# coding: utf-8

"""
This filter based on Jesús Jerez <jerezmoreno@gmail.com> code [1].

[1] https://bitbucket.org/jhuss/webassets-libsass
"""

from webassets.filter import Filter


__all__ = ('LibSass',)


class LibSass(Filter):
    """Converts `Sass <http://sass-lang.com/>`_ markup to real CSS.

    Requires the ``libsass`` package (https://pypi.python.org/pypi/libsass)::

        pip install libsass

    `libsass <http://dahlia.kr/libsass-python>`_ is binding to C/C++
    implementation of a Sass compiler `Libsass
    <https://github.com/hcatlin/libsass>`_

    *Configuration options:*

    LIBSASS_STYLE (style)
        an optional coding style of the compiled result. choose one of:
        `nested` (default), `expanded`, `compact`, `compressed`

    LIBSASS_INCLUDES (includes)
        an optional list of paths to find @imported SASS/CSS source files

    LIBSASS_AS_OUTPUT
        use this filter as an "output filter", meaning the source files
        will first be concatenated, and then the Sass filter is applied.

    See libsass documentation for full documentation about these configuration
    options:

        http://hongminhee.org/libsass-python/sass.html#sass.compile

    *Example:*

    Define a bundle for ``style.scss`` that contains ``@imports`` to files in
    subfolders:

    .. code-block:: python

        Bundle('style.scss', filters='libsass', output='style.css', depends='**/*.scss')
    
    """
    name = 'libsass'
    options = {
        'style': 'LIBSASS_STYLE',
        'includes': 'LIBSASS_INCLUDES',
        'as_output': 'LIBSASS_AS_OUTPUT',
    }
    max_debug_level = None

    def _apply_sass(self, _in, out):
        args = dict(
            output_style=self.style,
            include_paths=(self.includes if self.includes else [])
        )

        if self.as_output:
            args['string'] = _in.read()
        else:
            args['filename'] = _in

        out.write(
            # http://hongminhee.org/libsass-python/sass.html#sass.compile
            self.sass.compile(**args)
        )

    def setup(self):
        super(LibSass, self).setup()

        try:
            import sass
        except ImportError:
            raise EnvironmentError('The "libsass" package is not installed.')
        else:
            self.sass = sass

        if not self.style:
            self.style = 'nested'

    def input(self, _in, out, source_path, **kwargs):
        if self.as_output:
            out.write(_in.read())
        else:
            self._apply_sass(source_path, out)

    def output(self, _in, out, **kwargs):
        if not self.as_output:
            out.write(_in.read())
        else:
            self._apply_sass(_in, out)
