/**
 * Posts, reads, edits and deletes dumps, for the feeds, the dump page, its
 * edit page and the create form. `:dumpId` is a dump's id; the dump page reads
 * a dump by its path, through `GET /api/users/:key/dumps/:slug`. A private
 * dump answers 404 to anyone but its poster, moderators included. Its file and
 * thumbnail are served by `routes/files.ts` and `routes/thumbnails.ts`, its
 * comments by `routes/comments.ts`.
 *
 * - `POST /api/dumps` — signed in. Posts a link (JSON body) or a file
 *   (multipart `file`, with `title`, `comment`, `isPrivate` and `categoryIds`).
 * - `GET /api/dumps?page=&limit=` — optional sign-in. Answers a page of the
 *   dumps the caller may see, newest first.
 * - `GET /api/dumps?category=&page=&limit=` — optional sign-in. The same, in
 *   the category with that slug; 404 when there is none.
 * - `GET /api/dumps?follow=users&category=&page=&limit=` — signed in. The
 *   index's "follow" tab: a page of the public dumps of the users the caller
 *   follows, newest first, optionally in one category.
 * - `GET /api/dumps?follow=playlists&category=&page=&limit=` — signed in. Its
 *   `/follow/playlists` view: a page of the public dumps in the public
 *   playlists the caller follows, most recently added first.
 * - `GET /api/dumps?url=` — optional sign-in. Answers the dumps already
 *   pointing at the same thing as `url`, for the create form's duplicate hint.
 * - `GET /api/dumps/:dumpId` — optional sign-in. Answers a dump.
 * - `GET /api/dumps/:dumpId/voters?page=&limit=` — optional sign-in. Answers a
 *   page of the users who upvoted it.
 * - `GET /api/dumps/:dumpId/related` — optional sign-in. Answers the dumps
 *   linked to or from it.
 * - `GET /api/dumps/:dumpId/playlists` — optional sign-in. Answers the
 *   playlists it appears in.
 * - `PUT /api/dumps/:dumpId` — signed in, as its poster or with
 *   `dump:moderate`. Updates its title, slug, comment, visibility, categories,
 *   and a link's URL. A new slug keeps the old one as an alias, 3 times a day
 *   at most but for those with `dump:moderate`.
 * - `POST /api/dumps/:dumpId/metadata` — signed in, as its poster or with
 *   `dump:moderate`. Fetches a link's preview again.
 * - `DELETE /api/dumps/:dumpId` — signed in, as its poster or with
 *   `dump:moderate`. Deletes it.
 *
 * @module
 */

import { Router } from "@oak/oak";

import { type APIResponse, type PaginatedData } from "../../shared/api.ts";
import { APIException } from "../lib/api-exception.ts";
import type { Dump, DumpUrlMatch } from "../../shared/dump.ts";
import {
  isCreateUrlDumpRequest,
  isUpdateDumpRequest,
  parseCategoryIds,
} from "../validators/dump.ts";
import type { Playlist } from "../../shared/playlist.ts";
import type { PublicUser } from "../../shared/user.ts";
import { toPublicUser } from "../model/user.ts";

import { authMiddleware } from "../middleware/auth.ts";
import { can } from "../lib/permissions.ts";
import { parseOptionalAuth } from "../lib/auth.ts";
import { type Page, parsePagination } from "../lib/pagination.ts";
import {
  createFileDump,
  createUrlDump,
  deleteDump,
  findDumpsByUrl,
  getDump,
  listDumps,
  refreshDumpMetadata,
  updateDump,
} from "../services/dump-service.ts";
import {
  getCategoryBySlug,
  listDumpsByCategory,
} from "../services/category-service.ts";
import {
  getFollowedPlaylistsDumpFeed,
  getFollowedUsersDumpFeed,
} from "../services/follow-service.ts";
import { FOLLOW_VIEWS, type FollowView } from "../../shared/paths.ts";
import { getDumpVoters } from "../services/vote-service.ts";
import { getRelatedDumps } from "../services/backlink-service.ts";
import { getPlaylistsForDump } from "../services/playlist-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/dumps" });

// Each handler resolves `:dumpId` with getDump, which checks privacy, before
// acting on the dump.

router.post(
  "/",
  authMiddleware,
  async (ctx) => {
    const userId = ctx.state.user.userId;
    const contentType = ctx.request.headers.get("content-type") ?? "";

    let dump: Dump;

    if (contentType.includes("multipart/form-data")) {
      const formData = await ctx.request.body.formData();
      const file = formData.get("file");
      const comment = formData.get("comment");
      const title = formData.get("title");
      const isPrivate = formData.get("isPrivate") === "true";

      if (!(file instanceof File)) {
        throw new APIException(400, "A file is required");
      }

      dump = await createFileDump(
        file,
        typeof comment === "string" && comment ? comment : undefined,
        userId,
        isPrivate,
        typeof title === "string" && title ? title : undefined,
        parseCategoryIds(formData.get("categoryIds")),
      );
    } else {
      const body: unknown = await ctx.request.body.json();

      if (!isCreateUrlDumpRequest(body)) {
        throw new APIException(400, "Invalid dump data");
      }

