Enable automatic browsing upvotes

src/reddit/comment-client.ts

@@ -31,6 +31,14 @@ export type CommentPostResult =
   /** Anything else: transient, safe to retry later. */
   | { status: 'failed'; reason: string };
 
+/** Result of a single upvote. A failed/uncertain request is never retried. */
+export type VoteResult =
+  | { status: 'submitted' }
+  | { status: 'rate-limited'; retryAfterMs: number; reason: string }
+  | { status: 'session-invalid'; reason: string }
+  | { status: 'blocked'; reason: string }
+  | { status: 'failed'; reason: string };
+
 /** Why a modhash lookup failed, so the caller can pick a proportionate response. */
 type ModhashResult =
   | { ok: true; modhash: string }
@@ -206,6 +214,50 @@ export class RedditCommentClient {
     return { status: 'posted', fullname: created.fullname, permalink: created.permalink };
   }
 
+  /** Submit one upvote through the same authenticated browser session as comments. */
+  async upvote(thingFullname: string): Promise<VoteResult> {
+    if (!/^t[13]_[a-z0-9]+$/i.test(thingFullname)) {
+      return { status: 'failed', reason: `"${thingFullname}" is not a post or comment fullname` };
+    }
+    const modhash = await this.ensureModhash();
+    if (!modhash.ok) return modhash.kind === 'signed-out'
+      ? { status: 'session-invalid', reason: modhash.reason }
+      : { status: 'failed', reason: modhash.reason };
+
+    let response: HttpTextResponse;
+    try {
+      response = await this.scheduler.schedule(() => this.transport.postForm(
+        `${REDDIT_WRITE_ORIGIN}/api/vote`,
+        { id: thingFullname, dir: '1', api_type: 'json', uh: modhash.modhash },
+        { 'X-Modhash': modhash.modhash, 'Content-Type': 'application/x-www-form-urlencoded' },
+      ));
+    } catch (error) {
+      return { status: 'failed', reason: errorMessage(error) };
+    }
+    if (response.status === 429) {
+      const retryAfterMs = 10 * 60_000;
+      this.scheduler.extendCooldown(retryAfterMs);
+      return { status: 'rate-limited', retryAfterMs, reason: 'Reddit returned HTTP 429 for the vote' };
+    }
+    if (response.status === 403) {
+      if (!looksLikeJson(response.body)) return { status: 'blocked', reason: blockPageReason(response) };
+      this.modhash = null;
+      return { status: 'session-invalid', reason: 'Reddit rejected the vote with HTTP 403' };
+    }
+    if (response.status >= 500) return { status: 'failed', reason: `Reddit returned HTTP ${response.status}` };
+    const payload = parseJson(response.body);
+    if (!payload) return { status: 'failed', reason: `Reddit returned an unreadable vote response (HTTP ${response.status})` };
+    const errors = readErrors(payload);
+    if (errors.length > 0) {
+      const classified = this.classifyError(errors[0], 'the selected community');
+      if (classified.status === 'rate-limited') return { status: 'rate-limited', retryAfterMs: classified.retryAfterMs, reason: classified.reason };
+      if (classified.status === 'session-invalid' || classified.status === 'blocked') return classified;
+      return { status: 'failed', reason: 'reason' in classified ? classified.reason : 'Reddit rejected the vote' };
+    }
+    this.logger.info(`Submitted Reddit upvote for ${thingFullname}`);
+    return { status: 'submitted' };
+  }
+
   /**
    * Current score and removal state for previously posted comments, from the
    * account's own authenticated view. Batched because Reddit accepts up to 100