package main

import (
	"bufio"
	"fmt"
	"io"
	"io/ioutil"
	"net"
	"os"
	"os/user"
	"path"
	"regexp"
	"strconv"
	"strings"
	"syscall"
	"time"

	"git.wecise.com/wecise/common/logger"
	"golang.org/x/crypto/ssh"
	"golang.org/x/crypto/ssh/terminal"
)

var (
	DefaultCiphers = []string{
		"aes128-ctr",
		"aes192-ctr",
		"aes256-ctr",
		"aes128-gcm@openssh.com",
		"chacha20-poly1305@openssh.com",
		"arcfour256",
		"arcfour128",
		"arcfour",
		"aes128-cbc",
		"3des-cbc",
		"blowfish-cbc",
		"cast128-cbc",
		"aes192-cbc",
		"aes256-cbc",
	}
)

type Client interface {
	Login()
}

type defaultClient struct {
	clientConfig *ssh.ClientConfig
	node         *Node
}

func genSSHConfig(node *Node) *defaultClient {
	u, err := user.Current()
	if err != nil {
		logger.Error(err)
		return nil
	}

	var authMethods []ssh.AuthMethod

	var pemBytes []byte
	if node.KeyPath == "" {
		pemBytes, err = ioutil.ReadFile(path.Join(u.HomeDir, ".ssh/id_rsa"))
	} else {
		pemBytes, err = ioutil.ReadFile(node.KeyPath)
	}
	if err != nil && !os.IsNotExist(err) {
		logger.Error(err)
	} else if len(pemBytes) > 0 {
		var signer ssh.Signer
		if node.Passphrase != "" {
			signer, err = ssh.ParsePrivateKeyWithPassphrase(pemBytes, []byte(node.Passphrase))
		} else {
			signer, err = ssh.ParsePrivateKey(pemBytes)
		}
		if err != nil {
			logger.Error(err)
		} else {
			authMethods = append(authMethods, ssh.PublicKeys(signer))
		}
	}

	password := node.password()

	if password != nil {
		authMethods = append(authMethods, password)
	}

	authMethods = append(authMethods, ssh.KeyboardInteractive(func(user, instruction string, questions []string, echos []bool) ([]string, error) {
		answers := make([]string, 0, len(questions))
		for i, q := range questions {
			fmt.Print(q)
			if echos[i] {
				scan := bufio.NewScanner(os.Stdin)
				if scan.Scan() {
					answers = append(answers, scan.Text())
				}
				err := scan.Err()
				if err != nil {
					return nil, err
				}
			} else {
				b, err := terminal.ReadPassword(int(syscall.Stdin))
				if err != nil {
					return nil, err
				}
				fmt.Println()
				answers = append(answers, string(b))
			}
		}
		return answers, nil
	}))

	config := &ssh.ClientConfig{
		User:            node.user(),
		Auth:            authMethods,
		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
		Timeout:         time.Second * 10,
	}

	config.SetDefaults()
	config.Ciphers = append(config.Ciphers, DefaultCiphers...)

	return &defaultClient{
		clientConfig: config,
		node:         node,
	}
}

func NewClient(node *Node) Client {
	return genSSHConfig(node)
}

func (c *defaultClient) Login() {
	host := c.node.Host
	port := strconv.Itoa(c.node.port())
	jNodes := c.node.Jump

	var client *ssh.Client

	if len(jNodes) > 0 {
		jNode := jNodes[0]
		jc := genSSHConfig(jNode)
		proxyClient, err := ssh.Dial("tcp", net.JoinHostPort(jNode.Host, strconv.Itoa(jNode.port())), jc.clientConfig)
		if err != nil {
			logger.Error(err)
			return
		}
		conn, err := proxyClient.Dial("tcp", net.JoinHostPort(host, port))
		if err != nil {
			logger.Error(err)
			return
		}
		ncc, chans, reqs, err := ssh.NewClientConn(conn, net.JoinHostPort(host, port), c.clientConfig)
		if err != nil {
			logger.Error(err)
			return
		}
		client = ssh.NewClient(ncc, chans, reqs)
	} else {
		client1, err := ssh.Dial("tcp", net.JoinHostPort(host, port), c.clientConfig)
		client = client1
		if err != nil {
			msg := err.Error()
			// use terminal password retry
			if strings.Contains(msg, "no supported methods remain") && !strings.Contains(msg, "password") {
				fmt.Printf("%s@%s's password:", c.clientConfig.User, host)
				var b []byte
				b, err = terminal.ReadPassword(int(syscall.Stdin))
				if err == nil {
					p := string(b)
					if p != "" {
						c.clientConfig.Auth = append(c.clientConfig.Auth, ssh.Password(p))
					}
					fmt.Println()
					client, err = ssh.Dial("tcp", net.JoinHostPort(host, port), c.clientConfig)
				}
			}
		}
		if err != nil {
			logger.Error(err)
			return
		}
	}
	defer client.Close()

