/**
 * Posts, reads, edits and deletes dumps, for the index feed, the dump page, its
 * edit page and the create form. `:dumpId` takes an id or a slug. A private
 * dump answers 404 to anyone but its poster, moderators included.
 *
 * - `POST /api/dumps` — signed in. Posts a link (JSON body) or a file
 *   (multipart `file`, with `title`, `comment`, `isPrivate` and `categoryIds`).
 * - `GET /api/dumps/by-url?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.
 * - `GET /api/dumps?page=&limit=` — optional sign-in. Answers a page of the
 *   dumps the caller may see, newest first.
 * - `PUT /api/dumps/:dumpId/file` — signed in, as its poster or with
 *   `dump:moderate`. Replaces a file dump's upload and comment, and any of its
 *   title, categories and visibility (multipart).
 * - `PUT /api/dumps/:dumpId` — signed in, as its poster or with
 *   `dump:moderate`. Updates its title, comment, visibility, categories, and a
 *   link's URL.
 * - `PUT /api/dumps/:dumpId/thumbnail` — signed in, as its poster or with
 *   `dump:moderate`. Replaces its custom thumbnail (multipart `file`, at most 5
 *   MB).
 * - `DELETE /api/dumps/:dumpId/thumbnail` — signed in, as its poster or with
 *   `dump:moderate`. Removes its custom thumbnail.
 * - `POST /api/dumps/:dumpId/refresh-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,
} 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 { parsePagination } from "../lib/pagination.ts";
import { replaceUploadedFile, validateImageUpload } from "../lib/upload.ts";
import { THUMBNAILS_DIR } from "../config.ts";
import {
  createFileDump,
  createUrlDump,
  deleteDump,
  findDumpsByUrl,
  getDump,
  listDumps,
  refreshDumpMetadata,
  removeDumpThumbnail,
  replaceFileDump,
  setDumpThumbnail,
  updateDump,
} from "../services/dump-service.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 and takes
// a slug, and passes `dump.id` on: the services' writes match on the id alone.

/**
 * Parses a multipart form's `categoryIds`, a JSON array sent as a string. A
 * missing or malformed value counts as no category.
 */
function parseCategoryIds(value: FormDataEntryValue | null): string[] {
  if (typeof value !== "string" || !value) return [];
  try {
    const parsed: unknown = JSON.parse(value);
    return Array.isArray(parsed)
      ? parsed.filter((v): v is string => typeof v === "string")
      : [];
  } catch {
    return [];
  }
}

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;
  },
);

// Registered ahead of "/:dumpId" so the literal path wins over the parameter.
router.get("/by-url", async (ctx) => {
  const requestingUserId = await parseOptionalAuth(ctx) ?? undefined;
  const url = ctx.request.url.searchParams.get("url") ?? "";
  const responseBody: APIResponse<DumpUrlMatch[]> = {
    success: true,
    data: findDumpsByUrl(url, requestingUserId),
  };
  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 { page, limit } = parsePagination(ctx.request.url.searchParams);
  const { items, hasMore } = listDumps(page, limit, requestingUserId);
  const responseBody: APIResponse<PaginatedData<Dump>> = {
    success: true,
    data: { items, hasMore },
  };
  ctx.response.body = responseBody;
});

router.put("/:dumpId/file", 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 formData = await ctx.request.body.formData();
  const file = formData.get("file");
  const comment = formData.get("comment");
  const title = formData.get("title");

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

  const updatedDump = await replaceFileDump(
    dump.id,
    file,
    typeof comment === "string" && comment ? comment : undefined,
    typeof title === "string" && title ? title : undefined,
    formData.has("categoryIds")
      ? parseCategoryIds(formData.get("categoryIds"))
      : undefined,
    formData.has("isPrivate")
      ? formData.get("isPrivate") === "true"
      : undefined,
  );
  const responseBody: APIResponse<Dump> = { success: true, data: updatedDump };
  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);
  const responseBody: APIResponse<Dump> = { success: true, data: updatedDump };
  ctx.response.body = responseBody;
});

router.put("/:dumpId/thumbnail", 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 formData = await ctx.request.body.formData();
  const file = formData.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 setDumpThumbnail announces it, or clients would fetch it
  // too early.
  await replaceUploadedFile(`${THUMBNAILS_DIR}/${dump.id}-custom`, data);
  const updatedDump = setDumpThumbnail(dump.id, mime);

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

router.delete("/:dumpId/thumbnail", 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 removeDumpThumbnail(dump.id);
  const responseBody: APIResponse<Dump> = { success: true, data: updatedDump };
  ctx.response.body = responseBody;
});

router.post("/:dumpId/refresh-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;