Streaming and static video serving with Deno & Oak

mod.js

import {
  Application,
  Router,
  send,
} from "https://deno.land/x/oak@v6.3.2/mod.ts";

const app = new Application();

const router = new Router();

router
  .get("/video", async ({request, response}) => {
    const range = request.headers.get("range");

    const fileName = "public/Hannibal_1_1.mp4";
    const videoSize = (await Deno.stat(fileName)).size;

    if (!range) {
      response.headers.set("Content-Length", videoSize);
      response.headers.set("Content-Type", "video/mp4");

      response.body = await Deno.readFile(new URL(fileName, import.meta.url));
    }else{  
      let [start, end] = range.replace(/bytes=/, '').split('-');
      start = parseInt(start, 10);
      end = end ? parseInt(end, 10) : videoSize - 1;
      const maxChunk = 1024 * 1024;
      if (((end - start + 1)) > maxChunk) {
        end = start + maxChunk - 1;
      }

      response.headers.set("Content-Range", `bytes ${start}-${end}/${videoSize}`);
      response.headers.set("Accept-Ranges", "bytes");
      response.headers.set("Content-Length", (end - start) + 1);

      let seek;
      if(start === 0){
        seek = Deno.SeekMode.Start;
      }else if(end === videoSize - 1){
        seek = Deno.SeekMode.End;
      }else{
        seek = Deno.SeekMode.Current;
      }

      const file = await Deno.open(new URL(fileName, import.meta.url), {read: true});
      await Deno.seek(file.rid, start, seek);
      const content = new Uint8Array(end - start + 1);
      await file.read(content);
      file.close();
  
      response.type = "video/mp4";
      response.status = 206;
      response.body = content;
    }
  });

app.use(router.routes());
app.use(router.allowedMethods());

app.use(async (context) => {
  await send(context, context.request.url.pathname, {
    index: "index.html",
    root: `public`,
  });
});

app.listen({
  port: 80
});