/*
 * Copyright (c) 2005, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package com.sun.tools.javac.processing;

import java.io.Closeable;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.FilterOutputStream;
import java.io.Reader;
import java.io.Writer;
import java.io.FilterWriter;
import java.io.PrintWriter;
import java.io.IOException;
import java.util.*;

import static java.util.Collections.*;

import javax.annotation.processing.*;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.NestingKind;
import javax.lang.model.element.Modifier;
import javax.lang.model.element.Element;
import javax.tools.*;
import javax.tools.JavaFileManager.Location;

import static javax.tools.StandardLocation.SOURCE_OUTPUT;
import static javax.tools.StandardLocation.CLASS_OUTPUT;

import com.sun.tools.javac.code.Lint;
import com.sun.tools.javac.code.Symbol.ClassSymbol;
import com.sun.tools.javac.code.Symbol.ModuleSymbol;
import com.sun.tools.javac.code.Symtab;
import com.sun.tools.javac.comp.Modules;
import com.sun.tools.javac.model.JavacElements;
import com.sun.tools.javac.util.*;
import com.sun.tools.javac.util.DefinedBy.Api;

import static com.sun.tools.javac.code.Lint.LintCategory.PROCESSING;
import com.sun.tools.javac.code.Symbol.PackageSymbol;
import com.sun.tools.javac.main.Option;

The FilerImplementation class must maintain a number of
constraints.  First, multiple attempts to open the same path within
the same invocation of the tool results in an IOException being
thrown.  For example, trying to open the same source file twice:
createSourceFile("foo.Bar")
...
createSourceFile("foo.Bar")

is disallowed as is opening a text file that happens to have
the same name as a source file:
createSourceFile("foo.Bar")
...
createTextFile(SOURCE_TREE, "foo", new File("Bar"), null)

Additionally, creating a source file that corresponds to an
already created class file (or vice versa) also results in an
IOException since each type can only be created once.  However, if
the Filer is used to create a text file named *.java that happens
to correspond to an existing class file, a warning is *not*
generated.  Similarly, a warning is not generated for a binary file
named *.class and an existing source file.
The reason for this difference is that source files and class
files are registered with the tool and can get passed on as
declarations to the next round of processing.  Files that are just
named *.java and *.class are not processed in that manner; although
having extra source files and class files on the source path and
class path can alter the behavior of the tool and any final
compile.
This is NOT part of any supported API.
If you write code that depends on this, you do so at your own risk.
This code and its internal interfaces are subject to change or
deletion without notice.
/**
 * The FilerImplementation class must maintain a number of
 * constraints.  First, multiple attempts to open the same path within
 * the same invocation of the tool results in an IOException being
 * thrown.  For example, trying to open the same source file twice:
 *
 * <pre>
 * createSourceFile("foo.Bar")
 * ...
 * createSourceFile("foo.Bar")
 * </pre>
 *
 * is disallowed as is opening a text file that happens to have
 * the same name as a source file:
 *
 * <pre>
 * createSourceFile("foo.Bar")
 * ...
 * createTextFile(SOURCE_TREE, "foo", new File("Bar"), null)
 * </pre>
 *
 * <p>Additionally, creating a source file that corresponds to an
 * already created class file (or vice versa) also results in an
 * IOException since each type can only be created once.  However, if
 * the Filer is used to create a text file named *.java that happens
 * to correspond to an existing class file, a warning is *not*
 * generated.  Similarly, a warning is not generated for a binary file
 * named *.class and an existing source file.
 *
 * <p>The reason for this difference is that source files and class
 * files are registered with the tool and can get passed on as
 * declarations to the next round of processing.  Files that are just
 * named *.java and *.class are not processed in that manner; although
 * having extra source files and class files on the source path and
 * class path can alter the behavior of the tool and any final
 * compile.
 *
 * <p><b>This is NOT part of any supported API.
 * If you write code that depends on this, you do so at your own risk.
 * This code and its internal interfaces are subject to change or
 * deletion without notice.</b>
 */
public class JavacFiler implements Filer, Closeable {
    // TODO: Implement different transaction model for updating the
    // Filer's record keeping on file close.

    private static final String ALREADY_OPENED =
        "Output stream or writer has already been opened.";
    private static final String NOT_FOR_READING =
        "FileObject was not opened for reading.";
    private static final String NOT_FOR_WRITING =
        "FileObject was not opened for writing.";

