; test integer->char function

; Is R5RS, but ScriptFu supports unicode

; Also test the inverse operation: char->integer

; TinyScheme does not implement some char functions in MIT Scheme.
; For example char->name char->digit

; TODO test char=? char-upcase

; General test strategy:
; Generate char atom using integer->char.
; Convert each such char atom to string.
; In all cases where it was possible to create such a string, test length is 1.

; See also number->string which is similar to (atom->string (integer->char <foo>) <base>)


; integer->char takes only unsigned (positive or zero) codepoints
; -1 in twos complement is out of range of UTF-8
(assert-error `(integer->char -1)
              "integer->char: argument 1 must be: non-negative integer")



;            ASCII NUL character.

; 0 is a valid codepoint.
; But ASCII null terminates the string early, so to speak.

; Since null byte terminates string early
; the repr in the REPL of codepoint 0 is #\

; re-test
; (integer->char 0)
; #\

(assert (= (char->integer (integer->char 0))
           0))

; codepoint zero equals its sharp char hex repr
(assert (equal? (integer->char 0)
                #\x0))

; Converting the atom to string yields an empty string
(assert `(string=? (atom->string (integer->char 0))
                   ""))

; You can also represent as escaped hex "x\00"
(assert `(string=? "\x00"
                   ""))

; Escaped hex must have more than one hex digit.
; Testing framework can't test: (assert-error `(string? "\x0") "Error reading string ")

; re-test REPL
; (null? "\x0")
; Error: Error reading string


;           the first non-ASCII character (often the euro sign)

(assert (integer->char 128))

; converted string is equivalent to a string literal that displays
(assert `(string=? (atom->string (integer->char 128))
                   "€"))

;           first Unicode character outside the 8-bit range

; evaluates without complaint
(assert (integer->char 256))

(assert (= (char->integer (integer->char 256))
           256))

; length of converted string is 1
; The length is count of characters, not the count of bytes.
(assert `(= (string-length (atom->string (integer->char 256)))
            1))

; converted string is equivalent to a string literal that displays
(assert `(string=? (atom->string (integer->char 256))
                   "Ā"))


;      first Unicode character outside the Basic Multilingual Plane
(assert (integer->char 65536))

(assert (= (char->integer (integer->char 65536))
           65536))

(assert `(= (string-length (atom->string (integer->char 65536)))
            1))

; The usual glyph in some editors is a wide box with these digits inside:
;   010
;   000
; Other editors may display a small empty box.
(assert `(string=? (atom->string (integer->char 65536))
                   "𐀀"))

; re-test REPL yields a sharp char expr
; (integer->char 65536)
; #\𐀀