const (
	// SessionDefaultKey is default key for okrzeja session's cookie key.
	SessionDefaultKey = "okrzeja-session"

	// SessionDefaultTTL is default time to live for okrzeja session, which
	// is two days.
	SessionDefaultTTL = time.Hour * 48
)

const (
	// CSRFHeaderKey is key for CSRF token header value.
	CSRFHeaderKey = "X-CSRF-Token"
)

const FileSystemResource = "filesystem"

const UsersResource = "users"

var ErrCSRFInvalid error = NewErrorFromCode(
	http.StatusUnauthorized,
	ErrorMetadata{
		Description: "invalid CSRF token fails verification",
		Message:     "Cross site request forgery attempt.",
	},
)

var ErrCSRFNotFound error = NewErrorFromCode(
	http.StatusInternalServerError,
	ErrorMetadata{
		Description: "there is no CSRF token in the context",
		Message:     "Internal Server Error, please try again later.",
	},
)

var SessionDefaultEncoding = base64.URLEncoding

type AdminReader interface {
	// AdminConfirm returns true if user with given UUID is admin.
	AdminConfirm(context.Context, uuid.UUID) (bool, error)
}

type Authenticator interface {
	// AuthenticateUser authorizes user with given username and passwords. It returns
	// authorized user's ID or error if authorization failed.
	AuthenticateUser(ctx context.Context, username, password string) (uuid.UUID, error)
}

type CSRF struct {
	// contains filtered or unexported fields
}

type CSRFReadRepository interface {
	// CSRFTokenRead returns token associated with given unique session ID.
	CSRFTokenRead(ctx context.Context, sessionID uuid.UUID) (string, error)
}

type CSRFRepository interface {
	CSRFReadRepository
	CSRFWriteRepository
}

type CSRFWriteRepository interface {
	// CSRFTokenWrite saves token associated with session in the CSRF
	// token storage.
	CSRFTokenWrite(ctx context.Context, req CSRFWriteRequest) error
}

type CSRFWriteRequest struct {
	// Token is string of characters, that is: unique, secret and unpredictable.
	Token string

	// SessionID is unique session's identifier associated
	// with new CSRF token.
	SessionID uuid.UUID
}

type Clock func() time.Time

type Commands struct {
	// Login accepts login credentials data for signing in with
	// existing account.
	//
	// HTTP request details:
	//
	//   POST /login
	//
	// Gateway can guard clients with active session from accessing
	// Login command.
	Login http.HandlerFunc

	// Register accepts registration data for creating new account
	// for user.
	//
	// HTTP request details:
	//
	//   POST /register
	//
	// Gateway can guard clients with active session from accessing
	// Register command.
	Register http.HandlerFunc

	// HandlerLogout purges current user's session, if there is any.
	//
	// HTTP request details:
	//
	//   POST /logout
	//
	// Gateway can guard clients without active session from accessing
	// Register command.
	Logout http.HandlerFunc

	// FileUpdateContent updates content of the file with ID provided in the
	// URL path.
	//
	// HTTP request details:
	//
	//   PUT /files/{id}
	//
	// Path parameters:
	//
	// * id - unique identifier of file.
	//
	// Gateway can guard clients without active session or proper
	// permissions from accessing FileUpdateContent command.
	FileUpdateContent http.HandlerFunc

	// FileDelete removes file, with ID passed by the path, from filesystem.
	//
	// HTTP request details:
	//
	//   DELETE /files/{id}
	//
	// Path parameters:
	//
	// * id - unique identifier of file.
	//
	// Gateway can guard clients without active session or proper
	// permissions from accessing FileDelete command.
	FileDelete http.HandlerFunc

	// FileNew creates new file or directory in the directory pointed out by
	// identifier in the path.
	//
	// HTTP request details:
	//
	//   PUT /files/{id}/new
	//
	// Path parameters:
	//
	// * id - unique identifier of file.
	//
	// Gateway can guard clients without active session or proper
	// permissions from accessing FileNew command.
	FileNew http.HandlerFunc

	// FileUpdateName updates name of the file with ID provided in the
	// URL path.
	//
	// HTTP request details:
	//
	//   PUT /files/{id}/name
	//
	// Path parameters:
	//
	// * id - unique identifier of file.
	//
	// Gateway can guard clients without active session or proper
	// permissions from accessing FileUpdateName command.
	FileUpdateName http.HandlerFunc

	// UserChangePassword updates password of the user with ID from
	// URL path with assumption that users know their old password.
	//
	// HTTP request details:
	//
	//   PUT /users/{id}/password
	//
	// Gateway can guard clients without active session or proper
	// permissions from accessing UserChangePassword command.
	UserChangePassword http.HandlerFunc

	// AdminChangeUserPassword command changes user password with the
	// new one provided in the form.
	//
	// HTTP request details:
	//
	//   PUT /admin/users/{id}/password
	//
	// Path parameters:
	//
	// * id - unique identifier of user.
	//
	// Gateway can guard clients from accessing AdminChangeUserPassword
	// endpoint without active session and admin permissions.
	AdminChangeUserPassword http.HandlerFunc

