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Functional Deno IO

Deno IO methods as valid Task monads perfect to write great point-free software in JavaScript.

deno land deno version GitHub release GitHub licence

Usage

This example uses the Ramda library - for simplification - but you should be able to use any library that implements the Fantasy-land specifications. 

import { compose, chain, curry } from "https://x.nest.land/ramda@0.27.0/source/index.js";
import Either from "https://deno.land/x/functional@v1.0.0/library/Either.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";
import Buffer from "https://deno.land/x/functional_io@v0.4.2/library/Buffer.js";
import File from "https://deno.land/x/functional_io@v0.4.2/library/File.js";
import { close, writeAll, create } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";

const writeNewFile = curry(
  (buffer, destinationFile) =>
    File.isOrThrow(destinationFile)
    && compose(
      chain(close),
      chain(writeAll(buffer)),
      create
    )(destinationFile)
);

// Calling `writeNewFile` results in an instance of `Task` keeping the function pure.
assert(
  Task.is(writeNewFile(File.fromPath(`${Deno.cwd()}/hoge`), Buffer.fromString("Hello Deno")))
);

// Finally, calling `Task#run` will call copy to the new file and return a promise
writeNewFile(File.fromPath(`${Deno.cwd()}/hoge`), Buffer.fromString("Hello Deno")).run()
  .then(container => {
    // The returned value should be an instance of `Either.Right` or `Either.Left`
    assert(Either.Right.is(container));
    // Forcing to coerce the container to string will show that the final value is our File representation.
    assert(container.toString(), `Either.Right(File("${Deno.cwd()}/piyo", ...))`);
  });

// await copyToNewFile(sourceFile, destinationFile).run() === Either.Right(File a)

Buffer

The Buffer is the most basic type; it only has one attribute which is a typed array named “raw”. Any type that share the raw attribute is composable with Buffer (and each other) and interoperable.

The Buffer type implements the following algebras:

  • Group
  • Comonad
  • Monad

Example

const buffer = Buffer.fromString("Hoge").concat(Buffer.fromString("Fuga"));

assert(Buffer.is(buffer));

Directory

The Directory type represents a directory on the file system. It is the only type with the same shape as URL. It has only one attributes: the path of the directory. A Directory is interoperable with a URL or a File. It also has interoperability with a File through the FileSystemCollection type.

The Directory type implements the following algebras:

  • Ord
  • Comonad
  • Monad

Example

assert(Directory(`${Deno.cwd()}/hoge`).lte(Directory(`${Deno.cwd()}/piyo`)));

File

The File type extends the Resource type. It represents a file with a path. It has three attributes: the first is the path of the file, the second is a typed array named “raw” and the last is the Resource ID (rid). A File is composable and interoperable with a Resource or a Buffer – It also has some interoperability with a Location through the FileSystemCollection.

The File type implements the following algebras:

  • Group
  • Bifunctor
  • Comonad
  • Monad

Example

const file = File(`${Deno.cwd()}/hoge`, new Uint8Array([ 65, 66, 67, 68, 69 ]), 3)
  .concat(File(`${Deno.cwd()}/piyo`, new Uint8Array([ 70, 71, 72, 73, 74 ]), 3));

assert(File.is(file));

File System Collection

The FileSystemCollection is represents a collection of Location, namely of Directory and File. This of it as an Array for those types.

The FileSystemCollection type implements the following algebras:

  • Group
  • Comonad
  • Monad
  • Traversable

⚠️ The FileSystemCollection type as a traversable is experimental.

Example

const containerA = Maybe.Just(42).map(x => x + 2);
const containerB = Maybe.Nothing.map(x => x + 2);

assert(Maybe.Just.is(containerA));
assert(containerA.extract() === 44);
assert(Maybe.Nothing.is(containerB));

Request

The Request represent a HTTP request. It has two attributes: the first is an object for the response “header” and the second is a typed array named “raw”. The Request type is mostly interoperable with Resource, File and Response.

