/*
 * Copyright 1999-2011 Alibaba Group Holding Ltd.
 *
 * 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.alibaba.druid.util;

import com.alibaba.druid.support.logging.Log;
import com.alibaba.druid.support.logging.LogFactory;

/**
 * @author sandzhang<sandzhangtoo@gmail.com>
 */
public class StringUtils {

    private final static Log LOG = LogFactory.getLog(StringUtils.class);

    /**
     * Example: subString("12345","1","4")=23
     * 
     * @param src
     * @param start
     * @param to
     * @return
     */
    public static Integer subStringToInteger(String src, String start, String to) {
        return stringToInteger(subString(src, start, to));
    }

    /**
     * Example: subString("abcd","a","c")="b"
     * 
     * @param src
     * @param start null while start from index=0
     * @param to null while to index=src.length
     * @return
     */
    public static String subString(String src, String start, String to) {
        int indexFrom = start == null ? 0 : src.indexOf(start);
        int indexTo = to == null ? src.length() : src.indexOf(to);
        if (indexFrom < 0 || indexTo < 0 || indexFrom > indexTo) {
            return null;
        }
        indexFrom += start.length();
        return src.substring(indexFrom, indexTo);

    }

    /**
     * @param in
     * @return
     */
    public static Integer stringToInteger(String in) {
        if (in == null) {
            return null;
        }
        in = in.trim();
        if (in.length() == 0) {
            return null;
        }
        
        try {
            return Integer.parseInt(in);
        } catch (NumberFormatException e) {
            LOG.warn("stringToInteger fail,string=" + in, e);
            return null;
        }
    }

    public static boolean equals(String a, String b) {
        if (a == null) {
            return b == null;
        }
        return a.equals(b);
    }

    public static boolean isEmpty(String value) {
        if (value == null || value.length() == 0) {
            return true;
        }

        return false;
    }
}
