package main

import (
	"github.com/pkg/sftp"
	"golang.org/x/crypto/ssh"
	"io"
	"log"
	"os"
	"strings"
	"bufio"
	"fmt"
	"path/filepath"
	)

func main() {

	user   := "user"
	pass   := "password"
	remote := "10.x.x.x"
	port   := ":22"

	// get host public key
	hostKey := getHostKey(remote)
    fmt.Println("HOSTKEY:",  hostKey)
	config := &ssh.ClientConfig{
		User: user,
		Auth: []ssh.AuthMethod{
			ssh.Password(pass),
		},
		// HostKeyCallback: ssh.InsecureIgnoreHostKey(),
		HostKeyCallback: ssh.FixedHostKey(hostKey),
	}

	// connect
	conn, err := ssh.Dial("tcp", remote+port, config)
	if err != nil {
	   log.Fatal(err)
	}
	defer conn.Close()

	// create new SFTP client
	client, err := sftp.NewClient(conn)
	if err != nil {
	   log.Fatal(err)
	}
	defer client.Close()

	// create destination file
	dstFile, err := os.Create("./file.zip")
	if err != nil {
	   log.Fatal(err)
	}
	defer dstFile.Close()

	// open source file
	srcFile, err := client.Open("/opt/to/file-1.zip")
	if err != nil {
	   log.Fatal(err)
	}

	// copy source file to destination file
	bytes, err := io.Copy(dstFile, srcFile)
	if err != nil {
	   log.Fatal(err)
	}
	fmt.Printf("%d bytes copied\n", bytes)

	// flush in-memory copy
	err = dstFile.Sync()
	if err != nil {
	   log.Fatal(err)
	}
}

func getHostKey(host string) ssh.PublicKey {
	// parse OpenSSH known_hosts file
	// ssh or use ssh-keyscan to get initial key
		home, err := os.UserHomeDir()
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("HOME:",  home)

	file, err := os.Open(filepath.Join(home, ".ssh", "known_hosts"))
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	var hostKey ssh.PublicKey
	for scanner.Scan() {
		fields := strings.Split(scanner.Text(), " ")
		if len(fields) != 3 {
			continue
		}
		if strings.Contains(fields[0], host) {
			var err error
			hostKey, _, _, _, err = ssh.ParseAuthorizedKey(scanner.Bytes())
			if err != nil {
				log.Fatalf("error parsing %q: %v", fields[2], err)
			}
			break
		}
	}

	if hostKey == nil {
		log.Fatalf("no hostkey found for %s", host)
	}

	return hostKey
}