    
Wrap a JavaFileObject to manage writing by the Filer.
/**
     * Wrap a JavaFileObject to manage writing by the Filer.
     */
    private class FilerOutputFileObject extends ForwardingFileObject<FileObject> {
        private boolean opened = false;
        private ModuleSymbol mod;
        private String name;

        FilerOutputFileObject(ModuleSymbol mod, String name, FileObject fileObject) {
            super(fileObject);
            this.mod = mod;
            this.name = name;
        }

        @Override @DefinedBy(Api.COMPILER)
        public synchronized OutputStream openOutputStream() throws IOException {
            if (opened)
                throw new IOException(ALREADY_OPENED);
            opened = true;
            return new FilerOutputStream(mod, name, fileObject);
        }

        @Override @DefinedBy(Api.COMPILER)
        public synchronized Writer openWriter() throws IOException {
            if (opened)
                throw new IOException(ALREADY_OPENED);
            opened = true;
            return new FilerWriter(mod, name, fileObject);
        }

        // Three anti-literacy methods
        @Override @DefinedBy(Api.COMPILER)
        public InputStream openInputStream() throws IOException {
            throw new IllegalStateException(NOT_FOR_READING);
        }

        @Override @DefinedBy(Api.COMPILER)
        public Reader openReader(boolean ignoreEncodingErrors) throws IOException {
            throw new IllegalStateException(NOT_FOR_READING);
        }

        @Override @DefinedBy(Api.COMPILER)
        public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException {
            throw new IllegalStateException(NOT_FOR_READING);
        }

        @Override @DefinedBy(Api.COMPILER)
        public boolean delete() {
            return false;
        }
    }

    private class FilerOutputJavaFileObject extends FilerOutputFileObject implements JavaFileObject {
        private final JavaFileObject javaFileObject;
        FilerOutputJavaFileObject(ModuleSymbol mod, String name, JavaFileObject javaFileObject) {
            super(mod, name, javaFileObject);
            this.javaFileObject = javaFileObject;
        }

        @DefinedBy(Api.COMPILER)
        public JavaFileObject.Kind getKind() {
            return javaFileObject.getKind();
        }

        @DefinedBy(Api.COMPILER)
        public boolean isNameCompatible(String simpleName,
                                        JavaFileObject.Kind kind) {
            return javaFileObject.isNameCompatible(simpleName, kind);
        }

        @DefinedBy(Api.COMPILER)
        public NestingKind getNestingKind() {
            return javaFileObject.getNestingKind();
        }

        @DefinedBy(Api.COMPILER)
        public Modifier getAccessLevel() {
            return javaFileObject.getAccessLevel();
        }
    }

    
Wrap a JavaFileObject to manage reading by the Filer.
/**
     * Wrap a JavaFileObject to manage reading by the Filer.
     */
    private class FilerInputFileObject extends ForwardingFileObject<FileObject> {
        FilerInputFileObject(FileObject fileObject) {
            super(fileObject);
        }

        @Override @DefinedBy(Api.COMPILER)
        public OutputStream openOutputStream() throws IOException {
            throw new IllegalStateException(NOT_FOR_WRITING);
        }

        @Override @DefinedBy(Api.COMPILER)
        public Writer openWriter() throws IOException {
            throw new IllegalStateException(NOT_FOR_WRITING);
        }

        @Override @DefinedBy(Api.COMPILER)
        public boolean delete() {
            return false;
        }
    }

    private class FilerInputJavaFileObject extends FilerInputFileObject implements JavaFileObject {
        private final JavaFileObject javaFileObject;
        FilerInputJavaFileObject(JavaFileObject javaFileObject) {
            super(javaFileObject);
            this.javaFileObject = javaFileObject;
        }

        @DefinedBy(Api.COMPILER)
        public JavaFileObject.Kind getKind() {
            return javaFileObject.getKind();
        }

        @DefinedBy(Api.COMPILER)
        public boolean isNameCompatible(String simpleName,
                                        JavaFileObject.Kind kind) {
            return javaFileObject.isNameCompatible(simpleName, kind);
        }

        @DefinedBy(Api.COMPILER)
        public NestingKind getNestingKind() {
            return javaFileObject.getNestingKind();
        }

        @DefinedBy(Api.COMPILER)
        public Modifier getAccessLevel() {
            return javaFileObject.getAccessLevel();
        }
    }


