/*
 * Copyright (c) 2014, 2020, 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.platform;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.URI;
import java.nio.charset.Charset;
import java.nio.file.DirectoryStream;
import java.nio.file.FileSystem;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.ProviderNotFoundException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.TreeSet;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import javax.annotation.processing.Processor;
import javax.tools.ForwardingJavaFileObject;
import javax.tools.JavaFileManager;
import javax.tools.JavaFileManager.Location;
import javax.tools.JavaFileObject;
import javax.tools.JavaFileObject.Kind;
import javax.tools.StandardJavaFileManager;
import javax.tools.StandardLocation;

import com.sun.source.util.Plugin;
import com.sun.tools.javac.code.Source;
import com.sun.tools.javac.code.Source.Feature;
import com.sun.tools.javac.file.CacheFSInfo;
import com.sun.tools.javac.file.JavacFileManager;
import com.sun.tools.javac.jvm.Target;
import com.sun.tools.javac.main.Option;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.Log;
import com.sun.tools.javac.util.StringUtils;

PlatformProvider for JDK N.
 
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.
/** PlatformProvider for JDK N.
 *
 *  <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 JDKPlatformProvider implements PlatformProvider {

    @Override
    public Iterable<String> getSupportedPlatformNames() {
        return SUPPORTED_JAVA_PLATFORM_VERSIONS;
    }

    @Override
    public PlatformDescription getPlatform(String platformName, String options) {
        return new PlatformDescriptionImpl(platformName);
    }

    private static final String[] symbolFileLocation = { "lib", "ct.sym" };

    private static final Set<String> SUPPORTED_JAVA_PLATFORM_VERSIONS;
    public static final Comparator<String> NUMERICAL_COMPARATOR = (s1, s2) -> {
        int i1;
        try {
            i1 = Integer.parseInt(s1);
        } catch (NumberFormatException ex) {
            i1 = Integer.MAX_VALUE;
        }
        int i2;
        try {
            i2 = Integer.parseInt(s2);
        } catch (NumberFormatException ex) {
            i2 = Integer.MAX_VALUE;
        }
        return i1 != i2 ? i1 - i2 : s1.compareTo(s2);
    };

    static {
        SUPPORTED_JAVA_PLATFORM_VERSIONS = new TreeSet<>(NUMERICAL_COMPARATOR);
        Path ctSymFile = findCtSym();
        if (Files.exists(ctSymFile)) {
            try (FileSystem fs = FileSystems.newFileSystem(ctSymFile, (ClassLoader)null);
                 DirectoryStream<Path> dir =
                         Files.newDirectoryStream(fs.getRootDirectories().iterator().next())) {
                for (Path section : dir) {
                    if (section.getFileName().toString().contains("-"))
                        continue;
                    for (char ver : section.getFileName().toString().toCharArray()) {
                        String verString = Character.toString(ver);
                        Target t = Target.lookup("" + Integer.parseInt(verString, Character.MAX_RADIX));

                        if (t != null) {
                            SUPPORTED_JAVA_PLATFORM_VERSIONS.add(targetNumericVersion(t));
                        }
                    }
                }
            } catch (IOException | ProviderNotFoundException ex) {
            }
        }
    }

    private static String targetNumericVersion(Target target) {
        return Integer.toString(target.ordinal() - Target.JDK1_1.ordinal() + 1);
    }

    static class PlatformDescriptionImpl implements PlatformDescription {

        private final Map<Path, FileSystem> ctSym2FileSystem = new HashMap<>();
        private final String sourceVersion;
        private final String ctSymVersion;

        PlatformDescriptionImpl(String sourceVersion) {
            this.sourceVersion = sourceVersion;
            this.ctSymVersion =
                    StringUtils.toUpperCase(Integer.toString(Integer.parseInt(sourceVersion), Character.MAX_RADIX));
        }

        @Override
        public JavaFileManager getFileManager() {
            Context context = new Context();
            PrintWriter pw = new PrintWriter(System.err, true);
            context.put(Log.errKey, pw);
            CacheFSInfo.preRegister(context);
            JavacFileManager fm = new JavacFileManager(context, true, null) {
                @Override
                public boolean hasLocation(Location location) {
                    return super.hasExplicitLocation(location);
                }

                @Override
                public JavaFileObject getJavaFileForInput(Location location, String className,
                                                          Kind kind) throws IOException {
                    if (kind == Kind.CLASS) {
                        String fileName = className.replace('.', '/');
                        JavaFileObject result =
                                (JavaFileObject) getFileForInput(location,
                                                                 "",
                                                                 fileName + ".sig");

                        if (result == null) {
                            //in jrt://, the classfile may have the .class extension:
                            result = (JavaFileObject) getFileForInput(location,
                                                                      "",
                                                                      fileName + ".class");
                        }

                        if (result != null) {
                            return new SigJavaFileObject(result);
                        } else {
                            return null;
                        }
                    }

                    return super.getJavaFileForInput(location, className, kind);
                }

                @Override
                public Iterable<JavaFileObject> list(Location location,
                                                     String packageName,
                                                     Set<Kind> kinds,
                                                     boolean recurse) throws IOException {
                    Set<Kind> enhancedKinds = EnumSet.copyOf(kinds);

                    enhancedKinds.add(Kind.OTHER);

                    Iterable<JavaFileObject> listed = super.list(location, packageName,
                                                                 enhancedKinds, recurse);

                    return () -> new Iterator<JavaFileObject>() {
                        private final Iterator<JavaFileObject> original = listed.iterator();
                        private JavaFileObject next;
                        @Override
                        public boolean hasNext() {
                            if (next == null) {
                                while (original.hasNext()) {
                                    JavaFileObject fo = original.next();

