/*
 * Copyright (c) 1997, 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 jdk.javadoc.internal.tool;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.BreakIterator;
import java.text.Collator;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.IllformedLocaleException;
import java.util.List;
import java.util.Locale;
import java.util.Objects;
import java.util.Set;
import java.util.function.Supplier;
import java.util.stream.Collectors;

import javax.tools.JavaFileManager;
import javax.tools.JavaFileObject;
import javax.tools.StandardJavaFileManager;

import com.sun.tools.javac.api.JavacTrees;
import com.sun.tools.javac.file.BaseFileManager;
import com.sun.tools.javac.file.JavacFileManager;
import com.sun.tools.javac.jvm.Target;
import com.sun.tools.javac.main.Arguments;
import com.sun.tools.javac.main.CommandLine;
import com.sun.tools.javac.util.ClientCodeException;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.Log;
import com.sun.tools.javac.util.StringUtils;

import jdk.javadoc.doclet.Doclet;
import jdk.javadoc.doclet.Doclet.Option;
import jdk.javadoc.doclet.DocletEnvironment;
import jdk.javadoc.doclet.StandardDoclet;
import jdk.javadoc.internal.Versions;
import jdk.javadoc.internal.tool.Main.Result;
import jdk.javadoc.internal.tool.ToolOptions.ToolOption;

import static javax.tools.DocumentationTool.Location.*;

import static jdk.javadoc.internal.tool.Main.Result.*;

Main program of Javadoc.
Previously named "Main".
 
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.
/**
 * Main program of Javadoc.
 * Previously named "Main".
 *
 *  <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 Start {

    
Context for this invocation. /** Context for this invocation. */
    private final Context context;

    private static final String ProgramName = "javadoc";

    private Messager messager;

    private final String docletName;

    private final ClassLoader classLoader;

    private Class<?> docletClass;

    private Doclet doclet;

    // used to determine the locale for the messager
    private Locale locale;

    
In API mode, exceptions thrown while calling the doclet are
propagated using ClientCodeException.
/**
     * In API mode, exceptions thrown while calling the doclet are
     * propagated using ClientCodeException.
     */
    private boolean apiMode;

    private JavaFileManager fileManager;

    private final ToolOptions options;

    Start() {
        this(null, null, null, null, null, null);
    }

    Start(PrintWriter outWriter, PrintWriter errWriter) {
        this(null, null, outWriter, errWriter, null, null);
    }

    Start(Context context, String programName,
            PrintWriter outWriter, PrintWriter errWriter,
            String docletName, ClassLoader classLoader) {
        this.context = context == null ? new Context() : context;
        String pname = programName == null ? ProgramName : programName;
        this.messager = (outWriter == null && errWriter == null)
                ? new Messager(this.context, pname)
                : new Messager(this.context, pname, outWriter, errWriter);
        this.docletName = docletName;
        this.classLoader = classLoader;
        this.docletClass = null;
        this.locale = Locale.getDefault();

        options = getToolOptions();
    }

    public Start(Context context) {
        this.docletClass = null;
        this.context = Objects.requireNonNull(context);
        this.apiMode = true;
        this.docletName = null;
        this.classLoader = null;
        this.locale = Locale.getDefault();

        Log log = context.get(Log.logKey);
        if (log instanceof Messager) {
            messager = (Messager) log;
        } else {
            PrintWriter out = context.get(Log.errKey);
            messager = (out == null)
                    ? new Messager(context, ProgramName)
                    : new Messager(context, ProgramName, out, out);
        }

        options = getToolOptions();
    }

    private ToolOptions getToolOptions() {
        ToolOptions.ShowHelper helper =  new ToolOptions.ShowHelper() {
            @Override
            public void usage() {
                showUsage("main.usage", ToolOption.Kind.STANDARD, "main.usage.foot");
            }

            @Override
            public void Xusage() {
                showUsage("main.Xusage", ToolOption.Kind.EXTENDED, "main.Xusage.foot");
            }

            @Override
            public void version() {
                showVersion("javadoc.version", orDefault(() -> Versions.shortVersionStringOf(toolVersion())));
            }

