Implement some File System methods

Author: sebastienfilion

LICENSE

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+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.

README.md

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+# Functional Deno IO
+
+Deno IO methods as valid Task monads perfect to write great point-free software in JavaScript that is compatible with most modern browsers and Deno.
+
+[![deno land](http://img.shields.io/badge/available%20on-deno.land/x-lightgrey.svg?logo=deno&labelColor=black)](https://deno.land/x/[email protected])
+[![deno version](https://img.shields.io/badge/deno-^1.3.2-lightgrey?logo=deno)](https://github.com/denoland/deno)
+[![GitHub release](https://img.shields.io/github/v/release/sebastienfilion/functional-deno-io)](https://github.com/sebastienfilion/functional-deno-io/releases)
+[![GitHub licence](https://img.shields.io/github/license/sebastienfilion/functional-deno-io)](https://github.com/sebastienfilion/functional-deno-io/blob/v0.1.0/LICENSE)
+
+  * [File System](#file-system)
+  * [Network](#network)
+  
+# Usage
+
+This example uses the [Ramda library](https://ramdajs.com) - for simplification - but you should be able to use any library that implements
+the [Fantasy-land specifications](https://github.com/fantasyland/fantasy-land). 
+
+```js
+import { compose, chain, curry } from "https://x.nest.land/[email protected]/source/index.js";
+import Either from "https://deno.land/x/[email protected]/Either.js";
+import Task from "https://deno.land/x/[email protected]/Task.js";
+import { File } from "https://deno.land/x/[email protected]/types.js";
+import { close, copyFile, create } from "https://deno.land/x/[email protected]/fs.js";
+
+const copyToNewFile = curry(
+  (sourceFile, destinationFile) =>
+    File.isOrThrow(sourceFile)
+    && File.isOrThrow(destinationFile)
+    && compose(
+      chain(close),
+      chain(copyFile(sourceFile)),
+      create
+    )(destinationFile)
+);
+
+// Calling `copyToNewFile` results in an instance of `Task` keeping the function pure.
+assert(
+  Task.is(copyToNewFile(File.fromPath(`${Deno.cwd()}/hoge`), File.fromPath(`${Deno.cwd()}/piyo`)))
+);
+
+// Finally, calling `Task#run` will call copy to the new file and return a promise
+copyToNewFile(File.fromPath(`${Deno.cwd()}/hoge`), File.fromPath(`${Deno.cwd()}/piyo`)).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("${Deno.cwd()}/piyo", ...))`);
+  });
+
+// await copyToNewFile(sourceFile, destinationFile).run() === Either.Right(File a)
+```
+
+## File System
+
+### `chdir` [📕](https://doc.deno.land/builtin/stable#Deno.chdir)
+
+Change the current working directory to the specified path.
+
+`chdir :: Directory a -> Task e Directory a`
+
+```js
+import { chdir } from "https://deno.land/x/[email protected]/fs.js";
+import { Directory } from "https://deno.land/x/[email protected]/types.js";
+import Task from "https://deno.land/x/[email protected]/Task.js";
+
+const container = chdir(Directory(".."));
+
+assert(Task.is(container));
+```
+
+### `chmod` [📕](https://doc.deno.land/builtin/stable#Deno.chmod)
+
+Changes the permission of a specific file/directory of specified path. Ignores the process's umask.  
+
+`chmod :: Number -> File a -> Task e File a`
+
+```js
+import { chmod } from "https://deno.land/x/[email protected]/fs.js";
+import { File } from "https://deno.land/x/[email protected]/types.js";
+import Task from "https://deno.land/x/[email protected]/Task.js";
+
+const container = chmod(0o000, File.fromPath(`${Deno.cwd()}/hoge`));
+
+assert(Task.is(container));
+```
+
+### `chown` [📕](https://doc.deno.land/builtin/stable#Deno.chown)
+
+Change owner of a regular file or directory. This functionality is not available on Windows.
+
+`chown :: Number -> Number -> File a -> Task e File a`
+
+```js
+import { chown } from "https://deno.land/x/[email protected]/fs.js";
+import { File } from "https://deno.land/x/[email protected]/types.js";
+import Task from "https://deno.land/x/[email protected]/Task.js";
+
+const container = chown(null, null, File.fromPath(`${Deno.cwd()}/hoge`));
+
+assert(Task.is(container));
+```
+
+### `close` [📕](https://doc.deno.land/builtin/stable#Deno.close)
+
