Simple cron program (#15)

* Create main.ts

* wip `cf:deploy` task

* add `cloudflare/workers/daily.ts`

* bump version

* add `cf:push`, `cf:serve` task

Resolves <#15 (comment)>.

* rename `/cf`

* wip

* fix denoflare

### Inspiration

[Discord conversation](https://discord.com/channels/684898665143206084/1147601703131152494/1147905102582132869):
> [7:45 AM]John Spurlock: just define a scheduled handler alongside your module fetch handler like any other worker.  Full signature looks like:
> ```ts
> scheduled(event: ModuleWorkerScheduledEvent, env: MyWorkerEnv, ctx: ModuleWorkerContext): Promise<void>;
> ```
> [Image](https://cdn.discordapp.com/attachments/1147601703131152494/1147905102334664704/image.png)
> [7:47 AM]John Spurlock: there's no way to simulate cron events locally - for my workers I just call into common code that's also reachable by an admin endpoint from fetch for easy testing

### Results

So what I ended up doing was following John Spurlock's advice in just defining `scheduled` as an adjacent method to the required `fetch` method.

* Update .env.example

* aesthetic changes

.gitignore

@@ -1,3 +1,4 @@
 
 .env
 ngrok.exe
+.denoflare

cf/dailies/dailies.ts

@@ -0,0 +1,69 @@
+/**
+ * ScheduledEvent is the expected Cloudflare event for this worker.
+ */
+export interface ScheduledEvent {
+  cron: string;
+}
+
+/**
+ * Env is the expected environment variables for this worker.
+ */
+export interface Env {
+  WEBHOOK_URL: string;
+}
+
+/**
+ * Ctx is the expected context for this worker.
+ */
+interface Ctx {
+  waitUntil(promise: Promise<unknown>): void;
+}
+
+export default {
+  /**
+   * fetch is executed on every request.
+   */
+  async fetch(request: Request, env: Env) {
+    if (request.method !== "GET") {
+      return new Response("Method not allowed", { status: 405 });
+    }
+
+    const url = new URL(request.url);
+    if (url.pathname !== "/__scheduled") {
+      return new Response("Not found", { status: 404 });
+    }
+
+    const cron = url.searchParams.get("cron");
+    if (cron !== CRON_EXPRESSION) {
+      return new Response("Unexpected cron expression", { status: 400 });
+    }
+
+    return await execute(env.WEBHOOK_URL);
+  },
+
+  /**
+   * scheduled is executed daily at 12:00 AM UTC.
+   *
+   * See:
+   * - <https://developers.cloudflare.com/workers/runtime-apis/scheduled-event/>
+   */
+  scheduled(event: ScheduledEvent, env: Env, ctx: Ctx) {
+    if (event.cron !== CRON_EXPRESSION) {
+      return;
+    }
+
+    ctx.waitUntil(execute(env.WEBHOOK_URL));
+  },
+};
+
+function execute(webhookURL: string) {
+  return fetch(webhookURL, { method: "POST" });
+}
+
+/**
+ * CRON_EXPRESSION is the cron expression for the scheduled event.
+ *
+ * See:
+ * - <https://crontab.guru/#0_0_*_*_*>
+ */
+const CRON_EXPRESSION = "0 0 * * *";

