package ssh

import (
	"fmt"
	"os"
	"os/user"
	"path"
	"path/filepath"
	"strconv"
)

const (
	BackendName = "ssh"

	HostKeyPolicyStrict    HostKeyPolicy = "strict"
	HostKeyPolicyAcceptNew HostKeyPolicy = "accept-new"
	HostKeyPolicyOff       HostKeyPolicy = "off"
)

type HostKeyPolicy string

type Options struct {
	Host               string
	User               string
	Port               int
	Root               string
	KeyFile            string
	KnownHosts         string
	HostKeyPolicy      HostKeyPolicy
	ReadOnlyKnownHosts bool
}

func (o Options) normalized() (Options, error) {
	if o.Host == "" {
		return Options{}, fmt.Errorf("host is required")
	}
	if o.User == "" {
		current, err := user.Current()
		if err != nil || current.Username == "" {
			return Options{}, fmt.Errorf("user is required when current OS user cannot be determined")
		}
		o.User = current.Username
	}
	if o.Port == 0 {
		o.Port = 22
	}
	if o.Port < 1 || o.Port > 65535 {
		return Options{}, fmt.Errorf("port must be between 1 and 65535")
	}
	if o.Root == "" {
		return Options{}, fmt.Errorf("path is required")
	}
	o.Root = path.Clean(o.Root)
	if o.HostKeyPolicy == "" {
		o.HostKeyPolicy = HostKeyPolicyAcceptNew
	}
	switch o.HostKeyPolicy {
	case HostKeyPolicyStrict, HostKeyPolicyAcceptNew, HostKeyPolicyOff:
	default:
		return Options{}, fmt.Errorf("host_key_policy must be strict, accept-new, or off")
	}
	if o.KnownHosts == "" && o.HostKeyPolicy != HostKeyPolicyOff {
		o.KnownHosts = defaultKnownHostsPath()
	}
	return o, nil
}

func (o Options) address() string {
	return o.Host + ":" + strconv.Itoa(o.Port)
}

func defaultKnownHostsPath() string {
	home, err := os.UserHomeDir()
	if err != nil || home == "" {
		return ""
	}
	return filepath.Join(home, ".ssh", "known_hosts")
}