# HG changeset patch
# User Evan Hanson <evhan@foldling.org>
# Date 1608791706 -46800
#      Thu Dec 24 19:35:06 2020 +1300
# Node ID d2ae14a69c89e964305b7b604b340197d4c4f1bb
# Parent  7b55f61fa8fec440819af5d94f3fc545f4e30f7b
Improve input format heuristics

diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -89,6 +89,8 @@
 - The program should probably just execute jq when `--json` is used with JSON inputs.
 - There is no validation of command line flags for compatibility.
 - Error messages for invalid S-expression inputs are not very helpful.
+- Inputs must be entirely in one format, you cannot mix JSON and S-expressions.
+- It is not currently possible to specify the format of the input.
 - There are no tests.
 
 ## License
diff --git a/sq.scm b/sq.scm
--- a/sq.scm
+++ b/sq.scm
@@ -137,15 +137,26 @@
 (define (proxy input output)
   (let-values (((input* rewind) (make-rewindable-input-port input)))
     (handle-exceptions e
-        (if ((condition-predicate 'syntax) e)
-            (proxy-string (rewind) output)
-            (proxy-scheme (rewind) output))
-      ;; skip whitespace
-      (read-token char-whitespace? input*)
-      ;; look for a parenthesis or valid scheme datum
-      (or (eq? (peek-char input*) #\()
-          (read input*))
-      (signal 'scheme))))
+        (if (eq? e 'scheme)
+            (proxy-scheme (rewind) output)
+            (proxy-string (rewind) output))
+      (let loop ()
+        (read-token char-whitespace? input*)
+        (or (let ((x (peek-char input*)))
+              (cond
+                ((eq? x #\{) (signal 'json))
+                ((eq? x #\[) (signal 'json))
+                ((eq? x #\() (signal 'scheme))
+                ((eq? x #\#) (signal 'scheme))
+                (else #f)))
+            (let ((x (read input*)))
+              (cond
+                ((eq? x 'true) (signal 'json))
+                ((eq? x 'false) (signal 'json))
+                ((eq? x 'null) (loop))
+                ((string? x) (loop))
+                ((integer? x) (loop))
+                (else (signal 'scheme)))))))))
 
 (define (proxy-scheme input output)
   (copy-port* input output read json-write*))