package services

import (
	"context"
	"github.com/gin-gonic/gin"
	"github.com/gisle/stufflog/config"
	"github.com/gisle/stufflog/database"
	"github.com/gisle/stufflog/internal/generate"
	"github.com/gisle/stufflog/models"
	"github.com/gisle/stufflog/slerrors"
	"golang.org/x/crypto/bcrypt"
	"time"
)

var dummyPassword []byte

type ctxKey string

const sessionCookie = "stufflog_sessid"
const sessionCtxKey = ctxKey("stufflog_session")
const userCtxKey = ctxKey("stufflog_user")

type AuthService struct {
	db database.Database
}

// UserFromContext gets the User object stored in the context.
func (s *AuthService) UserFromContext(ctx context.Context) *models.User {
	if gctx, ok := ctx.(*gin.Context); ok {
		ctx = gctx.Request.Context()
	}

	session := s.SessionFromContext(ctx)
	if session == nil {
		return nil
	}

	user, _ := ctx.Value(userCtxKey).(*models.User)
	return user
}

// SessionFromContext gets the Session object stored in the context.
func (s *AuthService) SessionFromContext(ctx context.Context) *models.UserSession {
	if gctx, ok := ctx.(*gin.Context); ok {
		ctx = gctx.Request.Context()
	}

	session, _ := ctx.Value(sessionCtxKey).(*models.UserSession)
	if session == nil || time.Now().After(session.Expires) {
		return nil
	}

	return session
}

// Register registers a new user.
func (s *AuthService) Register(ctx context.Context, username, password string) (*models.User, error) {
	if !config.Get().Users.AllowRegister {
		return nil, &slerrors.SLError{Code: 403, Text: "Registration is disabled"}
	}

	if len(password) < 6 {
		return nil, &slerrors.SLError{Code: 400, Text: "Password is too short"}
	}
	if len(username) == 0 {
		return nil, &slerrors.SLError{Code: 400, Text: "No username provided"}
	}

	if _, err := s.db.Users().FindID(ctx, username); !slerrors.IsNotFound(err) {
		return nil, &slerrors.SLError{Code: 409, Text: "Username is not available"}
	}

	user := models.User{
		ID:   username,
		Name: username,
	}
	err := user.SetPassword(password)
	if err != nil {
		return nil, err
	}
	err = s.db.Users().Save(ctx, user)

	return &user, nil
}

// Login logs in the user and creates the session. The session is not saved to the request. For that you need to use
// GinSaveSession on the returned session.
func (s *AuthService) Login(ctx context.Context, userID, password string) (*models.User, *models.UserSession, error) {
	user, err := s.db.Users().FindID(ctx, userID)
	if err != nil {
		_ = bcrypt.CompareHashAndPassword(dummyPassword, []byte("u r a dummy too"))
		return nil, nil, slerrors.LoginFailed()
	}

	err = user.CheckPassword(password)
	if err != nil {
		return nil, nil, slerrors.LoginFailed()
	}

	session := models.UserSession{
		ID:      generate.ID("S", 64),
		Expires: time.Now().Add(time.Hour * 24 * 30),
		UserID:  user.ID,
	}
	err = s.db.UserSessions().Save(ctx, session)
	if err != nil {
		return nil, nil, err
	}

	return user, &session, nil
}

// Logout deletes the session associated with the context.
func (s *AuthService) Logout(ctx context.Context) error {
	session := s.SessionFromContext(ctx)
	if session == nil {
		return slerrors.Unauthorized().WithText("You're already logged out.")
	}

	session.Expires = time.Time{}

	return s.db.UserSessions().Remove(ctx, *session)
}

// SaveSession saves a session to gin.
func (s *AuthService) GinSaveSession(c *gin.Context, session models.UserSession) {
	c.SetCookie(sessionCookie, session.ID, 336*3600, "", "", false, true)
}

// SaveSession saves a session to gin.
func (s *AuthService) GinClearSession(c *gin.Context) {
	c.SetCookie(sessionCookie, "", 0, "", "", false, true)
}

// Middleware is a middleware that adds a session to the context, or
// gives a 403 Unauthorized error if there is none.
func (s *AuthService) GinSessionMiddleware(required bool) gin.HandlerFunc {
	return func(c *gin.Context) {
		ctx := c.Request.Context()

		// Find cookie
		cookie, err := c.Cookie(sessionCookie)
		if err != nil || cookie == "" {
			if required {
				slerrors.GinRespond(c, slerrors.Unauthorized())
				c.Abort()
				return
			}

			c.Next()
			return
		}

		// Check session existence
		session, err := s.db.UserSessions().FindID(ctx, cookie)
		if err != nil {
			c.SetCookie(sessionCookie, "", 0, "", "", false, true)

			if required {
				slerrors.GinRespond(c, slerrors.Unauthorized())
				c.Abort()
				return
			}

			c.Next()
			return
		}
		ctx = context.WithValue(ctx, sessionCtxKey, session)

		// Find the user associated with the session
		user, err := s.db.Users().FindID(ctx, session.UserID)
		if err != nil {
			c.SetCookie(sessionCookie, "", 0, "", "", false, true)
			_ = s.db.UserSessions().Remove(ctx, *session)

			if required {
				slerrors.GinRespond(c, slerrors.Unauthorized())
				c.Abort()
				return
			}

			c.Next()
			return
		}
		ctx = context.WithValue(ctx, userCtxKey, user)

		// Check if session has expired
		if time.Now().After(session.Expires) {
			c.SetCookie(sessionCookie, "", 0, "", "", false, true)
			_ = s.db.UserSessions().Remove(ctx, *session)

			if required {
				slerrors.GinRespond(c, slerrors.Unauthorized())
				c.Abort()
				return
			}

			c.Next()
			return
		}

		// If there's less than 27.75 days, reset expiry.
		if time.Until(session.Expires) < time.Hour*666 {
			session.Expires = time.Now().Add(time.Hour * 672)
			s.GinSaveSession(c, *session)
			_ = s.db.UserSessions().Save(c.Request.Context(), *session)
		}

		// Proceed.
		c.Request = c.Request.WithContext(ctx)
		c.Next()
	}
}

func NewAuthService(db database.Database) *AuthService {
	return &AuthService{db: db}
}

func init() {
	dummyPassword, _ = bcrypt.GenerateFromPassword([]byte("u r a dummy"), bcrypt.DefaultCost)
}