/*

 * Copyright (c) 2005, 2013, 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 javax.lang.model;

import java.util.Collections;

import java.util.Set;

import java.util.HashSet;

/**

 * Source versions of the Java™ programming language.

 *

 * See the appropriate edition of

 * <cite>The Java&trade; Language Specification</cite>

 * for information about a particular source version.

 *

 * <p>Note that additional source version constants will be added to

 * model future releases of the language.

 *

 * @author Joseph D. Darcy

 * @author Scott Seligman

 * @author Peter von der Ahé

 * @since 1.6

 */

public enum SourceVersion {

    /*

     * Summary of language evolution

     * 1.1: nested classes

     * 1.2: strictfp

     * 1.3: no changes

     * 1.4: assert

     * 1.5: annotations, generics, autoboxing, var-args...

     * 1.6: no changes

     * 1.7: diamond syntax, try-with-resources, etc.

     * 1.8: lambda expressions and default methods

     * 1.9: To be determined

     */

    /**

     * The original version.

     *

     * The language described in

     * <cite>The Java&trade; Language Specification, First Edition</cite>.

     */

    RELEASE_0,

    /**

     * The version recognized by the Java Platform 1.1.

     *

     * The language is {@code RELEASE_0} augmented with nested classes as described in the 1.1 update to

     * <cite>The Java&trade; Language Specification, First Edition</cite>.

     */

    RELEASE_1,

    /**

     * The version recognized by the Java 2 Platform, Standard Edition,

     * v 1.2.

     *

     * The language described in

     * <cite>The Java&trade; Language Specification,

     * Second Edition</cite>, which includes the {@code

     * strictfp} modifier.

     */

    RELEASE_2,

    /**

     * The version recognized by the Java 2 Platform, Standard Edition,

     * v 1.3.

     *

     * No major changes from {@code RELEASE_2}.

     */

    RELEASE_3,

    /**

     * The version recognized by the Java 2 Platform, Standard Edition,

     * v 1.4.

     *

     * Added a simple assertion facility.

     */

    RELEASE_4,

    /**

     * The version recognized by the Java 2 Platform, Standard

     * Edition 5.0.

     *

     * The language described in

     * <cite>The Java&trade; Language Specification,

     * Third Edition</cite>.  First release to support

     * generics, annotations, autoboxing, var-args, enhanced {@code

     * for} loop, and hexadecimal floating-point literals.

     */

    RELEASE_5,

    /**

     * The version recognized by the Java Platform, Standard Edition

     * 6.

     *

     * No major changes from {@code RELEASE_5}.

     */

    RELEASE_6,

    /**

     * The version recognized by the Java Platform, Standard Edition

     * 7.

     *

     * Additions in this release include, diamond syntax for

     * constructors, {@code try}-with-resources, strings in switch,

     * binary literals, and multi-catch.

     * @since 1.7

     */

    RELEASE_7,

    /**

     * The version recognized by the Java Platform, Standard Edition

     * 8.

     *

     * Additions in this release include lambda expressions and default methods.

     * @since 1.8

     */

    RELEASE_8,

    /**

     * The version recognized by the Java Platform, Standard Edition

     * 9.

     *

     * @since 1.9

     */

     RELEASE_9;

    // Note that when adding constants for newer releases, the

    // behavior of latest() and latestSupported() must be updated too.

    /**

     * Returns the latest source version that can be modeled.

     *

     * @return the latest source version that can be modeled

     */

    public static SourceVersion latest() {

        return RELEASE_9;

    }

    private static final SourceVersion latestSupported = getLatestSupported();

    private static SourceVersion getLatestSupported() {

        try {

            String specVersion = System.getProperty("java.specification.version");

            switch (specVersion) {

                case "1.9":

                    return RELEASE_9;

                case "1.8":

                    return RELEASE_8;

                case "1.7":

                    return RELEASE_7;

                case "1.6":

                    return RELEASE_6;

            }

        } catch (SecurityException se) {}

        return RELEASE_5;

    }

    /**

     * Returns the latest source version fully supported by the

     * current execution environment.  {@code RELEASE_5} or later must

     * be returned.

     *

     * @return the latest source version that is fully supported

     */

    public static SourceVersion latestSupported() {

        return latestSupported;

    }

    /**

     * Returns whether or not {@code name} is a syntactically valid

     * identifier (simple name) or keyword in the latest source

     * version.  The method returns {@code true} if the name consists

     * of an initial character for which {@link

     * Character#isJavaIdentifierStart(int)} returns {@code true},

     * followed only by characters for which {@link

     * Character#isJavaIdentifierPart(int)} returns {@code true}.

     * This pattern matches regular identifiers, keywords, and the

     * literals {@code "true"}, {@code "false"}, and {@code "null"}.

     * The method returns {@code false} for all other strings.

     *

     * @param name the string to check

     * @return {@code true} if this string is a

     * syntactically valid identifier or keyword, {@code false}

     * otherwise.

     */

    public static boolean isIdentifier(CharSequence name) {

        String id = name.toString();

        if (id.length() == 0) {

            return false;

        }

        int cp = id.codePointAt(0);

        if (!Character.isJavaIdentifierStart(cp)) {

            return false;

        }

        for (int i = Character.charCount(cp);

                i < id.length();

                i += Character.charCount(cp)) {

            cp = id.codePointAt(i);

            if (!Character.isJavaIdentifierPart(cp)) {

                return false;

            }

        }

        return true;

    }

    /**

     *  Returns whether or not {@code name} is a syntactically valid

     *  qualified name in the latest source version.  Unlike {@link

     *  #isIdentifier isIdentifier}, this method returns {@code false}

     *  for keywords and literals.

     *

     * @param name the string to check

     * @return {@code true} if this string is a

     * syntactically valid name, {@code false} otherwise.

     * @jls 6.2 Names and Identifiers

     */

    public static boolean isName(CharSequence name) {

        String id = name.toString();

        for(String s : id.split("\\.", -1)) {

            if (!isIdentifier(s) || isKeyword(s))

                return false;

        }

        return true;

    }

    private final static Set<String> keywords;

    static {

        Set<String> s = new HashSet<>();

        String [] kws = {

            "abstract", "continue",     "for",          "new",          "switch",

            "assert",   "default",      "if",           "package",      "synchronized",

            "boolean",  "do",           "goto",         "private",      "this",

            "break",    "double",       "implements",   "protected",    "throw",

            "byte",     "else",         "import",       "public",       "throws",

            "case",     "enum",         "instanceof",   "return",       "transient",

            "catch",    "extends",      "int",          "short",        "try",

            "char",     "final",        "interface",    "static",       "void",

            "class",    "finally",      "long",         "strictfp",     "volatile",

            "const",    "float",        "native",       "super",        "while",

            // literals

            "null",     "true",         "false"

        };

        for(String kw : kws)

            s.add(kw);

        keywords = Collections.unmodifiableSet(s);

    }

    /**

     *  Returns whether or not {@code s} is a keyword or literal in the

     *  latest source version.

     *

     * @param s the string to check

     * @return {@code true} if {@code s} is a keyword or literal, {@code false} otherwise.

     */

    public static boolean isKeyword(CharSequence s) {

        return keywords.contains(s.toString());

    }

}