            @Override
            public void fullVersion() {
                showVersion("javadoc.fullversion", orDefault(() -> Versions.fullVersionStringOf(toolVersion())));
            }

            private String orDefault(Supplier<String> s) {
                try {
                    return s.get();
                } catch (RuntimeException e) {
                    assert false : e;
                    return Log.getLocalizedString("version.not.available");
                }
            }
        };
        return new ToolOptions(context, messager, helper);
    }

    private Runtime.Version toolVersion() {
        return Versions.javadocVersion();
    }

    private void showUsage() {
        showUsage("main.usage", ToolOption.Kind.STANDARD, "main.usage.foot");
    }

    private void showUsage(String headerKey, ToolOption.Kind kind, String footerKey) {
        messager.notice(headerKey);
        showToolOptions(kind);

        // let doclet print usage information
        if (docletClass != null) {
            showDocletOptions(kind == ToolOption.Kind.EXTENDED
                    ? Option.Kind.EXTENDED
                    : Option.Kind.STANDARD);
        }
        if (footerKey != null)
            messager.notice(footerKey);
    }

    private void showVersion(String labelKey, String value) {
        messager.notice(labelKey, messager.programName, value);
    }

    private void showToolOptions(ToolOption.Kind kind) {
        Comparator<ToolOption> comp = new Comparator<ToolOption>() {
            final Collator collator = Collator.getInstance(Locale.US);
            { collator.setStrength(Collator.PRIMARY); }

            @Override
            public int compare(ToolOption o1, ToolOption o2) {
                return collator.compare(o1.primaryName, o2.primaryName);
            }
        };

        options.getSupportedOptions().stream()
                    .filter(opt -> opt.kind == kind)
                    .sorted(comp)
                    .forEach(this::showToolOption);
    }

    private void showToolOption(ToolOption option) {
        List<String> names = option.getNames();
        String primaryName = option.primaryName;
        String parameters;
        if (option.hasArg || primaryName.endsWith(":")) {
            String sep = primaryName.endsWith(":")
                    || primaryName.equals(ToolOptions.AT)
                    || primaryName.equals(ToolOptions.J)
                    ? "" : " ";
            parameters = sep + option.getParameters(messager);
        } else {
            parameters = "";
        }
        String description = option.getDescription(messager);
        showOption(names, parameters, description);
    }

    private void showDocletOptions(Option.Kind kind) {
        String name = doclet.getName();
        Set<? extends Option> options = getSupportedOptionsOf(doclet);
        if (options.isEmpty()) {
            return;
        }
        messager.notice("main.doclet.usage.header", name);

        Comparator<Doclet.Option> comp = new Comparator<Doclet.Option>() {
            final Collator collator = Collator.getInstance(Locale.US);
            { collator.setStrength(Collator.PRIMARY); }

            @Override
            public int compare(Doclet.Option o1, Doclet.Option o2) {
                return collator.compare(o1.getNames().get(0), o2.getNames().get(0));
            }
        };

        options.stream()
                .filter(opt -> opt.getKind() == kind)
                .sorted(comp)
                .forEach(this::showDocletOption);
    }

    private void showDocletOption(Doclet.Option option) {
        List<String> names = option.getNames();
        String parameters;
        String primaryName = names.get(0);
        if (option.getArgumentCount() > 0 || primaryName.endsWith(":")) {
            String sep = primaryName.endsWith(":") ? "" : " ";
            parameters = sep + option.getParameters();
        } else {
            parameters = "";
        }
        String description = option.getDescription();
        showOption(names, parameters, description);
    }

    // The following constants are intended to format the output to
    // be similar to that of the java launcher: i.e. "java -help".

    
The indent for the option synopsis. /** The indent for the option synopsis. */
    private static final String SMALL_INDENT = " ".repeat(4);
    
The automatic indent for the description. /** The automatic indent for the description. */
    private static final String LARGE_INDENT = " ".repeat(18);
    
The space allowed for the synopsis, if the description is to be shown on the same line. /** The space allowed for the synopsis, if the description is to be shown on the same line. */
    private static final int DEFAULT_SYNOPSIS_WIDTH = 13;
    
The nominal maximum line length, when seeing if text will fit on a line. /** The nominal maximum line length, when seeing if text will fit on a line. */
    private static final int DEFAULT_MAX_LINE_LENGTH = 80;
    
