(module typed-reader mzscheme
  (require (lib "etc.ss"))
  
  (require-for-template "private/prims.ss")  
  
  ;; Provides raise-read-error and raise-read-eof-error
  (require (lib "readerr.ss" "syntax"))
  
  (define (skip-whitespace port)
    ;; Skips whitespace characters, sensitive to the current
    ;; readtable's definition of whitespace
    (let ([ch (peek-char port)])
      (unless (eof-object? ch)
        ;; Consult current readtable:
        (let-values ([(like-ch/sym proc dispatch-proc) 
                      (readtable-mapping (current-readtable) ch)])
          ;; If like-ch/sym is whitespace, then ch is whitespace
          (when (and (char? like-ch/sym)
                     (char-whitespace? like-ch/sym))
            (read-char port)
            (skip-whitespace port))))))
  
  (define (skip-comments read-one port src)
    ;; Recursive read, but skip comments and detect EOF
    (let loop ()
      (let ([v (read-one)])
        (cond
          [(special-comment? v) (loop)]
          [(eof-object? v)
           (let-values ([(l c p) (port-next-location port)])
             (raise-read-eof-error "unexpected EOF in type annotation" src l c p 1))]
          [else v]))))

  (define (parse port read-one src)    
    (skip-whitespace port)
    (let ([name (read-one)])
      (begin0
        (begin (skip-whitespace port)
               (let ([next (read-one)])
                 (case (syntax-e next)
                   ;; type annotation
                   [(:) (skip-whitespace port)
                        (syntax-property name 'type-label (syntax-object->datum (read-one)))]
                   [(::) (skip-whitespace port)
                         (datum->syntax-object name `(ann ,name : ,(read-one)))]
                   [(@) (let ([elems (let loop ([es '()])
                                       (skip-whitespace port)
                                       (if (equal? #\} (peek-char port))
                                           (reverse es)
                                           (loop (cons (read-one) es))))])
                          (datum->syntax-object name `(inst ,name : ,@elems)))]
                   ;; arbitrary property annotation
                   [(PROP) (skip-whitespace port)
                           (let* ([prop-name (syntax-e (read-one))])   
                             (skip-whitespace port)
                             (syntax-property name prop-name (read-one)))]
                   ;; type annotation
                   [else (syntax-property name 'type-label (syntax-object->datum next))])))
        (skip-whitespace port)
        (let ([c (read-char port)])
          #;(printf "char: ~a" c)
          (unless (equal? #\} c)
            (let-values ([(l c p) (port-next-location port)])
              (raise-read-error (format "typed expression ~a not properly terminated" (syntax-object->datum name)) src l c p 1)))))))
  
  (define parse-id-type
    (case-lambda
      [(ch port src line col pos)
       ;; `read-syntax' mode
       (datum->syntax-object
        #f
        (parse port 
                     (lambda () (read-syntax src port ))
                     src)
        (let-values ([(l c p) (port-next-location port)])
          (list src line col pos (and pos (- p pos)))))]))

  (define readtable
    (make-readtable #f #\{ 'dispatch-macro parse-id-type))
  
  (define (*read inp)
    (parameterize ([current-readtable readtable])
      (read inp)))
  
  (define (*read-syntax src port)
    (parameterize ([current-readtable readtable])
      (read-syntax src port)))
  
  (provide (rename *read read) (rename *read-syntax read-syntax))
  )