crush/README.md

crush
=====

**crush** - The uncomplicated LÖVE external module system.

**crush** is a minimalistic dependency-less package system for the LÖVE engine.
It provides a structured approach to retrieve external libraries for your game project.

## Why?

Lua knows some excellent dependency management system,
like [LuaRocks](https://luarocks.org).
Though, they are inconvenient for a game project, where:

* External libraries should be packed along with the game for distribution.
* Libraries are often small, and their code should be readily hackable by developers (library versions are not tremendously important).
* Depending on a complex package manager is undesireable.

LÖVE games have limited ways to manage external libraries:

1. Manually, directly copying external libraries in the game source tree.

   * Pulling latest changes in the library requires more copy-pasting.
   * Harder to use libraries if they depend on other libraries themselves.

2. Using a package manager during development, and carefully
   pack external libraries with the game manually upon distribution.

   * Introduce additional step to distribution phase.
   * Many existing LÖVE libraries have no package manager support.

**crush** provides an alternative approach, offering the following features:

* Fetch external libraries directly from their source code repository,
  ensuring the ability to pull, or even push, the latest changes from your project.
* Automatically pack external libraries inside the project source tree, inside a well-known `lib` folder.
* Resolves dependencies recursively, making possible for libraries that depend on other libraries, saving the
  developer all the manual dependency tracking.
* Works automatically with most existing LÖVE libraries, since it directly uses `git` to clone their sources.
* Does not require any complex package manager or native code, just a single Lua source file.
* Does not require any centralized package repository to publish or fetch libraries.

## How to use it?

To use **crush** follow these steps:

1. Copy the latest `crush.lua` into your project's root folder.
2. Create a `.lovedeps` file in the same directory, here you will list every dependency (more in the next section).
3. Once you have `crush.lua` and `.lovedeps` in place, you can populate or refresh project dependencies by running:

```sh
lua crush.lua
```

**crush** fetches the project's dependencies recursively, cloning them inside a `lib` subdirectory.
Hence, you may use them comfortably in your code with the usual `require()`, like this:

```lua
local serialize = require 'lib.serialize'
```

**crush** flattens every dependency in the `lib` folder.
This implies that libraries common to different packages must be named and accessed consistently in the source code.
A reasonable limitation given **crush** use-case.

## The .lovedeps file

The `.lovedeps` file is a regular Lua text file, containing a table where every entry specifies a dependency:

```lua
['dependency-name'] = "git-url"
```

The following example shows a `.lovedeps` file depending on three external libraries,
named `df-serialize`, `gear` and `yui`, every dependency has a corresponding `git` repository URL.
There dependency name is not required to match the actual repository name, but names **should** be consistent
within the entire project, otherwise the same repository may be cloned several times under different names.

```lua
{
    -- Fetch lib/df-serialize from https://git.doublefourteen.io/lua/df-serialize
    -- needs ['quote'] syntax due to '-'
    ['df-serialize'] = "https://git.doublefourteen.io/lua/df-serialize",

    -- Fetch lib/gear from https://git.doublefourteen.io/lua/gear
    gear = "https://git.doublefourteen.io/lua/gear",

    -- Fetch lib/yui from https://git.doublefourteen.io/lua/yui
    yui = "https://git.doublefourteen.io/lua/yui"

    -- NOTE: Any dependency may also pull additional subdependencies,
    --       these will also be cloned within lib/
}
```

## Philosophy

**crush** is somehow opinionated and tied to its intended use-case.
It obeys the following rules:

`MUST`:

* Be self-contained, only a single Lua file: `crush.lua`.
* Must only depend on Lua, LÖVE and `git`, expected to be available on any LÖVE developer machine.
* Do one thing: fetch the dependencies listed in the `.lovedeps` file.
* Be simple and predictable, integrating **crush** into a LÖVE game must be as intuitive as possible.
* Be hackable, its code must be reasonably trivial, understandable and adaptable.
* Enforce one way to do things, encouraging consistency.

`MUST NOT`:

* Give in to feature creep.
* Provide a centralized repository.
* Be completely general, its scope is limited to the average LÖVE game or library.
* Be entirely safe, there is no demand for checksum or strict versioning in **crush** use case.

`SHOULD NOT`:

* Break compatibility with older `.lovedeps` files.


If this does not meet your requirements, code should still be sufficiently hackable to
provide some room for customization.

## Similar projects

* [LÖVERocks](https://github.com/Alloyed/loverocks) is a more involved project aiming to bring LuaRocks features to LÖVE.

## License

MIT, see [LICENSE](LICENSE) for details.