package com.ntsky.note;

import java.io.*;
//定義一個類CodeFilter
public class CodeFilter{
	public CodeFilter(){
	}
	//特殊字符轉為Html
	public static String toHtml(String s){
		if(s == null){
			s = "";
			return s;
		}
		s = Replace(s.trim(),"&","&");
        s = Replace(s.trim(),"<","&lt;");
		s = Replace(s.trim(),">","&gt;");
		s = Replace(s.trim(),"\t","    ");
		s = Replace(s.trim(),"\r\n","\n");
		s = Replace(s.trim(),"\n","<br>");
		s = Replace(s.trim(),"  "," &nbsp;");
		s = Replace(s.trim(),"'","&#39;");
		s = Replace(s.trim(),"\\","&#92;");
		return s;
    }

	//逆
    public static String unHtml(String s){
		s = Replace(s,"<br>","\n");
		s = Replace(s,"&nbsp;"," ");
		return s;
  	}

  //Replace
   public static String Replace(String source,String oldString,String newString){

		StringBuffer output = new StringBuffer();

		int lengthOfsource = source.length();//源字符串長度
		int lengthOfold = oldString.length();//老字符串長度

		int posStart = 0;//開始搜索位置
		int pos;//搜索到的老字符串的位置

		//source.indexOf(oldString,posStart)檢索某子串在字符串postStart以后第一次出現的位置,如果未找到就返回一個-1。
		while((pos = source.indexOf(oldString,posStart)) >= 0){//得到字符串的位置(eg:如果有<br>就執行，沒有就跳出，不要處理。)

			//將以posStart起始以pos-1結束之間的內容拷貝到另一個字符串中。因為posStar從0開始的。
			output.append(source.substring(posStart,pos));//append方法將文本添加到當前StringBuffer對象內容的結尾。
			output.append(newString);//替換成新字符串

			posStart = pos + lengthOfold;//位置也變為找到了之后的位置,pos為得到第一次出現字符的位置，lengthold為字符的長度

		}

		if(posStart < lengthOfsource){
			//source.substring(posStart)以lengthOfsource開始的字符串拷貝到列一個字符串中
	        output.append(source.substring(posStart));
		}
		//這個方法將其內容轉換成一個可以被用于輸出的字符串對象。它允許操作對應的文本用于輸出或數據存儲。
		return output.toString();
   }
 }