cf/dailies/env.ts

@@ -0,0 +1,42 @@
+import { load } from "lc-dailies/deps.ts";
+import {
+  denoflare,
+  DENOFLARE_VERSION_TAG,
+} from "lc-dailies/lib/denoflare/mod.ts";
+
+await load({ export: true });
+
+const CF_ACCOUNT_ID = Deno.env.get("CF_ACCOUNT_ID")!;
+const CF_API_TOKEN = Deno.env.get("CF_API_TOKEN")!;
+const WEBHOOK_URL = Deno.env.get("WEBHOOK_URL")!;
+
+const DENOFLARE_SCRIPT_NAME = "lc-dailies";
+const DENOFLARE_SCRIPT_SPECIFIER = "cf/dailies/dailies.ts";
+
+async function daily(...args: string[]) {
+  return await denoflare({
+    versionTag: DENOFLARE_VERSION_TAG,
+    scriptName: DENOFLARE_SCRIPT_NAME,
+    path: DENOFLARE_SCRIPT_SPECIFIER,
+    cfAccountID: CF_ACCOUNT_ID,
+    cfAPIToken: CF_API_TOKEN,
+    localPort: 8080,
+    args,
+  });
+}
+
+export async function serve() {
+  return await daily(
+    "serve",
+    DENOFLARE_SCRIPT_NAME,
+    "--secret-binding",
+    `WEBHOOK_URL:${WEBHOOK_URL}`,
+  );
+}
+
+export async function push() {
+  return await daily(
+    "push",
+    DENOFLARE_SCRIPT_NAME,
+  );
+}

cf/dailies/push/main.ts

@@ -0,0 +1,5 @@
+import { push } from "../env.ts";
+
+if (import.meta.main) {
+  await push();
+}

cf/dailies/serve/main.ts

@@ -0,0 +1,5 @@
+import { serve } from "../env.ts";
+
+if (import.meta.main) {
+  await serve();
+}

deno.jsonc

@@ -6,7 +6,9 @@
     "all": "deno task udd && deno lint && deno fmt",
     "test": "deno test --unstable",
     "start": "deno run -A --unstable main.ts",
-    "ngrok": "ngrok http 8080"
+    "ngrok": "ngrok http 8080",
+    "cf:push": "deno run -A cf/dailies/push/main.ts",
+    "cf:serve": "deno run -A cf/dailies/serve/main.ts"
   },
   "imports": {
     "lc-dailies/": "./"

lib/denoflare/denoflare.ts

@@ -0,0 +1,68 @@
+const DENOFLARE_CONFIG_FILENAME = ".denoflare";
+
+/**
+ * DENOFLARE_VERSION_TAG is the version tag of denoflare.
+ */
+export const DENOFLARE_VERSION_TAG = "v0.5.12";
+
+/**
+ * DenoflareOptions is the options for denoflare.
+ */
+export interface DenoflareOptions {
+  versionTag: string;
+  scriptName: string;
+  path: string;
+  cfAccountID: string;
+  cfAPIToken: string;
+  localPort: number;
+  args: string[];
+}
+
+/**
+ * denoflare is a helper for interfacing with the denoflare CLI.
+ *
+ * See: https://denoflare.dev/cli/
+ */
+export async function denoflare(options: DenoflareOptions) {
+  const moduleURL = `https://deno.land/x/denoflare@${options.versionTag}`;
+  const config = {
+    $schema: `${moduleURL}/common/config.schema.json`,
+    scripts: {
+      [options.scriptName]: {
+        path: options.path,
+        localPort: options.localPort,
+      },
+    },
+    profiles: {
+      profile: {
+        accountId: options.cfAccountID,
+        apiToken: options.cfAPIToken,
+      },
+    },
+  };
+  await Deno.writeTextFile(
+    DENOFLARE_CONFIG_FILENAME,
+    JSON.stringify(config),
+  );
+
+  try {
+    // Create a child process running denoflare CLI.
+    const child = new Deno.Command(Deno.execPath(), {
+      args: [
+        "run",
+        "-A",
+        "--unstable",
+        `${moduleURL}/cli/cli.ts`,
+        ...options.args,
+      ],
+      stdin: "piped",
+      stdout: "piped",
+    }).spawn();
+
+    // Pipe the child process stdout to stdout.
+    await child.stdout.pipeTo(Deno.stdout.writable);
+  } finally {
+    // Delete the temporary config file.
+    await Deno.remove(DENOFLARE_CONFIG_FILENAME);
+  }
+}

lib/denoflare/mod.ts

@@ -0,0 +1 @@
+export * from "./denoflare.ts";