/*

 * Copyright (c) 2005, 2019, 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 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

     *   9: modules, small cleanups to 1.7 and 1.8 changes

     *  10: local-variable type inference (var)

     *  11: local-variable syntax for lambda parameters

     */

    /**

     * 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.

     *

     * Additions in this release include modules and removal of a

     * single underscore from the set of legal identifier names.

     *

     * @since 9

     */

     RELEASE_9,

    /**

     * The version recognized by the Java Platform, Standard Edition

     * 10.

     *

     * Additions in this release include local-variable type inference

     * ({@code var}).

     *

     * @since 10

     */

     RELEASE_10,

    /**

     * The version recognized by the Java Platform, Standard Edition

     * 11.

     *

     * Additions in this release include local-variable syntax for

     * lambda parameters.

     *

     * @since 11

     */

     RELEASE_11,

    /**

     * The version recognized by the Java Platform, Standard Edition

     * 12.

     *

     * @since 12

     */

     RELEASE_12,

    /**

     * The version recognized by the Java Platform, Standard Edition

     * 13.

     *

     * @since 13

     */

     RELEASE_13;

    // 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_13;

    }

    private static final SourceVersion latestSupported = getLatestSupported();

    /*

     * The integer version to enum constant mapping implemented by

     * this method assumes the JEP 322: "Time-Based Release

     * Versioning" scheme is in effect. This scheme began in JDK

     * 10. If the JDK versioning scheme is revised, this method may

     * need to be updated accordingly.

     */

    private static SourceVersion getLatestSupported() {

        int intVersion = Runtime.version().feature();

        return (intVersion >= 11) ?

            valueOf("RELEASE_" + Math.min(13, intVersion)):

            RELEASE_10;

    }

    /**

     * Returns the latest source version fully supported by the

     * current execution environment.  {@code RELEASE_9} or later must

     * be returned.

     *

     * @apiNote This method is included alongside {@link latest} to

     * allow identification of situations where the language model API

     * is running on a platform version different than the latest

     * version modeled by the API. One way that sort of situation can

     * occur is if an IDE or similar tool is using the API to model

     * source version <i>N</i> while running on platform version

     * (<i>N</i>&nbsp;-&nbsp;1). Running in this configuration is

     * supported by the API. Running an API on platform versions

     * earlier than (<i>N</i>&nbsp;-&nbsp;1) or later than <i>N</i>

     * may or may not work as an implementation detail. If an

     * annotation processor was generating code to run under the

     * current execution environment, the processor should only use

     * platform features up to the {@code latestSupported} release,

     * which may be earlier than the {@code latest} release.

     *

     * @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, restricted

     * keywords, restricted identifiers and the literals {@code "true"},

     * {@code "false"}, {@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, boolean literals, and the null literal.

     *

     * This method returns {@code true} for <i>restricted

     * keywords</i> and <i>restricted identifiers</i>

     *

     * @param name the string to check

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

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

     * @jls 3.9 Keywords

     * @jls 6.2 Names and Identifiers

     */

    public static boolean isName(CharSequence name) {

        return isName(name, latest());

    }

    /**

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

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

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

     * for keywords, boolean literals, and the null literal.

     *

     * This method returns {@code true} for <i>restricted

     * keywords</i> and <i>restricted identifiers</i>

     *

     * @param name the string to check

     * @param version the version to use

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

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

     * @jls 3.9 Keywords

     * @jls 6.2 Names and Identifiers

     * @since 9

     */

    public static boolean isName(CharSequence name, SourceVersion version) {

        String id = name.toString();

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

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

                return false;

        }

        return true;

    }

    /**

     * Returns whether or not {@code s} is a keyword, boolean literal,

     * or null literal in the latest source version.

     * This method returns {@code false} for <i>restricted

     * keywords</i> and <i>restricted identifiers</i>.

     *

     * @param s the string to check

     * @return {@code true} if {@code s} is a keyword, or boolean

     * literal, or null literal, {@code false} otherwise.

     * @jls 3.9 Keywords

     * @jls 3.10.3 Boolean Literals

     * @jls 3.10.7 The Null Literal

     */

    public static boolean isKeyword(CharSequence s) {

        return isKeyword(s, latest());

    }

    /**

     * Returns whether or not {@code s} is a keyword, boolean literal,

     * or null literal in the given source version.

     * This method returns {@code false} for <i>restricted

     * keywords</i> and <i>restricted identifiers</i>.

     *

     * @param s the string to check

     * @param version the version to use

     * @return {@code true} if {@code s} is a keyword, or boolean

     * literal, or null literal, {@code false} otherwise.

     * @jls 3.9 Keywords

     * @jls 3.10.3 Boolean Literals

     * @jls 3.10.7 The Null Literal

     * @since 9

     */

    public static boolean isKeyword(CharSequence s, SourceVersion version) {

        String id = s.toString();

        switch(id) {

            // A trip through history

        case "strictfp":

            return version.compareTo(RELEASE_2) >= 0;

        case "assert":

            return version.compareTo(RELEASE_4) >= 0;

        case "enum":

            return version.compareTo(RELEASE_5) >= 0;

        case "_":

            return version.compareTo(RELEASE_9) >= 0;

            // Keywords common across versions

            // Modifiers

        case "public":    case "protected": case "private":

        case "abstract":  case "static":    case "final":

        case "transient": case "volatile":  case "synchronized":

        case "native":

            // Declarations

        case "class":     case "interface": case "extends":

        case "package":   case "throws":    case "implements":

            // Primitive types and void

        case "boolean":   case "byte":      case "char":

        case "short":     case "int":       case "long":

        case "float":     case "double":

        case "void":

            // Control flow

        case "if":      case "else":

        case "try":     case "catch":    case "finally":

        case "do":      case "while":

        case "for":     case "continue":

        case "switch":  case "case":     case "default":

        case "break":   case "throw":    case "return":

            // Other keywords

        case  "this":   case "new":      case "super":

        case "import":  case "instanceof":

            // Forbidden!

        case "goto":        case "const":

            // literals

        case "null":         case "true":       case "false":

            return true;

        default:

            return false;

        }

    }

}