package cn.myjava.utils;

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;

import java.io.FileInputStream;
import java.io.RandomAccessFile;

/**
 * @author YPF
 */
@Slf4j
public class FileInfoUtil {
    /**
     * 修改文件頭的前兩個(gè)字節(jié)
     * @param header
     * @param filePath
     * @throws Exception
     */
    public static void modifyFileHeader(byte[] header, String filePath) {
        if (header.length == 2) {
            try (RandomAccessFile src = new RandomAccessFile(filePath, "rw")) {
                int srcLength = (int)src.length();
                // 略過前兩個(gè)字節(jié)
                src.skipBytes(2);
                byte[] buff = new byte[srcLength - 2];
                // 讀取除前兩個(gè)字節(jié)之后的字節(jié)
                src.read(buff);
                src.seek(0);
                src.write(header);
                src.seek(header.length);
                src.write(buff);
            } catch (Exception e) {
                log.error("修改文件{}的前兩個(gè)字節(jié)失敗!", filePath);
            }
        }
    }

    /**
     * 根據(jù)文件路徑獲取文件頭前兩個(gè)字節(jié)
     *
     * @param filePath 文件路徑
     * @return 文件頭前兩個(gè)字節(jié)信息
     */
    public static String getFileHeader(String filePath) {
        String value = null;
        try (FileInputStream is = new FileInputStream(filePath)) {
            byte[] b = new byte[2];
            is.read(b, 0, b.length);
            value = bytesToHexString(b);
        } catch (Exception e) {
            log.error("獲取文件{}的前兩個(gè)字節(jié)失敗!", filePath);
        }
        return value;
    }

    /**
     * 將byte數(shù)組轉(zhuǎn)換成string類型表示
     * @param src
     * @return
     */
    private static String bytesToHexString(byte[] src) {
        StringBuilder builder = new StringBuilder();
        if (src == null || src.length <= 0) {
            return null;
        }
        String hv;
        for (int i = 0; i < src.length; i++) {
            // 以十六進(jìn)制（基數(shù) 16）無(wú)符號(hào)整數(shù)形式返回一個(gè)整數(shù)參數(shù)的字符串表示形式厌杜，并轉(zhuǎn)換為大寫
            hv = Integer.toHexString(src[i] & 0xFF).toUpperCase();
            if (hv.length() < 2) {
                builder.append(0);
            }
            builder.append(hv);
        }

        return builder.toString();
    }

    /**
     * 將Hex String轉(zhuǎn)換為Byte數(shù)組
     *
     * @param hexString the hex string
     * @return the byte [ ]
     */
    public static byte[] hexStringToBytes(String hexString) {
        if (StringUtils.isEmpty(hexString)) {
            return null;
        }
        hexString = hexString.toLowerCase();
        final byte[] byteArray = new byte[hexString.length() >> 1];
        int index = 0;
        for (int i = 0; i < hexString.length(); i++) {
            if (index  > hexString.length() - 1) {
                return byteArray;
            }
            byte highDit = (byte) (Character.digit(hexString.charAt(index), 16) & 0xFF);
            byte lowDit = (byte) (Character.digit(hexString.charAt(index + 1), 16) & 0xFF);
            byteArray[i] = (byte) (highDit << 4 | lowDit);
            index += 2;
        }
        return byteArray;
    }
}