package com.artfess.file.util;


import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

import org.mozilla.intl.chardet.nsDetector;
import org.mozilla.intl.chardet.nsICharsetDetectionObserver;

/**
 * 文本文件编码探测工具类
 *
 * @company 广州宏天软件股份有限公司
 * @author heyifan
 * @email heyf@jee-soft.cn
 * @date 2018年9月30日
 */
public class FileCharsetDetector {

	/**
	 * 传入一个文件(File)对象，检查文件编码
	 *
	 * @param file File对象实例
	 * @return 文件编码，若无，则返回null
	 * @throws FileNotFoundException
	 * @throws IOException
	 */
	public static Observer guessFileEncoding(File file)
			throws FileNotFoundException, IOException {
		return guessFileEncoding(file, new nsDetector());
	}

	/**
	 * <pre>
	 * 获取文件的编码
	 * @param file
	 *            File对象实例
	 * @param languageHint
	 *            语言提示区域代码 @see #nsPSMDetector ,取值如下：
	 *             1 : Japanese
	 *             2 : Chinese
	 *             3 : Simplified Chinese
	 *             4 : Traditional Chinese
	 *             5 : Korean
	 *             6 : Dont know(default)
	 * </pre>
	 *
	 * @return 文件编码，eg：UTF-8,GBK,GB2312形式(不确定的时候，返回可能的字符编码序列)；若无，则返回null
	 * @throws FileNotFoundException
	 * @throws IOException
	 */
	public static Observer guessFileEncoding(File file, int languageHint)
			throws FileNotFoundException, IOException {
		return guessFileEncoding(file, new nsDetector(languageHint));
	}

	/**
	 * 获取文件的编码
	 *
	 * @param file
	 * @param det
	 * @return
	 * @throws FileNotFoundException
	 * @throws IOException
	 */
	private static Observer guessFileEncoding(File file, nsDetector det)
			throws IOException {
		// new Observer
		Observer observer = new Observer();
		// set Observer
		// The Notify() will be called when a matching charset is found.
		det.Init(observer);
		try (BufferedInputStream imp = new BufferedInputStream(new FileInputStream(file));){
			byte[] buf = new byte[1024];
			int len;
			boolean done = false;
			boolean isAscii = false;

			while ((len = imp.read(buf, 0, buf.length)) != -1) {
				// Check if the stream is only ascii.
				isAscii = det.isAscii(buf, len);
				if (isAscii) {
					break;
				}
				// DoIt if non-ascii and not done yet.
				done = det.DoIt(buf, len, false);
				if (done) {
					break;
				}
			}
			det.DataEnd();

			if (isAscii) {
				observer.encoding = "ASCII";
				observer.found = true;
			}

		if (!observer.isFound()) {
			String[] prob = det.getProbableCharsets();
			if (prob.length > 0) {
				// 在没有发现情况下,去第一个可能的编码
				observer.encoding = prob[0];
			} else {
				observer.encoding = null;
			}
			}
	    } catch (Exception e) {}
		return observer;
	}

	/**
	 * 文件字符编码观察者, 判断出字符编码时调用
	 *
	 * @company 广州宏天软件股份有限公司
	 * @author heyifan
	 * @email heyf@jee-soft.cn
	 * @date 2018年9月30日
	 */
	public static class Observer implements nsICharsetDetectionObserver {

		/**
		 * @Fields encoding : 字符编码
		 */
		private String encoding = null;
		/**
		 * @Fields found : 是否找到字符集
		 */
		private boolean found = false;

		@Override
		public void Notify(String charset) {
			this.encoding = charset;
			this.found = true;
		}

		public String getEncoding() {
			return encoding;
		}

		public boolean isFound() {
			return found;
		}

		@Override
		public String toString() {
			return "Observer [encoding=" + encoding + ", found=" + found + "]";
		}
	}

}