    
Wrap a OutputStream returned from the 
JavaFileManager to properly register source or class files when they are closed. /**
     * Wrap a {@code OutputStream} returned from the {@code
     * JavaFileManager} to properly register source or class files
     * when they are closed.
     */
    private class FilerOutputStream extends FilterOutputStream {
        ModuleSymbol mod;
        String typeName;
        FileObject fileObject;
        boolean closed = false;

        
Params:
typeName – name of class or null if just a binary file/**
         * @param typeName name of class or {@code null} if just a
         * binary file
         */
        FilerOutputStream(ModuleSymbol mod, String typeName, FileObject fileObject) throws IOException {
            super(fileObject.openOutputStream());
            this.mod = mod;
            this.typeName = typeName;
            this.fileObject = fileObject;
        }

        public synchronized void close() throws IOException {
            if (!closed) {
                closed = true;
                /*
                 * If an IOException occurs when closing the underlying
                 * stream, still try to process the file.
                 */

                closeFileObject(mod, typeName, fileObject);
                out.close();
            }
        }
    }

    
Wrap a Writer returned from the JavaFileManager to properly register source or class files when they are closed. /**
     * Wrap a {@code Writer} returned from the {@code JavaFileManager}
     * to properly register source or class files when they are
     * closed.
     */
    private class FilerWriter extends FilterWriter {
        ModuleSymbol mod;
        String typeName;
        FileObject fileObject;
        boolean closed = false;

        
Params:
fileObject – the fileObject to be written to
typeName – name of source file or null if just a text file/**
         * @param fileObject the fileObject to be written to
         * @param typeName name of source file or {@code null} if just a
         * text file
         */
        FilerWriter(ModuleSymbol mod, String typeName, FileObject fileObject) throws IOException {
            super(fileObject.openWriter());
            this.mod = mod;
            this.typeName = typeName;
            this.fileObject = fileObject;
        }

        public synchronized void close() throws IOException {
            if (!closed) {
                closed = true;
                /*
                 * If an IOException occurs when closing the underlying
                 * Writer, still try to process the file.
                 */

                closeFileObject(mod, typeName, fileObject);
                out.close();
            }
        }
    }

    JavaFileManager fileManager;
    JavacElements elementUtils;
    Log log;
    Modules modules;
    Names names;
    Symtab syms;
    Context context;
    boolean lastRound;

    private final boolean lint;

    
Initial inputs passed to the tool.  This set must be
synchronized.
/**
     * Initial inputs passed to the tool.  This set must be
     * synchronized.
     */
    private final Set<FileObject> initialInputs;

    
Logical names of all created files.  This set must be
synchronized.
/**
     * Logical names of all created files.  This set must be
     * synchronized.
     */
    private final Set<FileObject> fileObjectHistory;

    
Names of types that have had files created but not closed.
/**
     * Names of types that have had files created but not closed.
     */
    private final Set<String> openTypeNames;

    
Names of source files closed in this round.  This set must be
synchronized.  Its iterators should preserve insertion order.
/**
     * Names of source files closed in this round.  This set must be
     * synchronized.  Its iterators should preserve insertion order.
     */
    private Set<String> generatedSourceNames;

    
Names and class files of the class files closed in this round.
This set must be synchronized.  Its iterators should preserve
insertion order.
/**
     * Names and class files of the class files closed in this round.
     * This set must be synchronized.  Its iterators should preserve
     * insertion order.
     */
    private final Map<ModuleSymbol, Map<String, JavaFileObject>> generatedClasses;

    
JavaFileObjects for source files closed in this round.  This
set must be synchronized.  Its iterators should preserve
insertion order.
/**
     * JavaFileObjects for source files closed in this round.  This
     * set must be synchronized.  Its iterators should preserve
     * insertion order.
     */
    private Set<JavaFileObject> generatedSourceFileObjects;

    
Names of all created source files.  Its iterators should
preserve insertion order.
/**
     * Names of all created source files.  Its iterators should
     * preserve insertion order.
     */
    private final Set<Pair<ModuleSymbol, String>> aggregateGeneratedSourceNames;

    
Names of all created class files.  Its iterators should
preserve insertion order.
/**
     * Names of all created class files.  Its iterators should
     * preserve insertion order.
     */
    private final Set<Pair<ModuleSymbol, String>> aggregateGeneratedClassNames;

    private final Set<String> initialClassNames;

    private final String defaultTargetModule;