	logger.Warnf("connect server ssh -p %d %s@%s version: %s\n", c.node.port(), c.node.user(), host, string(client.ServerVersion()))

	session, err := client.NewSession()
	if err != nil {
		logger.Error(err)
		return
	}
	defer session.Close()

	fd := int(os.Stdin.Fd())
	w, h, err := terminal.GetSize(fd)
	if err != nil {
		logger.Error(err)
		return
	}

	modes := ssh.TerminalModes{
		ssh.ECHO:          0,
		ssh.TTY_OP_ISPEED: 14400,
		ssh.TTY_OP_OSPEED: 14400,
	}
	err = session.RequestPty("xterm", h, w, modes)
	if err != nil {
		logger.Error(err)
		return
	}

	stdinPipe, err := session.StdinPipe()
	if err != nil {
		logger.Error(err)
		session.Stdin = os.Stdin
	}
	stdoutPipe, err := session.StdoutPipe()
	if err != nil {
		logger.Error(err)
		session.Stdout = os.Stdout
	}
	stderrPipe, err := session.StderrPipe()
	if err != nil {
		logger.Error(err)
		session.Stderr = os.Stderr
	}

	err = session.Shell()
	if err != nil {
		logger.Error(err)
		return
	}

	cmdidx := 0
	regxpassword := regexp.MustCompile(`.*[Pp]assword: *$`)
	regxprompt := regexp.MustCompile(`.*[%#\$\>]\s*$`)
	outputproc := func(stdoutbtr *BTReader, localstdout io.Writer, stdinPipe io.Writer) {
		as := ""
		change := false
		for {
			bs, err := stdoutbtr.ReadTimeout(10 * time.Millisecond)
			if err != nil {
				if err == io.EOF {
					return
				}
				logger.Error(err)
				return
			}
			if len(bs) > 0 {
				change = true
				s := string(bs)
				localstdout.Write([]byte(s))
				as += s
			} else if change {
				change = false
				if regxpassword.MatchString(as) {
					p := c.node.Commands[cmdidx].Password
					if p == "" {
						p = c.node.Commands[0].Password
					}
					// don't echo password, os.Stdout.Write([]byte(p + "\n"))
					stdinPipe.Write([]byte(p + "\n"))
				}
				if regxprompt.MatchString(as) {
					cmdidx++
					if cmdidx >= len(c.node.Commands) {
						localstdout.Write([]byte("exit" + "\n"))
						stdinPipe.Write([]byte("exit" + "\n"))
					} else {
						localstdout.Write([]byte(c.node.Commands[cmdidx].Cmd + "\n"))
						stdinPipe.Write([]byte(c.node.Commands[cmdidx].Cmd + "\n"))
					}
				}
				if len(as) > 1024 {
					as = as[len(as)-1024:]
				}
			}
		}
	}
	go outputproc(&BTReader{Reader: bufio.NewReader(stdoutPipe)}, os.Stdout, stdinPipe)
	go outputproc(&BTReader{Reader: bufio.NewReader(stderrPipe)}, os.Stderr, stdinPipe)

	go func() {
		for {
			bs := make([]byte, 1024)
			n, err := os.Stdin.Read(bs)
			if err != nil {
				if err == io.EOF {
					return
				}
				logger.Error(err)
				return
			}
			s := string(bs[:n])
			stdinPipe.Write([]byte(s))
		}
	}()

	// interval get terminal size
	// fix resize issue
	go func() {
		var (
			ow = w
			oh = h
		)
		for {
			cw, ch, err := terminal.GetSize(fd)
			if err != nil {
				break
			}

			if cw != ow || ch != oh {
				err = session.WindowChange(ch, cw)
				if err != nil {
					break
				}
				ow = cw
				oh = ch
			}
			time.Sleep(time.Second)
		}
	}()

	// send keepalive
	go func() {
		for {
			time.Sleep(time.Second * 10)
			client.SendRequest("nop", false, nil)
		}
	}()

	session.Wait()
	logger.Warnf("disconnected")
}

type BTReader struct {
	*bufio.Reader
	bufop int32
	chbs  chan []byte
}

func (me *BTReader) ReadTimeout(d time.Duration) (rbs []byte, err error) {
	if me.chbs == nil {
		me.chbs = make(chan []byte)
		go func() {
			n := 0
			bs := make([]byte, me.Size())
			for {
				_, err = me.ReadByte()
				if err != nil {
					return
				}
				err = me.UnreadByte()
				if err != nil {
					return
				}
				n, err = me.Read(bs[0:me.Buffered()])
				if err != nil {
					return
				}
				me.chbs <- bs[0:n]
			}
		}()
	}
	t := time.NewTimer(d)
	select {
	case rbs = <-me.chbs:
		return
	case <-t.C:
		return
	}
}