/*

 * Copyright (c) 2015, 2018, 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

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 */

package jdk.internal.editor.external;

import java.io.IOException;

import java.nio.charset.Charset;

import java.nio.file.ClosedWatchServiceException;

import java.nio.file.FileSystems;

import java.nio.file.FileVisitResult;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.SimpleFileVisitor;

import java.nio.file.WatchKey;

import java.nio.file.WatchService;

import java.nio.file.attribute.BasicFileAttributes;

import java.util.Arrays;

import java.util.Scanner;

import java.util.function.Consumer;

import java.util.stream.Collectors;

import java.util.stream.Stream;

import static java.nio.file.StandardWatchEventKinds.ENTRY_CREATE;

import static java.nio.file.StandardWatchEventKinds.ENTRY_DELETE;

import static java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY;

/**

 * Wrapper for controlling an external editor.

 */

public class ExternalEditor {

    private final Consumer<String> errorHandler;

    private final Consumer<String> saveHandler;

    private final boolean wait;

    private final Runnable suspendInteractiveInput;

    private final Runnable resumeInteractiveInput;

    private final Runnable promptForNewLineToEndWait;

    private WatchService watcher;

    private Thread watchedThread;

    private Path dir;

    private Path tmpfile;

    /**

     * Launch an external editor.

     *

     * @param cmd the command to launch (with parameters)

     * @param initialText initial text in the editor buffer

     * @param errorHandler handler for error messages

     * @param saveHandler handler sent the buffer contents on save

     * @param suspendInteractiveInput a callback to suspend caller (shell) input

     * @param resumeInteractiveInput a callback to resume caller input

     * @param wait true, if editor process termination cannot be used to

     * determine when done

     * @param promptForNewLineToEndWait a callback to prompt for newline if

     * wait==true

     */

    public static void edit(String[] cmd, String initialText,

            Consumer<String> errorHandler,

            Consumer<String> saveHandler,

            Runnable suspendInteractiveInput,

            Runnable resumeInteractiveInput,

            boolean wait,

            Runnable promptForNewLineToEndWait) {

        ExternalEditor ed = new ExternalEditor(errorHandler, saveHandler, suspendInteractiveInput,

             resumeInteractiveInput, wait, promptForNewLineToEndWait);

        ed.edit(cmd, initialText);

    }

    ExternalEditor(Consumer<String> errorHandler,

            Consumer<String> saveHandler,

            Runnable suspendInteractiveInput,

            Runnable resumeInteractiveInput,

            boolean wait,

            Runnable promptForNewLineToEndWait) {

        this.errorHandler = errorHandler;

        this.saveHandler = saveHandler;

        this.wait = wait;

        this.suspendInteractiveInput = suspendInteractiveInput;

        this.resumeInteractiveInput = resumeInteractiveInput;

        this.promptForNewLineToEndWait = promptForNewLineToEndWait;

    }

    private void edit(String[] cmd, String initialText) {

        try {

            setupWatch(initialText);

            launch(cmd);

        } catch (IOException ex) {

            errorHandler.accept(ex.getMessage());

        } finally {

            deleteDirectory();

        }

    }

    /**

     * Creates a WatchService and registers the given directory

     */

    private void setupWatch(String initialText) throws IOException {

        this.watcher = FileSystems.getDefault().newWatchService();

        this.dir = Files.createTempDirectory("extedit");

        this.tmpfile = Files.createTempFile(dir, null, ".java");

        Files.write(tmpfile, initialText.getBytes(Charset.forName("UTF-8")));

        dir.register(watcher,

                ENTRY_CREATE,

                ENTRY_DELETE,

                ENTRY_MODIFY);

        watchedThread = new Thread(() -> {

            for (;;) {

                WatchKey key;

                try {

                    key = watcher.take();

                } catch (ClosedWatchServiceException ex) {

                    // The watch service has been closed, we are done

                    break;

                } catch (InterruptedException ex) {

                    // tolerate an interrupt

                    continue;

                }

                if (!key.pollEvents().isEmpty()) {

                    saveFile();

                }

                boolean valid = key.reset();

                if (!valid) {

                    // The watch service has been closed, we are done

                    break;

                }

            }

        });

        watchedThread.start();

    }

    private void launch(String[] cmd) throws IOException {

        String[] params = Arrays.copyOf(cmd, cmd.length + 1);

        params[cmd.length] = tmpfile.toString();

        ProcessBuilder pb = new ProcessBuilder(params);

        pb = pb.inheritIO();

        try {

            suspendInteractiveInput.run();

            Process process = pb.start();

            // wait to exit edit mode in one of these ways...

            if (wait) {

                // -wait option -- ignore process exit, wait for carriage-return

                Scanner scanner = new Scanner(System.in);

                promptForNewLineToEndWait.run();

                scanner.nextLine();

            } else {

                // wait for process to exit

                process.waitFor();

            }

        } catch (IOException ex) {

            errorHandler.accept("process IO failure: " + ex.getMessage());

        } catch (InterruptedException ex) {

            errorHandler.accept("process interrupt: " + ex.getMessage());

        } finally {

            try {

                watcher.close();

                watchedThread.join(); //so that saveFile() is finished.

                saveFile();

            } catch (InterruptedException ex) {

                errorHandler.accept("process interrupt: " + ex.getMessage());

            } finally {

                resumeInteractiveInput.run();

            }

        }

    }

    private void saveFile() {

        try (Stream<String> lines = Files.lines(tmpfile)) {

            saveHandler.accept(lines.collect(Collectors.joining("\n", "", "\n")));

        } catch (IOException ex) {

            errorHandler.accept("Failure in read edit file: " + ex.getMessage());

        }

    }

    private void deleteDirectory() {

        try {

            Files.walkFileTree(dir, new SimpleFileVisitor<Path>() {

                @Override

                public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)

                        throws IOException {

                    Files.delete(file);

                    return FileVisitResult.CONTINUE;

                }

                @Override

                public FileVisitResult postVisitDirectory(Path directory, IOException fail)

                        throws IOException {

                    if (fail == null) {

                        Files.delete(directory);

                        return FileVisitResult.CONTINUE;

                    }

                    throw fail;

                }

            });

        } catch (IOException exc) {

            // ignore: The end-user will not want to see this, it is in a temp

            // directory so it will go away eventually, and tests verify that

            // the deletion is occurring.

        }

    }

}