#lang racket
(require (for-syntax racket/base))
(require "coerce/value.rkt")

(provide when/block)

;; improves the syntax for conditional blocks in templates
;; ordinarily it would be @when[condition]{@list{stuff ...}}
;; now it can be @when/block[condition]{stuff ...}
;; has to be a macro otherwise body expressions will be evaluated regardless of condition
;; this is bad: if condition is false, expression should exit
(define-syntax (when/block stx)
  (syntax-case stx ()
    [(_ condition body ...)
     #'(if condition (string-append* 
                      (with-handlers ([exn:fail? (λ(exn) (error (format "when/block: ~a" (exn-message exn))))])
                        (map ->string (list body ...))))
           "")]))