package com.estate.expert.admin.utils;

import java.io.*;
import java.net.*;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardCopyOption;
import java.util.Map;
import java.util.HashMap;

public class FileDownloader {
    
    /**
     * 增强的文件下载方法
     */
    public byte[] downloadFile(String fileUrl) throws Exception {
        // 验证URL
        if (fileUrl == null || fileUrl.trim().isEmpty()) {
            throw new IllegalArgumentException("URL不能为空");
        }
        
        URL url = new URL(fileUrl);
        
        // 设置超时和请求头
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");
        connection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36");
        connection.setRequestProperty("Accept", "application/vnd.openxmlformats-officedocument.wordprocessingml.document, application/msword");
        connection.setConnectTimeout(30000);
        connection.setReadTimeout(60000);
        connection.setInstanceFollowRedirects(true);
        
        int responseCode = connection.getResponseCode();
        
        if (responseCode != HttpURLConnection.HTTP_OK) {
            throw new IOException("HTTP请求失败，状态码: " + responseCode);
        }
        
        // 检查内容类型
        String contentType = connection.getContentType();
        if (contentType == null || 
            (!contentType.contains("word") && 
             !contentType.contains("octet-stream") &&
             !contentType.contains("document"))) {
            System.out.println("警告: 内容类型可能不是Word文档: " + contentType);
        }
        
        // 获取文件大小
        int contentLength = connection.getContentLength();
        System.out.println("文件大小: " + (contentLength > 0 ? contentLength + " 字节" : "未知"));
        
        // 下载文件
        try (InputStream inputStream = connection.getInputStream();
             ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
            
            byte[] buffer = new byte[8192];
            int bytesRead;
            long totalBytes = 0;
            
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
                totalBytes += bytesRead;
                
                if (contentLength > 0) {
                    int progress = (int) ((totalBytes * 100) / contentLength);
                    if (progress % 10 == 0) {
                        System.out.print("\r下载进度: " + progress + "%");
                    }
                }
            }
            
            byte[] fileData = outputStream.toByteArray();
            
            if (fileData.length == 0) {
                throw new IOException("下载的文件内容为空");
            }
            
            System.out.println("\n下载完成，实际大小: " + fileData.length + " 字节");
            
            // 验证文件格式（检查是否是有效的Word文档）
            if (!isValidWordDocument(fileData)) {
                System.out.println("警告: 下载的文件可能不是有效的Word文档");
            }
            
            return fileData;
            
        } finally {
            connection.disconnect();
        }
    }
    
    /**
     * 验证是否为有效的Word文档
     */
    private boolean isValidWordDocument(byte[] data) {
        if (data.length < 4) {
            return false;
        }
        
        // 检查.docx格式 (ZIP格式)
        if (data[0] == 0x50 && data[1] == 0x4B && data[2] == 0x03 && data[3] == 0x04) {
            return true;
        }
        
        // 检查.doc格式 (OLE格式)
        if (data[0] == (byte)0xD0 && data[1] == (byte)0xCF && 
            data[2] == 0x11 && data[3] == (byte)0xE0) {
            return true;
        }
        
        return false;
    }
    
    /**
     * 下载并保存到文件
     */
    public File downloadToFile(String fileUrl, String outputPath) throws Exception {
        byte[] data = downloadFile(fileUrl);
        
        File outputFile = new File(outputPath);
        File parentDir = outputFile.getParentFile();
        if (parentDir != null && !parentDir.exists()) {
            parentDir.mkdirs();
        }
        
        try (FileOutputStream fos = new FileOutputStream(outputFile)) {
            fos.write(data);
        }
        
        System.out.println("文件已保存到: " + outputFile.getAbsolutePath());
        return outputFile;
    }
    
    /**
     * 批量下载
     */
    public Map<String, byte[]> batchDownload(String[] urls) {
        Map<String, byte[]> results = new HashMap<>();
        
        for (String url : urls) {
            try {
                System.out.println("下载: " + url);
                byte[] data = downloadFile(url);
                results.put(url, data);
                System.out.println("✓ 下载成功");
            } catch (Exception e) {
                System.err.println("✗ 下载失败: " + e.getMessage());
                results.put(url, null);
            }
        }
        
        return results;
    }
    
    /**
     * 使用NIO下载（更高效）
     */
    public void downloadWithNIO(String fileUrl, String outputPath) throws Exception {
        URL url = new URL(fileUrl);
        
        try (InputStream inputStream = url.openStream();
             ReadableByteChannel rbc = Channels.newChannel(inputStream);
             FileOutputStream fos = new FileOutputStream(outputPath)) {
            
            fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
        }
        
        System.out.println("NIO下载完成: " + outputPath);
    }
}