object_chain.concatSteps

src/object_chain.ts

@@ -203,6 +203,24 @@ export function makePureStep
     return addPureStep(chain, step)
 }
 
+// return a new ObjectChain with the addSteps concatenated
+export function concatSteps
+    <Input extends ChainTagged,
+        const ChainSteps extends cons.NRConsList<UPObjectStepSpec>,
+        const NewSteps extends cons.NRConsList<UPObjectStepSpec>>
+    (chain: ObjectChain<Input, ChainSteps>,
+        addSteps: NewSteps) {
+
+    const newSteps = 
+        // deno-lint-ignore no-explicit-any
+        cons.concat<UPObjectStepSpec>()(chain.steps as any, addSteps as any)
+
+    // deno-lint-ignore no-explicit-any
+    return objectChain<Input>()(chain.tag, newSteps as any) as
+        ObjectChain<Input, cons.Concat<UPObjectStepSpec, ChainSteps, NewSteps>>
+
+}
+
 ////////////////////////////////// recursion support ////////////////////
 
 // idea is that a chain will have an associated service, and we use the 

src/object_chain_test.ts

@@ -5,6 +5,7 @@ import * as cons from "./cons_list.ts"
 import {
     objectChain, addFxStep, makeFxStep,
     addPureStep, makePureStep,
+    concatSteps,
     objectChainFxFn, provideObjectChainServiceImpl
 } from "./object_chain.ts"
 import {
@@ -172,6 +173,38 @@ Deno.test("makeFxStep and makePureStep add steps", () => {
     })
 })
 
+Deno.test("concatSteps concatenates steps", () => { 
+    const firstSteps =
+        [getOrgObjectStepSpec,
+            [getUserObjectStepSpec,
+                cons.None]] as const
+
+    const moreSteps =
+        [pureFormatPushNotificationStepSpec,
+            [sendPusnNotificationStepSpec, cons.None]] as const
+
+    const shortChain = objectChain<SendPushNotification>()(SendPushNotificationTag,
+        firstSteps)
+
+    const chain = concatSteps(shortChain, moreSteps)
+
+    const input: SendPushNotification = {
+        _tag: "sendPushNotification" as const,
+        data: { org_nick: "foo", user_id: "bar" }
+    }
+    const effect = chain.program(input)
+    const runnable = Effect.provide(effect, testServiceContext)
+    const r = Effect.runSync(runnable)
+
+    assertEquals(r, {
+        ...input,
+        org: { id: "foo", name: "Foo" },
+        user: { id: "bar", name: "Bar" },
+        formatPushNotification: "Welcome Bar of Foo",
+        sendPush: "push sent OK: Welcome Bar of Foo"
+    })
+})
+
 // make a getOrg chain which can be run as a step
 type GetOrg = {
     readonly _tag: "getOrg",