package auth

// package for authenticating websockets
// we use a homespun jwt knock-off because no tls on lan
// authentication adds you to the AuthenticatedClients map
// broadcasts get sent to members of this map

import (
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"goseg/config"
	"goseg/structs"
	"net"
	"net/http"
	"strings"
	"sync"
	"time"

	"github.com/gorilla/websocket"
	"golang.org/x/crypto/nacl/secretbox"
)

var (
	// maps a websocket conn to a tokenid
	// tokenid's can be referenced from the global conf
	AuthenticatedClients = struct {
		Conns map[string]*websocket.Conn
		sync.RWMutex
	}{
		Conns: make(map[string]*websocket.Conn),
	}
	UnauthClients = struct {
		Conns map[string]*websocket.Conn
		sync.RWMutex
	}{
		Conns: make(map[string]*websocket.Conn),
	}
)

// check if websocket-token pair is auth'd
func WsIsAuthenticated(conn *websocket.Conn, token string) bool {
	AuthenticatedClients.RLock()
	defer AuthenticatedClients.RUnlock()
	if AuthenticatedClients.Conns[token] == conn {
		return true
	} else {
		return false
	}
}

// quick check if websocket is authed at all for unauth broadcast (not for actual auth)
func WsAuthCheck(conn *websocket.Conn) bool {
	AuthenticatedClients.RLock()
	defer AuthenticatedClients.RUnlock()
	for _, con := range AuthenticatedClients.Conns {
		if con == conn {
			config.Logger.Info("Client in auth map")
			return true
		}
	}
	config.Logger.Info("Client not in auth map")
	return false
}

// this takes a bool for auth/unauth -- also persists to config
func AddToAuthMap(conn *websocket.Conn, token map[string]string, authed bool) error {
	tokenStr := token["token"]
	tokenId := token["id"]
	hashed := sha256.Sum256([]byte(tokenStr))
	hash := hex.EncodeToString(hashed[:])
	if authed {
		AuthenticatedClients.Lock()
		AuthenticatedClients.Conns[tokenId] = conn
		AuthenticatedClients.Unlock()
		UnauthClients.Lock()
		if _, ok := UnauthClients.Conns[tokenId]; ok {
			delete(UnauthClients.Conns, tokenId)
		}
		UnauthClients.Unlock()
	} else {
		UnauthClients.Lock()
		UnauthClients.Conns[tokenId] = conn
		UnauthClients.Unlock()
		AuthenticatedClients.Lock()
		if _, ok := AuthenticatedClients.Conns[tokenId]; ok {
			delete(AuthenticatedClients.Conns, tokenId)
		}
		AuthenticatedClients.Unlock()
	}
	now := time.Now().Format("2006-01-02_15:04:05")
	err := AddSession(tokenId, hash, now, authed)
	if err != nil {
		return err
	}
	return nil
}

// check the validity of the token
func CheckToken(token map[string]string, conn *websocket.Conn, r *http.Request, setup bool) bool {
	// great you have token. we see if valid.
	if token["token"] == "" {
		return false
	}
	config.Logger.Info(fmt.Sprintf("Checking token %s",token["id"]))
	conf := config.Conf()
	key := conf.KeyFile
	res, err := KeyfileDecrypt(token["token"], key)
	if err != nil {
		config.Logger.Warn("Invalid token provided")
		return false
	} else {
		// so you decrypt. now we see the useragent and ip.
		var ip string
		if forwarded := r.Header.Get("X-Forwarded-For"); forwarded != "" {
			ip = strings.Split(forwarded, ",")[0]
		} else {
			ip, _, _ = net.SplitHostPort(r.RemoteAddr)
		}
		userAgent := r.Header.Get("User-Agent")
		hashed := sha256.Sum256([]byte(token["token"]))
		hash := hex.EncodeToString(hashed[:])
		// you in auth map?
		if WsIsAuthenticated(conn, hash) {
			if ip == res["ip"] && userAgent == res["user_agent"] {
				config.Logger.Info("Token authenticated")
				return true
			} else {
				config.Logger.Warn("Token doesn't match session!")
				return false
			}
		} else {
			config.Logger.Warn("Token isn't an authenticated session")
			return false
		}
	}
	return false
}

