package main

import (
	"flag"
	"fmt"
	"io"
	"log"
	"os"
	"syscall"

	"github.com/pkg/sftp"
	"golang.org/x/crypto/ssh"
	"golang.org/x/term"
)

// 创建 SFTP 客户端
func connectSFTP(config SSHConfig) (*sftp.Client, *ssh.Client, error) {
	var authMethods []ssh.AuthMethod

	// 使用密码认证
	if config.Password != "" {
		authMethods = append(authMethods, ssh.Password(config.Password))
	}

	// 使用私钥认证
	if config.PrivateKey != "" {
		key, err := os.ReadFile(config.PrivateKey)
		if err != nil {
			return nil, nil, fmt.Errorf("failed to read private key file: %w", err)
		}

		var signer ssh.Signer
		if config.Passphrase != "" {
			signer, err = ssh.ParsePrivateKeyWithPassphrase(key, []byte(config.Passphrase))
		} else {
			signer, err = ssh.ParsePrivateKey(key)
		}

		if err != nil {
			return nil, nil, fmt.Errorf("failed to parse private key: %w", err)
		}
		authMethods = append(authMethods, ssh.PublicKeys(signer))
	}

	if len(authMethods) == 0 {
		return nil, nil, fmt.Errorf("no authentication method provided")
	}

	sshConfig := &ssh.ClientConfig{
		User:            config.User,
		Auth:            authMethods,
		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
	}

	// 建立 SSH 连接
	address := fmt.Sprintf("%s:%d", config.Host, config.Port)
	sshClient, err := ssh.Dial("tcp", address, sshConfig)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to connect to SSH: %w", err)
	}

	// 创建 SFTP 客户端
	sftpClient, err := sftp.NewClient(sshClient)
	if err != nil {
		sshClient.Close()
		return nil, nil, fmt.Errorf("failed to create SFTP client: %w", err)
	}

	return sftpClient, sshClient, nil
}

// downloadFile 通过 SFTP 协议从远程服务器下载文件到本地
func downloadFile(sftpClient *sftp.Client, remotePath, localPath string) error {
	// 打开远程文件
	remoteFile, err := sftpClient.Open(remotePath)
	if err != nil {
		return fmt.Errorf("failed to open remote file: %w", err)
	}
	defer remoteFile.Close()

	// 获取远程文件信息以确定文件大小
	fileInfo, err := remoteFile.Stat()
	if err != nil {
		return fmt.Errorf("failed to get remote file info: %w", err)
	}

	// 创建本地文件（创建或覆盖）
	localFile, err := os.Create(localPath)
	if err != nil {
		return fmt.Errorf("failed to create local file: %w", err)
	}
	defer localFile.Close()

	// 分块复制文件内容
	const bufferSize = 32 * 1024 // 32KB
	buf := make([]byte, bufferSize)
	var totalBytes int64 = 0
	for {
		n, err := remoteFile.Read(buf)
		if err != nil && err != io.EOF {
			return fmt.Errorf("failed to read from remote file: %w", err)
		}
		if n == 0 {
			break
		}
		if _, err := localFile.Write(buf[:n]); err != nil {
			return fmt.Errorf("failed to write to local file: %w", err)
		}
		totalBytes += int64(n)
		fmt.Printf("\rDownloaded %d / %d bytes", totalBytes, fileInfo.Size())
	}
	fmt.Println() // 换行

	return nil
}

// 上传文件
func uploadFile(sftpClient *sftp.Client, localPath, remotePath string) error {
	// 打开本地文件
	localFile, err := os.Open(localPath)
	if err != nil {
		return fmt.Errorf("failed to open local file: %w", err)
	}
	defer localFile.Close()

	// 打开远程文件（创建或覆盖）
	RemoteFile, err := sftpClient.Create(remotePath)
	if err != nil {
		return fmt.Errorf("failed to create remote file: %w", err)
	}
	defer RemoteFile.Close()

	// 分块复制文件内容
	const bufferSize = 32 * 1024 // 32KB
	buf := make([]byte, bufferSize)
	for {
		n, err := localFile.Read(buf)
		if err != nil && err.Error() != "EOF" {
			return fmt.Errorf("failed to read local file: %w", err)
		}
		if n == 0 {
			break
		}
		if _, err := RemoteFile.Write(buf[:n]); err != nil {
			return fmt.Errorf("failed to write to remote file: %w", err)
		}
	}

	return nil
}

func _sftp() error {

	var err error

	// 校验参数
	if *h == "" || *u == "" || *l == "" || *r == "" || (*e == "" && *k == "") {
		fmt.Println("Error: Missing required parameters")
		flag.Usage()
		os.Exit(1)
	}

	// 如果使用私钥且需要密码解锁，则提示用户输入密码
	var passphrase string
	if *k != "" {
		fmt.Print("Enter passphrase for private key: ")
		bytePassword, err := term.ReadPassword(int(syscall.Stdin))
		if err != nil {
			log.Printf("Failed to read passphrase: %v", err)
		}
		passphrase = string(bytePassword)
		fmt.Println()
	}

	// 构造 SSH 配置
	config := SSHConfig{
		Host:       *h,
		Port:       *p,
		User:       *u,
		Password:   *e,
		PrivateKey: *k,
		Passphrase: passphrase,
	}

	// 连接 SFTP
	sftpClient, sshClient, err := connectSFTP(config)
	if err != nil {
		log.Printf("Failed to connect to SFTP: %v", err)
	}
	defer sftpClient.Close()
	defer sshClient.Close()

	// 上传文件
	err = uploadFile(sftpClient, *l, *r)
	if err != nil {
		log.Printf("Failed to upload file: %v", err)
	}

	fmt.Println("File uploaded successfully!")
	return err
}