refactor: normalize delivery context

Co-authored-by: adam91holt <adam91holt@users.noreply.github.com>

src/utils/delivery-context.test.ts

@@ -2,6 +2,7 @@ import { describe, expect, it } from "vitest";
 
 import {
   deliveryContextKey,
+  deliveryContextFromSession,
   mergeDeliveryContext,
   normalizeDeliveryContext,
 } from "./delivery-context.js";
@@ -42,4 +43,19 @@ describe("delivery context helpers", () => {
     );
     expect(deliveryContextKey({ channel: "whatsapp" })).toBeUndefined();
   });
+
+  it("derives delivery context from a session entry", () => {
+    expect(
+      deliveryContextFromSession({
+        channel: "webchat",
+        lastChannel: " whatsapp ",
+        lastTo: " +1777 ",
+        lastAccountId: " acct-9 ",
+      }),
+    ).toEqual({
+      channel: "whatsapp",
+      to: "+1777",
+      accountId: "acct-9",
+    });
+  });
 });

src/utils/delivery-context.ts

@@ -6,6 +6,13 @@ export type DeliveryContext = {
   accountId?: string;
 };
 
+type DeliveryContextSessionSource = {
+  channel?: string;
+  lastChannel?: string;
+  lastTo?: string;
+  lastAccountId?: string;
+};
+
 export function normalizeDeliveryContext(context?: DeliveryContext): DeliveryContext | undefined {
   if (!context) return undefined;
   const channel = typeof context.channel === "string" ? context.channel.trim() : undefined;
@@ -19,6 +26,17 @@ export function normalizeDeliveryContext(context?: DeliveryContext): DeliveryCon
   };
 }
 
+export function deliveryContextFromSession(
+  entry?: DeliveryContextSessionSource,
+): DeliveryContext | undefined {
+  if (!entry) return undefined;
+  return normalizeDeliveryContext({
+    channel: entry.lastChannel ?? entry.channel,
+    to: entry.lastTo,
+    accountId: entry.lastAccountId,
+  });
+}
+
 export function mergeDeliveryContext(
   primary?: DeliveryContext,
   fallback?: DeliveryContext,