(defparameter *map* (make-hash-table))

(define-condition make-error (error)
  ((args :initarg :args :reader make-error-args))
  (:report (lambda (condition stream)
             (format stream "Entry ~a not recognized."
                     (make-error-args condition)))))

(defmacro make-room (name &optional (title nil) &body forms)
  (labels ((is-direction-p (dir)
             (or
              (eq dir 'north)
              (eq dir 'south)
              (eq dir 'west)
              (eq dir 'east)
              (eq dir 'up)
              (eq dir 'down))))
    (let* ((exits nil)
           (funcs nil)
           (room
            (loop for f in forms append
                 (let* ((key (car f))
                        (rest (cdr f))
                        (first (car rest)))
                   (cond ((eq key 'loc) `(:loc ',first))
                         ((eq key 'desc) `(:desc ',rest))
                         ((eq key 'flags) `(:flags ',rest))
                         ((eq key 'action) `(:action ,rest))
                         ((eq key 'global) `(:global ',rest))
                         ((is-direction-p key)
                          (cond ((eq (cadr rest) 'if)
                                 (let* ((sym (gensym))
                                        (func (caddr rest))
                                        (else (last rest)))
                                   (push `(,sym ,func) funcs)
                                   (push `(list ',key ',first ,sym ',else) exits)))
                                (t
                                 (push `(list ',key ',first) exits)))
                          nil)
                         (t
                          (error 'make-error :args f)))))))
      `(let (,@funcs)
         (setf (gethash ',name *map*) (list :title ,title ,@room :exits (list ,@exits)))))))

(defun have-boat ()
  (have 'boat))

(make-room marsh "Marsh"
  (west marsh-wall if #'have-boat "You are stuck")
  (south stone-arch if #'have-boat "You are stuck"))