print unprintable characters as \u escapes

sms.fnl

@@ -20,12 +20,12 @@
 
 (test= (+ 5 4) 9)
 
-(fn escape-for-logging [s]
-  (s:gsub "%c" (fn [x] (.. "{" (string.byte x) "}"))))
+(fn escape-readably [s]
+  (s:gsub "%c" (fn [x] (string.format "\\u{%.3x}"  (string.byte x)))))
 
 (fn tx [fd s]
   (write fd s)
-  (print (.. ">>> " (escape-for-logging s)))
+  (print (.. ">>> " (escape-readably s)))
   (nanosleep {:tv_sec 0 :tv_nsec (* 10 1000 1000)}))
 
 (fn chars [i]
@@ -38,18 +38,21 @@
 (fn unicode->gsm [s]
   (s:gsub "." (fn [c] (chars (. gsm-char (string.byte c))))))
 
-;(print (escape-for-logging (unicode-to-gsm "hello")))
-;(print (escape-for-logging (unicode-to-gsm "{he@llo}€")))
+(test= (unicode->gsm "abc123") "abc123")
+(test= (unicode->gsm "abc{123}") "abc\x1b(123\x1b)")
+
+;(print (escape-readably(unicode-to-gsm "hello")))
+;(print (escape-readably(unicode-to-gsm "{he@llo}€")))
 
 (fn expect [fd pattern fail-pattern]
   (let [b (read fd 1024)]
     (if (> (# b) 0)
         (do
-          (print (.. "<<< " (escape-for-logging b)))
+          (print (.. "<<< " (escape-readably b)))
           (if (string.find b pattern)
               (do (print "found" pattern) true)
               (and fail-pattern (string.find b fail-pattern))
-              (error (.. "Expected " pattern ", got " (escape-for-logging b)))
+              (error (.. "Expected " pattern ", got " (escape-readably b)))
               (expect fd pattern)))
         nil)))