The Resource type implements the following algebras:

  • Group
  • Bifunctor
  • Monad

Example

const request = Request({}, new Uint8Array([ 65, 66, 67, 68, 69 ]))
  .concat(Resource(new Uint8Array([ 70, 71, 72, 73, 74 ]), 3));

assert(Request.is(request));

Utilities

The Request namespace comes with 4 methods for convenience to create an instance of Request with a common verb. The methods are curried when necessary. Object -> Unint8Array -> Response

const container = compose(
  lift(Request.post({ ["Content-Type"]: "application/json" })),
  readFile
)(File.fromPath(`${Deno.cwd()}/hoge`));

assert((await container.run()).extract().headers.method === "POST");
Method name Has 2 arguments
delete / DELETE false
get / GET false
post / POST true
put / PUT true

✢ The capitalized version of the methods were added because delete is a TypeScript reserved word.

Resource

The Resource type extends the Buffer type. It represents a system resource with a handle, eg: STDOUT, STDIN or a file. It has two attributes: the first is a typed array named “raw” and the second is the Resource ID (rid). Any type that share the Resource attributes is composable and interoperable.

The Resource type implements the following algebras:

  • Group
  • Bifunctor
  • Comonad
  • Monad

Example

const resource = Resource(new Uint8Array([ 65, 66, 67, 68, 69 ]), 3)
  .concat(Resource(new Uint8Array([ 70, 71, 72, 73, 74 ]), 3));

assert(Resource.is(resource));

Response

The Response represent a HTTP response. It has two attributes: the first is an object for the response “header” and the second is a typed array named “raw”. The Response type is mostly interoperable with Resource, File and Request.

The Resource type implements the following algebras:

  • Alternative
  • Group
  • Bifunctor
  • Monad

Example

const response = Response.Success({}, new Uint8Array([ 65, 66, 67, 68, 69 ]))
  .concat(Resource(new Uint8Array([ 70, 71, 72, 73, 74 ]), 3));

assert(Response.is(response));

Utilities

The Response namespace comes with 38 methods for convenience to create an instance of Response with a common status. The methods are curried: Object -> Uint8Array -> Response

const container = compose(
  lift(Response.OK({ ["Content-Type"]: "application/json" })),
  readFile
)(File.fromPath(`${Deno.cwd()}/hoge`));

assert((await container.run()).extract().headers.status === 200);
Method name Status
OK 200
Created 201
Accepted 202
NoContent 204
MultipleChoice 300
MovePermanently 301
Found 302
NotModified 304
TemporaryRedirect 307
PermanentRedirect 308
BadRequest 400
Unauthorized 401
Forbidden 403
NotFound 404
MethodNotAllowed 405
NotAcceptable 406
RequestTimeout 408
Conflict 409
Gone 410
ImATeapot 418
InternalServerError 500
NotImplemented 501
BadGateway 502
ServiceUnavailable 503
GatewayTimeout 504
PermissionDenied 550

URL

The URL type represents an URL; either of a location on the file system or on a remote server. It has only one attributes: the path of the URL. A URL is interoperable with a File or a Directory. It also has interoperability with a File or a Directory through the FileSystemCollection type.

The URL type implements the following algebras:

  • Ord
  • Comonad
  • Monad

Example

assert(URL(`${Deno.cwd()}/hoge`).lte(URL(`${Deno.cwd()}/piyo`)));

File System

⚠️ Note Deno.cwd is used in the following example; if you use Deno.cwd to compose your paths, your functions are no longer pure.

chdir 📕

Change the current working directory to the specified path.

chdir :: Directory a -> Task e Directory a

import { chdir } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Directory from "https://deno.land/x/functional_io@v0.4.2/library/Directory.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = chdir(Directory(".."));

assert(Task.is(container));

chmod 📕

Changes the permission of a specific file/directory of specified path. Ignores the process’s umask.

