package com.datacloudsec.utils;

import org.apache.commons.lang.StringUtils;

/**
 * 文本相似度比较
 * @author Administrator
 */
public class ComputeTextUtil {
	
	private ComputeTextUtil(){
	}
	
	/**
	 * 获取两字符串的相似度
	 * @param str
	 * @param target
	 * @return
	 */
	public static double similarDegree(String str, String target) {
		boolean strBlank = StringUtils.isBlank(str);
		boolean targetBlank = StringUtils.isBlank(target);
		if(strBlank && targetBlank){
			return 1D;
		}
		if(strBlank || targetBlank){
			return 1D;
		}
		
		final int maxLen = Math.max(str.length(), target.length());
		int allowMaxLen = 7000;
		double num = 0D;
		double total = 0D;
		for(int i=0;i<maxLen;i+=allowMaxLen){
			int strIndex = Math.min(i+allowMaxLen,str.length());
			int targetIndex = Math.min(i+allowMaxLen,target.length());
			double tmpR;
			if(i >= strIndex || i >= targetIndex){
				tmpR = 0D;
			}else{
				String tmpStr = str.substring(i,strIndex);
				String tmpTarget = target.substring(i,targetIndex);
				tmpR = 1 - (double) compare(tmpStr, tmpTarget) / Math.max(tmpStr.length(), tmpTarget.length());
			}
			total += tmpR;
			num++;
		}
		return total / num;
	}
	
	private static int compare(String str, String target) {
		int d[][]; // 矩阵
		int n = str.length();
		int m = target.length();
		int i; // 遍历str的
		int j; // 遍历target的
		char ch1; // str的
		char ch2; // target的
		int temp; // 记录相同字符,在某个矩阵位置值的增量,不是0就是1
		if (n == 0) {
			return m;
		}
		if (m == 0) {
			return n;
		}
		d = new int[n + 1][m + 1];
		for (i = 0; i <= n; i++) { // 初始化第一列
			d[i][0] = i;
		}

		for (j = 0; j <= m; j++) { // 初始化第一行
			d[0][j] = j;
		}

		for (i = 1; i <= n; i++) { // 遍历str
			ch1 = str.charAt(i - 1);
			// 去匹配target
			for (j = 1; j <= m; j++) {
				ch2 = target.charAt(j - 1);
				if (ch1 == ch2) {
					temp = 0;
				} else {
					temp = 1;
				}

				// 左边+1,上边+1, 左上角+temp取最小
				d[i][j] = min(d[i - 1][j] + 1, d[i][j - 1] + 1, d[i - 1][j - 1]
						+ temp);
			}
		}
		return d[n][m];
	}

	private static int min(int one, int two, int three) {
		return (one = one < two ? one : two) < three ? one : three;
	}

	public static void main(String[] args) throws Exception {
		long l = System.currentTimeMillis();
		String str = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaac";
		String target = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaac";
		System.out.println("similarityRatio=" + ComputeTextUtil.similarDegree(str,target));
		System.out.println("用时：" + (System.currentTimeMillis()-l));
	}
}