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The ANTLR 4 grammar compiler.
There is a newer version: 4.13.2
/*
 * Copyright (c) 2012-2016 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

package org.antlr.v4.codegen.target;

import org.antlr.v4.codegen.CodeGenerator;
import org.antlr.v4.codegen.Target;
import org.antlr.v4.tool.ast.GrammarAST;
import org.stringtemplate.v4.STGroup;
import org.stringtemplate.v4.StringRenderer;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Locale;
import java.util.Set;

/**
 *
 * @author Eric Vergnaud
 */
public class JavaScriptTarget extends Target {

	/** Source: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Lexical_grammar */
	protected static final String[] javaScriptKeywords = {
		"break", "case", "class", "catch", "const", "continue", "debugger",
		"default", "delete", "do", "else", "export", "extends", "finally", "for",
		"function", "if", "import", "in", "instanceof", "let", "new", "return",
		"super", "switch", "this", "throw", "try", "typeof", "var", "void",
		"while", "with", "yield",
		//future reserved
		"enum", "await", "implements", "package", "protected", "static",
		"interface", "private", "public",
		//future reserved in older standards
		"abstract", "boolean", "byte", "char", "double", "final", "float",
		"goto", "int", "long", "native", "short", "synchronized", "transient",
		"volatile",
		//literals
		"null", "true", "false"
	};

	/** Avoid grammar symbols in this set to prevent conflicts in gen'd code. */
	protected final Set badWords = new HashSet();

	public JavaScriptTarget(CodeGenerator gen) {
		super(gen, "JavaScript");
	}

    @Override
    public String getVersion() {
        return "4.6";
    }

    public Set getBadWords() {
		if (badWords.isEmpty()) {
			addBadWords();
		}

		return badWords;
	}

	protected void addBadWords() {
		badWords.addAll(Arrays.asList(javaScriptKeywords));
		badWords.add("rule");
		badWords.add("parserRule");
	}

	/**
	 * {@inheritDoc}
	 * 
	 * For Java, this is the translation {@code 'a\n"'} → {@code "a\n\""}.
	 * Expect single quotes around the incoming literal. Just flip the quotes
	 * and replace double quotes with {@code \"}.
	 * 
	 * Note that we have decided to allow people to use '\"' without penalty, so
	 * we must build the target string in a loop as {@link String#replace}
	 * cannot handle both {@code \"} and {@code "} without a lot of messing
	 * around.
	 */
	@Override
	public String getTargetStringLiteralFromANTLRStringLiteral(
		CodeGenerator generator,
		String literal, boolean addQuotes)
	{
		StringBuilder sb = new StringBuilder();
		String is = literal;

		if ( addQuotes ) sb.append('"');

		for (int i = 1; i < is.length() -1; i++) {
			if  (is.charAt(i) == '\\') {
				// Anything escaped is what it is! We assume that
				// people know how to escape characters correctly. However
				// we catch anything that does not need an escape in Java (which
				// is what the default implementation is dealing with and remove
				// the escape. The C target does this for instance.
				//
				switch (is.charAt(i+1)) {
					// Pass through any escapes that Java also needs
					//
					case    '"':
					case    'n':
					case    'r':
					case    't':
					case    'b':
					case    'f':
					case    '\\':
						// Pass the escape through
						sb.append('\\');
						break;

					case    'u':    // Assume unnnn
						// Pass the escape through as double \\
						// so that Java leaves as \u0000 string not char
						sb.append('\\');
						sb.append('\\');
						break;

					default:
						// Remove the escape by virtue of not adding it here
						// Thus \' becomes ' and so on
						break;
				}

				// Go past the \ character
				i++;
			} else {
				// Characters that don't need \ in ANTLR 'strings' but do in Java
				if (is.charAt(i) == '"') {
					// We need to escape " in Java
					sb.append('\\');
				}
			}
			// Add in the next character, which may have been escaped
			sb.append(is.charAt(i));
		}

		if ( addQuotes ) sb.append('"');

		return sb.toString();
	}

	@Override
	public String encodeIntAsCharEscape(int v) {
		if (v < Character.MIN_VALUE || v > Character.MAX_VALUE) {
			throw new IllegalArgumentException(String.format("Cannot encode the specified value: %d", v));
		}

		if (v >= 0 && v < targetCharValueEscape.length && targetCharValueEscape[v] != null) {
			return targetCharValueEscape[v];
		}

		if (v >= 0x20 && v < 127) {
			return String.valueOf((char)v);
		}

		String hex = Integer.toHexString(v|0x10000).substring(1,5);
		return "\\u"+hex;
	}

	@Override
	public int getSerializedATNSegmentLimit() {
		return 2 ^ 31;
	}

	@Override
	public int getInlineTestSetWordSize() {
		return 32;
	}

	@Override
	protected boolean visibleGrammarSymbolCausesIssueInGeneratedCode(GrammarAST idNode) {
		return getBadWords().contains(idNode.getText());
	}

	@Override
	protected STGroup loadTemplates() {
		STGroup result = super.loadTemplates();
		result.registerRenderer(String.class, new JavaStringRenderer(), true);
		return result;
	}

	protected static class JavaStringRenderer extends StringRenderer {

		@Override
		public String toString(Object o, String formatString, Locale locale) {
			if ("java-escape".equals(formatString)) {
				// 5C is the hex code for the \ itself
				return ((String)o).replace("\\u", "\\u005Cu");
			}

			return super.toString(o, formatString, locale);
		}

	}

	@Override
	public boolean wantsBaseListener() {
		return false;
	}

	@Override
	public boolean wantsBaseVisitor() {
		return false;
	}

	@Override
	public boolean supportsOverloadedMethods() {
		return false;
	}
}