/**
 * Serves the chat's history to the chatbox (`ChatModal`). Messages are sent,
 * edited and deleted over the socket instead (`routes/ws.ts`).
 *
 * - `GET /api/chat?limit=&before=&beforeId=&after=&afterId=`, signed in.
 *   Returns messages oldest first, at most `limit` (50 by default, 100 at
 *   most). With no cursor, it returns the latest. With `before`, it returns
 *   the page just older than that cursor, for "load older". With `after`, it
 *   returns what follows it, for the resync after a reconnect. A cursor is a
 *   message's ISO `created_at`, and its id breaks ties. Without `afterId`,
 *   messages at the `after` timestamp itself are included.
 *
 * @module
 */

import { Router } from "@oak/oak";
import type { APIResponse } from "../../shared/api.ts";
import type { ChatMessage } from "../../shared/chat.ts";
import { authMiddleware } from "../middleware/auth.ts";
import {
  getChatMessagesAfter,
  getRecentChatMessages,
} from "../services/chat-service.ts";

/**
 * Mounted by `api/main.ts` behind the error, Open Graph and CORS middleware.
 * An `APIException` thrown by a handler becomes the JSON error response there.
 */
const router: Router = new Router({ prefix: "/api/chat" });

router.get("/", authMiddleware, (ctx) => {
  const params = ctx.request.url.searchParams;
  const limitParam = params.get("limit");
  const limit = limitParam ? Number(limitParam) : NaN;
  const cappedLimit = Number.isFinite(limit) ? limit : undefined;
  const before = params.get("before");
  const after = params.get("after");
  const messages = after
    ? getChatMessagesAfter(
      { createdAt: after, id: params.get("afterId") ?? undefined },
      cappedLimit,
    )
    : getRecentChatMessages(
      cappedLimit,
      before
        ? { createdAt: before, id: params.get("beforeId") ?? undefined }
        : undefined,
    );
  const responseBody: APIResponse<ChatMessage[]> = {
    success: true,
    data: messages,
  };
  ctx.response.body = responseBody;
});

export default router;