chmod :: Number -> Location a -> Task e Location a

import { chmod } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import File from "https://deno.land/x/functional_io@v0.4.2/library/File.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = chmod(0o000, File.fromPath(`${Deno.cwd()}/hoge`));

assert(Task.is(container));

chown 📕

Change owner of a regular file or directory. This functionality is not available on Windows.

chown :: Number -> Number -> Location a -> Task e Location a

import { chown } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import File from "https://deno.land/x/functional_io@v0.4.2/library/File.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = chown(null, null, File.fromPath(`${Deno.cwd()}/hoge`));

assert(Task.is(container));

close 📕

Close the given resource which has been previously opened, such as via opening or creating a file. Closing a file when you are finished with it is important to avoid leaking resources.

close :: File a -> Task e File a

import { close } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import File from "https://deno.land/x/functional_io@v0.4.2/library/File.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = close(File(`${Deno.cwd()}/hoge`, new Uint8Array([]), 3));

assert(Task.is(container));

copy 📕

Copies from a source to a destination until either EOF (null) is read from the source, or an error occurs.

copy :: Options -> Buffer a -> Buffer b -> Task e Buffer a

import { copy } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Buffer from "https://deno.land/x/functional_io@v0.4.2/library/Buffer.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = copy({}, Buffer(new Uint8Array([ 65, 66, 67, 68, 69 ])), Buffer(new Uint8Array([])));

assert(Task.is(container));

copyFile 📕

Copies the contents and permissions of one file to another specified file, by default creating a new file if needed, else overwriting. Fails if target path is a directory or is unwritable.

copyFile :: File a -> File b -> Task e File b

import { copyFile } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import File from "https://deno.land/x/functional_io@v0.4.2/library/File.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = copyFile(File.fromPath(`${Deno.cwd()}/hoge`), File.fromPath(`${Deno.cwd()}/piyo`));

assert(Task.is(container));

create 📕

Creates a file if none exists or truncates an existing file.

create :: File a -> Task e File a

import { create } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import File from "https://deno.land/x/functional_io@v0.4.2/library/File.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = create(File.fromPath(`${Deno.cwd()}/hoge`));

assert(Task.is(container));

cwd 📕

Return a Directory representation of the current working directory.

cwd :: () -> Task e Directory a

import { cwd } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = cwd();

assert(Task.is(container));

emptyDir 📕

Ensures that a directory is empty. Deletes directory contents if the directory is not empty. If the directory does not exist, it is created. The directory itself is not deleted.

emptyDir :: Directory a -> Task e Directory a

import { emptyDir } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Directory from "https://deno.land/x/functional_io@v0.4.2/library/Directory.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = emptyDir(Directory(`${Deno.cwd()}/hoge`));

assert(Task.is(container));

ensureDir 📕

Ensures that the directory exists. If the directory structure does not exist, it is created. Like mkdir -p.

ensureDir :: Directory a -> Task e Directory a

import { ensureDir } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Directory from "https://deno.land/x/functional_io@v0.4.2/library/Directory.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = emptyDir(Directory(`${Deno.cwd()}/hoge`));

assert(Task.is(container));

exists 📕

Test whether the given path exists by checking with the file system. If the file or directory doesn’t exist, it will resolve to Either.Left(null).

exists :: Location a -> Task null Location a

import { exists } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Directory from "https://deno.land/x/functional_io@v0.4.2/library/Directory.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = exists(Directory(`${Deno.cwd()}/hoge`));

assert(Task.is(container));

mkdir 📕

Creates a new directory with the specified path.

mkdir :: Options -> Directory a -> Task e Directory a

import { mkdir } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Directory from "https://deno.land/x/functional_io@v0.4.2/library/Directory.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = mkdir({}, Directory(`${Deno.cwd()}/hoge`));

assert(Task.is(container));

move 📕

Moves a file or directory.

