Added implementation of workflow pattern based on /// Inspired by htt…

…ps://blog.bittacklr.be/the-workflow-pattern.html

samples/hotelManagement/.vscode/settings.json

@@ -4,7 +4,9 @@
   "editor.formatOnSave": true,
 
   "editor.codeActionsOnSave": {
-    "source.fixAll.eslint": "explicit"
+    "source.organizeImports": "explicit",
+    "source.fixAll.eslint": "explicit",
+    "source.addMissingImports": "always"
   },
 
   "editor.tabSize": 2,
@@ -13,5 +15,7 @@
     "node_modules/": true,
     "dist/": true
   },
-  "files.eol": "\n"
+  "files.eol": "\n",
+
+  "typescript.preferences.importModuleSpecifier": "relative"
 }

samples/hotelManagement/package.json

@@ -41,7 +41,8 @@
     "dotenv-cli": "7.3.0",
     "express": "4.18.2",
     "immutable": "5.0.0-beta.4",
-    "mongodb": "6.3.0"
+    "mongodb": "6.3.0",
+    "ts-essentials": "9.4.1"
   },
   "devDependencies": {
     "@types/convict": "6.1.6",

samples/hotelManagement/src/core/command.ts

@@ -1,7 +1,12 @@
+import { Flavour } from './typing';
+
 export type Command<
   CommandType extends string = string,
   CommandData extends Record<string, unknown> = Record<string, unknown>,
-> = Readonly<{
-  type: Readonly<CommandType>;
-  data: Readonly<CommandData>;
-}>;
+> = Flavour<
+  Readonly<{
+    type: Readonly<CommandType>;
+    data: Readonly<CommandData>;
+  }>,
+  'Command'
+>;

samples/hotelManagement/src/core/event.ts

@@ -1,7 +1,12 @@
+import { Flavour } from './typing';
+
 export type Event<
   EventType extends string = string,
   EventData extends Record<string, unknown> = Record<string, unknown>,
-> = Readonly<{
-  type: Readonly<EventType>;
-  data: Readonly<EventData>;
-}>;
+> = Flavour<
+  Readonly<{
+    type: Readonly<EventType>;
+    data: Readonly<EventData>;
+  }>,
+  'Event'
+>;

samples/hotelManagement/src/core/typing.ts

@@ -0,0 +1,2 @@
+export type Brand<K, T> = K & { readonly __brand: T };
+export type Flavour<K, T> = K & { readonly __brand?: T };

samples/hotelManagement/src/core/workflow.ts

@@ -0,0 +1,19 @@
+import { Command } from './command';
+import { Event } from './event';
+
+/// Inspired by https://blog.bittacklr.be/the-workflow-pattern.html
+
+export type WorkflowEvent<Output extends Command | Event> = Extract<
+  Output,
+  { __brand?: 'Event' }
+>;
+
+export type Workflow<
+  Input extends Event | Command,
+  State,
+  Output extends Event | Command,
+> = {
+  decide: (command: Input, state: State) => Output[];
+  evolve: (currentState: State, event: WorkflowEvent<Output>) => State;
+  getInitialState: () => State;
+};

samples/hotelManagement/src/processManagers/groupCheckouts/groupCheckoutProcessManager.ts

@@ -1,6 +1,5 @@
-import { Map } from 'immutable';
 import { Command } from '#core/command';
-import { enqueue, ProcesssingResult, schedule } from '#core/processManager';
+import { Map } from 'immutable';
 import {
   CheckOut,
   GuestCheckedOut,
@@ -19,10 +18,7 @@ export type GroupCheckoutProcessManagerEvent =
   | GuestCheckedOut
   | GuestCheckoutFailed;
 
-export type GroupCheckoutProcessingResult = ProcesssingResult<
-  CheckOut,
-  GroupCheckoutEvent
->;
+export type GroupCheckoutProcessingResult = CheckOut | GroupCheckoutEvent;
 
 export type InitiateGroupCheckout = Command<
   'InitiateGroupCheckout',
@@ -68,27 +64,29 @@ export const GroupCheckoutProcessManager = (
 
       if (state.status === 'Finished') return [];
 
-      const checkoutGuestStays = event.guestStayAccountIds.map((id) => {
-        return schedule<CheckOut>({
-          type: 'CheckOut',
-          data: {
-            guestStayAccountId: id,
-            now: event.initiatedAt,
-            groupCheckoutId: event.groupCheckoutId,
-          },
-        });
-      });
+      const checkoutGuestStays: CheckOut[] = event.guestStayAccountIds.map(
+        (id) => {
+          return {
+            type: 'CheckOut',
+            data: {
+              guestStayAccountId: id,
+              now: event.initiatedAt,
+              groupCheckoutId: event.groupCheckoutId,
+            },
+          };
+        },
+      );
 
       return [
         ...checkoutGuestStays,
-        enqueue({
+        {
           type: 'GuestCheckoutsInitiated',
           data: {
             groupCheckoutId: event.groupCheckoutId,
             initiatedGuestStayIds: event.guestStayAccountIds,
             initiatedAt: event.initiatedAt,
           },
-        }),
+        },
       ];
     }
 
@@ -137,11 +135,8 @@ export const GroupCheckoutProcessManager = (
             };
 
       return areAnyOngoingCheckouts(guestStayAccountIds)
-        ? enqueue(finished)
-        : [
-            enqueue(finished),
-            enqueue(finish(groupCheckoutId, state.guestStayAccountIds, now)),
-          ];
+        ? finished
+        : [finished, finish(groupCheckoutId, state.guestStayAccountIds, now)];
     }
   }
 };