                                    if (fo.getKind() == Kind.OTHER &&
                                        fo.getName().endsWith(".sig")) {
                                        next = new SigJavaFileObject(fo);
                                        break;
                                    }

                                    if (kinds.contains(fo.getKind())) {
                                        next = fo;
                                        break;
                                    }
                                }
                            }
                            return next != null;
                        }

                        @Override
                        public JavaFileObject next() {
                            if (!hasNext())
                                throw new NoSuchElementException();
                            JavaFileObject result = next;
                            next = null;
                            return result;
                        }

                    };
                }

                @Override
                public String inferBinaryName(Location location, JavaFileObject file) {
                    if (file instanceof SigJavaFileObject) {
                        file = ((SigJavaFileObject) file).getDelegate();
                    }
                    return super.inferBinaryName(location, file);
                }

            };

            fm.handleOption(Option.MULTIRELEASE, sourceVersion);

            Path file = findCtSym();
            // file == ${jdk.home}/lib/ct.sym
            if (Files.exists(file)) {
                try {
                    FileSystem fs = ctSym2FileSystem.get(file);
                    if (fs == null) {
                        ctSym2FileSystem.put(file, fs = FileSystems.newFileSystem(file, (ClassLoader)null));
                    }

                    Path root = fs.getRootDirectories().iterator().next();
                    boolean hasModules =
                            Feature.MODULES.allowedInSource(Source.lookup(sourceVersion));
                    Path systemModules = root.resolve(ctSymVersion).resolve("system-modules");
                    Charset utf8 = Charset.forName("UTF-8");

                    if (!hasModules) {
                        List<Path> paths = new ArrayList<>();

                        try (DirectoryStream<Path> dir = Files.newDirectoryStream(root)) {
                            for (Path section : dir) {
                                if (section.getFileName().toString().contains(ctSymVersion) &&
                                    !section.getFileName().toString().contains("-")) {
                                    try (DirectoryStream<Path> modules = Files.newDirectoryStream(section)) {
                                        for (Path module : modules) {
                                            paths.add(module);
                                        }
                                    }
                                }
                            }
                        }

                        fm.setLocationFromPaths(StandardLocation.PLATFORM_CLASS_PATH, paths);
                    } else if (Files.isRegularFile(systemModules)) {
                        fm.handleOption("--system", Arrays.asList("none").iterator());

                        Path jrtModules =
                                FileSystems.getFileSystem(URI.create("jrt:/"))
                                           .getPath("modules");
                        try (Stream<String> lines =
                                Files.lines(systemModules, utf8)) {
                            lines.map(line -> jrtModules.resolve(line))
                                 .filter(mod -> Files.exists(mod))
                                 .forEach(mod -> setModule(fm, mod));
                        }
                    } else {
                        Map<String, List<Path>> module2Paths = new HashMap<>();

                        try (DirectoryStream<Path> dir = Files.newDirectoryStream(root)) {
                            for (Path section : dir) {
                                if (section.getFileName().toString().contains(ctSymVersion) &&
                                    !section.getFileName().toString().contains("-")) {
                                    try (DirectoryStream<Path> modules = Files.newDirectoryStream(section)) {
                                        for (Path module : modules) {
                                            module2Paths.computeIfAbsent(module.getFileName().toString(), dummy -> new ArrayList<>()).add(module);
                                        }
                                    }
                                }
                            }
                        }

                        fm.handleOption("--system", Arrays.asList("none").iterator());

                        for (Entry<String, List<Path>> e : module2Paths.entrySet()) {
                            fm.setLocationForModule(StandardLocation.SYSTEM_MODULES,
                                                    e.getKey(),
                                                    e.getValue());
                        }
                    }

                    return fm;
                } catch (IOException ex) {
                    throw new IllegalStateException(ex);
                }
            } else {
                throw new IllegalStateException("Cannot find ct.sym!");
            }
        }

        private static void setModule(StandardJavaFileManager fm, Path mod) {
            try {
                fm.setLocationForModule(StandardLocation.SYSTEM_MODULES,
                                        mod.getFileName().toString(),
                                        Collections.singleton(mod));
            } catch (IOException ex) {
                throw new IllegalStateException(ex);
            }
        }

        private static class SigJavaFileObject extends ForwardingJavaFileObject<JavaFileObject> {

            public SigJavaFileObject(JavaFileObject fileObject) {
                super(fileObject);
            }

            @Override
            public Kind getKind() {
                return Kind.CLASS;
            }

            @Override
            public boolean isNameCompatible(String simpleName, Kind kind) {
                return super.isNameCompatible(simpleName + ".sig", Kind.OTHER);
            }

            public JavaFileObject getDelegate() {
                return fileObject;
            }
        }

        @Override
        public String getSourceVersion() {
            return sourceVersion;
        }

        @Override
        public String getTargetVersion() {
            return sourceVersion;
        }

        @Override
        public List<PluginInfo<Processor>> getAnnotationProcessors() {
            return Collections.emptyList();
        }

        @Override
        public List<PluginInfo<Plugin>> getPlugins() {
            return Collections.emptyList();
        }

        @Override
        public List<String> getAdditionalOptions() {
            return Collections.emptyList();
        }

        @Override
        public void close() throws IOException {
            for (FileSystem fs : ctSym2FileSystem.values()) {
                fs.close();
            }
            ctSym2FileSystem.clear();
        }

    }

    static Path findCtSym() {
        String javaHome = System.getProperty("java.home");
        Path file = Paths.get(javaHome);
        // file == ${jdk.home}
        for (String name : symbolFileLocation)
            file = file.resolve(name);
        return file;
    }

}