The format for a single-line help entry. /** The format for a single-line help entry. */
    private static final String COMPACT_FORMAT = SMALL_INDENT + "%-" + DEFAULT_SYNOPSIS_WIDTH + "s %s";

    void showOption(List<String> names, String parameters, String description) {
        String synopses = names.stream()
                .map(s -> s + parameters)
                .collect(Collectors.joining(", "));
        // If option synopses and description fit on a single line of reasonable length,
        // display using COMPACT_FORMAT
        if (synopses.length() < DEFAULT_SYNOPSIS_WIDTH
                && !description.contains("\n")
                && (SMALL_INDENT.length() + DEFAULT_SYNOPSIS_WIDTH + 1 + description.length() <= DEFAULT_MAX_LINE_LENGTH)) {
            messager.printNotice(String.format(COMPACT_FORMAT, synopses, description));
            return;
        }

        // If option synopses fit on a single line of reasonable length, show that;
        // otherwise, show 1 per line
        if (synopses.length() <= DEFAULT_MAX_LINE_LENGTH) {
            messager.printNotice(SMALL_INDENT + synopses);
        } else {
            for (String name: names) {
                messager.printNotice(SMALL_INDENT + name + parameters);
            }
        }

        // Finally, show the description
        messager.printNotice(LARGE_INDENT + description.replace("\n", "\n" + LARGE_INDENT));
    }


    
Main program - external wrapper. In order to maintain backward
CLI compatibility, the execution is dispatched to the appropriate
Start mechanism, depending on the doclet variant.
The doclet tests are performed in the begin method, further on,
this is to minimize argument processing and most importantly the impact
of class loader creation, needed to detect the doclet class variants.
/**
     * Main program - external wrapper. In order to maintain backward
     * CLI compatibility, the execution is dispatched to the appropriate
     * Start mechanism, depending on the doclet variant.
     *
     * The doclet tests are performed in the begin method, further on,
     * this is to minimize argument processing and most importantly the impact
     * of class loader creation, needed to detect the doclet class variants.
     */
    @SuppressWarnings("deprecation")
    Result begin(String... argv) {
        // Preprocess @file arguments
        List<String> allArgs;
        try {
            allArgs = CommandLine.parse(List.of(argv));
        } catch (IOException e) {
            error("main.cant.read", e.getMessage());
            return ERROR;
        }
        return begin(allArgs, Collections.emptySet());
    }

    // Called by the JSR 199 API
    public boolean begin(Class<?> docletClass,
                         Iterable<String> options,
                         Iterable<? extends JavaFileObject> fileObjects)
    {
        this.docletClass = docletClass;
        List<String> opts = new ArrayList<>();
        for (String opt: options)
            opts.add(opt);

        return begin(opts, fileObjects).isOK();
    }

    private Result begin(List<String> options, Iterable<? extends JavaFileObject> fileObjects) {
        fileManager = context.get(JavaFileManager.class);
        if (fileManager == null) {
            JavacFileManager.preRegister(context);
            fileManager = context.get(JavaFileManager.class);
            if (fileManager instanceof BaseFileManager) {
                ((BaseFileManager) fileManager).autoClose = true;
            }
        }

        // Perform an initial scan of the options to determine the doclet to be used (if any),
        // so that it may participate in the main round of option processing.
        try {
            doclet = preprocess(options);
        } catch (ToolException te) {
            if (!te.result.isOK()) {
                if (te.message != null) {
                    messager.printError(te.message);
                }
                Throwable t = te.getCause();
                dumpStack(t == null ? te : t);
            }
            return te.result;
        } catch (OptionException oe) {
            if (oe.message != null) {
                messager.printError(oe.message);
            }
            oe.m.run();
            Throwable t = oe.getCause();
            dumpStack(t == null ? oe : t);
            return oe.result;
        }

