From 4785f68c8b26775a07831ec8c92897c7235d654a Mon Sep 17 00:00:00 2001
From: Eduardo Julian
Date: Wed, 28 Dec 2016 19:21:51 -0400
Subject: - Fixed the bug that caused some commits to be lost.

---
 stdlib/source/lux/concurrency/stm.lux | 81 +++++++++++++++++++++++++----------
 1 file changed, 59 insertions(+), 22 deletions(-)

diff --git a/stdlib/source/lux/concurrency/stm.lux b/stdlib/source/lux/concurrency/stm.lux
index 914920773..b9f337024 100644
--- a/stdlib/source/lux/concurrency/stm.lux
+++ b/stdlib/source/lux/concurrency/stm.lux
@@ -10,7 +10,8 @@
                 monad)
        (codata [io #- run])
        (data (struct [list #* "List/" Functor<List>]
-                     [dict #+ Dict])
+                     [dict #+ Dict]
+                     ["Q" queue])
              [product]
              [text]
              maybe
@@ -20,7 +21,7 @@
        (macro [ast]
               ["s" syntax #+ syntax: Syntax])
        (concurrency [atom #+ Atom atom]
-                    [promise #+ Promise "Promise/" Monad<Promise>]
+                    ["P" promise #+ Promise "Promise/" Monad<Promise>]
                     [frp])
        ))
 
@@ -181,14 +182,14 @@
 
 (def: #export (update! f var)
   (All [a] (-> (-> a a) (Var a) (Promise [a a])))
-  (promise;future (io (loop [_ []]
-                        (let [(^@ state [value observers]) (io;run (atom;get var))
-                              value' (f value)]
-                          (if (io;run (atom;compare-and-swap state
-                                                             [value' observers]
-                                                             var))
-                            [value value']
-                            (recur [])))))))
+  (P;future (io (loop [_ []]
+                  (let [(^@ state [value observers]) (io;run (atom;get var))
+                        value' (f value)]
+                    (if (io;run (atom;compare-and-swap state
+                                                       [value' observers]
+                                                       var))
+                      [value value']
+                      (recur [])))))))
 
 (def: #export (update f var)
   (All [a] (-> (-> a a) (Var a) (STM [a a])))
@@ -212,16 +213,51 @@
 
 (def: fresh-tx Tx (list))
 
-(def: (commit' output stm-proc)
-  (All [a] (-> (Promise a) (STM a) (Promise Unit)))
-  (promise;future (io (let [[finished-tx value] (stm-proc fresh-tx)]
-                        (if (can-commit? finished-tx)
-                          (exec (List/map commit-var finished-tx)
-                            (io;run (promise;resolve value output))
-                            [])
-                          (exec (commit' output stm-proc)
-                            []))
-                        ))))
+(def: pending-commits
+  (Var (Ex [a] [(STM a) (Promise a)]))
+  (var (:!! [])))
+
+(def: commit-processor-flag
+  (Atom Bool)
+  (atom false))
+
+(def: (process-commit commits)
+  (-> (frp;Chan [(STM Unit) (Promise Unit)])
+      (Promise Unit))
+  (do P;Monad<Promise>
+    [?head+tail commits]
+    (case ?head+tail
+      (#;Cons [stm-proc output] tail)
+      (do @
+        [#let [[finished-tx value] (stm-proc fresh-tx)]]
+        (exec (if (can-commit? finished-tx)
+                (exec (List/map commit-var finished-tx)
+                  (io;run (P;resolve value output))
+                  [])
+                (exec (io;run (write! [stm-proc output] pending-commits))
+                  []))
+          (process-commit tail)))
+
+      #;Nil
+      (undefined)
+      )))
+
+(def: init-processor!
+  (IO Unit)
+  (do Monad<IO>
+    [flag (atom;get commit-processor-flag)]
+    (if flag
+      (wrap [])
+      (do @
+        [was-first? (atom;compare-and-swap flag true commit-processor-flag)]
+        (if was-first?
+          (do Monad<IO>
+            [inputs (follow "commit-processor" pending-commits)]
+            (exec (process-commit (:! (frp;Chan [(STM Unit) (Promise Unit)])
+                                      inputs))
+              (wrap [])))
+          (wrap [])))
+      )))
 
 (def: #export (commit stm-proc)
   {#;doc "Commits a transaction and returns its result (asynchronously).
@@ -230,6 +266,7 @@
 
           For this reason, it's important to note that transactions must be free from side-effects, such as I/O."}
   (All [a] (-> (STM a) (Promise a)))
-  (let [output (promise;promise)]
-    (exec (commit' output stm-proc)
+  (let [output (P;promise ($ +0))]
+    (exec (io;run init-processor!)
+      (io;run (write! [stm-proc output] pending-commits))
       output)))
-- 
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