Review file (#7)

The reviewer writes its review to a file whose first line is the verdict, instead of relying on a narration-free final message. Sonnet put `Yes` after three paragraphs of narration on memona #936 (review 595), which the fail-closed verdict posted as a plain comment.

Reviewed-on: #7
Co-authored-by: Danny Kim <temeddix@gmail.com>
Co-committed-by: Danny Kim <temeddix@gmail.com>

run.ts

@@ -59,9 +59,11 @@ async function postComment(body: string): Promise<void> {
   });
 }
 
-// A pull request event is a review request, so the response becomes a review.
-// Its first line is the verdict; anything unexpected only comments, never
-// approves.
+// A pull request event is a review request, so the review is posted instead
+// of the response. It comes through a file, because a final chat message picks
+// up narration while a file's first line is written on purpose. That line is
+// the verdict; anything unexpected only comments, never approves.
+const REVIEW_PATH = `${await Deno.makeTempDir()}/review.md`;
 const VERDICTS: Record<string, string> = {
   Yes: "APPROVED",
   No: "REQUEST_CHANGES",
@@ -70,9 +72,12 @@ const VERDICTS: Record<string, string> = {
 
 async function postResult(body: string): Promise<void> {
   if (EVENT !== "pull_request") return postComment(body);
-  const [verdict] = body.split("\n", 1);
+  const review = await Deno.readTextFile(REVIEW_PATH).catch(() => {
+    throw new Error(`no review was written to ${REVIEW_PATH}`);
+  });
+  const [verdict] = review.split("\n", 1);
   await gitea(REVIEWER_TOKEN, `repos/${REPO}/pulls/${INDEX}/reviews`, {
-    body: stripAnsi(body),
+    body: stripAnsi(review),
     event: VERDICTS[verdict.trim()] ?? "COMMENT",
   });
 }
@@ -118,6 +123,7 @@ async function renderPrompt(): Promise<string> {
     GITEA_API_URL: API,
     GITEA_REPOSITORY: REPO,
     ISSUE_INDEX: INDEX,
+    REVIEW_PATH,
   };
   const template = await Deno.readTextFile(
     new URL("prompt.md", import.meta.url),