Experimental: xstate example

patterns-use-cases/xstate/.eslintignore

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+node_modules
+dist

patterns-use-cases/xstate/.eslintrc.json

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+{
+  "env": {
+    "browser": true,
+    "commonjs": true,
+    "es2021": true
+  },
+  "extends": ["eslint:recommended", "plugin:@typescript-eslint/recommended"],
+  "overrides": [],
+  "parser": "@typescript-eslint/parser",
+  "parserOptions": {
+    "ecmaVersion": "latest"
+  },
+  "plugins": ["@typescript-eslint"],
+  "rules": {}
+}

patterns-use-cases/xstate/README.md

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+# Deploying a XState state machine on Restate
+
+This example shows how to integrate Restate deeply with
+[XState](https://stately.ai/docs/xstate). The code in [lib.ts](./lib.ts) and
+[promise.ts](./promise.ts) converts an XState machine into two Restate
+services:
+
+1. A keyed service, which stores the state of the state machine, keyed on an
+   identifier for this instance of the machine. This service is called with
+   every event that must be processed by the state machine. XState machines are
+   generally pure and are not async; side effects generally happen through
+   [Promise Actors](https://stately.ai/docs/promise-actors). As such, this
+   service should never block the machine, so other events can always be
+   processed.
+2. An unkeyed service, which exists solely to execute Promise Actors and call
+   back to the state machine with their result. As this is an unkeyed service,
+   the Promise won't hold up any other events. This service doesn't need to be
+   called by you directly.
+
+Both services are set up and managed automatically by interpreting the state
+machine definition, and should generally be deployed together, whether as a
+Lambda or as a long-lived service.
+
+In `app.ts` you will see an example of an XState machine that uses cross-machine
+communication, delays, and Promise actors, all running in Restate. However,
+most XState machines should work out of the box; this is still experimental, so
+we haven't tested everything yet!
+
+To try out this example:
+
+```bash
+# start a local Restate instance
+restate-server
+# start the service
+npm run example
+# register the state machine service against restate
+restate dep register http://localhost:9080
+
+# create a state machine
+curl http://localhost:8080/auth/myMachine/create
+# watch the state
+watch -n1 'curl -s http://localhost:8080/auth/myMachine/snapshot'
+# kick off the machine
+curl http://localhost:8080/auth/myMachine/send --json '{"event": {"type": "AUTH"}}'
+# and watch the auth flow progress!
+```