	// AdminDeleteUser removes user with provided ID from the system.
	//
	// HTTP request details:
	//
	//   DELETE /admin/users/{id}
	//
	// Path parameters:
	//
	// * id - unique identifier of user.
	//
	// Gateway can guard clients from accessing AdminDeleteUser
	// endpoint without active session and admin permissions.
	AdminDeleteUser http.HandlerFunc

	// AdminPushConfig updates config with new version of it.
	//
	// HTTP request details:
	//
	//   POST /admin/config
	//
	// Gateway can guard clients from accessing AdminPushConfig
	// endpoint without active session and admin permissions.
	AdminPushConfig http.HandlerFunc

	// AdminPostBatchOfUsers adds multiple user accounts at once.
	//
	// HTTP request details:
	//
	//   POST /admin/users
	//
	// Gateway can guard clients from accessing AdminPostBatchOfUsers
	// endpoint without active session and admin permissions.
	AdminPostBatchOfUsers http.HandlerFunc
}

type CookiesSession struct {
	// contains filtered or unexported fields
}

type DefaultCookieSessionRequest struct {
	SessionStorage
	Authenticator
	CSRF *CSRF
}

type Error struct {
	// Code is HTTP status code.
	Code int

	// Wrapped error value. Can be nil if Error isn't wrapping
	// any error value.
	Wrapped error

	// Description of error for debug purposes. It shouldn't
	// be displayed to users. You can omit description if you're
	// wrapping already existing error value.
	Description string

	// Title is human readable title, which is safe
	// for output to users.
	Title string

	// Message is human readable error message, which is
	// safe to output to users.
	Message string
}

type ErrorHandler interface {
	// ErrorHandler returns http.Handler for given error value.
	//
	// Consider the fact that err error value can be of type *Error.
	HandleError(err error) http.Handler
}

type ErrorHandlerFunc func(err error) http.Handler

type ErrorMetadata struct {
	// Wrapped error value. Can be nil if Error isn't wrapping
	// any error value.
	Wrapped error

	// Description of error for debug purposes. It shouldn't
	// be displayed to users. You can omit description if you're
	// wrapping already existing error value.
	Description string

	// Message is human readable error message, which is
	// safe to output to users.
	Message string
}

type Gateway struct {
	// contains filtered or unexported fields
}

type GatewayBuilder struct {
	// contains filtered or unexported fields
}

type Handlers struct {
	// Views are view handlers.
	Views

	// Commands are command handlers.
	Commands
}

type PersonalFileSystemReader interface {
	// PersonalFileSystem returns http.FileSystem that is able to read files from
	// users' personal file systems.
	PersonalFileSystem(ctx context.Context) http.FileSystem
}

type RegistrationGuard interface {
	// RegistrationEnabled returns true if registration for appliation
	// is currently enabled.
	RegistrationEnabled(context.Context) (bool, error)
}

type ResourceAction uint8

const (
	// ResourceRead allows to read resource.
	ResourceRead ResourceAction = 1 << iota

	// ResourceWrite allows to write to the resource.
	ResourceWrite

	// ResourceDelete allows to remove resources from storage.
	ResourceDelete
)

type ResourceAuthorizationRequest struct {
	// Action of the request.
	Action ResourceAction

	// ResourceName is name of the resource.
	ResourceName string

	// ResourceID is unique resource's identifier.
	ResourceID uuid.UUID

	// UserID is unique user's identifier.
	UserID uuid.UUID
}

type ResourceAuthorizer interface {
	// ActionAuthorize returns true if user with given unique identifier is
	// authorized to perform Action on the resource with given unique resource's
	// identifier. Otherwise it returns false.
	ActionAuthorize(ctx context.Context, req ResourceAuthorizationRequest) (bool, error)
}

type SessionHandlerRequest struct {
	// Username of the user.
	Username string

	// Password for user's account.
	Password string
}

type SessionOwner struct {
	ID       uuid.UUID `json:"id"`
	Username string    `json:"username"`
}

type SessionState struct {
	ID        uuid.UUID     `json:"id"`
	CreatedAt time.Time     `json:"createdAt"`
	TTL       time.Duration `json:"ttl"`
	Owner     SessionOwner  `json:"owner"`
}

type SessionStorage interface {
	SessionStorageWriter
	SessionStorageReader
	SessionStorageDeleter
}

type SessionStorageDeleter interface {
	// DeleteSession removes completely information about session
	// with given ID from storage.
	DeleteSession(context.Context, uuid.UUID) error
}

type SessionStorageReader interface {
	// ReadSession reads session's state with provided uuid from
	// session's storage.
	ReadSession(context.Context, uuid.UUID) (*SessionState, error)
}

type SessionStorageWriter interface {
	// WriteSession writes given session to session storage.
	WriteSession(context.Context, SessionState) error
}

type Views struct {
	// Index shows main index page.
	//
	// HTTP request details:
	//
	//   GET /
	Index http.HandlerFunc

	// Login shows login form page.
	//
	// HTTP request details:
	//
	//   GET /login
	//
	// Gateway can guard clients from accessing Login page
	// with active session.
	Login http.HandlerFunc

