/**
 * Copyright (c) 2011-2019, James Zhan 詹波 (jfinal@126.com).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.jfinal.template.stat;

/**
 * CharTable 空间换时间优化字符判断性能
 * 负值参数强转 char 会自动变正值，无需判断负值数组下标
 * isLetter(EOF) 不会下标越界
 */
public class CharTable {
	
	private static final char[] letterChars = buildLetterChars();
	private static final char[] letterOrDigitChars = buildLetterOrDigitChars();
	private static final char[] exprChars = buildExprChars();
	private static final char NULL = 0;
	private static final char SIZE = 128;
	private CharTable(){}
	
	private static char[] createCharArray() {
		char[] ret = new char[SIZE];
		for (char i=0; i<SIZE; i++) {
			ret[i] = NULL;
		}
		return ret;
	}
	
	private static char[] buildLetterChars() {
		char[] ret = createCharArray();
		for (char i='a'; i<='z'; i++) {
			ret[i] = i;
		}
		for (char i='A'; i<='Z'; i++) {
			ret[i] = i;
		}
		ret['_'] = '_';			// 包含下划线字符 '_'
		return ret;
	}
	
	private static char[] buildLetterOrDigitChars() {
		char[] ret = buildLetterChars();
		for (char i='0'; i<='9'; i++) {
			ret[i] = i;
		}
		return ret;
	}
	
	private static char[] buildExprChars() {
		char[] ret = createCharArray();
		ret['\t'] = '\t';
		ret['\n'] = '\n';
		ret['\r'] = '\r';
		for (char i=' '; i<='}'; i++) {
			ret[i] = i;
		}
		
		ret['#'] = NULL;
		ret['$'] = NULL;
		ret['@'] = NULL;
		ret['\\'] = NULL;
		ret['^'] = NULL;
		ret['`'] = NULL;
		return ret;
	}
	
	public static boolean isLetter(char c) {
		return c < SIZE && letterChars[c] != NULL;
	}
	
	public static boolean isLetterOrDigit(char c) {
		return c < SIZE && letterOrDigitChars[c] != NULL;
	}
	
	public static boolean isExprChar(char c) {
		return c < SIZE && exprChars[c] != NULL;
	}
	
	public static boolean isDigit(char c) {
		return c >= '0' && c <= '9';
	}
	
	public static boolean isBlank(char c) {
		return c == ' ' || c == '\t';								// \t\r\u000C
	}
	
	public static boolean isBlankOrLineFeed(char c) {
		return c == ' ' || c == '\t' || c == '\r' || c == '\n';		// \t\r\n\u000C
	}
	
	public static boolean isHexadecimalDigit(char c) {
		return (c >= '0' && c <= '9') || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f');
	}
	
	public static boolean isOctalDigit(char c) {
		return c >= '0' && c <= '7';
	}
}