(defpackage #:app-constants
  (:use #:cl)
  (:export #:define-constant
	   #:+false+
	   #:+true+))

(in-package #:app-constants)

#| Switched to `DEFINE-CONSTANT' from `DEFCONSTANT'.
================================================================================
Because this website uses Steel Bank Common Lisp (SBCL), I need to go through a
cycle of confirming changes to the constant values even though they have not
changed. This behaviour is explained in the SBCL Manual 2.1.3 2021-03 (Section
2.3.4 Defining Constants, page 5 (printed) page 13 (PDF)). The key part of the
section is,
'ANSI says that doing `DEFCONSTANT' of the same symbol more than once is
undefined unless the new value is eql to the old value.'
http://www.sbcl.org/manual/#Defining-Constants (this URL should provide the
latest information of the subject).
A workaround, provided by the SBCL Manual is to use the `DEFINE-CONSTANT' macro
instead of `DEFCONST'. By doing this, I can use Quickload to reload the code
(after a big change for example) and not have to repeat the cycle of 'updating'
the constants when they have not changed.
|#
(defmacro define-constant (name value &optional doc)
  `(defconstant ,name (if (boundp ',name) (symbol-value ',name) ,value)
     ,@(when doc (list doc))))

#| SQLite does not have Boolean value types.
================================================================================
At the time of writing (February 2022), the website uses SQLite as its
database. So, I have made these constants to reduce hard-coded `1'
and/or `0' values when `TRUE' and `NIL'/`FALSE' values are want is
meant (in the code-base).
|#
(define-constant +false+ 0
  "An integer representing 'false' (for SQLite mostly).")
(define-constant +true+ 1
  "An integer representing 'true' (for SQLite mostly.")