1 files changed, 29 insertions, 1 deletions
diff --git a/haunt/jakob/dynamic/util.scm b/haunt/jakob/dynamic/util.scm
index a7fd38d..f6f0382 100644
--- a/haunt/jakob/dynamic/util.scm
+++ b/haunt/jakob/dynamic/util.scm
@@ -26,7 +26,8 @@
             base64-length
             decode-form
             date<?
-            hash-append!))
+            hash-append!
+            emoji?))
 
 (define (assoc-value alist key)
   "Return the `car' of `(assoc alist key)' if truthy"
@@ -82,3 +83,30 @@ If KEY does not exist in TABLE, initialize kEY to (list ITEM)"
   (if (hash-ref table key)
       (hash-set! table key (cons item (hash-ref table key)))
       (hash-set! table key (list item))))
+
+(define (emoji? str)
+  "Determine if `str' is an 'acceptable' emoji character
+
+Acceptable is the following subset:
+
+- The 'Emoticons' block
+- The 'Supplemental Symbols and Pictographs' block, excluding U+1F900
+  through U+1F90B
+- The hand symbols from the 'Miscellaneous Symbols and Pictographs'
+  block
+- The hand symbols from the 'Dingbats' block
+- U+1F37B and U+1F440
+
+Notably, U+1F946 isn't normally treated an emoji, but it is here. I
+think it should be! As an American, I should be able to use pictographs
+to express my God-given constitutional rights!"
+  (and (string? str)
+       (= 1 (string-length str))
+       (let ((codepoint (char->integer
+                         (first (string->list str)))))
+         (or (<= #x1F600 codepoint #x1F64F)
+             (<= #x1F90C codepoint #x1F9FF)
+             (<= #x1F446 codepoint #x1F450)
+             (<= #x270A codepoint #x270D)
+             (= codepoint #x1F37B)
+             (= codepoint #x1F440)))))