    JavacFiler(Context context) {
        this.context = context;
        fileManager = context.get(JavaFileManager.class);
        elementUtils = JavacElements.instance(context);

        log = Log.instance(context);
        modules = Modules.instance(context);
        names = Names.instance(context);
        syms = Symtab.instance(context);

        initialInputs = synchronizedSet(new LinkedHashSet<>());
        fileObjectHistory = synchronizedSet(new LinkedHashSet<>());
        generatedSourceNames = synchronizedSet(new LinkedHashSet<>());
        generatedSourceFileObjects = synchronizedSet(new LinkedHashSet<>());

        generatedClasses = synchronizedMap(new LinkedHashMap<>());

        openTypeNames  = synchronizedSet(new LinkedHashSet<>());

        aggregateGeneratedSourceNames = new LinkedHashSet<>();
        aggregateGeneratedClassNames  = new LinkedHashSet<>();
        initialClassNames  = new LinkedHashSet<>();

        lint = (Lint.instance(context)).isEnabled(PROCESSING);

        Options options = Options.instance(context);

        defaultTargetModule = options.get(Option.DEFAULT_MODULE_FOR_CREATED_FILES);
    }

    @Override @DefinedBy(Api.ANNOTATION_PROCESSING)
    public JavaFileObject createSourceFile(CharSequence nameAndModule,
                                           Element... originatingElements) throws IOException {
        Pair<ModuleSymbol, String> moduleAndClass = checkOrInferModule(nameAndModule);
        return createSourceOrClassFile(moduleAndClass.fst, true, moduleAndClass.snd);
    }

    @Override @DefinedBy(Api.ANNOTATION_PROCESSING)
    public JavaFileObject createClassFile(CharSequence nameAndModule,
                                          Element... originatingElements) throws IOException {
        Pair<ModuleSymbol, String> moduleAndClass = checkOrInferModule(nameAndModule);
        return createSourceOrClassFile(moduleAndClass.fst, false, moduleAndClass.snd);
    }

    private Pair<ModuleSymbol, String> checkOrInferModule(CharSequence moduleAndPkg) throws FilerException {
        String moduleAndPkgString = moduleAndPkg.toString();
        int slash = moduleAndPkgString.indexOf('/');
        String module;
        String pkg;

        if (slash == (-1)) {
            //module name not specified:
            int lastDot = moduleAndPkgString.lastIndexOf('.');
            String pack = lastDot != (-1) ? moduleAndPkgString.substring(0, lastDot) : "";
            ModuleSymbol msym = inferModule(pack);

            if (msym != null) {
                return Pair.of(msym, moduleAndPkgString);
            }

            if (defaultTargetModule == null) {
                throw new FilerException("Cannot determine target module.");
            }

            module = defaultTargetModule;
            pkg = moduleAndPkgString;
        } else {
            //module name specified:
            module = moduleAndPkgString.substring(0, slash);
            pkg = moduleAndPkgString.substring(slash + 1);
        }

        ModuleSymbol explicitModule = syms.getModule(names.fromString(module));

        if (explicitModule == null) {
            throw new FilerException("Module: " + module + " does not exist.");
        }

        if (!modules.isRootModule(explicitModule)) {
            throw new FilerException("Cannot write to the given module.");
        }

        return Pair.of(explicitModule, pkg);
    }

    private JavaFileObject createSourceOrClassFile(ModuleSymbol mod, boolean isSourceFile, String name) throws IOException {
        Assert.checkNonNull(mod);

        if (lint) {
            int periodIndex = name.lastIndexOf(".");
            if (periodIndex != -1) {
                String base = name.substring(periodIndex);
                String extn = (isSourceFile ? ".java" : ".class");
                if (base.equals(extn))
                    log.warning("proc.suspicious.class.name", name, extn);
            }
        }
        checkNameAndExistence(mod, name, isSourceFile);
        Location loc = (isSourceFile ? SOURCE_OUTPUT : CLASS_OUTPUT);

        if (modules.multiModuleMode) {
            loc = this.fileManager.getLocationForModule(loc, mod.name.toString());
        }
        JavaFileObject.Kind kind = (isSourceFile ?
                                    JavaFileObject.Kind.SOURCE :
                                    JavaFileObject.Kind.CLASS);

