A simple HTTP server inspired by Express and in tune with Functional Programming principles in JavaScript for Deno.

• Simple HTTP server
• Routing
• Server
• Utilities

Usage

Functional HTTP Server is optimized to write elegant and powerful point-free functions. This example uses the Ramda library - for simplification - but you should be able to use any library that implements the Fantasy-land specifications.

This example showcase how to create an endpoint handler for POST /hoge that writes to a local file and to Redis simultaneously the content of the request's body and, replies with 201.

import Task from "https://deno.land/x/functional@v1.3.2/library/Task.js";
import {
  decodeRaw,
  encodeText,
  evert,
  safeExtract
} from "https://deno.land/x/functional@v1.3.2/library/utilities.js";
import File from "https://deno.land/x/functional_io@v1.1.0/library/File.js";
import Request from "https://deno.land/x/functional_io@v1.1.0/library/Request.js";
import Response from "https://deno.land/x/functional_io@v1.1.0/library/Response.js";
import { fetch } from "https://deno.land/x/functional_io@v1.1.0/library/browser_safe.js";
import { writeFile } from "https://deno.land/x/functional_io@v1.1.0/library/fs.js";
import RedisRequest from "https://deno.land/x/functional_redis@v0.2.0/library/RedisRequest.js";
import { $$rawPlaceholder } from "https://deno.land/x/functional_redis@v0.2.0/library/Symbol.js";
import { executeRedisCommandWithSession } from "https://deno.land/x/functional_redis@v0.2.0/library/client.js";

import { handlers, route } from "https://deno.land/x/functional_http_server@v0.3.1/library/route.js";
import startHTTPServer from "https://deno.land/x/functional_http_server@v0.3.1/library/server.js";

startHTTPServer(
  { port: 8080 },
  route(
    handlers.post(
      "/hoge",
      compose(
        map(_ => Response.Created({ 'content-type': "text/plain" }, encodeText("Created!"))),
        converge(
          (...tasks) => evert(Task, tasks),
          [
            compose(
              executeRedisCommandWithSession({ port: 6379 }),
              concat(RedisRequest("SET", new Uint8Array([]), [ "hoge", $$rawPlaceholder ]))
            ),
            compose(
              writeFile({}),
              concat(File.fromPath(`${Deno.cwd()}/hoge`))
            )
          ]
        )
      )
    )
  )
);

const container = await fetch(
  Request(
    {
      headers: {
        'accept': 'text/plain',
        'content-type': 'text/plain'
      },
      method: 'POST',
      url: 'http://localhost:8080/hoge'
    },
    encodeText("Hello, Hoge!")
  )
).run()

const response = safeExtract("Failed to unpack the response", container);

assert(Response.Success.is(response));
assertEquals(response.headers.status, 201);

server.close();

Simple HTTP server

The fastest way to start a HTTP server is to use the startHTTPServer function. The function takes two arguments; the first argument is the options, and the second is a unary function that takes a Request and return a Task of a Response.

import Task from "https://deno.land/x/functional@v1.3.2/library/Task.js";
import Response from "https://deno.land/x/functional_io@v1.1.0/library/Response.js";
import startHTTPServer from "https://deno.land/x/functional_http_server@v0.3.1/library/server.js";

startHTTPServer({ port: 8080 }, request => Task.of(Response.OK({}, request.raw)));

You can test this simple server by executing it your file

$ deno run --allow-net server.js

$ curl localhost:8080 -d "Hello, Hoge!"
> Hello, Hoge!

---

Routing

The main routing tool that comes bundled with this library is conveniently called route. It takes a non-zero number of arguments which are defined by a pair of functions. The first function of the pair is used to assert whether or not to execute the second function. The assertion function takes a Request and return a Boolean, the handling function takes a Request and must return a Task of a Response.

import Task from "https://deno.land/x/functional@v1.3.2/library/Task.js";
import { encodeText } from "https://deno.land/x/functional@v1.3.2/library/utilities.js";
import Response from "https://deno.land/x/functional_io@v1.1.0/library/Response.js";
import { route } from "https://deno.land/x/functional_http_server@v0.3.1/library/route.js";

startHTTPServer(
  { port: 8080 },
  route(
    [
      request => request.headers.method === 'GET',
      _ => Task.of(Response.OK({ 'content-type': 'text/plain' }, encodeText("Hello, Hoge!")))
    ]
  );
);

Routing handlers

Because the pattern is common, this library also offers a collection of handler that automatically creates the assertion function. Each handler takes a String or a RegExp and a unary function.

import Task from "https://deno.land/x/functional@v1.3.2/library/Task.js";
import { encodeText } from "https://deno.land/x/functional@v1.3.2/library/utilities.js";
import Response from "https://deno.land/x/functional_io@v1.1.0/library/Response.js";
import { handlers, route } from "https://deno.land/x/functional_http_server@v0.3.1/library/route.js";

startHTTPServer(
  { port: 8080 },
  route(
    handlers.get('/', _ => Task.of(Response.OK({ 'content-type': 'text/plain' }, encodeText("Hello, Hoge!"))))
  )
);

handlers.delete

String|RegExp → (Request → Task Response) → Task Response

This function takes a string or a regex and a unary function that takes a Request and return a task of a Response. The handler will apply the unary function to a HTTP requests that uses the DELETE method if the path equals or match the first argument.

