Hasmin - A Haskell CSS Minifier
====
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Aside from the usual techniques (e.g. whitespace removal, color minification,
etc.), the idea was to explore new possibilities, by implementing things
other minifiers weren't doing, or they were, but not taking full advantage of.

Also, the minifier implements some techniques that do nothing for minified
sizes, but attempt to improve post-compression sizes (at least when using
DEFLATE, i.e. gzip).

For a list of techniques, see [the wiki](https://github.com/contivero/hasmin/wiki).
To use it as a library, see
[below](https://github.com/contivero/hasmin#library).

## Building & Installing
### Stack
The easiest and prefered way is using
[stack](https://docs.haskellstack.org/en/stable/README/). Clone the repo, then:
```sh
$ cd path/to/hasmin/repo
$ stack build
```
After that, you can install it with `stack install` (installs by default to `~/.local/bin`).
If you'd rather just try it out, use `stack exec hasmin` (keep in mind it has
a slight additional delay at the beginning when run this way).

### Cabal
Alternatively, you can use [cabal](https://www.haskell.org/cabal/):
```sh
$ cd path/to/hasmin/repo
$ cabal update                      # Make sure to have the latest package list
$ cabal sandbox init                # Initialise a sandbox
$ cabal install --only-dependencies # Install dependencies into the sandbox
$ cabal build                       # Build hasmin inside the sandbox
```

## Minifier Usage
Hasmin expects a path to the CSS file, and outputs the minified result to
stdout. Say you have a `sheet.css` and want to minify it, and save it as
`sheet.min.css`. Then, run:
```sh
$ hasmin sheet.css > sheet.min.css
```

Every technique is enabled by default, except for:
 1. Escaped character conversions (e.g. converting `\2714` into `✔`, enabled
    with `--convert-escaped-characters`).
 2. Dimension minifications (e.g. converting `12px` to `9pt`, enabled with
    `--dimension-min`, or just `-d`).
 3. Lexicographical sorting of declarations (enabled with
    `--sort-declarations`).

The first two are disabled mainly because they are—on average, not
always—detrimental for DEFLATE compression. As for declaration sorting, whether
it benefits or hurts compression rates is very stylesheet-dependent, and the
current implementation is quite naive, hence unsafe.

When something needs to be disabled, use the appropriate flag. Not every
technique can be toggled, but if there is any one in particular that you need to
and can't, open an issue about it.

Note: there is a problem in Windows when using the
`--convert-escaped-characters` flag to enable the conversion of escaped
characters. A workaround is changing the code page, which can be done by running
`chcp 65001` in the terminal (whether cmd, or cygwin).

## Library
The preferable way to use Hasmin as a library is to `import Hasmin`; a usage
example can be seen in the [module's documentation](https://hackage.haskell.org/package/hasmin/docs/Hasmin.html).
That is currently the only module that is sure to abide by
[PVP](https://pvp.haskell.org/). Most other exposed modules are so because tests
need it, and thus definitions there may be changed anytime. In case something
internal is needed though, feel free to open an issue about it.

## Zopfli Integration
Hasmin uses bindings to Google's
[Zopfli library](https://en.wikipedia.org/wiki/Zopfli), allowing the
possibility to compress the result.

Since the output is a gzip file, it can be used for the web. It tipically
produces files 3~8% smaller than zlib, at the cost of being around 80 times
slower, so it is only a good idea if you don't need compression on the fly.


Zopfli is [released under the Apache License, Version 2.0](https://github.com/google/zopfli/blob/master/COPYING).