From 88fd8c772afe66e8828c00c2520d957d515d86f0 Mon Sep 17 00:00:00 2001
From: Dominic Monroe <dominic@dominic.io>
Date: Sat, 9 Oct 2021 14:53:28 +0100
Subject: [PATCH] WIP: Make possible to supply custom chains

Fix #3
Relates to #2
---
 src/juxt/clip/core.cljc | 37 +++++++++++++++++++++++++++----------
 src/juxt/clip/edn.clj   | 10 ++++++++++
 2 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/src/juxt/clip/core.cljc b/src/juxt/clip/core.cljc
index ad6ca38..db5b6b0 100644
--- a/src/juxt/clip/core.cljc
+++ b/src/juxt/clip/core.cljc
@@ -33,15 +33,29 @@
   of requiring a code form, in addition the anaphoric variable `this` is
   available to refer to the started component."
   [system-config]
-  (let [{:keys [components executor]
-         :or {executor impl/exec-queue}} system-config
+  (let [{:keys [components executor chains]
+         :or {executor impl/exec-queue
+              chains {:start
+                      (fn [component-chain]
+                        (for [component component-chain
+                              f [(impl/pre-starting-f components)
+                                 (impl/starting-f components)
+                                 (impl/post-starting-f components)]]
+                          (f component)))}}} system-config
         [_ component-chain] (safely-derive-parts components [])]
     (executor
-      (for [component component-chain
-            f [(impl/pre-starting-f components)
-               (impl/starting-f components)
-               (impl/post-starting-f components)]]
-        (f component)))))
+      ((get chains :start) component-chain))))
+
+(comment
+  (let [components {:a '{:pre-start (println "pre" 1)
+                         :start (inc 2)
+                         :post-start (println "iam" this)}}]
+    (start
+      {:components components
+       :chains {:start [#_(impl/pre-starting-f components)
+                        (impl/starting-f components)
+                        (impl/post-starting-f components)]}}))
+  )
 
 (defn stop
   "Takes a system config to stop.
@@ -51,13 +65,16 @@
   the target is AutoClosable then .close will be called on it, otherwise
   nothing."
   [system-config running-system]
-  (let [{:keys [components executor]
-         :or {executor impl/exec-queue}} system-config
+  (let [{:keys [components executor chains]
+         :or {executor impl/exec-queue
+              chains {:stop
+                      (fn [component-chain]
+                        (map impl/stopping-f component-chain))}}} system-config
         [_ component-chain] (safely-derive-parts
                               (select-keys components (keys running-system))
                               ())]
     (executor
-      (map impl/stopping-f component-chain)
+      ((get chains :stop) component-chain)
       running-system)))
 
 (comment
diff --git a/src/juxt/clip/edn.clj b/src/juxt/clip/edn.clj
index 2ef7c74..bb3b288 100644
--- a/src/juxt/clip/edn.clj
+++ b/src/juxt/clip/edn.clj
@@ -14,6 +14,16 @@
     executor
     (requiring-resolve executor)))
 
+(defmethod edn->clj :chains
+  [_k chains]
+  (reduce-kv
+    (fn [chains method chain]
+      (if (symbol? chain)
+        (assoc chains method (requiring-resolve chain))
+        chains))
+    chains
+    chains))
+
 (defn analyze
   [system-config]
   (reduce-kv