package sshclient

import (
	"bytes"
	"fmt"
	"net"
	"os"
	"regexp"
	"strings"
	"time"

	"golang.org/x/crypto/ssh"
)

// Client SSH客户端
type Client struct {
	client          *ssh.Client
	timeout         time.Duration
	host            string
	port            int
	username        string
	password        string
	keyFile         string
	insecureCiphers bool
}

// Config SSH客户端配置
type Config struct {
	Host            string
	Port            int
	Username        string
	Password        string
	KeyFile         string
	Timeout         time.Duration
	InsecureCiphers bool // 启用不安全的加密算法(用于兼容老旧设备)
}

// NewClient 创建新的SSH客户端
func NewClient(config Config) *Client {
	if config.Port == 0 {
		config.Port = 22
	}
	if config.Timeout == 0 {
		config.Timeout = 30 * time.Second
	}
	return &Client{
		host:            config.Host,
		port:            config.Port,
		username:        config.Username,
		password:        config.Password,
		keyFile:         config.KeyFile,
		timeout:         config.Timeout,
		insecureCiphers: config.InsecureCiphers,
	}
}

// Connect 连接到SSH服务器
func (c *Client) Connect() error {
	config := &ssh.ClientConfig{
		User:            c.username,
		Auth:            []ssh.AuthMethod{},
		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
		Timeout:         c.timeout,
	}

	// 添加密码认证
	if c.password != "" {
		config.Auth = append(config.Auth, ssh.Password(c.password))
	}

	// 添加密钥认证
	if c.keyFile != "" {
		key, err := loadPrivateKey(c.keyFile)
		if err != nil {
			return fmt.Errorf("failed to load private key: %w", err)
		}
		config.Auth = append(config.Auth, ssh.PublicKeys(key))
	}

	// 如果启用不安全加密算法,添加旧版算法支持(用于兼容老旧设备)
	if c.insecureCiphers {
		config.Ciphers = []string{
			"aes128-ctr", "aes192-ctr", "aes256-ctr",
			"aes128-gcm@openssh.com", "aes256-gcm@openssh.com",
			"chacha20-poly1305@openssh.com",
			"aes128-cbc", "aes256-cbc", // 旧版CBC算法
		}
		config.KeyExchanges = []string{
			"curve25519-sha256", "curve25519-sha256@libssh.org",
			"ecdh-sha2-nistp256", "ecdh-sha2-nistp384", "ecdh-sha2-nistp521",
			"diffie-hellman-group14-sha256", "diffie-hellman-group16-sha512",
			"diffie-hellman-group14-sha1", "diffie-hellman-group1-sha1", // 旧版KEX算法
		}
		config.MACs = []string{
			"hmac-sha2-256-etm@openssh.com", "hmac-sha2-512-etm@openssh.com",
			"hmac-sha2-256", "hmac-sha2-512",
			"hmac-sha1", "hmac-sha1-96", // 旧版MAC算法
		}
	}

	// 连接
	addr := fmt.Sprintf("%s:%d", c.host, c.port)
	client, err := ssh.Dial("tcp", addr, config)
	if err != nil {
		return fmt.Errorf("failed to connect to %s: %w", addr, err)
	}

	c.client = client
	return nil
}

// Close 关闭SSH连接
func (c *Client) Close() error {
	if c.client != nil {
		return c.client.Close()
	}
	return nil
}

// ExecuteCommand 执行命令并返回输出（每个命令使用新会话）
func (c *Client) ExecuteCommand(command string) (string, error) {
	if c.client == nil {
		return "", fmt.Errorf("not connected")
	}

	// 创建新会话
	session, err := c.client.NewSession()
	if err != nil {
		return "", fmt.Errorf("failed to create session: %w", err)
	}
	defer session.Close()

	var stdoutBuf bytes.Buffer
	session.Stdout = &stdoutBuf
	session.Stderr = &stdoutBuf

	err = session.Run(command)
	if err != nil {
		return stdoutBuf.String(), fmt.Errorf("command '%s' failed: %w", command, err)
	}

	return stdoutBuf.String(), nil
}

// ExecuteCommands 执行多个命令（使用Shell模式，在同一个会话中顺序执行）
func (c *Client) ExecuteCommands(commands []string) ([]string, error) {
	if c.client == nil {
		return nil, fmt.Errorf("not connected")
	}

	// 创建一个shell会话
	session, err := c.client.NewSession()
	if err != nil {
		return nil, fmt.Errorf("failed to create session: %w", err)
	}
	defer session.Close()

	// 请求PTY
	modes := ssh.TerminalModes{
		ssh.ECHO:          0,     // 禁用回显
		ssh.TTY_OP_ISPEED: 14400, // 输入速度
		ssh.TTY_OP_OSPEED: 14400, // 输出速度
	}
	if err := session.RequestPty("dumb", 200, 1000, modes); err != nil {
		return nil, fmt.Errorf("failed to request pty: %w", err)
	}

	// 获取stdin管道
	stdin, err := session.StdinPipe()
	if err != nil {
		return nil, fmt.Errorf("failed to get stdin pipe: %w", err)
	}

