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	# Majic

	Majic provides a robust integration of [libmagic](http://man7.org/linux/man-pages/man3/libmagic.3.html) for Elixir.

	With this library, you can start an one-off process to run a single check, or run the process as a daemon if you expect to run
	many checks.

	It is a friendly fork of [gen_magic](https://github.com/evadne/gen_magic) featuring a (arguably) more robust C-code
	using erl_interface, built in pooling, unified/clean API, and an optional Plug.

	This package is regulary tested on multiple platforms (Debian, macOS, Fedora, Alpine, FreeBSD) to ensure it'll work fine
	in any environment.

	## Installation

	The package can be installed by adding `majic` to your list of dependencies in `mix.exs`:

	```elixir
	def deps do
	[
	{:majic, "~> 1.0"}
	]
	end
	```

	You must also have [libmagic](http://man7.org/linux/man-pages/man3/libmagic.3.html) installed locally with headers, alongside common compilation tools (i.e. build-essential). These can be acquired by apt-get, yum, brew, etc.

	Compilation of the underlying C program is automatic and handled by [elixir_make](https://github.com/elixir-lang/elixir_make).

	## Usage

	Depending on the use case, you may utilise a single (one-off) Majic process without reusing it as a daemon, or utilise a connection pool (such as Poolboy) in your application to run multiple persistent Majic processes.

	To use Majic directly, you can use `Majic.Once.perform/1`:

	```elixir
	iex(1)> Majic.perform(".", once: true)
	{:ok,
	%Majic.Result{
	content: "directory",
	encoding: "binary",
	mime_type: "inode/directory"
	}}
	```

	To use the Majic server as a daemon, you can start it first, keep a reference, then feed messages to it as you require:

	```elixir
	{:ok, pid} = Majic.Server.start_link([])
	{:ok, result} = Majic.perform(path, server: pid)
	```

	See `Majic.Server.start_link/1` and `t:Majic.Server.option/0` for more information on startup parameters.

	See `Majic.Result` for details on the result provided.

	## Configuration

	When using `Majic.Server.start_link/1` to start a persistent server, or `Majic.Helpers.perform_once/2` to run an ad-hoc request, you can override specific options to suit your use case.

	\| Name \| Default \| Description \|
	\| - \| - \| - \|
	\| `:startup_timeout` \| 1000 \| Number of milliseconds to wait for client startup \|
	\| `:process_timeout` \| 30000 \| Number of milliseconds to process each request \|
	\| `:recycle_threshold` \| 10 \| Number of cycles before the C process is replaced \|
	\| `:database_patterns` \| `[:default]` \| Databases to load \|

	See `t:Majic.Server.option/0` for details.

	__Note__ `:recycle_thresold` is only useful if you are using a libmagic `<5.29`, where it was susceptible to memleaks
	([details](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=840754)]). In future versions of `majic` this option could
	be ignored.

	### Reloading / Altering databases

	If you want `majic` to reload its database(s), run `Majic.Server.reload(ref)`.

	If you want to add or remove databases to a running server, you would have to run `Majic.Server.reload(ref, databases)`
	where databases being the same argument as `database_patterns` on start. `Majic` does not support adding/removing
	databases at runtime without a port reload.

	### Use Cases

	#### Ad-Hoc Requests

	For ad-hoc requests, you can use the helper method `Majic.Once.perform_once/2`:

	```elixir
	iex(1)> Majic.perform(Path.join(File.cwd!(), "Makefile"), once: true)
	{:ok,
	%Majic.Result{
	content: "makefile script, ASCII text",
	encoding: "us-ascii",
	mime_type: "text/x-makefile"
	}}
	```

	#### Supervised Requests

	The Server should be run under a supervisor which provides resiliency.

	Here we run it under a supervisor in an application:

	```elixir
	children =
	[
	# ...
	{Majic.Server, [name: YourApp.Majic]}
	]

	opts = [strategy: :one_for_one, name: YourApp.Supervisor]
	Supervisor.start_link(children, opts)
	```

	Now we can ask it to inspect a file:

	```elixir
	iex(2)> Majic.perform(Path.expand("~/.bash_history"), server: YourApp.Majic)
	{:ok, %Majic.Result{mime_type: "text/plain", encoding: "us-ascii", content: "ASCII text"}}
	```

	Note that in this case we have opted to use a named process.

	#### Pool

	For concurrency and resiliency, you may start the `Majic.Pool`. By default, it will start a `Majic.Server`
	worker per online scheduler:

	You can add a pool in your application supervisor by adding it as a child:

	```elixir
	children =
	[
	# ...
	{Majic.Pool, [name: YourApp.MajicPool, pool_size: 2]}
	]

	opts = [strategy: :one_for_one, name: YourApp.Supervisor]
	Supervisor.start_link(children, opts)
	```

	And then you can use it with `Majic.perform/2` with `pool: YourApp.MajicPool` option:

	```elixir
	iex(1)> Majic.perform(Path.expand("~/.bash_history"), pool: YourApp.MajicPool)
	{:ok, %Majic.Result{mime_type: "text/plain", encoding: "us-ascii", content: "ASCII text"}}
	```
	#### Fixing extensions

	You may also want to fix the user-provided filename according to its detected MIME type. To do this, you can use `Majic.Extension.fix/3`:

	```elixir
	iex(1)> {:ok, result} = Majic.perform("cat.jpeg", once: true)
	{:ok, %Majic.Result{mime_type: "image/webp", ...}}
	iex(1)> Majic.Extension.fix("cat.jpeg", result)
	"cat.webp"
	```

	#### Use with Plug.Upload

	If you use Plug or Phoenix, you may want to automatically verify the content type of every `Plug.Upload`. The
	`Majic.Plug` is there for this.

	Enable it by using `plug Majic.Plug, pool: YourApp.MajicPool` in your pipeline or controller. Then, every `Plug.Upload`
	in `conn.params` and `conn.body_params` is now verified. The filename is also altered with an extension matching its
	content-type, using `Majic.Extension`.

	## Notes

	### Soak Test

	Run an endless cycle to prove that the program is resilient:

	```bash
	find /usr/share/ -name *png \| xargs mix run test/soak.exs
	find . -name *ex \| xargs mix run test/soak.exs
	```

	## Acknowledgements

	During design and prototype development of this library, the Author has drawn inspiration from the following individuals, and therefore
	thanks all contributors for their generosity:

	- [Evadne Wu](https://github.com/evadne)
	- Original [gen_magic](https://github.com/evadne/gen_magic) author.
	- [James Every](https://github.com/devstopfix)
	- Enhanced Elixir Wrapper (based on GenServer)
	- Initial Hex packaging (v.0.22)
	- Soak Testing
	- Matthias and Ced for helping the author with C oddities
	- [Hecate](https://github.com/Kleidukos) for laughing at aforementionned oddities
	- majic for giving inspiration for the lib name (magic, majic, get it? hahaha..)

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