Implement basic summarize logic (#2)

package.json

@@ -22,6 +22,7 @@
   },
   "devDependencies": {
     "@cloudflare/workers-types": "^4.20240208.0",
+    "@octokit/webhooks-types": "^7.3.2",
     "eslint": "^8.56.0",
     "eslint-config-prettier": "^9.1.0",
     "eslint-plugin-unicorn": "^51.0.1",
@@ -36,6 +37,8 @@
   "dependencies": {
     "@cfworker/sentry": "^2.0.0",
     "@octokit/auth-app": "^6.0.3",
-    "octokit": "^3.1.2"
+    "octokit": "^3.1.2",
+    "parse-git-diff": "^0.0.15",
+    "zod": "^3.22.4"
   }
 }

src/diff.ts

@@ -0,0 +1,8 @@
+import parseGitDiff from "parse-git-diff";
+
+export function genDiffSummary(diffFile: string) {
+  const diff = parseGitDiff(diffFile);
+
+  // TODO: Implement diff summary and return label as well
+  return "```json\n" + JSON.stringify(diff) + "\n```";
+}

src/index.ts

@@ -14,7 +14,7 @@ router.post("/github/webhook", async (req, env) => {
   const octoApp = useOctoApp(env);
 
   await octoApp.webhooks.verifyAndReceive({
-    id: unwrap(req.headers.get("x-request-id")),
+    id: unwrap(req.headers.get("x-github-hook-id")),
     name: unwrap(req.headers.get("x-github-event")) as any,
     signature: unwrap(req.headers.get("x-hub-signature")),
     payload: await req.text(),

src/octo.ts

@@ -1,4 +1,107 @@
-import { App } from "octokit";
+import { App, type Octokit } from "octokit";
+import type { PullRequest } from "@octokit/webhooks-types";
+import { genDiffSummary } from "./diff";
+import { unwrap } from "./utils";
+import { z } from "zod";
+
+const ViewerSchema = z.object({
+  viewer: z.object({
+    databaseId: z.number(),
+  }),
+});
+
+/**
+ * Find PR comment number to edit, if we have already left a comment there.
+ *
+ * If this is a new PR we haven't touched before, this will return `null`,
+ * suggesting we should create a new comment.
+ */
+async function findPRComment(octo: Octokit, pr: PullRequest) {
+  // IDK how to get the app's user ID with rest API. But this is trivial with
+  // graphQL
+  const viewerQuery = await octo.graphql(`query { viewer { databaseId } }`);
+  const viewer = ViewerSchema.parse(viewerQuery);
+
+  // Only listing the first page for pr comments. This endpoint sorts comments
+  // in ascending order of comment number (which means commenting order/creation
+  // time). Assuming we are fast and be the first few bots leaving comments in
+  // the PR.
+  const comments = await octo.request(
+    "GET /repos/{owner}/{repo}/issues/{issue_number}/comments",
+    {
+      owner: pr.base.repo.owner.login,
+      repo: pr.base.repo.name,
+      issue_number: pr.number,
+    },
+  );
+
+  for (const comment of comments.data) {
+    if (comment.user?.id === viewer.viewer.databaseId) {
+      return comment.id;
+    }
+  }
+
+  return null;
+}
+
+async function handle(app: App, installation_id: number, pr: PullRequest) {
+  console.log(
+    `Handling PR ${pr.base.repo.full_name}#${pr.number}. Installation ID = ${installation_id}`,
+  );
+
+  const octo = await app.getInstallationOctokit(installation_id);
+
+  if (pr.state === "closed") {
+    console.info("PR is closed. Ignoring the webhook");
+    return;
+  }
+
+  console.log("Fetching diff for the PR");
+  const response = await octo.request(
+    "GET /repos/{owner}/{repo}/pulls/{pull_number}",
+    {
+      owner: pr.base.repo.owner.login,
+      repo: pr.base.repo.name,
+      pull_number: pr.number,
+      mediaType: {
+        format: "diff",
+      },
+    },
+  );
+  // The cast is suggested here. Cast is necessary coz octokit does not support
+  // mediaType in typing.
+  // https://github.com/octokit/request.js/issues/463#issuecomment-1164800888
+  const diffFile = response.data as unknown as string;
+
+  const summary = genDiffSummary(diffFile);
+
+  console.log("Finding existing PR comment");
+  const commentID = await findPRComment(octo, pr);
+
+  if (commentID == null) {
+    console.info("Cannot find existing PR. Leaving new comment");
+    await octo.request(
+      "POST /repos/{owner}/{repo}/issues/{issue_number}/comments",
+      {
+        owner: pr.base.repo.owner.login,
+        repo: pr.base.repo.name,
+        issue_number: pr.number,
+        body: summary,
+      },
+    );
+  } else {
+    console.info(`Updating PR comment ${commentID}`);
+    await octo.request(
+      "PATCH /repos/{owner}/{repo}/issues/comments/{comment_id}",
+      {
+        owner: pr.base.repo.owner.login,
+        repo: pr.base.repo.name,
+        comment_id: commentID,
+        body: summary,
+      },
+    );
+  }
+}
 
 export function useOctoApp(env: Env) {
   const app = new App({
@@ -7,5 +110,46 @@ export function useOctoApp(env: Env) {
     webhooks: { secret: env.GH_WEBHOOK_SECRET },
   });
 
+  app.webhooks.on("pull_request.edited", (event) =>
+    handle(
+      app,
+      unwrap(
+        event.payload.installation?.id,
+        "Missing installation.id in webhook payload",
+      ),
+      event.payload.pull_request,
+    ),
+  );
+  app.webhooks.on("pull_request.synchronize", (event) =>
+    handle(
+      app,
+      unwrap(
+        event.payload.installation?.id,
+        "Missing installation.id in webhook payload",
+      ),
+      event.payload.pull_request,
+    ),
+  );
+  app.webhooks.on("pull_request.opened", (event) =>
+    handle(
+      app,
+      unwrap(
+        event.payload.installation?.id,
+        "Missing installation.id in webhook payload",
+      ),
+      event.payload.pull_request,
+    ),
+  );
+  app.webhooks.on("pull_request.reopened", (event) =>
+    handle(
+      app,
+      unwrap(
+        event.payload.installation?.id,
+        "Missing installation.id in webhook payload",
+      ),
+      event.payload.pull_request,
+    ),
+  );
+
   return app;
 }

src/utils.ts

@@ -1,6 +1,9 @@
-export function unwrap<T>(value: T): NonNullable<T> {
+export function unwrap<T>(
+  value: T,
+  message: string = "Tried to unwrap a nullish value",
+): NonNullable<T> {
   if (value == null) {
-    throw new Error("Tried to unwrap a nullish value");
+    throw new Error(message);
   }
 
   return value;