move :: Options -> String -> Location a -> Task e Location b

import { move } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Directory from "https://deno.land/x/functional_io@v0.4.2/library/Directory.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = move({}, `${Deno.cwd()}/piyo`, Directory(`${Deno.cwd()}/hoge`));

assert(Task.is(container));

open 📕

Open a file and resolve to an instance of File. The file does not need to previously exist if using the create or createNew open options. It is the callers responsibility to close the file when finished with it.

open :: Options -> File a -> Task e File a

import { open } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Directory from "https://deno.land/x/functional_io@v0.4.2/library/Directory.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = open({ read: true, write: true }, File.fromPath(`${Deno.cwd()}/hoge`));

assert(Task.is(container));

read 📕

Read from a Resource given it has a non-zero raw buffer.

read :: Resource a -> Task e Resource a

import { read } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import File from "https://deno.land/x/functional_io@v0.4.2/library/File.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = read(File(`${Deno.cwd()}/hoge`, new Uint8Array(5), 3));

assert(Task.is(container));

readAll 📕

Read from a Resource.

readAll :: Resource a -> Task e Resource a

import { readAll } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Buffer from "https://deno.land/x/functional_io@v0.4.2/library/Buffer.js";
import File from "https://deno.land/x/functional_io@v0.4.2/library/File.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = readAll(File(`${Deno.cwd()}/hoge`, new Uint8Array([]), 3));

assert(Task.is(container));

rename 📕

Renames a file or directory.

rename :: String -> Location a -> Task e Location b

import { rename } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Directory from "https://deno.land/x/functional_io@v0.4.2/library/Directory.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = rename(`${Deno.cwd()}/piyo`, Directory(`${Deno.cwd()}/hoge`));

assert(Task.is(container));

write 📕

Write to a Resource given it has a non-zero raw buffer.

write :: Resource a -> Task e Resource a

import { write } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import File from "https://deno.land/x/functional_io@v0.4.2/library/File.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = write(
  File(`${Deno.cwd()}/hoge`, new Uint8Array([ 65, 66, 67, 68, 69 ]), _file.rid)
);

assert(Task.is(container));

writeAll 📕

Write all to a Resource from a Buffer.

writeAll :: Buffer b -> Resource a -> Task e Resource b

import { writeAll } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Buffer from "https://deno.land/x/functional_io@v0.4.2/library/Buffer.js";
import File from "https://deno.land/x/functional_io@v0.4.2/library/File.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = writeAll(
  Buffer(new Uint8Array([ 65, 66, 67, 68, 69 ])),
  File(`${Deno.cwd()}/hoge`, new Uint8Array([]), _file.rid)
);

assert(Task.is(container));

writeFile 📕

Write a File to the file system.

writeFile :: Options -> File a -> Task e File b

import { writeFile } from "https://deno.land/x/functional_io@v0.4.2/library/fs.js";
import Buffer from "https://deno.land/x/functional_io@v0.4.2/library/Buffer.js";
import File from "https://deno.land/x/functional_io@v0.4.2/library/File.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const container = writeFile(
  {},
  File(`${Deno.cwd()}/hoge`, new Uint8Array([]), _file.rid)
);

assert(Task.is(container));

Browser Safe

fetch

Fetches a resource on a local/remote server.

fetch :: Request a -> Task e Response b

import { fetch } from "https://deno.land/x/functional_io@v0.4.2/library/browser-safe.js";
import Request from "https://deno.land/x/functional_io@v0.4.2/library/Request.js";
import Response from "https://deno.land/x/functional_io@v0.4.2/library/Response.js";
import Task from "https://deno.land/x/functional@v1.0.0/library/Task.js";

const containerA = fetch(Request.GET("http://localhost:8000"));

assert(Task.is(containerA));

const containerB = await container.run().extract();

assert(Response.Success.is(containerB));

Deno

This codebase uses Deno.

MIT 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.