/*
 * Copyright (c) 2012-2017 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.runtime;

import java.util.Arrays;

This class provides a default implementation of the Vocabulary interface. 
Author:
Sam Harwell/**
 * This class provides a default implementation of the {@link Vocabulary}
 * interface.
 *
 * @author Sam Harwell
 */
public class VocabularyImpl implements Vocabulary {
	private static final String[] EMPTY_NAMES = new String[0];

	
Gets an empty Vocabulary instance. 
 No literal or symbol names are assigned to token types, so getDisplayName(int) returns the numeric value for all tokens except Token.EOF.
/**
	 * Gets an empty {@link Vocabulary} instance.
	 *
	 * <p>
	 * No literal or symbol names are assigned to token types, so
	 * {@link #getDisplayName(int)} returns the numeric value for all tokens
	 * except {@link Token#EOF}.</p>
	 */
	public static final VocabularyImpl EMPTY_VOCABULARY = new VocabularyImpl(EMPTY_NAMES, EMPTY_NAMES, EMPTY_NAMES);


	private final String[] literalNames;

	private final String[] symbolicNames;

	private final String[] displayNames;

	private final int maxTokenType;

	
Constructs a new instance of VocabularyImpl from the specified literal and symbolic token names. 
Params:
literalNames – The literal names assigned to tokens, or null if no literal names are assigned.
symbolicNames – The symbolic names assigned to tokens, or null if no symbolic names are assigned.
See Also:
getLiteralName(int)
getSymbolicName(int)/**
	 * Constructs a new instance of {@link VocabularyImpl} from the specified
	 * literal and symbolic token names.
	 *
	 * @param literalNames The literal names assigned to tokens, or {@code null}
	 * if no literal names are assigned.
	 * @param symbolicNames The symbolic names assigned to tokens, or
	 * {@code null} if no symbolic names are assigned.
	 *
	 * @see #getLiteralName(int)
	 * @see #getSymbolicName(int)
	 */
	public VocabularyImpl(String[] literalNames, String[] symbolicNames) {
		this(literalNames, symbolicNames, null);
	}

	
Constructs a new instance of VocabularyImpl from the specified literal, symbolic, and display token names. 
Params:
literalNames – The literal names assigned to tokens, or null if no literal names are assigned.
symbolicNames – The symbolic names assigned to tokens, or null if no symbolic names are assigned.
displayNames – The display names assigned to tokens, or null to use the values in literalNames and symbolicNames as the source of display names, as described in getDisplayName(int).
See Also:
getLiteralName(int)
getSymbolicName(int)
getDisplayName(int)/**
	 * Constructs a new instance of {@link VocabularyImpl} from the specified
	 * literal, symbolic, and display token names.
	 *
	 * @param literalNames The literal names assigned to tokens, or {@code null}
	 * if no literal names are assigned.
	 * @param symbolicNames The symbolic names assigned to tokens, or
	 * {@code null} if no symbolic names are assigned.
	 * @param displayNames The display names assigned to tokens, or {@code null}
	 * to use the values in {@code literalNames} and {@code symbolicNames} as
	 * the source of display names, as described in
	 * {@link #getDisplayName(int)}.
	 *
	 * @see #getLiteralName(int)
	 * @see #getSymbolicName(int)
	 * @see #getDisplayName(int)
	 */
	public VocabularyImpl(String[] literalNames, String[] symbolicNames, String[] displayNames) {
		this.literalNames = literalNames != null ? literalNames : EMPTY_NAMES;
		this.symbolicNames = symbolicNames != null ? symbolicNames : EMPTY_NAMES;
		this.displayNames = displayNames != null ? displayNames : EMPTY_NAMES;
		// See note here on -1 part: https://github.com/antlr/antlr4/pull/1146
		this.maxTokenType =
			Math.max(this.displayNames.length,
					 Math.max(this.literalNames.length, this.symbolicNames.length)) - 1;
	}

	
Returns a VocabularyImpl instance from the specified set of token names. This method acts as a compatibility layer for the single tokenNames array generated by previous releases of ANTLR. 
The resulting vocabulary instance returns null for getLiteralName(int) and getSymbolicName(int), and the value from tokenNames for the display names.
Params:
tokenNames – The token names, or null if no token names are available.
Returns:
A Vocabulary instance which uses tokenNames for the display names of tokens./**
	 * Returns a {@link VocabularyImpl} instance from the specified set of token
	 * names. This method acts as a compatibility layer for the single
	 * {@code tokenNames} array generated by previous releases of ANTLR.
	 *
	 * <p>The resulting vocabulary instance returns {@code null} for
	 * {@link #getLiteralName(int)} and {@link #getSymbolicName(int)}, and the
	 * value from {@code tokenNames} for the display names.</p>
	 *
	 * @param tokenNames The token names, or {@code null} if no token names are
	 * available.
	 * @return A {@link Vocabulary} instance which uses {@code tokenNames} for
	 * the display names of tokens.
	 */
	public static Vocabulary fromTokenNames(String[] tokenNames) {
		if (tokenNames == null || tokenNames.length == 0) {
			return EMPTY_VOCABULARY;
		}

		String[] literalNames = Arrays.copyOf(tokenNames, tokenNames.length);
		String[] symbolicNames = Arrays.copyOf(tokenNames, tokenNames.length);
		for (int i = 0; i < tokenNames.length; i++) {
			String tokenName = tokenNames[i];
			if (tokenName == null) {
				continue;
			}

			if (!tokenName.isEmpty()) {
				char firstChar = tokenName.charAt(0);
				if (firstChar == '\'') {
					symbolicNames[i] = null;
					continue;
				}
				else if (Character.isUpperCase(firstChar)) {
					literalNames[i] = null;
					continue;
				}
			}

			// wasn't a literal or symbolic name
			literalNames[i] = null;
			symbolicNames[i] = null;
		}

		return new VocabularyImpl(literalNames, symbolicNames, tokenNames);
	}

	@Override
	public int getMaxTokenType() {
		return maxTokenType;
	}

	@Override
	public String getLiteralName(int tokenType) {
		if (tokenType >= 0 && tokenType < literalNames.length) {
			return literalNames[tokenType];
		}

		return null;
	}

	@Override
	public String getSymbolicName(int tokenType) {
		if (tokenType >= 0 && tokenType < symbolicNames.length) {
			return symbolicNames[tokenType];
		}

		if (tokenType == Token.EOF) {
			return "EOF";
		}

		return null;
	}

	@Override
	public String getDisplayName(int tokenType) {
		if (tokenType >= 0 && tokenType < displayNames.length) {
			String displayName = displayNames[tokenType];
			if (displayName != null) {
				return displayName;
			}
		}

		String literalName = getLiteralName(tokenType);
		if (literalName != null) {
			return literalName;
		}

		String symbolicName = getSymbolicName(tokenType);
		if (symbolicName != null) {
			return symbolicName;
		}

		return Integer.toString(tokenType);
	}
}