biscuit

commit 6ecfc60ceec1dd4f45e6a52e5d4160968e16ac7f
parent 1eb1450686030116ffa5c9ff107e2cb52acd2551
Author: Daniel Barlow <dan@telent.net>
Date:   Tue, 10 Mar 2026 12:10:50 +0000

handle errorful tile fetches

if the tile data is not parseable as json, we re-fetch

Diffstat:
M
pkgs/maps/tiles.fnl
 | 
66
++++++++++++++++++++++++++++++++++++++----------------------------

1 file changed, 38 insertions(+), 28 deletions(-)
diff --git a/pkgs/maps/tiles.fnl b/pkgs/maps/tiles.fnl
@@ -135,35 +135,45 @@
 (fn tile-name [x y zoom]
   (.. x "_" y "_" zoom))
 
-(fn jsond [s]
-  (case (pcall json.decode s)
-    (true val) val
-    (false err) (values nil err)))
 
-(fn fetch [cq x y zoom cb]
+(fn tile-status- [x y zoom]
   (let [k (tile-name x y zoom)
-        pathname (.. "/tmp/tiles/" k ".json")]
-    (if (file-exists? pathname)
-        (let [payload (with-open [i (io.open pathname :r)] (i:read "*a"))]
-          (when (not (= payload ""))
-            (case (jsond payload)
-              val (cb (canvas (. val :elements) zoom))
-              (nil err) (print "json decode error" pathname))))
-        (let [out (io.open pathname :w)]
-          (cq:wrap (fn []
-                     (print "getting " k)
-                     (var payload nil)
-                     (with-open [f out]
-                       (while (not payload)
-                         (set payload (unparsed-for-xyz x y zoom))
-                         (when (not payload)
-                           (print "sleeping " k)
-                           (cqueues.sleep (math.random 2 6))))
-                       (print "got " k)
-                       (f:write payload)
-                       (case (jsond payload)
-                         val (cb (canvas (. val :elements) zoom))
-                         (nil err) (print "json decode error" pathname))
-                       true)))))))
+        pathname (.. "/tmp/tiles/" k ".json")
+        payload (match (io.open pathname :r)
+                  f (with-open [i f] (i:read "*a"))
+                  _ nil)
+        (valid val) (if payload (pcall json.decode payload))]
+    (if (or (= payload nil) (not valid))
+        (values :missing pathname)
+        (= payload "")
+        (values :pending)
+        valid
+        (values :json val)
+        true
+        (values :unknown))))
+
+(fn tile-status [x y zoom]
+  (let [(s v) (tile-status- x y zoom)]
+    (values s v)))
+
+(fn fetch [cq x y zoom cb]
+  (print "fetch" x y zoom)
+  (case (tile-status x y zoom)
+    (:pending) nil
+    (:json val) (cb (canvas (. val :elements) zoom))
+    (:missing pathname)
+    (cq:wrap
+     (fn []
+       (print "getting " pathname)
+       (var payload nil)
+       (with-open [f (io.open pathname :w)]
+         (while (not payload)
+           (set payload (unparsed-for-xyz x y zoom))
+           (when (not payload)
+             (print "sleeping " pathname)
+             (cqueues.sleep (math.random 2 6))))
+         (print "got " pathname)
+         (f:write payload))
+       (fetch cq x y zoom cb)))))
 
 { : fetch : latlon->tile :name tile-name }