// create a new session token
func CreateToken(conn *websocket.Conn, r *http.Request, setup bool) (map[string]string, error) {
	// extract conn info
	var ip string
	if forwarded := r.Header.Get("X-Forwarded-For"); forwarded != "" {
		ip = strings.Split(forwarded, ",")[0]
	} else {
		ip, _, _ = net.SplitHostPort(r.RemoteAddr)
	}
	userAgent := r.Header.Get("User-Agent")
	conf := config.Conf()
	now := time.Now().Format("2006-01-02_15:04:05")
	// generate random strings for id, secret, and padding
	id := config.RandString(32)
	secret := config.RandString(128)
	padding := config.RandString(32)
	contents := map[string]string{
		"id":         id,
		"ip":         ip,
		"user_agent": userAgent,
		"secret":     secret,
		"padding":    padding,
		"authorized": fmt.Sprintf("%v", setup),
		"created":    now,
	}
	// encrypt the contents
	key := conf.KeyFile
	encryptedText, err := KeyfileEncrypt(contents, key)
	if err != nil {
		config.Logger.Error(fmt.Sprintf("failed to encrypt token: %v", err))
		return nil, fmt.Errorf("failed to encrypt token: %v", err)
	}
	token := map[string]string{
		"id":    id,
		"token": encryptedText,
	}
	// Update sessions in the system's configuration
	AddToAuthMap(conn, token, setup)
	return token, nil
}

// take session details and add to SysConfig
func AddSession(tokenID string, hash string, created string, authorized bool) error {
	session := structs.SessionInfo{
		Hash:    hash,
		Created: created,
	}
	if authorized {
		update := map[string]interface{}{
			"Sessions": map[string]interface{}{
				"Authorized": map[string]string{
					"Hash":    session.Hash,
					"Created": session.Created,
				},
			},
		}
		if err := config.UpdateConf(update); err != nil {
			return fmt.Errorf("Error adding session: %v", err)
		}
		if err := config.RemoveSession(tokenID, false); err != nil {
			return fmt.Errorf("Error removing session: %v", err)
		}
	} else {
		update := map[string]interface{}{
			"Sessions": map[string]interface{}{
				"Unauthorized": map[string]string{
					"Hash":    session.Hash,
					"Created": session.Created,
				},
			},
		}
		if err := config.UpdateConf(update); err != nil {
			return fmt.Errorf("Error adding session: %v", err)
		}
		if err := config.RemoveSession(tokenID, true); err != nil {
			return fmt.Errorf("Error removing session: %v", err)
		}
	}
	return nil
}

// encrypt the contents using stored keyfile val
func KeyfileEncrypt(contents map[string]string, key string) (string, error) {
	contentBytes, err := json.Marshal(contents)
	if err != nil {
		return "", err
	}
	// convert key to bytes
	keyBytes := []byte(key)
	if len(keyBytes) != 32 {
		return "", fmt.Errorf("key must be 32 bytes in length")
	}
	var keyArray [32]byte
	copy(keyArray[:], keyBytes)
	// generate nonce
	var nonce [24]byte
	if _, err := rand.Read(nonce[:]); err != nil {
		return "", err
	}
	// encrypt contents
	encrypted := secretbox.Seal(nonce[:], contentBytes, &nonce, &keyArray)
	return base64.URLEncoding.EncodeToString(encrypted), nil
}

// decrypt routine
func KeyfileDecrypt(encryptedText string, key string) (map[string]string, error) {
	// get bytes
	keyBytes := []byte(key)
	var keyArray [32]byte
	copy(keyArray[:], keyBytes)
	encryptedBytes, err := base64.URLEncoding.DecodeString(encryptedText)
	if err != nil {
		return nil, err
	}
	// get nonce
	var nonce [24]byte
	copy(nonce[:], encryptedBytes[:24])
	// attempt decrypt
	decrypted, ok := secretbox.Open(nil, encryptedBytes[24:], &nonce, &keyArray)
	if !ok {
		return nil, fmt.Errorf("Decryption failed")
	}
	var contents map[string]string
	if err := json.Unmarshal(decrypted, &contents); err != nil {
		return nil, err
	}
	return contents, nil
}

// salted sha256
func Hasher(password string) string {
	conf := config.Conf()
	salt := conf.Salt
	toHash := salt + password
	res := sha256.Sum256([]byte(toHash))
	return hex.EncodeToString(res[:])
}

// check if pw matches sysconfig
func AuthenticateLogin(password string) bool {
	conf := config.Conf()
	hash := Hasher(password)
	if hash == conf.PwHash {
		return true
	} else {
		config.Logger.Warn(fmt.Sprintf("debug: failed pw hash: %v", hash))
		return false
	}
}