package ssh

import (
	"context"
	"errors"
	"fmt"
	"os"
	"path"
	"strings"
	"sync"

	"github.com/Neur0toxine/sshpoke/internal/config"
	"github.com/Neur0toxine/sshpoke/internal/server/driver/base"
	"github.com/Neur0toxine/sshpoke/internal/server/driver/ssh/types"
	"github.com/Neur0toxine/sshpoke/internal/server/driver/util"
	"github.com/Neur0toxine/sshpoke/internal/server/proto/sshtun"
	"github.com/Neur0toxine/sshpoke/pkg/dto"
	"golang.org/x/crypto/ssh"
)

type SSH struct {
	base.Base
	params   Params
	sessions map[string]conn
	keys     []ssh.Signer
	wg       sync.WaitGroup
}

type conn struct {
	container dto.Container
	tun       *sshtun.Tunnel
}

func New(ctx context.Context, name string, params config.DriverParams) (base.Driver, error) {
	drv := &SSH{
		Base:     base.New(ctx, name),
		sessions: make(map[string]conn),
	}
	if err := util.UnmarshalParams(params, &drv.params); err != nil {
		return nil, err
	}
	drv.populateFromSSHConfig()
	if err := drv.parseKeys(); err != nil {
		return nil, err
	}
	return drv, nil
}

func (d *SSH) populateFromSSHConfig() {
	if d.params.Auth.Directory == "" {
		return
	}
	cfg, err := parseSSHConfig(types.SmartPath(path.Join(string(d.params.Auth.Directory), "config")))
	if err != nil {
		return
	}
	if user, err := cfg.Get(d.params.Address, "User"); err == nil && user != "" {
		d.params.Auth.User = user
	}
	if usePass, err := cfg.Get(d.params.Address, "PasswordAuthentication"); err == nil && usePass == "yes" {
		d.params.Auth.Type = types.AuthTypePassword
	}
	if keyfile, err := cfg.Get(d.params.Address, "IdentityFile"); err == nil && keyfile != "" {
		resolvedKeyFile, err := types.SmartPath(keyfile).Resolve(false)
		if err == nil {
			d.params.Auth.Type = types.AuthTypeKey
			d.params.Auth.Keyfile = resolvedKeyFile
		}
	}
}

func (d *SSH) Handle(event dto.Event) error {
	// TODO: Implement event handling & connections management.
	return errors.New("server handler is not implemented yet")
}

func (d *SSH) Driver() config.DriverType {
	return config.DriverSSH
}

func (d *SSH) WaitForShutdown() {
	d.wg.Wait()
}

func (d *SSH) parseKeys() error {
	if d.params.Auth.Type != types.AuthTypeKey {
		return nil
	}
	dir, err := d.params.Auth.Directory.Resolve(true)
	if err != nil {
		return fmt.Errorf("cannot parse keys: %s", err)
	}
	if d.params.Auth.Keyfile != "" {
		key, err := parseKey(path.Join(dir, d.params.Auth.Keyfile))
		if err != nil {
			return err
		}
		d.keys = []ssh.Signer{key}
		return nil
	}
	entries, err := os.ReadDir(dir)
	if err != nil {
		return fmt.Errorf("cannot read key directory: %s", err)
	}
	keys := []ssh.Signer{}
	for _, entry := range entries {
		if entry.IsDir() {
			d.Log().Debugf("skipping '%s' because it's a directory", entry.Name())
			continue
		}
		info, err := entry.Info()
		if err != nil {
			d.Log().Debugf("skipping '%s' because stat failed: %s", entry.Name(), err)
			continue
		}
		if strings.HasSuffix(entry.Name(), ".pub") {
			d.Log().Debugf("skipping '%s' because it's probably a public key", entry.Name())
			continue
		}
		if entry.Name() == "config" {
			d.Log().Debugf("skipping '%s' because it's probably a ssh-config file", entry.Name())
			continue
		}
		if entry.Name() == "known_hosts" {
			d.Log().Debugf(
				"skipping '%s' because it's probably a list of hosts generated by OpenSSH", entry.Name())
			continue
		}
		// this file is too small to be a private key
		if info.Size() < 256 {
			d.Log().Debugf("skipping '%s' because the file is smaller than 256 bytes", entry.Name())
			continue
		}
		key, err := parseKey(path.Join(dir, entry.Name()))
		if err != nil {
			d.Log().Debugf("skipping '%s' because it's probably not a key: %s", entry.Name(), err)
			continue
		}
		d.Log().Debugf("loading key '%s', type: %s", entry.Name(), key.PublicKey().Type())
		keys = append(keys, key)
	}
	if len(keys) == 0 {
		return errors.New("no keys in the provided directory")
	}
	d.keys = keys
	return nil
}

func parseKey(keyFile string) (ssh.Signer, error) {
	keyData, err := os.ReadFile(keyFile)
	if err != nil {
		return nil, err
	}
	key, err := ssh.ParsePrivateKey(keyData)
	if err != nil {
		return nil, err
	}
	return key, nil
}