        JavaFileObject fileObject =
            fileManager.getJavaFileForOutput(loc, name, kind, null);
        checkFileReopening(fileObject, true);

        if (lastRound)
            log.warning("proc.file.create.last.round", name);

        if (isSourceFile)
            aggregateGeneratedSourceNames.add(Pair.of(mod, name));
        else
            aggregateGeneratedClassNames.add(Pair.of(mod, name));
        openTypeNames.add(name);

        return new FilerOutputJavaFileObject(mod, name, fileObject);
    }

    @Override @DefinedBy(Api.ANNOTATION_PROCESSING)
    public FileObject createResource(JavaFileManager.Location location,
                                     CharSequence moduleAndPkg,
                                     CharSequence relativeName,
                                     Element... originatingElements) throws IOException {
        Tuple3<Location, ModuleSymbol, String> locationModuleAndPackage = checkOrInferModule(location, moduleAndPkg, true);
        location = locationModuleAndPackage.a;
        ModuleSymbol msym = locationModuleAndPackage.b;
        String pkg = locationModuleAndPackage.c;

        locationCheck(location);

        String strPkg = pkg.toString();
        if (strPkg.length() > 0)
            checkName(strPkg);

        FileObject fileObject =
            fileManager.getFileForOutput(location, strPkg,
                                         relativeName.toString(), null);
        checkFileReopening(fileObject, true);

        if (fileObject instanceof JavaFileObject)
            return new FilerOutputJavaFileObject(msym, null, (JavaFileObject)fileObject);
        else
            return new FilerOutputFileObject(msym, null, fileObject);
    }

    private void locationCheck(JavaFileManager.Location location) {
        if (location instanceof StandardLocation) {
            StandardLocation stdLoc = (StandardLocation) location;
            if (!stdLoc.isOutputLocation())
                throw new IllegalArgumentException("Resource creation not supported in location " +
                                                   stdLoc);
        }
    }

    @Override @DefinedBy(Api.ANNOTATION_PROCESSING)
    public FileObject getResource(JavaFileManager.Location location,
                                  CharSequence moduleAndPkg,
                                  CharSequence relativeName) throws IOException {
        Tuple3<Location, ModuleSymbol, String> locationModuleAndPackage = checkOrInferModule(location, moduleAndPkg, false);
        location = locationModuleAndPackage.a;
        String pkg = locationModuleAndPackage.c;

        if (pkg.length() > 0)
            checkName(pkg);

        // TODO: Only support reading resources in selected output
        // locations?  Only allow reading of non-source, non-class
        // files from the supported input locations?

        // In the following, getFileForInput is the "obvious" method
        // to use, but it does not have the "obvious" semantics for
        // SOURCE_OUTPUT and CLASS_OUTPUT. Conversely, getFileForOutput
        // does not have the correct semantics for any "path" location
        // with more than one component. So, for now, we use a hybrid
        // invocation.
        FileObject fileObject;
        if (location.isOutputLocation()) {
            fileObject = fileManager.getFileForOutput(location,
                    pkg,
                    relativeName.toString(),
                    null);
        } else {
            fileObject = fileManager.getFileForInput(location,
                    pkg,
                    relativeName.toString());
        }
        if (fileObject == null) {
            String name = (pkg.length() == 0)
                    ? relativeName.toString() : (pkg + "/" + relativeName);
            throw new FileNotFoundException(name);
        }

        // If the path was already opened for writing, throw an exception.
        checkFileReopening(fileObject, false);
        return new FilerInputFileObject(fileObject);
    }

    private Tuple3<JavaFileManager.Location, ModuleSymbol, String> checkOrInferModule(JavaFileManager.Location location,
                                                           CharSequence moduleAndPkg,
                                                           boolean write) throws IOException {
        String moduleAndPkgString = moduleAndPkg.toString();
        int slash = moduleAndPkgString.indexOf('/');
        boolean multiModuleLocation = location.isModuleOrientedLocation() ||
                                      (modules.multiModuleMode && location.isOutputLocation());
        String module;
        String pkg;

        if (slash == (-1)) {
            //module name not specified:
            if (!multiModuleLocation) {
                //package oriented location:
                return new Tuple3<>(location, modules.getDefaultModule(), moduleAndPkgString);
            }

            if (location.isOutputLocation()) {
                ModuleSymbol msym = inferModule(moduleAndPkgString);

                if (msym != null) {
                    Location moduleLoc =
                            fileManager.getLocationForModule(location, msym.name.toString());
                    return new Tuple3<>(moduleLoc, msym, moduleAndPkgString);
                }
            }

