/**
 * Serves the avatar endpoints. The profile page uploads the avatar, and the
 * client's `Avatar` component loads it, with the user's `updatedAt` as a
 * cache-busting version.
 *
 * - `POST /api/avatars/me` — signed in. Replaces the caller's avatar (multipart
 *   `file`, at most 5 MB), sends `user_updated` to everyone, and answers the
 *   caller's user.
 * - `GET /api/avatars/:userId` — public. Serves a user's avatar; 404 without
 *   one.
 *
 * @module
 */

import { Router } from "@oak/oak";
import { authMiddleware } from "../middleware/auth.ts";
import { getUserById, updateUserAvatar } from "../services/user-service.ts";
import {
  broadcastUserUpdated,
  updateClientAvatar,
} from "../services/ws-service.ts";
import { type APIResponse } from "../../shared/api.ts";
import { APIException } from "../lib/api-exception.ts";
import type { SelfUser } from "../../shared/user.ts";
import { toPublicUser, toSelfUser } from "../model/user.ts";
import {
  replaceUploadedFile,
  serveUploadedFile,
  validateImageUpload,
} from "../lib/upload.ts";
import { AVATARS_DIR } from "../config.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();

router.post("/api/avatars/me", authMiddleware, async (ctx) => {
  const authPayload = ctx.state.user;
  const contentType = ctx.request.headers.get("content-type") ?? "";
  if (!contentType.includes("multipart/form-data")) {
    throw new APIException(400, "Expected multipart/form-data");
  }

  const body = await ctx.request.body.formData();
  const file = body.get("file");

  if (!(file instanceof File)) {
    throw new APIException(400, "Missing file field");
  }

  const data = new Uint8Array(await file.arrayBuffer());
  const mime = validateImageUpload(data);

  // Written before the record announces it, or clients would fetch it too
  // early.
  await replaceUploadedFile(`${AVATARS_DIR}/${authPayload.userId}`, data);
  updateUserAvatar(authPayload.userId, mime);
  updateClientAvatar(authPayload.userId, mime);

  const user = getUserById(authPayload.userId);
  // Presence alone would update only the online list; `user_updated` reaches
  // every avatar on screen, and its bumped `updatedAt` busts their cache.
  broadcastUserUpdated(toPublicUser(user));
  const responseBody: APIResponse<SelfUser> = {
    success: true,
    data: toSelfUser(user),
  };
  ctx.response.body = responseBody;
});

router.get("/api/avatars/:userId", async (ctx) => {
  const { userId } = ctx.params;

  let user;
  try {
    user = getUserById(userId);
  } catch {
    ctx.response.status = 404;
    return;
  }

  if (!user.avatarMime) {
    ctx.response.status = 404;
    return;
  }

  await serveUploadedFile(ctx, `${AVATARS_DIR}/${userId}`, user.avatarMime);
});

export default router;