	// Register accepts registration data for creating new account
	// for user.
	//
	// HTTP request details:
	//
	// GET /register
	//
	// Gateway can guard clients from accessing Register page
	// with active session.
	Register http.HandlerFunc

	// Account shows all available account sub-pages for the user.
	//
	// HTTP request details:
	//
	//  GET /account
	//
	// Gateway can guard clients from accessing Account page
	// without active session.
	Account http.HandlerFunc

	// FormFields renders input fields for new file form with
	// type provided in the "kind" URL query parameter.
	//
	// HTTP request details:
	//
	//  GET /files/form/fields
	//
	// Gateway can guard clients from accessing this component
	// without active session.
	FormFields http.HandlerFunc

	// Files renders proper view for file with given ID, so directory will be
	// rendered differently than regular file with content etc.
	//
	// HTTP request details:
	//
	//  GET /files/{id}
	//
	// Path parameters:
	//
	// * id - unique identifier of file.
	//
	// Gateway can guard clients from accessing Files page
	// without active sessiona and without proper permissions.
	Files http.HandlerFunc

	// Editor shows editor for file with provided unique identifier as
	// path parameter.
	//
	// HTTP request details:
	//
	//  GET /files/{id}/editor
	//
	// Path parameters:
	//
	// * id - unique identifier of file.
	//
	// Gateway can guard clients from accessing Editor page
	// without active sessiona and without proper permissions.
	Editor http.HandlerFunc

	// FileNew renders form for adding new file or directory attached
	// to directory pointed by identifier from path.
	//
	// HTTP request details:
	//
	//   GET /files/{id}/new
	//
	// Path parameters:
	//
	// * id - unique identifier of file.
	//
	// Gateway can guard clients from accessing NewFile page
	// without active sessiona and without proper permissions.
	FileNew http.HandlerFunc

	// FileName renders view for inspecting and changing name of the file.
	//
	// HTTP request details:
	//
	//   GET /files/{id}/name
	//
	// Path parameters:
	//
	// * id - unique identifier of file.
	//
	// Gateway can guard clients from accessing FileName page
	// without active session and without proper permissions.
	FileName http.HandlerFunc

	// Settings component allows users to knob their account's settings
	// in a controlled way
	//
	// HTTP request details:
	//
	//   GET /settings
	//
	// Gateway can guard clients from accessing Settings page
	// without active session and proper permissions.
	Settings http.HandlerFunc

	// UserChangePasswordForm renders component with form for changing
	// password for user with particular ID.
	//
	// HTTP request details:
	//
	//   GET /users/{id}/password/form
	//
	// Gateway can guard clients from accessing UserChangePasswordForm
	// component without active session.
	UserChangePasswordForm http.HandlerFunc

	// UserActivities renders component with list of recent activities and allows
	// to query older activities by pointing to the last activity from the previous
	// query.
	//
	// HTTP request details:
	//
	//   GET /users/{id}/activities
	//
	// Gateway can guard clients from accessing UserActivities component
	// without active session and proper permissions.
	UserActivities http.HandlerFunc

	// Websites renders list of websites in the system. This endpoint is
	// publicly available, so outside clients can explore users' websites.
	//
	// HTTP request details:
	//
	//   GET /websites
	Websites http.HandlerFunc

	// AdminPanel renders admin panel for administrative tasks.
	//
	// HTTP request details:
	//
	//  GET /admin
	//
	// Gateway can guard clients from accessing AdminPanel page
	// without active session and admin permissions.
	AdminPanel http.HandlerFunc

	// AdminPanelUserActions renders actions component reserved for
	// single user entry in the admin panel.
	//
	// HTTP request details:
	//
	//   GET /admin/users/{id}/actions
	//
	// Path parameters:
	//
	// * id - unique identifier of user.
	//
	// Gateway can guard clients from accessing AdminPanelUserActions
	// component without active session and admin permissions.
	AdminPanelUserActions http.HandlerFunc

	// AdminResetPasswordForUser component is a form for resetting password
	// for user from admin perspective.
	//
	// HTTP request details:
	//
	//   GET /admin/users/{id}/password
	//
	// Path parameters:
	//
	// * id - unique identifier of user.
	//
	// Gateway can guard clients from accessing AdminResetPasswordForUser
	// component without active session and admin permissions.
	AdminResetPasswordForUser http.HandlerFunc

	// AdminQueryUsers is infinite scroll component with list of users
	// in the system for the admin panel.
	//
	// HTTP request details:
	//
	//   GET /admin/users
	//
	// Gateway can guard clients from accessing AdminQueryUsers
	// component without active session and admin permissions.
	AdminQueryUsers http.HandlerFunc

	// AdminPostBatchOfUsersForm is component with HTML form for
	// AdminPostBatchOfUsers command.
	//
	//
	// HTTP request details:
	//
	//   GET /admin/users/form
	//
	// Gateway can guard clients from accessing AdminPostBatchOfUsersForm
	// component without active session and admin permissions.
	AdminPostBatchOfUsersForm http.HandlerFunc
}