        Result result = OK;
        try {
            result = parseAndExecute(options, fileObjects);
        } catch (com.sun.tools.javac.main.Option.InvalidValueException e) {
            messager.printError(e.getMessage());
            Throwable t = e.getCause();
            dumpStack(t == null ? e : t);
            return ERROR;
        } catch (OptionException oe) {
            if (oe.message != null)
                messager.printError(oe.message);

            oe.m.run();
            Throwable t = oe.getCause();
            dumpStack(t == null ? oe : t);
            return oe.result;
        } catch (ToolException exc) {
            if (exc.message != null) {
                messager.printError(exc.message);
            }
            Throwable t = exc.getCause();
            if (result == ABNORMAL) {
                reportInternalError(t == null ? exc : t);
            } else {
                dumpStack(t == null ? exc : t);
            }
            return exc.result;
        } catch (OutOfMemoryError ee) {
            error("main.out.of.memory");
            result = SYSERR;
            dumpStack(ee);
        } catch (ClientCodeException e) {
            // simply rethrow these exceptions, to be caught and handled by JavadocTaskImpl
            throw e;
        } catch (Error | Exception ee) {
            error("main.fatal.error", ee);
            reportInternalError(ee);
            result = ABNORMAL;
        } finally {
            if (fileManager != null
                    && fileManager instanceof BaseFileManager
                    && ((BaseFileManager) fileManager).autoClose) {
                try {
                    fileManager.close();
                } catch (IOException ignore) {}
            }
            if (this.options.rejectWarnings() && messager.hasWarnings()) {
                error("main.warnings.Werror");
            }
            boolean haveErrors = messager.hasErrors();
            if (!result.isOK() && !haveErrors) {
                // the doclet failed, but nothing reported, flag it!.
                error("main.unknown.error");
            }
            if (haveErrors && result.isOK()) {
                result = ERROR;
            }
            messager.printErrorWarningCounts();
            messager.flush();
        }
        return result;
    }

    private void reportInternalError(Throwable t) {
        messager.printErrorUsingKey("doclet.internal.report.bug");
        dumpStack(true, t);
    }

    private void dumpStack(Throwable t) {
        dumpStack(false, t);
    }

    private void dumpStack(boolean enabled, Throwable t) {
        if (t != null && (enabled || options.dumpOnError())) {
            t.printStackTrace(System.err);
        }
    }

    
Main program - internal
/**
     * Main program - internal
     */
    private Result parseAndExecute(List<String> argList, Iterable<? extends JavaFileObject> fileObjects)
            throws ToolException, OptionException, com.sun.tools.javac.main.Option.InvalidValueException
    {
        final long startNanos = System.nanoTime();

        List<String> javaNames = new ArrayList<>();

        // Make sure no obsolete source/target messages are reported
        try {
            options.processCompilerOption(com.sun.tools.javac.main.Option.XLINT_CUSTOM, "-Xlint:-options");
        } catch (com.sun.tools.javac.main.Option.InvalidValueException ignore) {
        }

        Arguments arguments = Arguments.instance(context);
        arguments.init(ProgramName);
        arguments.allowEmpty();

        doclet.init(locale, messager);
        int beforeCount = messager.nerrors;
        boolean success = parseArgs(argList, javaNames);
        int afterCount = messager.nerrors;
        if (!success && beforeCount == afterCount) { // if there were failures but they have not been reported
            return CMDERR;
        }

        if (!arguments.handleReleaseOptions(extra -> true)) {
            // Arguments does not always increase the error count in the
            // case of errors, so increment the error count only if it has
            // not been updated previously, preventing complaints by callers
            if (!messager.hasErrors() && !messager.hasWarnings())
                messager.nerrors++;
            return CMDERR;
        }

        if (!arguments.validate()) {
            // Arguments does not always increase the error count in the
            // case of errors, so increment the error count only if it has
            // not been updated previously, preventing complaints by callers
            if (!messager.hasErrors() && !messager.hasWarnings())
                messager.nerrors++;
            return CMDERR;
        }

        if (fileManager instanceof BaseFileManager) {
            ((BaseFileManager) fileManager).handleOptions(options.fileManagerOptions());
        }

        String mr = com.sun.tools.javac.main.Option.MULTIRELEASE.primaryName;
        if (fileManager.isSupportedOption(mr) == 1) {
            Target target = Target.instance(context);
            List<String> list = List.of(target.multiReleaseValue());
            fileManager.handleOption(mr, list.iterator());
        }
        options.compilerOptions().notifyListeners();

        if (options.modules().isEmpty()) {
            if (options.subpackages().isEmpty()) {
                if (javaNames.isEmpty() && isEmpty(fileObjects)) {
                    String text = messager.getText("main.No_modules_packages_or_classes_specified");
                    throw new ToolException(CMDERR, text);
                }
            }
        }

