server/api/api/v1/accounts/familiar_followers/index.ts

import { apiRoute, auth, qsQuery } from "@/api";
import { createRoute, z } from "@hono/zod-openapi";
import {
    Account as AccountSchema,
    FamiliarFollowers as FamiliarFollowersSchema,
} from "@versia/client/schemas";
import { RolePermission } from "@versia/client/schemas";
import { User, db } from "@versia/kit/db";
import type { Users } from "@versia/kit/tables";
import { type InferSelectModel, sql } from "drizzle-orm";
import { ApiError } from "~/classes/errors/api-error";
import { rateLimit } from "~/middlewares/rate-limit";

const route = createRoute({
    method: "get",
    path: "/api/v1/accounts/familiar_followers",
    summary: "Get familiar followers",
    description:
        "Obtain a list of all accounts that follow a given account, filtered for accounts you follow.",
    externalDocs: {
        url: "https://docs.joinmastodon.org/methods/accounts/#familiar_followers",
    },
    tags: ["Accounts"],
    middleware: [
        auth({
            auth: true,
            scopes: ["read:follows"],
            permissions: [RolePermission.ManageOwnFollows],
        }),
        rateLimit(5),
        qsQuery(),
    ] as const,
    request: {
        query: z.object({
            id: z
                .array(AccountSchema.shape.id)
                .min(1)
                .max(10)
                .or(AccountSchema.shape.id.transform((v) => [v]))
                .openapi({
                    description:
                        "Find familiar followers for the provided account IDs.",
                    example: [
                        "f137ce6f-ff5e-4998-b20f-0361ba9be007",
                        "8424c654-5d03-4a1b-bec8-4e87db811b5d",
                    ],
                }),
        }),
    },
    responses: {
        200: {
            description: "Familiar followers",
            content: {
                "application/json": {
                    schema: z.array(FamiliarFollowersSchema),
                },
            },
        },
        401: ApiError.missingAuthentication().schema,
        422: ApiError.validationFailed().schema,
    },
});

export default apiRoute((app) =>
    app.openapi(route, async (context) => {
        const { user } = context.get("auth");
        const { id: ids } = context.req.valid("query");

        // Find followers of the accounts in "ids", that you also follow
        const finalUsers = await Promise.all(
            ids.map(async (id) => ({
                id,
                accounts: await User.fromIds(
                    (
                        await db.execute(sql<InferSelectModel<typeof Users>>`
                        SELECT "Users"."id" FROM "Users"
                        INNER JOIN "Relationships" AS "SelfFollowing"
                            ON "SelfFollowing"."subjectId" = "Users"."id"
                        WHERE "SelfFollowing"."ownerId" = ${user.id}
                            AND "SelfFollowing"."following" = true
                            AND EXISTS (
                                SELECT 1 FROM "Relationships" AS "IdsFollowers"
                                WHERE "IdsFollowers"."subjectId" = ${id}
                                    AND "IdsFollowers"."ownerId" = "Users"."id"
                                    AND "IdsFollowers"."following" = true
                            )
                    `)
                    ).rows.map((u) => u.id as string),
                ),
            })),
        );

        return context.json(
            finalUsers.map((u) => ({
                ...u,
                accounts: u.accounts.map((a) => a.toApi()),
            })),
            200,
        );
    }),
);