+Close the given resource which has been previously opened, such as via opening or creating a file. 
+Closing a file when you are finished with it is important to avoid leaking resources.  
+
+`copy :: File a -> Task e File a`
+
+```js
+import { close } from "https://deno.land/x/[email protected]/fs.js";
+import { File } from "https://deno.land/x/[email protected]/types.js";
+import Task from "https://deno.land/x/[email protected]/Task.js";
+
+const container = close(File(`${Deno.cwd()}/hoge`, new Uint8Array([]), 3));
+
+assert(Task.is(container));
+```
+
+### `copy` [📕](https://doc.deno.land/builtin/stable#Deno.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 Writer b`
+
+```js
+import { copy } from "https://deno.land/x/[email protected]/fs.js";
+import { Buffer } from "https://deno.land/x/[email protected]/types.js";
+import Task from "https://deno.land/x/[email protected]/Task.js";
+
+const container = copy({}, Buffer(new Uint8Array([ 65, 66, 67, 68, 69 ])), Buffer(new Uint8Array([])));
+
+assert(Task.is(container));
+```
+
+### `copyFile` [📕](https://doc.deno.land/builtin/stable#Deno.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`
+
+```js
+import { copyFile } from "https://deno.land/x/[email protected]/fs.js";
+import { File } from "https://deno.land/x/[email protected]/types.js";
+import Task from "https://deno.land/x/[email protected]/Task.js";
+
+const container = copyFile(File.fromPath(`${Deno.cwd()}/hoge`), File.fromPath(`${Deno.cwd()}/piyo`));
+
+assert(Task.is(container));
+```
+
+### `create` [📕](https://doc.deno.land/builtin/stable#Deno.create)
+
+Creates a file if none exists or truncates an existing file.
+
+`create :: File a -> Task e File a`
+
+```js
+import { create } from "https://deno.land/x/[email protected]/fs.js";
+import { File } from "https://deno.land/x/[email protected]/types.js";
+import Task from "https://deno.land/x/[email protected]/Task.js";
+
+const container = create(File.fromPath(`${Deno.cwd()}/hoge`));
+
+assert(Task.is(container));
+```
+
+### `cwd` [📕](https://doc.deno.land/builtin/stable#Deno.cwd)
+
+Return a Directory representation of the current working directory.
+
+`cwd :: () -> Task e Directory a`
+
+```js
+import { cwd } from "https://deno.land/x/[email protected]/fs.js";
+import Task from "https://deno.land/x/[email protected]/Task.js";
+
+const container = cwd();
+
+assert(Task.is(container));
+```
+
+### `emptyDir` [📕](https://deno.land/[email protected]/fs#emptydir)
+
+Ensures that a directory is empty. Deletes directory contents if the directory is not empty.
+If the directory does not exist, it is created. The directory itself is not deleted.
+
+`emptyDir :: Directory a -> Task e Directory a`
+
+```js
+import { emptyDir } from "https://deno.land/x/[email protected]/fs.js";
+import { Directory } from "https://deno.land/x/[email protected]/types.js";
+import Task from "https://deno.land/x/[email protected]/Task.js";
+
+const container = emptyDir(Directory(`${Deno.cwd()}/hoge`));
+
+assert(Task.is(container));
+```
+
+### `ensureDir` [📕](https://deno.land/[email protected]/fs#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`
+
+```js
+import { ensureDir } from "https://deno.land/x/[email protected]/fs.js";
+import { Directory } from "https://deno.land/x/[email protected]/types.js";
+import Task from "https://deno.land/x/[email protected]/Task.js";
+
+const container = emptyDir(Directory(`${Deno.cwd()}/hoge`));
+
+assert(Task.is(container));
+```
+
+### `exists` [📕](https://deno.land/[email protected]/fs#exists)
+
+Test whether the given path exists by checking with the file system. 
+If the file or directory doesn't exist, it will resolve to `Either.Left(null)`.
+
+`exists :: File a|Directory a -> Task null File a|Directory a`
+
+```js
+import { exists } from "https://deno.land/x/[email protected]/fs.js";
+import { Directory } from "https://deno.land/x/[email protected]/types.js";
+import Task from "https://deno.land/x/[email protected]/Task.js";
+
+const container = exists(Directory(`${Deno.cwd()}/hoge`));
+
+assert(Task.is(container));
+```
+ 
+## Deno
+
+This codebase uses [Deno](https://deno.land/#installation).
+
+### 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.