Building Slack integration

backend/config/normalizers.ts

@@ -111,3 +111,82 @@ export const normalizeLinear = (payload: unknown): NormalizedDelivery => {
     ],
   };
 };
+
+/** Stands in for the message body until the enrichment hook backfills it. */
+export const SLACK_PENDING_TEXT = '(pending Slack message text)';
+
+const DEFAULT_CAPTURE_REACTION = 'pushpin';
+
+/** Slack suffixes skin-tone modifiers onto emoji names; only the base name identifies the reaction. */
+const baseReaction = (name: string): string => name.split('::')[0];
+
+const nested = (value: unknown): Record<string, unknown> =>
+  typeof value === 'object' && value !== null && !Array.isArray(value)
+    ? (value as Record<string, unknown>)
+    : {};
+
+/**
+ * Slack Events API. Only one configured reaction is interesting; every other
+ * delivery is ordinary traffic and yields no notes rather than an error.
+ *
+ * A reaction_added event names a message but never carries its text, and this
+ * runs ahead of the HTTP ack inside Slack's three-second budget, so it cannot
+ * go fetch it. The note therefore carries placeholder text and needsMessageText,
+ * which is the enrichment hook's cue to backfill the real body out of band.
+ */
+export const normalizeSlack = (payload: unknown): NormalizedDelivery => {
+  const body = asRecord(payload);
+
+  if (body.type !== 'event_callback') {
+    throw new NormalizationError('Slack payload is not an event_callback');
+  }
+
+  const externalId = asString(body.event_id);
+  if (!externalId) {
+    throw new NormalizationError('Slack payload is missing event_id');
+  }
+
+  const event = nested(body.event);
+  if (event.type !== 'reaction_added') {
+    return { externalId, notes: [] };
+  }
+
+  // Read per call: the captured reaction is operator configuration, not a build-time constant.
+  const configured = asString(process.env.SLACK_CAPTURE_REACTION) ?? DEFAULT_CAPTURE_REACTION;
+  const reaction = asString(event.reaction);
+  if (!reaction || baseReaction(reaction) !== baseReaction(configured)) {
+    return { externalId, notes: [] };
+  }
+
+  const item = nested(event.item);
+  const channelId = asString(item.channel);
+  const messageTs = asString(item.ts);
+  if (item.type !== 'message' || !channelId || !messageTs) {
+    return { externalId, notes: [] };
+  }
+
+  const teamId = asString(body.team_id);
+  const reactedBy = asString(event.user);
+  const authorUserId = asString(event.item_user);
+
+  return {
+    externalId,
+    notes: [
+      {
+        id: noteId('slack', externalId),
+        text: SLACK_PENDING_TEXT,
+        author: authorUserId ?? reactedBy ?? 'unknown',
+        sourceMeta: {
+          ...provenance({ provider: 'slack', externalId }),
+          needsMessageText: true,
+          channelId,
+          messageTs,
+          reaction,
+          ...(teamId !== undefined ? { teamId } : {}),
+          ...(reactedBy !== undefined ? { reactedBy } : {}),
+          ...(authorUserId !== undefined ? { authorUserId } : {}),
+        },
+      },
+    ],
+  };
+};