import { handlers } from "https://deno.land/x/functional_http_server@v0.3.1/library/route.js";

startHTTPServer({ port: 8080 }, handlers.delete(/\/hoge\/(?<ID>[a-z]+)$/, handleDestroyHoge));

handlers.get

String|RegExp → (Request → Task Response) → Task Response

This function takes a string or a regex and a unary function that takes a Request and return a task of a Response. The handler will apply the unary function to a HTTP requests that uses the GET method if the path equals or match the first argument.

import { handlers } from "https://deno.land/x/functional_http_server@v0.3.1/library/route.js";

startHTTPServer({ port: 8080 }, handlers.get(/\/hoge\/(?<ID>[a-z]+)$/, handleRetrieveHoge));

handlers.patch

String|RegExp → (Request → Task Response) → Task Response

This function takes a string or a regex and a unary function that takes a Request and return a task of a Response. The handler will apply the unary function to a HTTP requests that uses the PATCH method if the path equals or match the first argument.

import { handlers } from "https://deno.land/x/functional_http_server@v0.3.1/library/route.js";

startHTTPServer({ port: 8080 }, handlers.patch(/\/hoge\/(?<ID>[a-z]+)$/, handleUpdateHoge));

handlers.post

String|RegExp → (Request → Task Response) → Task Response

This function takes a string or a regex and a unary function that takes a Request and return a task of a Response. The handler will apply the unary function to a HTTP requests that uses the POST method if the path equals or match the first argument.

import { handlers } from "https://deno.land/x/functional_http_server@v0.3.1/library/route.js";

startHTTPServer({ port: 8080 }, handlers.post('/hoge', handleCreateHoge));

handlers.put

String|RegExp → (Request → Task Response) → Task Response

This function takes a string or a regex and a unary function that takes a Request and return a task of a Response. The handler will apply the unary function to a HTTP requests that uses the PUT method if the path equals or match the first argument.

import { handlers } from "https://deno.land/x/functional_http_server@v0.3.1/library/route.js";

startHTTPServer({ port: 8080 }, handlers.put(/\/hoge\/(?<ID>[a-z]+)$/, handleUpdateHoge));

route

([ (Request → Boolean), (Request → Task Response) ],...) → Task Response

This functions takes an arbitrary amount of array pairs of functions and return a task of a Response. The first function of the pair is a predicate, it takes a Request and returns a Boolean. The second function of the pair is a unary function that takes a Request and return a task of a Response; it will be executed only if the first function returns true.

import { route } from "https://deno.land/x/functional_http_server@v0.3.1/library/route.js";

startHTTPServer(
  { port: 8080 },
  route(
    [
      request => request.headers.method === "POST" && request.headers.url === "/hoge",
      request => Task.of(Response.Created({}, encodeText("Created")))
    ]
  )
);

The handler can be easily composed using the spread operator.

startHTTPServer(
  { port: 8080 },
  route(
    ...hogeRouteHandlers,
    ...piyoRouteHandlers,
    ...fugaRouteHandlers
  )
);

The handler will be short-circuited if it's not passed a Request. This makes it easy to write a function to preflight a request.

For example, if you needed to discard any request that doesn't accept application/json, you could do the following.

import { compose } from "https://deno.land/x/ramda@v0.27.2/mod.ts";

startHTTPServer(
  { port: 8080 },
  compose(
    route(...routes),
    request => request.headers.accept !== 'application/json'
      ? Task.of(Response.BadRequest({}, new Uint8Array([])))
      : request
  )
);

---

Server

stream

(Request → Task Response) → AsyncIterator → _|_

This function takes a unaryFunction -- which itself takes a Request and, returns a Task of a Response -- and, an Async Iterator of a Deno HTTP request. The function doesn't resolve to a value.

startHTTPServer

Object → (Request → Response) → Listener

This function takes an object of options and, a unary function -- which itself takes a Request and, returns a Task of a Response. The function will return a server instance that can be closed (server.close()). See the Deno server library for reference.

import Task from "https://deno.land/x/functional@v1.3.2/library/Task.js";
import Response from "https://deno.land/x/functional_io@v1.1.0/library/Response.js";
import startHTTPServer from "https://deno.land/x/functional_http_server@v0.3.1/library/server.js";

startHTTPServer({ port: 8080 }, request => Task.of(Response.OK({}, request.raw)));

---

Utilities

parseBody

Request → a

This function takes a Request and return the most appropriate parsing of the body; an object if the content-type of the request is application/json or, a string if the content type of the request is text/*.

import { parseBody } from "https://deno.land/x/functional_http_server@v0.3.1/library/utilities.js";

assertEquals(
  parseBody(
    Request({ 'content-type': 'application/json' }, encodeText(JSON.stringify({ piyo: 'piyo' })))
  ),
  { piyo: 'piyo' }
);

parseQueryString

Request → Record

This function takes a Request and return an record of the query string.

import { parseQueryString } from "https://deno.land/x/functional_http_server@v0.3.1/library/utilities.js";

assertEquals(
  parseQueryString(Request({ url: '/?hoge=hoge' }, new Uint8Array([]))),
  { hoge: 'hoge' }
);

---

Contributing

We appreciate your help! Please, read the guidelines.

License

Copyright © 2020 - Sebastien Filion

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.