Adds basic interceptor functionality

pom.xml

@@ -11,7 +11,7 @@
 
   <groupId>dehli</groupId>
   <artifactId>serverless</artifactId>
-  <version>0.1.24</version>
+  <version>0.1.25</version>
   <name>serverless</name>
 
   <dependencies>

src/serverless/aws/api_gateway.cljs

@@ -30,3 +30,10 @@
 (def sub (comp :principalId authorizer))
 (def body #(-> % :body (json->clj :keywordize-keys true)))
 (def endpoint (comp #(str (:domainName %) "/" (:stage %)) request-context))
+
+;; Websocket event helpers
+(defn ws-event->deps [ws-event]
+  (let [api (management-api (endpoint ws-event))]
+    {:delete-connection (partial delete-connection api)
+     :get-connection (partial get-connection api)
+     :post-to-connection (partial post-to-connection api)}))

src/serverless/interceptors/core.cljs

@@ -0,0 +1,31 @@
+(ns serverless.interceptors.core
+  (:require [serverless.core.async :refer [go-try channel? <!]]))
+
+(defn- doseq-interceptors!
+  [fn-key context interceptors]
+  (go-try
+    (doseq [interceptor interceptors]
+      (let [next-fn (or (get interceptor fn-key) identity)
+            chan-or-val (next-fn @context)
+            new-context (if (channel? chan-or-val)
+                          (<! chan-or-val)
+                          chan-or-val)]
+        (reset! context new-context)))))
+
+(defn add-interceptors
+  [interceptors handler]
+  (fn [event]
+    (go-try
+      (let [context (atom event)]
+        ;; Go through interceptors (on enter)
+        (<! (doseq-interceptors!
+             :enter context
+             (concat interceptors [{:name :handler :enter handler}])))
+
+        ;; Go through interceptors (on leave)
+        (<! (doseq-interceptors!
+             :leave context
+             (reverse interceptors)))
+
+        ;; Return context
+        @context))))

src/serverless/interceptors/defaults.cljs

@@ -0,0 +1,15 @@
+(ns serverless.interceptors.defaults
+  (:require [serverless.aws.api-gateway :as api]))
+
+(def assoc-event
+  {:name :move-event
+   :enter (fn [event] {:event event})})
+
+(def merge-web-socket-deps
+  {:name :merge-web-socket-deps
+   :enter (fn [{:keys [event] :as context}]
+            (update context :deps merge (api/ws-event->deps event)))})
+
+(def web-socket-default-interceptors
+  [assoc-event
+   merge-web-socket-deps])

test/serverless/interceptors/core_test.cljs

@@ -0,0 +1,41 @@
+(ns serverless.interceptors.core-test
+  (:require [cljs.test :refer [async deftest is]]
+            [serverless.core.async :refer [go-try <!]]
+            [serverless.interceptors.core :as sut]))
+
+(deftest add-interceptors
+  (async done
+    (go-try
+      (let [interceptors [{:name :a
+                           :enter (fn [{:keys [test] :as ctx}]
+                                    (-> ctx
+                                        (assoc :a-enter test)
+                                        (update :test inc)))
+                           :leave (fn [{:keys [test] :as ctx}]
+                                    (-> ctx
+                                        (assoc :a-leave test)
+                                        (update :test inc)))}
+                          {:name :b
+                           :enter (fn [{:keys [test] :as ctx}]
+                                    (go-try
+                                      (-> ctx
+                                          (assoc :b-enter test)
+                                          (update :test inc))))
+                           :leave (fn [{:keys [test] :as ctx}]
+                                    (-> ctx
+                                        (assoc :b-leave test)
+                                        (update :test inc)))}]
+
+            handler (sut/add-interceptors interceptors
+                                          #(assoc % :handler (:test %)))]
+
+        (is (= (<! (handler {:event "test"}))
+               {:event "test"
+                :a-enter nil
+                :b-enter 1
+                :handler 2
+                :b-leave 2
+                :a-leave 3
+                :test 4}))
+
+        (done)))))