package com.cdzy.common.utils;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.nio.file.Files;
import java.nio.file.Path;

public class RemoteFileUtils {
    
    /**
     * 获取远程文件并返回File对象
     */
    public static File getRemoteFile(String fileUrl) throws IOException {
        return getRemoteFile(fileUrl, null);
    }
    
    /**
     * 获取远程文件并保存到指定路径
     */
    public static File getRemoteFile(String fileUrl, String localPath) throws IOException {
        validateUrl(fileUrl);
        
        URL url = new URL(fileUrl);
        File outputFile;
        
        if (localPath != null && !localPath.trim().isEmpty()) {
            outputFile = new File(localPath);
            // 确保目录存在
            outputFile.getParentFile().mkdirs();
        } else {
            // 使用临时文件
            String extension = getFileExtension(fileUrl);
            String prefix = "remote_file_" + System.currentTimeMillis() + "_";
            String suffix = extension != null ? "." + extension : ".tmp";
            Path tempPath = Files.createTempFile(prefix, suffix);
            outputFile = tempPath.toFile();
            
            // 程序退出时删除临时文件
            outputFile.deleteOnExit();
        }
        
        // 下载文件
        try (InputStream in = url.openStream();
             FileOutputStream out = new FileOutputStream(outputFile)) {
            
            byte[] buffer = new byte[8192];
            int bytesRead;
            long totalBytes = 0;
            
            while ((bytesRead = in.read(buffer)) != -1) {
                out.write(buffer, 0, bytesRead);
                totalBytes += bytesRead;
            }
        }
        
        return outputFile;
    }
    
    /**
     * 获取文件扩展名
     */
    private static String getFileExtension(String url) {
        if (url == null || url.isEmpty()) {
            return null;
        }
        
        int lastDotIndex = url.lastIndexOf('.');
        int lastSlashIndex = Math.max(url.lastIndexOf('/'), url.lastIndexOf('\\'));
        
        if (lastDotIndex > lastSlashIndex && lastDotIndex < url.length() - 1) {
            String extension = url.substring(lastDotIndex + 1);
            // 移除可能的查询参数
            int paramIndex = extension.indexOf('?');
            if (paramIndex != -1) {
                extension = extension.substring(0, paramIndex);
            }
            return extension;
        }
        
        return null;
    }
    
    /**
     * 验证URL格式
     */
    private static void validateUrl(String url) {
        if (url == null || url.trim().isEmpty()) {
            throw new IllegalArgumentException("URL cannot be null or empty");
        }
        
        if (!url.startsWith("http://") && !url.startsWith("https://")) {
            throw new IllegalArgumentException("URL must start with http:// or https://");
        }
    }
    
    /**
     * 获取文件信息
     */
    public static void printFileInfo(File file) {
        if (file != null && file.exists()) {
            System.out.println("File name: " + file.getName());
            System.out.println("File path: " + file.getAbsolutePath());
            System.out.println("File size: " + file.length() + " bytes");
            System.out.println("Is temporary: " + file.getName().startsWith("remote_file_"));
        }
    }
}