        JavadocTool comp = JavadocTool.make0(context);
        if (comp == null) return ABNORMAL;

        DocletEnvironment docEnv = comp.getEnvironment(options, javaNames, fileObjects);

        // release resources
        comp = null;

        if (options.breakIterator() || !locale.getLanguage().equals(Locale.ENGLISH.getLanguage())) {
            JavacTrees trees = JavacTrees.instance(context);
            trees.setBreakIterator(BreakIterator.getSentenceInstance(locale));
        }
        // pass off control to the doclet
        Result returnStatus = docEnv != null && doclet.run(docEnv)
                ? OK
                : ERROR;

        // We're done.
        if (options.verbose()) {
            long elapsedMillis = (System.nanoTime() - startNanos) / 1_000_000;
            messager.notice("main.done_in", Long.toString(elapsedMillis));
        }

        return returnStatus;
    }

    boolean matches(List<String> names, String arg) {
        for (String name : names) {
            if (StringUtils.toLowerCase(name).equals(StringUtils.toLowerCase(arg)))
                return true;
        }
        return false;
    }

    boolean matches(Doclet.Option option, String arg) {
        if (matches(option.getNames(), arg))
             return true;
        int sep = arg.indexOf(':');
        String targ = arg.substring(0, sep + 1);
        return matches(option.getNames(), targ);
    }

    private Set<? extends Doclet.Option> docletOptions = null;

    /*
     * Consumes an option along with its arguments. Returns an advanced index
     * modulo the sign. If the value is negative, it means there was a failure
     * processing one or more options.
     */
    int consumeDocletOption(int idx, List<String> args, boolean isToolOption) throws OptionException {
        if (docletOptions == null) {
            docletOptions = getSupportedOptionsOf(doclet);
        }
        String arg = args.get(idx);
        String argBase, argVal;
        if (arg.startsWith("--") && arg.contains("=")) {
            int sep = arg.indexOf("=");
            argBase = arg.substring(0, sep);
            argVal = arg.substring(sep + 1);
        } else {
            argBase = arg;
            argVal = null;
        }
        int m = 1;
        String text = null;
        for (Doclet.Option opt : docletOptions) {
            if (matches(opt, argBase)) {
                if (argVal != null) {
                    switch (opt.getArgumentCount()) {
                        case 0:
                            text = messager.getText("main.unnecessary_arg_provided", argBase);
                            throw new OptionException(ERROR, this::showUsage, text);
                        case 1:
                            if (!opt.process(arg, Collections.singletonList(argVal))) {
                                m = -1;
                            }
                            break;
                        default:
                            text = messager.getText("main.only_one_argument_with_equals", argBase);
                            throw new OptionException(ERROR, this::showUsage, text);
                    }
                } else {
                    if (args.size() - idx - 1 < opt.getArgumentCount()) {
                        text = messager.getText("main.requires_argument", arg);
                        throw new OptionException(ERROR, this::showUsage, text);
                    }
                    if (!opt.process(arg, args.subList(idx + 1, idx + 1 + opt.getArgumentCount()))) {
                        m = -1;
                    }
                    idx += opt.getArgumentCount();
                }
                return m * idx;
            }
        }
        // check if arg is accepted by the tool before emitting error
        if (!isToolOption) {
            text = messager.getText("main.invalid_flag", arg);
            throw new OptionException(ERROR, this::showUsage, text);
        }
        return m * idx;
    }

    private static Set<? extends Option> getSupportedOptionsOf(Doclet doclet) {
        Set<? extends Option> options = doclet.getSupportedOptions();
        return options == null ? Set.of() : options;
    }