            if (defaultTargetModule == null) {
                throw new FilerException("No module specified and the location is either " +
                                         "a module-oriented location, or a multi-module " +
                                         "output location.");
            }

            module = defaultTargetModule;
            pkg = moduleAndPkgString;
        } else {
            //module name specified:
            module = moduleAndPkgString.substring(0, slash);
            pkg = moduleAndPkgString.substring(slash + 1);
        }

        if (multiModuleLocation) {
            ModuleSymbol explicitModule = syms.getModule(names.fromString(module));

            if (explicitModule == null) {
                throw new FilerException("Module: " + module + " does not exist.");
            }

            if (write && !modules.isRootModule(explicitModule)) {
                throw new FilerException("Cannot write to the given module.");
            }

            Location moduleLoc = fileManager.getLocationForModule(location, module);

            return new Tuple3<>(moduleLoc, explicitModule, pkg);
        } else {
            throw new FilerException("Module specified but the location is neither " +
                                     "a module-oriented location, nor a multi-module " +
                                     "output location.");
        }
    }

    static final class Tuple3<A, B, C> {
        final A a;
        final B b;
        final C c;

        public Tuple3(A a, B b, C c) {
            this.a = a;
            this.b = b;
            this.c = c;
        }
    }

    private ModuleSymbol inferModule(String pkg) {
        if (modules.getDefaultModule() == syms.noModule)
            return modules.getDefaultModule();

        Set<ModuleSymbol> rootModules = modules.getRootModules();

        if (rootModules.size() == 1) {
            return rootModules.iterator().next();
        }

        PackageSymbol pack = elementUtils.getPackageElement(pkg);

        if (pack != null && pack.modle != syms.unnamedModule) {
            return pack.modle;
        }

        return null;
    }

    private void checkName(String name) throws FilerException {
        checkName(name, false);
    }

    private void checkName(String name, boolean allowUnnamedPackageInfo) throws FilerException {
        if (!SourceVersion.isName(name) && !isPackageInfo(name, allowUnnamedPackageInfo)) {
            if (lint)
                log.warning("proc.illegal.file.name", name);
            throw new FilerException("Illegal name " + name);
        }
    }

    private boolean isPackageInfo(String name, boolean allowUnnamedPackageInfo) {
        // Is the name of the form "package-info" or
        // "foo.bar.package-info"?
        final String PKG_INFO = "package-info";
        int periodIndex = name.lastIndexOf(".");
        if (periodIndex == -1) {
            return allowUnnamedPackageInfo ? name.equals(PKG_INFO) : false;
        } else {
            // "foo.bar.package-info." illegal
            String prefix = name.substring(0, periodIndex);
            String simple = name.substring(periodIndex+1);
            return SourceVersion.isName(prefix) && simple.equals(PKG_INFO);
        }
    }

    private void checkNameAndExistence(ModuleSymbol mod, String typename, boolean allowUnnamedPackageInfo) throws FilerException {
        // TODO: Check if type already exists on source or class path?
        // If so, use warning message key proc.type.already.exists
        checkName(typename, allowUnnamedPackageInfo);
        ClassSymbol existing;
        boolean alreadySeen = aggregateGeneratedSourceNames.contains(Pair.of(mod, typename)) ||
                              aggregateGeneratedClassNames.contains(Pair.of(mod, typename)) ||
                              initialClassNames.contains(typename) ||
                              ((existing = elementUtils.getTypeElement(typename)) != null &&
                               initialInputs.contains(existing.sourcefile));
        if (alreadySeen) {
            if (lint)
                log.warning("proc.type.recreate", typename);
            throw new FilerException("Attempt to recreate a file for type " + typename);
        }
        if (!mod.isUnnamed() && !typename.contains(".")) {
            throw new FilerException("Attempt to create a type in unnamed package of a named module: " + typename);
        }
    }