      dump = await createUrlDump(body, userId);
    }

    const responseBody: APIResponse<Dump> = { success: true, data: dump };
    ctx.response.status = 201;
    ctx.response.body = responseBody;
  },
);

router.get("/:dumpId", async (ctx) => {
  const requestingUserId = await parseOptionalAuth(ctx) ?? undefined;
  const dump = getDump(ctx.params.dumpId, requestingUserId);
  const responseBody: APIResponse<Dump> = { success: true, data: dump };
  ctx.response.body = responseBody;
});

router.get("/:dumpId/voters", async (ctx) => {
  const requestingUserId = await parseOptionalAuth(ctx) ?? undefined;
  const dump = getDump(ctx.params.dumpId, requestingUserId);
  const { page, limit } = parsePagination(ctx.request.url.searchParams);
  const { items, hasMore } = getDumpVoters(dump.id, page, limit);
  const responseBody: APIResponse<PaginatedData<PublicUser>> = {
    success: true,
    data: {
      items: items.map(toPublicUser),
      hasMore,
    },
  };
  ctx.response.body = responseBody;
});

router.get("/:dumpId/related", async (ctx) => {
  const requestingUserId = await parseOptionalAuth(ctx) ?? undefined;
  const dump = getDump(ctx.params.dumpId, requestingUserId);
  const related = getRelatedDumps(dump.id, requestingUserId);
  const responseBody: APIResponse<Dump[]> = { success: true, data: related };
  ctx.response.body = responseBody;
});

router.get("/:dumpId/playlists", async (ctx) => {
  const requestingUserId = await parseOptionalAuth(ctx) ?? undefined;
  const dump = getDump(ctx.params.dumpId, requestingUserId);
  const playlists = getPlaylistsForDump(dump.id, requestingUserId);
  const responseBody: APIResponse<Playlist[]> = {
    success: true,
    data: playlists,
  };
  ctx.response.body = responseBody;
});

router.get("/", async (ctx) => {
  const requestingUserId = await parseOptionalAuth(ctx) ?? undefined;
  const params = ctx.request.url.searchParams;
  const url = params.get("url");
  if (url !== null) {
    const responseBody: APIResponse<DumpUrlMatch[]> = {
      success: true,
      data: findDumpsByUrl(url, requestingUserId),
    };
    ctx.response.body = responseBody;
    return;
  }
  const { page, limit } = parsePagination(params);
  const category = params.get("category");
  const follow = params.get("follow");
  let feed: Page<Dump>;
  if (follow !== null) {
    if (!requestingUserId) throw new APIException(401, "Missing token");
    if (!(FOLLOW_VIEWS as readonly string[]).includes(follow)) {
      throw new APIException(400, "follow must be users or playlists");
    }
    const categoryId = category
      ? getCategoryBySlug("dump", category).id
      : undefined;
    feed = (follow as FollowView) === "users"
      ? getFollowedUsersDumpFeed(requestingUserId, page, limit, categoryId)
      : getFollowedPlaylistsDumpFeed(requestingUserId, page, limit, categoryId);
  } else {
    feed = category
      ? listDumpsByCategory(category, page, limit, requestingUserId)
      : listDumps(page, limit, requestingUserId);
  }
  const { items, hasMore } = feed;
  const responseBody: APIResponse<PaginatedData<Dump>> = {
    success: true,
    data: { items, hasMore },
  };
  ctx.response.body = responseBody;
});

router.put("/:dumpId", authMiddleware, async (ctx) => {
  const dumpId = ctx.params.dumpId;
  const userId = ctx.state.user.userId;
  const body: unknown = await ctx.request.body.json();

  if (!isUpdateDumpRequest(body)) {
    throw new APIException(400, "Erroneous user input");
  }

  const dump = getDump(dumpId, userId);

  if (userId !== dump.userId && !can(ctx.state.user, "dump:moderate")) {
    throw new APIException(403, "Not authorized to update dump");
  }

  const updatedDump = await updateDump(
    dump.id,
    body,
    can(ctx.state.user, "dump:moderate"),
  );
  const responseBody: APIResponse<Dump> = { success: true, data: updatedDump };
  ctx.response.body = responseBody;
});

router.post("/:dumpId/metadata", authMiddleware, async (ctx) => {
  const dumpId = ctx.params.dumpId;
  const userId = ctx.state.user.userId;
  const dump = getDump(dumpId, userId);

  if (userId !== dump.userId && !can(ctx.state.user, "dump:moderate")) {
    throw new APIException(403, "Not authorized to update dump");
  }

  const updatedDump = await refreshDumpMetadata(dump.id);
  const responseBody: APIResponse<Dump> = { success: true, data: updatedDump };
  ctx.response.body = responseBody;
});

router.delete("/:dumpId", authMiddleware, async (ctx) => {
  const dumpId = ctx.params.dumpId;
  const userId = ctx.state.user.userId;
  const dump = getDump(dumpId, userId);

  if (userId !== dump.userId && !can(ctx.state.user, "dump:moderate")) {
    throw new APIException(403, "Not authorized to delete dump");
  }

  await deleteDump(dump.id);

  const responseBody: APIResponse<null> = { success: true, data: null };
  ctx.response.body = responseBody;
});

export default router;