	// 捕获输出
	var stdoutBuf bytes.Buffer
	var stderrBuf bytes.Buffer
	session.Stdout = &stdoutBuf
	session.Stderr = &stderrBuf

	// 启动shell
	if err := session.Shell(); err != nil {
		return nil, fmt.Errorf("failed to start shell: %w", err)
	}

	// 执行命令并收集输出（使用分隔符标记）
	results := make([]string, 0, len(commands))
	
	for i, cmd := range commands {
		// 等待一段时间防止设备速率限制
		if i > 0 {
			time.Sleep(2 * time.Second)
		}

		// 生成分隔符标记命令边界
		delimiter := fmt.Sprintf("===CMD_BOUNDARY_%d===", i)
		
		// 发送命令
		if _, err := stdin.Write([]byte(cmd + "\n")); err != nil {
			return results, fmt.Errorf("failed to send command '%s': %w", cmd, err)
		}

		// 等待命令执行完成（不同命令需要不同等待时间）
		sleepTime := 1 * time.Second
		if cmd == "display interface" || strings.Contains(cmd, "display interface") {
			sleepTime = 8 * time.Second // 大输出命令需要更多时间
		} else if cmd == "display lldp neighbor-information" {
			sleepTime = 3 * time.Second
		}
		time.Sleep(sleepTime)
		
		// 发送分隔符（不执行任何操作，只是标记）
		if _, err := stdin.Write([]byte("echo " + delimiter + "\n")); err != nil {
			return results, fmt.Errorf("failed to send delimiter: %w", err)
		}
		
		// 等待分隔符输出
		time.Sleep(500 * time.Millisecond)

		// 获取完整输出并清理
		rawOutput := stdoutBuf.String()
		
		// 找到分隔符位置，提取当前命令的输出部分
		parts := strings.Split(rawOutput, delimiter)
		cmdOutput := ""
		if len(parts) > 1 {
			// 取最后一个分隔符之前的部分（当前命令的输出）
			cmdOutput = parts[len(parts)-2] // 倒数第二部分是当前命令输出，最后一部分是分隔符后的空内容
		} else {
			cmdOutput = rawOutput
		}
		
		cleanOutput := cleanCommandOutput(cmdOutput, cmd)
		results = append(results, cleanOutput)
		
		fmt.Printf("[SSH] Command '%s' extracted %d bytes from %d bytes raw output\n", 
			cmd, len(cleanOutput), len(rawOutput))
	}

	// 退出shell
	stdin.Write([]byte("exit\n"))
	session.Wait()

	return results, nil
}

// cleanCommandOutput 清理命令输出，移除命令回显、分页提示和提示符
func cleanCommandOutput(output, command string) string {
	// 清理\r\n为\n
	output = strings.ReplaceAll(output, "\r\n", "\n")

	lines := strings.Split(output, "\n")
	var cleanLines []string
	skipCommandEcho := true // 跳过命令本身的回显

	for _, line := range lines {
		trimmedLine := strings.TrimSpace(line)

		// 跳过空行（如果是开头）
		if trimmedLine == "" && len(cleanLines) == 0 {
			continue
		}

		// 跳过命令回显（第一次出现）
		if skipCommandEcho && trimmedLine == strings.TrimSpace(command) {
			skipCommandEcho = false
			continue
		}

		// 跳过分页提示
		if strings.Contains(trimmedLine, "---- More ----") {
			continue
		}

		// 跳过提示符行（如 <hostname> 或 [hostname]）
		if regexp.MustCompile(`^[<\[]\S+[>\]]$`).MatchString(trimmedLine) {
			continue
		}

		// 跳过版权信息（开头）
		if strings.HasPrefix(trimmedLine, "*********") {
			continue
		}
		if strings.HasPrefix(trimmedLine, "* Copyright") {
			continue
		}
		if strings.HasPrefix(trimmedLine, "* Without") {
			continue
		}
		if strings.HasPrefix(trimmedLine, "* no decompiling") {
			continue
		}

		cleanLines = append(cleanLines, trimmedLine)
	}

	return strings.Join(cleanLines, "\n")
}

// CheckSSH 检查主机是否开启SSH
func CheckSSH(host string, port int, timeout time.Duration) bool {
	if port == 0 {
		port = 22
	}
	if timeout == 0 {
		timeout = 2 * time.Second
	}

	addr := fmt.Sprintf("%s:%d", host, port)
	conn, err := net.DialTimeout("tcp", addr, timeout)
	if err != nil {
		return false
	}
	defer conn.Close()
	return true
}

// loadPrivateKey 加载私钥文件
func loadPrivateKey(keyFile string) (ssh.Signer, error) {
	keyData, err := os.ReadFile(keyFile)
	if err != nil {
		return nil, fmt.Errorf("failed to read key file: %w", err)
	}

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

	return signer, nil
}

// Ping 检查主机是否可达 (使用ICMP)
func Ping(host string, timeout time.Duration) bool {
	// 简单的TCP ping,实际项目可以使用专门的ICMP库
	ports := []int{22, 80, 443, 3389}
	for _, port := range ports {
		addr := fmt.Sprintf("%s:%d", host, port)
		conn, err := net.DialTimeout("tcp", addr, timeout)
		if err == nil {
			conn.Close()
			return true
		}
	}
	return false
}