# componentm

> An utility library to build multiple components (config, db, cache, logging,
> etc.) of an application in a traceable, reliable and efficient fashion

## Table Of Contents

* [Installation](#installation)
* [Purpose](#purpose)
 * [Differences with ResourceT](#differences-with-resourcet)
* [Development](#development)
* [Documentation](#documentation)
* [License](#license)

## Installation

[![Hackage](https://img.shields.io/hackage/v/componentm.svg)](https://img.shields.io/hackage/v/componentm.svg)
[![Stackage LTS](http://stackage.org/package/componentm/badge/lts)](http://stackage.org/lts/package/componentm)
[![Stackage Nightly](http://stackage.org/package/componentm/badge/nightly)](http://stackage.org/nightly/package/componentm)

Make sure you include the following entry on your [cabal file's
dependecies](https://www.haskell.org/cabal/users-guide/developing-packages.html#build-information)
section.

```cabal
library:
  build-depends: componentm
```

Or on your `package.yaml`

```
dependencies:
- componentm
```

## Purpose

This library is intended to be a high level API for the
[teardown](http://hackage.haskell.org/package/teardown) library; it provides a
high level monad interface that helps composition of resource
allocation/teardown in a safe and reliable way.

### Differences with ResourceT

The [resourcet](http://hackage.haskell.org/package/resourcet) library provides a
monad transformer that keeps track of allocated resources at runtime making sure
that if an exception happens or the block of execution finishes, the resources
allocated are cleaned up.

The [componentm](http://hackage.haskell.org/package/componentm) library on the
other hand, does not run as a Monad transformer, but rather it gets called at
the very beginning of your application, it builds the _environment_ needed by
your application environment to work (e.g. [Layer
1](http://www.parsonsmatt.org/2018/03/22/three_layer_haskell_cake.html)), and
provides helper _bracket style_ functions that cleanup all allocated resources
in the right order when your application terminates either normally or with an
error.

## Development
[![Build Status](https://travis-ci.org/roman/Haskell-componentm.svg?branch=master)](https://travis-ci.org/roman/Haskell-componentm)
[![Hackage Dependencies](https://img.shields.io/hackage-deps/v/componentm.svg)](http://packdeps.haskellers.com/feed?needle=componentm)
[![Github](https://img.shields.io/github/commits-since/roman/haskell-componentm/v0.0.0.2.svg)](https://img.shields.io/github/commits-since/roman/haskell-componentm/v0.0.0.2.svg)

This library is intended to be minimal, providing a few functions that work
reliably among many different kind of projects. If you want to contribute, Pull
Request are very welcome! Please try to follow these simple rules:

* Please create a topic branch for every separate change you make.
* Update the README.md file if necessary.
* Please _do not_ change the version number on your Pull Request.

### Open Commit Bit

This project has an open commit bit policy: Anyone with an accepted pull request
gets added as a repository collaborator. Please try to follow these simple
rules:

* Commit directly onto the master branch only for typos, improvements to the
  README and documentation.
* Create a feature branch and open a pull-request early for any new features to
  get feedback.
* Make sure you adhere to the general pull request rules above.

## License

Copyright (c) 2017-2018 Roman Gonzalez

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.