;; ==========================================================================
;; stdlib.sx — Standard library functions
;;
;; Functions expressed in SX using the irreducible primitive set.
;;
;; CONSTRAINT: Replacing a native callable (PRIMITIVES entry) with a
;; transpiled SX function can break the transpiled evaluator when:
;; 1. The function is called inside shift/reset (changes CEK capture)
;; 2. The function is used by platform internals (circular dependency)
;; 3. The transpiler doesn't support named-let (loop patterns)
;;
;; Only functions safe from all three constraints are moved here.
;; The rest remain as host-provided PRIMITIVES for now.
;; ==========================================================================


;; --------------------------------------------------------------------------
;; String predicates and aliases
;; --------------------------------------------------------------------------

(define upcase (fn (s) (upper s)))
(define downcase (fn (s) (lower s)))
(define string-length (fn (s) (len s)))
(define substring (fn (s start end) (slice s start end)))

(define string-contains?
  (fn (s needle) (!= (index-of s needle) -1)))

(define starts-with?
  (fn (s prefix) (= (index-of s prefix) 0)))

(define ends-with?
  (fn (s suffix)
    (let ((slen (len s))
          (plen (len suffix)))
      (if (< slen plen) false
        (= (slice s (- slen plen)) suffix)))))


;; --------------------------------------------------------------------------
;; Text utilities
;; --------------------------------------------------------------------------

(define pluralize
  (fn (count singular plural)
    (if (= count 1)
      (or singular "")
      (or plural "s"))))

(define escape
  (fn (s)
    (let ((r (str s)))
      (set! r (replace r "&" "&amp;"))
      (set! r (replace r "<" "&lt;"))
      (set! r (replace r ">" "&gt;"))
      (set! r (replace r "\"" "&quot;"))
      (set! r (replace r "'" "&#x27;"))
      r)))

(define parse-datetime
  (fn (s) (if s (str s) nil)))

(define assert
  (fn (condition message)
    (when (not condition)
      (error (or message "Assertion failed")))
    true))