    
Check to see if the file has already been opened; if so, throw
an exception, otherwise add it to the set of files.
/**
     * Check to see if the file has already been opened; if so, throw
     * an exception, otherwise add it to the set of files.
     */
    private void checkFileReopening(FileObject fileObject, boolean forWriting) throws FilerException {
        if (isInFileObjectHistory(fileObject, forWriting)) {
            if (lint)
                log.warning("proc.file.reopening", fileObject.getName());
            throw new FilerException("Attempt to reopen a file for path " + fileObject.getName());
        }
        if (forWriting)
            fileObjectHistory.add(fileObject);
    }

    private boolean isInFileObjectHistory(FileObject fileObject, boolean forWriting) {
        if (forWriting) {
            for(FileObject veteran : initialInputs) {
                try {
                    if (fileManager.isSameFile(veteran, fileObject)) {
                        return true;
                    }
                } catch (IllegalArgumentException e) {
                    //ignore...
                }
            }
            for (String className : initialClassNames) {
                try {
                    ClassSymbol existing = elementUtils.getTypeElement(className);
                    if (   existing != null
                        && (   (existing.sourcefile != null && fileManager.isSameFile(existing.sourcefile, fileObject))
                            || (existing.classfile != null && fileManager.isSameFile(existing.classfile, fileObject)))) {
                        return true;
                    }
                } catch (IllegalArgumentException e) {
                    //ignore...
                }
            }
        }

        for(FileObject veteran : fileObjectHistory) {
            if (fileManager.isSameFile(veteran, fileObject)) {
                return true;
            }
        }

        return false;
    }

    public boolean newFiles() {
        return (!generatedSourceNames.isEmpty())
            || (!generatedClasses.isEmpty());
    }

    public Set<String> getGeneratedSourceNames() {
        return generatedSourceNames;
    }

    public Set<JavaFileObject> getGeneratedSourceFileObjects() {
        return generatedSourceFileObjects;
    }

    public Map<ModuleSymbol, Map<String, JavaFileObject>> getGeneratedClasses() {
        return generatedClasses;
    }

    public void warnIfUnclosedFiles() {
        if (!openTypeNames.isEmpty())
            log.warning("proc.unclosed.type.files", openTypeNames.toString());
    }

    
Update internal state for a new round.
/**
     * Update internal state for a new round.
     */
    public void newRound() {
        clearRoundState();
    }

    void setLastRound(boolean lastRound) {
        this.lastRound = lastRound;
    }

    public void setInitialState(Collection<? extends JavaFileObject> initialInputs,
                                Collection<String> initialClassNames) {
        this.initialInputs.addAll(initialInputs);
        this.initialClassNames.addAll(initialClassNames);
    }

    public void close() {
        clearRoundState();
        // Cross-round state
        initialClassNames.clear();
        initialInputs.clear();
        fileObjectHistory.clear();
        openTypeNames.clear();
        aggregateGeneratedSourceNames.clear();
        aggregateGeneratedClassNames.clear();
    }

    private void clearRoundState() {
        generatedSourceNames.clear();
        generatedSourceFileObjects.clear();
        generatedClasses.clear();
    }

    
Debugging function to display internal state.
/**
     * Debugging function to display internal state.
     */
    public void displayState() {
        PrintWriter xout = context.get(Log.logKey).getWriter(Log.WriterKind.STDERR);
        xout.println("File Object History : " +  fileObjectHistory);
        xout.println("Open Type Names     : " +  openTypeNames);
        xout.println("Gen. Src Names      : " +  generatedSourceNames);
        xout.println("Gen. Cls Names      : " +  generatedClasses.keySet());
        xout.println("Agg. Gen. Src Names : " +  aggregateGeneratedSourceNames);
        xout.println("Agg. Gen. Cls Names : " +  aggregateGeneratedClassNames);
    }

    public String toString() {
        return "javac Filer";
    }

    
Upon close, register files opened by create{Source, Class}File
for annotation processing.
/**
     * Upon close, register files opened by create{Source, Class}File
     * for annotation processing.
     */
    private void closeFileObject(ModuleSymbol mod, String typeName, FileObject fileObject) {
        /*
         * If typeName is non-null, the file object was opened as a
         * source or class file by the user.  If a file was opened as
         * a resource, typeName will be null and the file is *not*
         * subject to annotation processing.
         */
        if ((typeName != null)) {
            if (!(fileObject instanceof JavaFileObject))
                throw new AssertionError("JavaFileOject not found for " + fileObject);
            JavaFileObject javaFileObject = (JavaFileObject)fileObject;
            switch(javaFileObject.getKind()) {
            case SOURCE:
                generatedSourceNames.add(typeName);
                generatedSourceFileObjects.add(javaFileObject);
                openTypeNames.remove(typeName);
                break;

            case CLASS:
                generatedClasses.computeIfAbsent(mod, m -> Collections.synchronizedMap(new LinkedHashMap<>())).put(typeName, javaFileObject);
                openTypeNames.remove(typeName);
                break;

            default:
                break;
            }
        }
    }

}