From f9c03998b8e5476c7d89f167552b44ee75db1315 Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Sun, 21 Apr 2024 13:19:17 +0100
Subject: [PATCH] implement subscriptions with callback

---
 pkgs/devout/devout.fnl | 27 ++++++++++++++++++---------
 pkgs/devout/test.fnl   | 14 ++++++++++----
 2 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/pkgs/devout/devout.fnl b/pkgs/devout/devout.fnl
index b1481fb..b6041ed 100644
--- a/pkgs/devout/devout.fnl
+++ b/pkgs/devout/devout.fnl
@@ -20,19 +20,28 @@
         (doto found (table.insert e))
         found)))
 
+(fn record-event [db subscribers str]
+  (let [e (parse-uevent str)]
+    (match e.action
+      :add (tset db e.path e)
+      :change (tset db e.path e)
+      ;; should we do something for bind?
+      :remove (tset db e.path nil)
+      )
+    (each [_ { : terms : callback } (ipairs subscribers)]
+      (if (event-matches? e terms) (callback e)))
+    e))
+
 (fn database []
-  (let [db {}]
+  (let [db {}
+        subscribers []]
     {
      :find (fn [_ terms] (find-in-database db terms))
-     :add (fn [_ event-string]
-            (let [e (parse-uevent event-string)]
-              (match e.action
-                :add (tset db e.path e)
-                :change (tset db e.path e)
-                ; ;bind ?
-                :remove (tset db e.path nil)
-                )))
+     :add (fn [_ event-string] (record-event db subscribers event-string))
      :at-path (fn [_ path] (. db path))
+     :subscribe (fn [_ callback terms]
+                  (table.insert subscribers {: callback : terms }))
+
      }))
 
 
diff --git a/pkgs/devout/test.fnl b/pkgs/devout/test.fnl
index ed7a106..8c61541 100644
--- a/pkgs/devout/test.fnl
+++ b/pkgs/devout/test.fnl
@@ -114,10 +114,16 @@ MINOR=17")
 
 ;;; tests for subscriptions
 
-(example "I can subscribe to some search terms")
-
-(example "my callback is invoked when devices matching those terms are
- added/changed/removed")
+(example
+ "I can subscribe to some search terms and be notified of matching events"
+ (var received [])
+ (let [db (database)
+       subscriber (fn [e] (table.insert received e))]
+   (db:subscribe subscriber {:devname "/dev/sdb1"})
+   (db:add sdb1-insert)
+   (db:add sda-uevent)
+   (db:add sdb1-remove)
+   (expect= (# received) 2)))
 
 
 (if failed (os.exit 1) (print "OK"))