/*
 * Copyright 2006-2025 www.anyline.org
 *
 * 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 org.anyline.util;
 
import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class TextUtil {
    /**
     * 相似度
     * @param doc1 doc1
     * @param doc2 doc2
     * @return double
     */
    public static double similarity(String doc1, String doc2) {
        if (doc1 != null && doc1.trim().length() > 0 && doc2 != null && doc2.trim().length() > 0) {

            Map<Integer, int[]> AlgorithmMap = new HashMap<Integer, int[]>();

            // 将两个字符串中的中文字符以及出现的总数封装到, AlgorithmMap中
            for (int i = 0; i < doc1.length(); i++) {
                char d1 = doc1.charAt(i);
                if(isHanZi(d1)) {//标点和数字不处理
                    int charIndex = getGB2312Id(d1);//保存字符对应的GB2312编码
                    if(charIndex != -1) {
                        int[] fq = AlgorithmMap.get(charIndex);
                        if(fq != null && fq.length == 2) {
                            fq[0]++;//已有该字符, 加1
                        }else {
                            fq = new int[2];
                            fq[0] = 1;
                            fq[1] = 0;
                            AlgorithmMap.put(charIndex, fq);//新增字符入map
                        }
                    }
                }
            }

            for (int i = 0; i < doc2.length(); i++) {
                char d2 = doc2.charAt(i);
                if(isHanZi(d2)) {
                    int charIndex = getGB2312Id(d2);
                    if(charIndex != -1) {
                        int[] fq = AlgorithmMap.get(charIndex);
                        if(fq != null && fq.length == 2) {
                            fq[1]++;
                        }else {
                            fq = new int[2];
                            fq[0] = 0;
                            fq[1] = 1;
                            AlgorithmMap.put(charIndex, fq);
                        }
                    }
                }
            }

            Iterator<Integer> iterator = AlgorithmMap.keySet().iterator();
            double sqdoc1 = 0;
            double sqdoc2 = 0;
            double denominator = 0; 
            while(iterator.hasNext()) {
                int[] c = AlgorithmMap.get(iterator.next());
                denominator += c[0]*c[1];
                sqdoc1 += c[0]*c[0];
                sqdoc2 += c[1]*c[1];
            }

            return denominator / Math.sqrt(sqdoc1*sqdoc2);//余弦计算
        } else {
            throw new NullPointerException(" the Document is null or have not cahrs!!");
        }
    }

    public static boolean isHanZi(char ch) {
        // 判断是否汉字
        return (ch >= 0x4E00 && ch <= 0x9FA5);
        /*if (ch >= 0x4E00 && ch <= 0x9FA5) {//汉字
            return true;
        }else{
            String str = "" + ch;
            boolean isNum = str.matches("[0-9]+"); 
            return isNum;
        }*/
        /*if(Character.isLetterOrDigit(ch)) {
            String str = "" + ch;
            if (str.matches("[0-9a-zA-Z\\u4e00-\\u9fa5]+")) {//非乱码
                return true;
            }else return false;
        }else return false;*/
    }

    /**
     * 根据输入的Unicode字符, 获取它的GB2312编码或者ascii编码,
     * 
     * @param ch 输入的GB2312中文字符或者ASCII字符(128个)
     * @return ch在GB2312中的位置, -1表示该字符不认识
     */
    public static short getGB2312Id(char ch) {
        try {
            byte[] buffer = Character.toString(ch).getBytes("GB2312");
            if (buffer.length != 2) {
                // 正常情况下buffer应该是两个字节, 否则说明ch不属于GB2312编码, 故返回'?', 此时说明不认识该字符
                return -1;
            }
            int b0 = (int) (buffer[0] & 0x0FF) - 161; // 编码从A1开始, 因此减去0xA1=161
            int b1 = (int) (buffer[1] & 0x0FF) - 161; 
            return (short) (b0 * 94 + b1);// 第一个字符和最后一个字符没有汉字, 因此每个区只收16*6-2=94个汉字
        } catch (UnsupportedEncodingException ignored) {
        }
        return -1;
    }
}
