# Faml
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Faster implementation of Haml template language.

## Installation

Add this line to your application's Gemfile:

```ruby
gem 'faml'
```

And then execute:

    $ bundle

Or install it yourself as:

    $ gem install faml

## Usage

Just replace your `gem 'haml'` with `gem 'faml'` .

## Incompatibilities
There are several incompatibilities.

### Hash attributes
Hash attributes are only supported to "data" attributes.

With original haml, `%span{foo: {bar: 'baz'}}` is rendered as `<span foo-bar='baz'></span>` .
With faml, it's rendered as `<span foo='{:bar=&gt;&quot;baz&quot;}'></span>` .

Only "data" attributes are converted to hyphenated attributes.

### HTML-escape by default
Even with non-Rails project, all string are HTML-escaped.

### "ugly" mode only
Only "ugly" mode in original haml is supported.

```haml
%div
  %div hello
```

is always rendered as

```html
<div>
<div>hello</div>
</div>
```

It's equivalent to haml's "ugly" mode.

### No Haml::Helpers except for preserve
I won't provide helper methods of Haml::Helpers except for `preserve` .
If you really need other helper methods, please open an issue.

### Others
If you find other incompatibility, please report it to me :-p.

## Why faml is faster?
### Temple backend
I use [temple](https://github.com/judofyr/temple) to achieve faster template rendering.
It's used by [slim](https://github.com/slim-template/slim) template language & engine which is known as fast.

1. Faml::Parser converts source language (Haml template) to own AST (Faml::Ast) .
    - You can see the Faml::Ast by running `faml parse template.haml` .
2. Faml::Compiler compiles Faml::Ast into Temple AST.
    - You can see the Temple AST by running `faml temple template.haml` .
3. Temple compiles its AST into Ruby code.
    - You can see the Ruby code by running `faml compile template.haml` .
    - During this process, several optimizations are performed such as Temple::Filters::MultiFlattener and Temple::Filters::StaticMerger.

### Attribute optimization
Although Haml allows arbitrary Ruby hash in the attribute syntax, most attributes are written in hash literal form.
All keys are string or symbol literals (i.e., not dynamic values) in typical case.

```haml
%div{class: some_helper_method(current_user)}
  %a{href: foo_path(@item)}= @item.name
```

There is an optimization chance if we could know the value is String.
I introduced incompatibility to expand the chance: all attribute values are converted to String by `#to_s` except for `id`, `class` and `data` .
This will enable us to avoid runtime expensive hash merging and rendering.
The runtime hash merging is implemented by C extension in faml.

Internally, attributes are categolized into three types.

1. Static attributes
    - Both the key and the value are literal.
    - Compiled into string literals.
    - Fastest.
    - e.g. `%input{checked: false}`
2. Dynamic attributes
    - The key is literal but the value isn't.
    - The key is compiled into string literal. The value is interpolated at run-time.
    - Relatively fast.
    - e.g. `%input{checked: helper_method(@record)}`
3. Ruby attributes
    - Both the key and the value are non-literal expression.
    - The attributes are stringified at run-time.
    - Slow.
    - e.g. `%input{helper_method(@record)}`

## Contributing

1. Fork it ( https://github.com/eagletmt/faml/fork )
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Add some feature'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create a new Pull Request