    
Performs an initial pass over the options, primarily to determine
the doclet to be used (if any), so that it may participate in the
main round of option decoding. This avoids having to specify that
the options to specify the doclet should appear before any options
that are handled by the doclet.
The downside of this initial phase is that we have to skip over
unknown options, and assume that we can reliably detect the options
we need to handle.
Params:
argv – the arguments to be processed
Throws:
ToolException – if an error occurs initializing the doclet
OptionException – if an error occurs while processing an option
Returns:
the doclet/**
     * Performs an initial pass over the options, primarily to determine
     * the doclet to be used (if any), so that it may participate in the
     * main round of option decoding. This avoids having to specify that
     * the options to specify the doclet should appear before any options
     * that are handled by the doclet.
     *
     * The downside of this initial phase is that we have to skip over
     * unknown options, and assume that we can reliably detect the options
     * we need to handle.
     *
     * @param argv the arguments to be processed
     * @return the doclet
     * @throws ToolException if an error occurs initializing the doclet
     * @throws OptionException if an error occurs while processing an option
     */
    private Doclet preprocess(List<String> argv) throws ToolException, OptionException {
        // doclet specifying arguments
        String userDocletPath = null;
        String userDocletName = null;

        // Step 1: loop through the args, set locale early on, if found.
        for (int i = 0; i < argv.size(); i++) {
            String arg = argv.get(i);
            if (arg.equals(ToolOptions.DUMP_ON_ERROR)) {
                // although this option is not needed in order to initialize the doclet,
                // it is helpful if it is set before trying to initialize the doclet
                options.setDumpOnError(true);
            } else if (arg.equals(ToolOptions.LOCALE)) {
                checkOneArg(argv, i++);
                String lname = argv.get(i);
                locale = getLocale(lname);
            } else if (arg.equals(ToolOptions.DOCLET)) {
                checkOneArg(argv, i++);
                if (userDocletName != null) {
                    if (apiMode) {
                        throw new IllegalArgumentException("More than one doclet specified (" +
                                userDocletName + " and " + argv.get(i) + ").");
                    }
                    String text = messager.getText("main.more_than_one_doclet_specified_0_and_1",
                            userDocletName, argv.get(i));
                    throw new ToolException(CMDERR, text);
                }
                if (docletName != null) {
                    if (apiMode) {
                        throw new IllegalArgumentException("More than one doclet specified (" +
                                docletName + " and " + argv.get(i) + ").");
                    }
                    String text = messager.getText("main.more_than_one_doclet_specified_0_and_1",
                            docletName, argv.get(i));
                    throw new ToolException(CMDERR, text);
                }
                userDocletName = argv.get(i);
            } else if (arg.equals(ToolOptions.DOCLET_PATH)) {
                checkOneArg(argv, i++);
                if (userDocletPath == null) {
                    userDocletPath = argv.get(i);
                } else {
                    userDocletPath += File.pathSeparator + argv.get(i);
                }
            }
        }

        // Step 3: doclet name specified ? if so find a ClassLoader,
        // and load it.
        if (docletClass == null) {
            if (userDocletName != null) {
                ClassLoader cl = classLoader;
                if (cl == null) {
                    if (!fileManager.hasLocation(DOCLET_PATH)) {
                        List<File> paths = new ArrayList<>();
                        if (userDocletPath != null) {
                            for (String pathname : userDocletPath.split(File.pathSeparator)) {
                                paths.add(new File(pathname));
                            }
                        }
                        try {
                            ((StandardJavaFileManager)fileManager).setLocation(DOCLET_PATH, paths);
                        } catch (IOException ioe) {
                            if (apiMode) {
                                throw new IllegalArgumentException("Could not set location for " +
                                        userDocletPath, ioe);
                            }
                            String text = messager.getText("main.doclet_could_not_set_location",
                                    userDocletPath);
                            throw new ToolException(CMDERR, text, ioe);
                        }
                    }
                    cl = fileManager.getClassLoader(DOCLET_PATH);
                    if (cl == null) {
                        // despite doclet specified on cmdline no classloader found!
                        if (apiMode) {
                            throw new IllegalArgumentException("Could not obtain classloader to load "

