package com.baidu;

import java.io.*;
import java.nio.file.*;
import java.security.*;
import java.util.*;

public class FileMD5Matcher {

    // 计算文件的 MD5 值
    public static String calculateMD5(Path path) throws Exception {
        MessageDigest md = MessageDigest.getInstance("MD5");
        try (InputStream is = Files.newInputStream(path);
             DigestInputStream dis = new DigestInputStream(is, md)) {
            byte[] buffer = new byte[8192];
            while (dis.read(buffer) != -1) {
            }

        }
        byte[] digest = md.digest();
        StringBuilder sb = new StringBuilder();
        for (byte b : digest) {
            sb.append(String.format("%02x", b));
        }
        return sb.toString();
    }

    // 构建原始目录的 MD5 -> 文件名 映射
    public static Map<String, String> buildOriginalMD5Map(String originalDir) throws Exception {
        Map<String, String> md5ToFilename = new HashMap<>();
        Files.list(Paths.get(originalDir))
                .filter(Files::isRegularFile)
                .forEach(path -> {
                    try {
                        String md5 = calculateMD5(path);
                        md5ToFilename.put(md5, path.getFileName().toString());
                    } catch (Exception e) {
                        System.err.println("无法处理文件: " + path + ", 错误: " + e.getMessage());
                    }
                });
        return md5ToFilename;
    }

    // 匹配新目录中的文件与原始目录中的 MD5
    public static void matchNewFilesWithOriginals(String newDir, Map<String, String> originalMD5Map) throws Exception {
        Map<String, String> matches = new HashMap<>();

        Files.list(Paths.get(newDir))
                .filter(Files::isRegularFile)
                .forEach(path -> {
                    try {
                        String md5 = calculateMD5(path);
                        String originalName = originalMD5Map.get(md5);
                        if (originalName != null) {
                            matches.put(path.getFileName().toString(), originalName);
                        }
                    } catch (Exception e) {
                        System.err.println("无法处理文件: " + path + ", 错误: " + e.getMessage());
                    }
                });

        matches.forEach((newName, originalName) ->
            System.out.println(newName + " -> " + originalName));
    }

    public static void main(String[] args) {
        String originalDir = "D:\\Project\\2025\\02.成都停车项目POC\\20250606\\source";
        String newDir = "D:\\Project\\2025\\02.成都停车项目POC\\20250606\\no";

        try {
            Map<String, String> originalMD5Map = buildOriginalMD5Map(originalDir);
            matchNewFilesWithOriginals(newDir, originalMD5Map);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}