache – the dependency cache file/**
     * Sets the dependency cache file.
     *
     * @param cache the dependency cache file
     */
    public void setCache(File cache) {
        this.cache = cache;
    }

    
If true, transitive dependencies are followed until the
closure of the dependency set if reached.
When not set, the depend task will only follow
direct dependencies between classes.
Params:
closure – indicate if dependency closure is required./**
     * If true, transitive dependencies are followed until the
     * closure of the dependency set if reached.
     * When not set, the depend task will only follow
     * direct dependencies between classes.
     *
     * @param closure indicate if dependency closure is required.
     */
    public void setClosure(boolean closure) {
        this.closure = closure;
    }

    
If true, the dependency information will be written
to the debug level log.
Params:
dump – set to true to dump dependency information to the log/**
     * If true, the dependency information will be written
     * to the debug level log.
     *
     * @param dump set to true to dump dependency information to the log
     */
    public void setDump(boolean dump) {
        this.dump = dump;
    }

    private Stream<File> directories(ResourceCollection rc) {
        return rc.stream().map(r -> r.as(FileProvider.class))
            .filter(Objects::nonNull).map(FileProvider::getFile)
            .filter(File::isDirectory);
    }
}