                                    + userDocletPath);
                        }
                        String text = messager.getText("main.doclet_no_classloader_found",
                                userDocletName);
                        throw new ToolException(CMDERR, text);
                    }
                }
                docletClass = loadDocletClass(userDocletName, cl);
            } else if (docletName != null){
                docletClass = loadDocletClass(docletName, getClass().getClassLoader());
            } else {
                docletClass = StandardDoclet.class;
            }
        }

        if (Doclet.class.isAssignableFrom(docletClass)) {
            messager.setLocale(Locale.getDefault());  // use default locale for console messages
            try {
                Object o = docletClass.getConstructor().newInstance();
                doclet = (Doclet) o;
            } catch (ReflectiveOperationException exc) {
                if (apiMode) {
                    throw new ClientCodeException(exc);
                }
                String text = messager.getText("main.could_not_instantiate_class", docletClass.getName());
                throw new ToolException(ERROR, text);
            }
        } else {
            String text = messager.getText("main.not_a_doclet", docletClass.getName());
            throw new ToolException(ERROR, text);
        }
        return doclet;
    }

    private Class<?> loadDocletClass(String docletName, ClassLoader classLoader) throws ToolException {
        try {
            return classLoader == null ? Class.forName(docletName) : classLoader.loadClass(docletName);
        } catch (ClassNotFoundException cnfe) {
            if (apiMode) {
                throw new IllegalArgumentException("Cannot find doclet class " + docletName);
            }
            String text = messager.getText("main.doclet_class_not_found", docletName);
            throw new ToolException(CMDERR, text, cnfe);
        }
    }

    private boolean parseArgs(List<String> args, List<String> javaNames)
            throws OptionException, com.sun.tools.javac.main.Option.InvalidValueException
    {
        boolean success = true;
        for (int i = 0; i < args.size(); i++) {
            String arg = args.get(i);
            ToolOption o = options.getOption(arg);
            if (o != null) {
                // handle a doclet argument that may be needed however
                // don't increment the index, and allow the tool to consume args
                if (consumeDocletOption(i, args, true) < 0) {
                    success = false;
                }
                if (o.hasArg) {
                    if (arg.startsWith("--") && arg.contains("=")) {
                        o.process(arg.substring(arg.indexOf('=') + 1));
                    } else {
                        checkOneArg(args, i++);
                        o.process(args.get(i));
                    }
                } else if (o.hasSuffix) {
                    o.process(arg);
                } else {
                    o.process();
                }
            } else if (arg.startsWith("-XD")) {
                // hidden javac options
                String s = arg.substring("-XD".length());
                int eq = s.indexOf('=');
                String key = (eq < 0) ? s : s.substring(0, eq);
                String value = (eq < 0) ? s : s.substring(eq + 1);
                options.compilerOptions().put(key, value);
            } else if (arg.startsWith("-")) {
                i = consumeDocletOption(i, args, false);
                if (i < 0) {
                    i = -i;
                    success = false;
                }
            } else {
                javaNames.add(arg);
            }
        }
        return success;
    }

    private <T> boolean isEmpty(Iterable<T> iter) {
        return !iter.iterator().hasNext();
    }

    
Check the one arg option.
Error and exit if one argument is not provided.
/**
     * Check the one arg option.
     * Error and exit if one argument is not provided.
     */
    private void checkOneArg(List<String> args, int index) throws OptionException {
        if ((index + 1) >= args.size() || args.get(index + 1).startsWith("-d")) {
            String text = messager.getText("main.requires_argument", args.get(index));
            throw new OptionException(CMDERR, this::showUsage, text);
        }
    }

    void error(String key, Object... args) {
        messager.printErrorUsingKey(key, args);
    }

    
Get the locale if specified on the command line
else return null and if locale option is not used
then return default locale.
/**
     * Get the locale if specified on the command line
     * else return null and if locale option is not used
     * then return default locale.
     */
    private Locale getLocale(String localeName) throws ToolException {
        try {
            // Tolerate, at least for a while, the older syntax accepted by javadoc,
            // using _ as the separator
            localeName = localeName.replace("_", "-");
            Locale l =  new Locale.Builder().setLanguageTag(localeName).build();
            // Ensure that a non-empty language is available for the <HTML lang=...> element
            return (l.getLanguage().isEmpty()) ? Locale.ENGLISH : l;
        } catch (IllformedLocaleException e) {
            String text = messager.getText("main.malformed_locale_name", localeName);
            throw new ToolException(CMDERR, text);
        }
    }

}