From df6e6cbb292706e1c185a9d8734ebd7e4e4805f9 Mon Sep 17 00:00:00 2001
From: Michiel Borkent <michielborkent@gmail.com>
Date: Sun, 16 May 2021 23:28:45 +0200
Subject: [PATCH] wip

---
 src/babashka/pods/impl.clj      | 18 ++++++++++++++++--
 src/babashka/pods/jvm.clj       |  6 ++++++
 src/babashka/pods/sci.clj       |  6 ++++++
 test-pod/pod/test_pod.clj       | 20 +++++++++++++++++---
 test-resources/test_program.clj |  5 +++++
 5 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/src/babashka/pods/impl.clj b/src/babashka/pods/impl.clj
index 2f4becd..9534a9d 100644
--- a/src/babashka/pods/impl.clj
+++ b/src/babashka/pods/impl.clj
@@ -39,14 +39,28 @@
 (defn next-id []
   (str (java.util.UUID/randomUUID)))
 
+(defonce transit-read-handlers (atom {}))
+
 (defn transit-json-read [^String s]
   (with-open [bais (java.io.ByteArrayInputStream. (.getBytes s "UTF-8"))]
-    (let [r (transit/reader bais :json)]
+    (let [r (transit/reader bais :json @transit-read-handlers)]
       (transit/read r))))
 
+;; https://www.cognitect.com/blog/2015/9/10/extending-transit
+(defn add-transit-read-handler [tag fn]
+  (let [rh (transit/read-handler fn)]
+    (swap! transit-read-handlers assoc tag rh)))
+
+(defonce transit-write-handlers (atom {}))
+
+;; https://www.cognitect.com/blog/2015/9/10/extending-transit
+(defn add-transit-write-handler [class tag fn]
+  (let [rh (transit/write-handler tag fn)]
+    (swap! transit-write-handlers assoc class rh)))
+
 (defn transit-json-write [^String s]
   (with-open [baos (java.io.ByteArrayOutputStream. 4096)]
-    (let [w (transit/writer baos :json)]
+    (let [w (transit/writer baos :json {:handlers @transit-write-handlers})]
       (transit/write w s)
       (str baos))))
 
diff --git a/src/babashka/pods/jvm.clj b/src/babashka/pods/jvm.clj
index 94aa545..5442369 100644
--- a/src/babashka/pods/jvm.clj
+++ b/src/babashka/pods/jvm.clj
@@ -69,3 +69,9 @@
 (defn invoke
   ([pod-id sym args] (invoke pod-id sym args {}))
   ([pod-id sym args opts] (impl/invoke-public pod-id sym args opts)))
+
+(defn add-transit-read-handler [tag fn]
+  (impl/add-transit-read-handler tag fn))
+
+(defn add-transit-write-handler [class tag fn]
+  (impl/add-transit-write-handler class tag fn))
diff --git a/src/babashka/pods/sci.clj b/src/babashka/pods/sci.clj
index 2b3ae83..a8794b5 100644
--- a/src/babashka/pods/sci.clj
+++ b/src/babashka/pods/sci.clj
@@ -79,3 +79,9 @@
 (defn invoke
   ([pod-id sym args] (invoke pod-id sym args {}))
   ([pod-id sym args opts] (impl/invoke-public pod-id sym args opts)))
+
+(defn add-transit-read-handler [tag fn]
+  (impl/add-transit-read-handler tag fn))
+
+(defn add-transit-write-handler [class tag fn]
+  (impl/add-transit-write-handler class tag fn))
diff --git a/test-pod/pod/test_pod.clj b/test-pod/pod/test_pod.clj
index b269ad1..f004d0a 100644
--- a/test-pod/pod/test_pod.clj
+++ b/test-pod/pod/test_pod.clj
@@ -36,12 +36,21 @@
 
 (defn transit-json-read [^String s]
   (with-open [bais (java.io.ByteArrayInputStream. (.getBytes s "UTF-8"))]
-    (let [r (transit/reader bais :json)]
+    (let [r (transit/reader bais :json {:handlers
+                                        {(str ::local-date-time)
+                                         (transit/read-handler
+                                          (fn [s]
+                                            (java.time.LocalDateTime/parse s)))}})]
       (transit/read r))))
 
 (defn transit-json-write [^String s]
   (with-open [baos (java.io.ByteArrayOutputStream. 4096)]
-    (let [w (transit/writer baos :json)]
+    (let [w (transit/writer baos :json {:handlers
+                                        {java.time.LocalDateTime
+                                         (transit/write-handler
+                                          (str ::local-date-time)
+                                          (fn [s]
+                                            (java.time.LocalDateTime/parse s)))}})]
       (transit/write w s)
       (str baos))))
 
@@ -193,7 +202,12 @@
                             (write out
                              {"status" ["done"]
                               "id" id
-                              "value" "#my/other-tag[1]"}))
+                              "value" "#my/other-tag[1]"})
+                            pod.test-pod/local-date-time
+                            (write out
+                                   {"status" ["done"]
+                                    "id" id
+                                    "value" (write-fn (java.time.LocalDateTime/now))}))
                           (recur))
                 :shutdown (System/exit 0)
                 :load-ns (let [ns (-> (get message "ns")
diff --git a/test-resources/test_program.clj b/test-resources/test_program.clj
index 5f458d8..e1e0641 100644
--- a/test-resources/test_program.clj
+++ b/test-resources/test_program.clj
@@ -64,6 +64,10 @@
 
 (def fn-called (pod.test-pod/fn-call inc 2))
 
+(def local-date-time
+  (when (= "transit+json" fmt)
+    (pod.test-pod/local-date-time)))
+
 (require '[pod.test-pod.only-code :as only-code])
 (def should-be-1 (only-code/foo))
 
@@ -90,4 +94,5 @@
  other-tagged
  loaded
  fn-called
+ local-date-time
  should-be-1]