/**
 * Serves and changes dumps' thumbnails, a sub-resource of their dump. The
 * cards and pages that show a file dump build the URL with
 * `dumpThumbnailUrl`, and the edit page uploads a custom one. Thumbnails made
 * from an upload are generated on first request by lib/ffmpeg.ts, which keeps
 * them.
 *
 * - `GET /api/dumps/:dumpId/thumbnail?v=&w=&token=` — public; a private
 *   dump's thumbnail needs its poster's media `token`. Serves the dump's
 *   custom thumbnail, else one made from its upload: a still of a video, or
 *   its image. An image comes scaled down to `w` (`shared/image.ts`), or to
 *   the widest of those widths without one, and as it is when no copy can be
 *   made; 404 when there is neither.
 * - `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.
 *
 * @module
 */

import { Router } from "@oak/oak";
import { APIException } from "../lib/api-exception.ts";
import type { APIResponse } from "../../shared/api.ts";
import type { Dump } from "../../shared/dump.ts";
import {
  customThumbnailPath,
  getDump,
  removeDumpThumbnail,
  setDumpThumbnail,
} from "../services/dump-service.ts";
import { serveFile } from "../lib/serve-file.ts";
import {
  replaceUploadedFile,
  serveImage,
  serveUploadedFile,
  validateImageUpload,
} from "../lib/upload.ts";
import { DUMPS_DIR } from "../config.ts";
import { MAX_IMAGE_WIDTH } from "../../shared/image.ts";
import { resolveMediaDump } from "../lib/dump-media.ts";
import { ensureGenerated, generatedPaths, videoStill } from "../lib/ffmpeg.ts";
import { can } from "../lib/permissions.ts";
import { type AuthContext, authMiddleware } from "../middleware/auth.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" });

router.get("/:dumpId/thumbnail", async (ctx) => {
  const { dumpId } = ctx.params;
  const { dump, cacheControl: generatedCache } = await resolveMediaDump(
    ctx,
    dumpId,
  );

  if (dump.thumbnailMime) {
    // Replacing it doesn't change the file's version, so it is always
    // revalidated.
    const served = await serveUploadedFile(
      ctx,
      customThumbnailPath(dump.id),
      dump.thumbnailMime,
      0,
      dump.isPrivate,
      MAX_IMAGE_WIDTH,
    );
    if (served) return;
  }

  const mime = dump.kind === "file" ? dump.fileMime ?? "" : "";
  const srcPath = `${DUMPS_DIR}/${dump.id}`;
  const generated = generatedPaths(dump.id);

  if (mime.startsWith("video/")) {
    const thumbPath = generated.still;
    if (
      !await ensureGenerated(thumbPath, () => videoStill(srcPath, thumbPath))
    ) {
      throw new APIException(404, "Could not generate thumbnail");
    }
    if (
      await serveFile(ctx, thumbPath, {
        mime: "image/jpeg",
        cacheControl: generatedCache,
      })
    ) return;
  }

  // A scaled-down copy for the feed; the original when there's none to make
  // (no ffmpeg, an image it can't read).
  if (
    /^image\/(png|jpeg|gif|webp|avif|bmp)$/.test(mime) &&
    await serveImage(ctx, srcPath, mime, generatedCache, MAX_IMAGE_WIDTH)
  ) return;

  throw new APIException(404, "No thumbnail for this dump");
});

/**
 * Returns the dump `ctx` names if the caller may change it, as its poster or
 * with `dump:moderate`.
 *
 * @throws {APIException} 404 when the caller can't see it, 403 when they may
 * not change it.
 */
function editableDump(ctx: AuthContext<"/:dumpId/thumbnail">): Dump {
  const userId = ctx.state.user.userId;
  const dump = getDump(ctx.params.dumpId, userId);
  if (userId !== dump.userId && !can(ctx.state.user, "dump:moderate")) {
    throw new APIException(403, "Not authorized to update dump");
  }
  return dump;
}

router.put(
  "/:dumpId/thumbnail",
  authMiddleware,
  async (ctx: AuthContext<"/:dumpId/thumbnail">) => {
    const dump = editableDump(ctx);
    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(customThumbnailPath(dump.id), data);
    const responseBody: APIResponse<Dump> = {
      success: true,
      data: setDumpThumbnail(dump.id, mime),
    };
    ctx.response.body = responseBody;
  },
);

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

export default router;