package com.baomidou.mybatisplus.toolkit;

/**
 * <p>
 * StringEscape ，数据库字符串转义
 * </p>
 *
 * @author Caratacus
 * @Date 2016-10-16
 */
public class StringEscape {
	/**
	 * 字符串是否需要转义
	 *
	 * @param str
	 * @param len
	 * @return
	 */
	private static boolean isEscapeNeededForString(String str, int len) {

		boolean needsHexEscape = false;

		for (int i = 0; i < len; ++i) {
			char c = str.charAt(i);

			switch (c) {
				case 0: /* Must be escaped for 'mysql' */

					needsHexEscape = true;
					break;

				case '\n': /* Must be escaped for logs */
					needsHexEscape = true;

					break;

				case '\r':
					needsHexEscape = true;
					break;

				case '\\':
					needsHexEscape = true;

					break;

				case '\'':
					needsHexEscape = true;

					break;

				case '"': /* Better safe than sorry */
					needsHexEscape = true;

					break;

				case '\032': /* This gives problems on Win32 */
					needsHexEscape = true;
					break;
			}

			if (needsHexEscape) {
				break; // no need to scan more
			}
		}
		return needsHexEscape;
	}

	/**
	 * 转义字符串
	 *
	 * @param escapeStr
	 * @return
	 */
	public static String escapeString(String escapeStr) {

		if (escapeStr.matches("\'(.+)\'")) {
			escapeStr = escapeStr.substring(1, escapeStr.length() - 1);
		}

		String parameterAsString = escapeStr;
		int stringLength = escapeStr.length();
		if (isEscapeNeededForString(escapeStr, stringLength)) {

			StringBuilder buf = new StringBuilder((int) (escapeStr.length() * 1.1));

			//
			// Note: buf.append(char) is _faster_ than appending in blocks,
			// because the block append requires a System.arraycopy().... go
			// figure...
			//

			for (int i = 0; i < stringLength; ++i) {
				char c = escapeStr.charAt(i);

				switch (c) {
					case 0: /* Must be escaped for 'mysql' */
						buf.append('\\');
						buf.append('0');

						break;

					case '\n': /* Must be escaped for logs */
						buf.append('\\');
						buf.append('n');

						break;

					case '\r':
						buf.append('\\');
						buf.append('r');

						break;

					case '\\':
						buf.append('\\');
						buf.append('\\');

						break;

					case '\'':
						buf.append('\\');
						buf.append('\'');

						break;

					case '"': /* Better safe than sorry */
						buf.append('\\');
						buf.append('"');

						break;

					case '\032': /* This gives problems on Win32 */
						buf.append('\\');
						buf.append('Z');

						break;

					default:
						buf.append(c);
				}
			}

			parameterAsString = buf.toString();
		}
		return "\'" + parameterAsString + "\'";
	}
}