From 8ec932cfaa6d4be79fa3241e3bada3c7f6362202 Mon Sep 17 00:00:00 2001
From: Roscoe Rubin-Rottenberg <roscoe@knotbin.com>
Date: Sun, 26 Apr 2026 13:58:23 -0400
Subject: [PATCH] feat: getKnownFollowers

---
 api/index.ts                           |   2 +
 api/so/sprk/graph/getKnownFollowers.ts | 135 +++++++++++++++++++++++++
 2 files changed, 137 insertions(+)
 create mode 100644 api/so/sprk/graph/getKnownFollowers.ts

diff --git a/api/index.ts b/api/index.ts
index 7539b13..7e516fa 100644
--- a/api/index.ts
+++ b/api/index.ts
@@ -15,6 +15,7 @@ import getAudios from "./so/sprk/sound/getAudios.ts";
 import getAudioPosts from "./so/sprk/sound/getAudioPosts.ts";
 import getFollows from "./so/sprk/graph/getFollows.ts";
 import getFollowers from "./so/sprk/graph/getFollowers.ts";
+import getKnownFollowers from "./so/sprk/graph/getKnownFollowers.ts";
 import getBlocks from "./so/sprk/graph/getBlocks.ts";
 import putPreferences from "./so/sprk/actor/putPreferences.ts";
 import getPreferences from "./so/sprk/actor/getPreferences.ts";
@@ -56,6 +57,7 @@ export default function (server: Server, ctx: AppContext) {
   getAudioPosts(server, ctx);
   getFollows(server, ctx);
   getFollowers(server, ctx);
+  getKnownFollowers(server, ctx);
   getBlocks(server, ctx);
   putPreferences(server, ctx);
   getPreferences(server, ctx);
diff --git a/api/so/sprk/graph/getKnownFollowers.ts b/api/so/sprk/graph/getKnownFollowers.ts
new file mode 100644
index 0000000..a1765ea
--- /dev/null
+++ b/api/so/sprk/graph/getKnownFollowers.ts
@@ -0,0 +1,135 @@
+import { InvalidRequestError, Server } from "@atp/xrpc-server";
+
+import { AppContext } from "../../../../context.ts";
+import { HydrateCtx, Hydrator } from "../../../../hydration/index.ts";
+import { $Params } from "../../../../lex/so/sprk/graph/getKnownFollowers.ts";
+import * as so from "../../../../lex/so.ts";
+import {
+  createPipeline,
+  filterSkeletonList,
+  HydrationFnInput,
+  mapSkeletonList,
+  PresentationFnInput,
+  RulesFnInput,
+  SkeletonFnInput,
+} from "../../../../pipeline.ts";
+import { Views } from "../../../../views/index.ts";
+import {
+  clearlyBadCursor,
+  createHydrateCtxFromAuth,
+  resHeaders,
+} from "../../../util.ts";
+
+export default function (server: Server, ctx: AppContext) {
+  const getKnownFollowers = createPipeline({
+    skeleton,
+    hydration,
+    rules: noBlocks,
+    presentation,
+  });
+  server.add(so.sprk.graph.getKnownFollowers, {
+    auth: ctx.authVerifier.standard,
+    handler: async ({ params, auth, req }) => {
+      const viewer = auth.credentials.iss;
+      const hydrateCtx = await createHydrateCtxFromAuth(
+        ctx,
+        req,
+        auth,
+        { viewer },
+      );
+
+      const result = await getKnownFollowers(
+        { ...params, hydrateCtx: hydrateCtx.copy({ viewer }) },
+        ctx,
+      );
+
+      return {
+        encoding: "application/json",
+        body: result,
+        headers: resHeaders({ labelers: hydrateCtx.labelers }),
+      };
+    },
+  });
+}
+
+const skeleton = async (
+  input: SkeletonFnInput<Context, Params>,
+): Promise<SkeletonState> => {
+  const { params, ctx } = input;
+  const [subjectDid] = await ctx.hydrator.actor.getDidsDefined([params.actor]);
+  if (!subjectDid) {
+    throw new InvalidRequestError(`Actor not found: ${params.actor}`);
+  }
+  if (clearlyBadCursor(params.cursor)) {
+    return { subjectDid, knownFollowers: [], cursor: undefined };
+  }
+
+  const res = await ctx.hydrator.dataplane.follows.getFollowsFollowing(
+    params.hydrateCtx.viewer,
+    [subjectDid],
+  );
+  const result = res.results.at(0);
+  const knownFollowers = result ? result.dids.slice(0, params.limit ?? 50) : [];
+
+  return {
+    subjectDid,
+    knownFollowers,
+    cursor: undefined,
+  };
+};
+
+const hydration = (
+  input: HydrationFnInput<Context, Params, SkeletonState>,
+) => {
+  const { ctx, params, skeleton } = input;
+  return ctx.hydrator.hydrateProfiles(
+    [skeleton.subjectDid, ...skeleton.knownFollowers],
+    params.hydrateCtx,
+  );
+};
+
+const noBlocks = (input: RulesFnInput<Context, Params, SkeletonState>) => {
+  const { ctx, hydration, skeleton } = input;
+  return filterSkeletonList(skeleton, "knownFollowers", (did) => {
+    return !ctx.views.viewerBlockExists(did, hydration);
+  });
+};
+
+const presentation = (
+  input: PresentationFnInput<Context, Params, SkeletonState>,
+) => {
+  const { ctx, hydration, params, skeleton } = input;
+  const isNoHosted = (did: string) => ctx.views.actorIsNoHosted(did, hydration);
+
+  const subject = ctx.views.profile(skeleton.subjectDid, hydration);
+  if (
+    !subject ||
+    (!params.hydrateCtx.includeTakedowns && isNoHosted(skeleton.subjectDid))
+  ) {
+    throw new InvalidRequestError(`Actor not found: ${params.actor}`);
+  }
+
+  const followers = mapSkeletonList(skeleton, "knownFollowers", (did) => {
+    if (!params.hydrateCtx.includeTakedowns && isNoHosted(did)) {
+      return;
+    }
+    return ctx.views.profile(did, hydration);
+  });
+
+  return { subject, followers, cursor: undefined };
+};
+
+type Context = {
+  hydrator: Hydrator;
+  views: Views;
+};
+
+type Params = $Params & {
+  hydrateCtx: HydrateCtx & { viewer: string };
+};
+
+type SkeletonState = {
+  subjectDid: string;
+  knownFollowers: string[];
+  cursor?: string;
+};
-- 
2.51.2