package ssh

import (
	"errors"
	"fmt"
	"io/ioutil"
	"net"
	"os"
	"strings"
	"syscall"

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

//HasAgent reports whether the SSH agent is available
func HasAgent() bool {
	authsock, ok := os.LookupEnv("SSH_AUTH_SOCK")
	if !ok {
		return false
	}
	if dirent, err := os.Stat(authsock); err != nil {
		if os.IsNotExist(err) {
			return false
		}
		if dirent.Mode()&os.ModeSocket == 0 {
			return false
		}
	}
	return true
}

// An implementation of ssh.KeyboardInteractiveChallenge that simply sends
// back the password for all questions. The questions are logged.
func passwordKeyboardInteractive(password string) ssh.KeyboardInteractiveChallenge {
	return func(user, instruction string, questions []string, echos []bool) ([]string, error) {
		// log.Printf("Keyboard interactive challenge: ")
		// log.Printf("-- User: %s", user)
		// log.Printf("-- Instructions: %s", instruction)
		// for i, question := range questions {
		// 	log.Printf("-- Question %d: %s", i+1, question)
		// }

		// Just send the password back for all questions
		answers := make([]string, len(questions))
		for i := range answers {
			answers[i] = password
		}

		return answers, nil
	}
}

// AuthWithKeyboardPassword Generate a password-auth'd ssh ClientConfig
func AuthWithKeyboardPassword(password string) (ssh.AuthMethod, error) {
	return ssh.KeyboardInteractive(passwordKeyboardInteractive(password)), nil
}

// AuthWithPassword Generate a password-auth'd ssh ClientConfig
func AuthWithPassword(password string) (ssh.AuthMethod, error) {
	return ssh.Password(password), nil
}

// AuthWithAgent use already authed user
func AuthWithAgent() (ssh.AuthMethod, error) {
	sock := os.Getenv("SSH_AUTH_SOCK")
	if sock == "" {
		// fmt.Println(errors.New("Agent Disabled"))
		return nil, errors.New("Agent Disabled")
	}
	socks, err := net.Dial("unix", sock)
	if err != nil {
		fmt.Println(err)
		return nil, err
	}
	// 1. 返回Signers函数的结果
	agent := agent.NewClient(socks)
	signers, err := agent.Signers()
	return ssh.PublicKeys(signers...), nil
	// 2. 返回Signers函数
	// getSigners := agent.NewClient(socks).Signers
	// return ssh.PublicKeysCallback(getSigners), nil

	// 3.简写方式
	// if sshAgent, err := net.Dial("unix", os.Getenv("SSH_AUTH_SOCK")); err == nil {
	// 	return ssh.PublicKeysCallback(agent.NewClient(sshAgent).Signers)
	// }
	// return nil
}

// AuthWithPrivateKeys 设置多个 ~/.ssh/id_rsa ,如果加密用passphrase尝试
func AuthWithPrivateKeys(keyFiles []string, passphrase string) (ssh.AuthMethod, error) {
	var signers []ssh.Signer

	for _, key := range keyFiles {

		pemBytes, err := ioutil.ReadFile(key)
		if err != nil {
			println(err.Error())
			// return
		}
		signer, err := ssh.ParsePrivateKey([]byte(pemBytes))
		if err != nil {
			if strings.Contains(err.Error(), "cannot decode encrypted private keys") {
				if signer, err = ssh.ParsePrivateKeyWithPassphrase(pemBytes, []byte(passphrase)); err != nil {
					continue
				}
			}
			// println(err.Error())
		}
		signers = append(signers, signer)

	}
	if signers == nil {
		return nil, errors.New("WithPrivateKeys: no keyfiles input")
	}
	return ssh.PublicKeys(signers...), nil
}

// AuthWithPrivateKey 自动监测是否带有密码
func AuthWithPrivateKey(keyfile string, passphrase string) (ssh.AuthMethod, error) {
	pemBytes, err := ioutil.ReadFile(keyfile)
	if err != nil {
		println(err.Error())
		return nil, err
	}

	var signer ssh.Signer
	signer, err = ssh.ParsePrivateKey(pemBytes)
	if err != nil {
		if strings.Contains(err.Error(), "cannot decode encrypted private keys") {
			signer, err = ssh.ParsePrivateKeyWithPassphrase(pemBytes, []byte(passphrase))
			if err == nil {
				return ssh.PublicKeys(signer), nil
			}
		}
		return nil, err
	}
	return ssh.PublicKeys(signer), nil

}

// AuthWithPrivateKeyString 直接通过字符串
func AuthWithPrivateKeyString(key string, password string) (ssh.AuthMethod, error) {
	var signer ssh.Signer
	var err error
	if password == "" {
		signer, err = ssh.ParsePrivateKey([]byte(key))
	} else {
		signer, err = ssh.ParsePrivateKeyWithPassphrase([]byte(key), []byte(password))
	}
	if err != nil {
		println(err.Error())
		return nil, err
	}
	return ssh.PublicKeys(signer), nil
}

// AuthWithPrivateKeyTerminal 通过终端读取带密码的 PublicKey
func AuthWithPrivateKeyTerminal(keyfile string) (ssh.AuthMethod, error) {
	pemBytes, err := ioutil.ReadFile(keyfile)
	if err != nil {

		println(err.Error())
		return nil, err
	}

	var signer ssh.Signer
	signer, err = ssh.ParsePrivateKey(pemBytes)
	if err != nil {
		if strings.Contains(err.Error(), "cannot decode encrypted private keys") {

			fmt.Fprintf(os.Stderr, "This SSH key is encrypted. Please enter passphrase for key '%s':", keyfile)
			passphrase, err := terminal.ReadPassword(int(syscall.Stdin))
			if err != nil {
				// println(err.Error())
				return nil, err
			}
			fmt.Fprintln(os.Stderr)
			if signer, err = ssh.ParsePrivateKeyWithPassphrase(pemBytes, []byte(passphrase)); err == nil {
				return ssh.PublicKeys(signer), nil
			}
		}
		return nil, err
	}
	return ssh.PublicKeys(signer), nil
}