changes middleware api to include an initialization phase

* middlware that wants to support long running processes - across multiple actions - can be written easier this way

NOTE

* introduces an issue that has been already discussed here: reduxjs/redux#1240

Author: encodeering

modules/conflate-api/src/main/kotlin/com/encodeering/conflate/api/Middleware.kt

@@ -2,7 +2,7 @@ package com.encodeering.conflate.api
 
 interface Middleware<in State> {
 
-    suspend fun dispatch (action : Action, connection : Connection<State>)
+    fun interceptor (connection : Connection<State>) : Interceptor
 
     interface Connection<out State> {
 
@@ -14,4 +14,10 @@ interface Middleware<in State> {
 
     }
 
+    interface Interceptor {
+
+        suspend fun dispatch (action : Action)
+
+    }
+
 }

modules/conflate-logging/src/main/kotlin/com/encodeering/conflate/logging/Logging.kt

@@ -15,7 +15,10 @@ class Logging<in State> (
         val exception : () -> Boolean = { true  }
 ) : Middleware<State> {
 
-    suspend override fun dispatch (action : Action, connection : Middleware.Connection<State>) {
+    override fun interceptor (connection : Middleware.Connection<State>) : Middleware.Interceptor {
+        return object : Middleware.Interceptor {
+
+            suspend override fun dispatch (action : Action) {
         if (before ()) debug (">>", action)
 
         try {
@@ -27,10 +30,13 @@ class Logging<in State> (
 
             throw e
         }
-    }
+            }
 
     private fun debug (prefix : CharSequence, action : Action) = log ("$prefix {}", action)
 
+        }
+    }
+
     companion object {
 
         private val logger : Logger by lazy { LoggerFactory.getLogger (Logging::class.java) }

modules/conflate-logging/src/test/kotlin/com/encodeering/conflate/logging/LoggingTest.kt

@@ -40,7 +40,7 @@ class LoggingTest : Spek({
             val logging = logging (before = true, log = log)
 
             co {
-                logging.dispatch (action, connection ())
+                logging.interceptor (connection ()).dispatch (action)
 
                 verify (log).invoke (">> {}", action)
                 verifyNoMoreInteractions (log)
@@ -54,7 +54,7 @@ class LoggingTest : Spek({
             val logging = logging (after = true, log = log)
 
             co {
-                logging.dispatch (action, connection ())
+                logging.interceptor (connection ()).dispatch (action)
 
                 verify (log).invoke ("-- {}", action)
                 verifyNoMoreInteractions (log)
@@ -70,7 +70,7 @@ class LoggingTest : Spek({
             throws<IllegalStateException> {
                 co {
                     try {
-                        logging.dispatch (action, connection (next = { throw IllegalStateException () }))
+                        logging.interceptor (connection (next = { throw IllegalStateException () })).dispatch (action)
                     } finally {
                         verify (log).invoke ("!! {}", action)
                         verifyNoMoreInteractions (log)
@@ -86,7 +86,7 @@ class LoggingTest : Spek({
             val logging = logging (exception = true, log = log ())
 
             co {
-                logging.dispatch (action, connection (next = next))
+                logging.interceptor (connection (next = next)).dispatch (action)
 
                 verify (next).invoke (action)
             }
@@ -100,7 +100,7 @@ class LoggingTest : Spek({
             val logging = logging (before = true, after = true, log = log)
 
             co {
-                logging.dispatch (action, connection (next = next))
+                logging.interceptor (connection (next = next)).dispatch (action)
 
                 val ordered = Mockito.inOrder (log, next)
                     ordered.verify (log).invoke (eq (">> {}"), eq (action))

modules/conflate-test/src/main/kotlin/com/encodeering/conflate/test/fixture/Middlewares.kt

@@ -27,10 +27,16 @@ object Middlewares {
                         after  : (Action, Middleware.Connection<T>) -> Unit = { _, _ -> Unit }) =
         object : Middleware<T> {
 
-            suspend override fun dispatch (action : Action, connection : Middleware.Connection<T>) {
+            override fun interceptor(connection : Middleware.Connection<T>) : Middleware.Interceptor {
+                return object : Middleware.Interceptor {
+
+                    suspend override fun dispatch (action : Action) {
                 before                    (action,          connection)
                 connection.next           (action)
                 after                     (action,          connection)
+                    }
+
+                }
             }
 
         }

modules/conflate/src/main/kotlin/com/encodeering/conflate/Conflate.kt

@@ -72,6 +72,8 @@ class Conflate<out State> (
 
     private class Next<out State> (private var resolve : () -> State, private val dispatch : suspend (Action) -> Unit, private val middleware : Middleware<State>, private val next : Middleware.Connection<State>) : Middleware.Connection<State> {
 
+        val interceptor = middleware.interceptor (next)
+
         override val state : State
             get () = resolve ()
 
@@ -80,7 +82,7 @@ class Conflate<out State> (
         }
 
         suspend override fun next    (action : Action) {
-            middleware.dispatch      (action, next)
+            interceptor.dispatch     (action)
         }
 
     }

modules/conflate/src/main/kotlin/com/encodeering/conflate/middleware/Codeblock.kt

@@ -5,10 +5,16 @@ import com.encodeering.conflate.api.Middleware
 
 internal class Codeblock<in State> (private val block : (Action, State) -> Unit) : Middleware<State> {
 
-    suspend override fun dispatch (action : Action, connection : Middleware.Connection<State>) {
+    override fun interceptor(connection : Middleware.Connection<State>) : Middleware.Interceptor {
+        return object : Middleware.Interceptor {
+
+            suspend override fun dispatch (action : Action) {
         connection.apply {
             block   (action, connection.state)
             next    (action)
+        }
+            }
+
         }
     }