from django.template import Node, TemplateSyntaxError
from django.template.library import parse_bits, Library
from django.shortcuts import render_to_string

register = Library()


class Button(Node):
    """
    Usage::

        {% button type="button" class="btn-primary" name="submit" icon="cog" %}
            Press me
        {% endbutton %}

    All arguments are optional.

    ``type``:
    - What kind of button to render. Possible values are "a", "button", and
      "submit", for `<a>`, `<button>`, and `<input type="submit">`
      respectively. Defaults to "a"

    ``class``:
    - Any CSS class names for the button. See the wagtailstyleguide for all the
      possible classes. Defaults to the standard button class.

    ``name``:
    - The name attribute for the button. Only applicable for "button" and
      "submit" button types. Defaults to no name.

    ``icon``:
    - Used to add an icon to the button. See the wagtailstyleguide for all
      the possible icons. Defaults to no icon
    """

    TAG_NAME = 'button'

    types = {
        'a': 'wagtailadmin/components/buttons/a.html',
        'button': 'wagtailadmin/components/buttons/button.html',
        'submit': 'wagtailadmin/components/buttons/submit.html',
    }

    def __init__(self, inner, type_var, class_var, icon_var, name_var):
        self.type_var = type_var
        self.class_var = class_var
        self.icon_var = icon_var
        self.name_var = name_var
        self.inner_nodelist = inner

    def render(self, context):

        classes = []
        if self.class_var:
            classes.append(self.class_var.resolve(context))
        if self.icon_var:
            classes.append('icon-' + self.icon_var.resolve(context))

        if self.type_var:
            button_type = self.type_var.resolve(context)
            if button_type not in self.types:
                raise TemplateSyntaxError("'%s' unknown button type %s" % (
                    self.TAG_NAME, button_type))
        else:
            button_type = 'a'

        template = self.types[button_type]
        return render_to_string(template, {
            'class': ' '.join(classes),
            'name': self.name_var.resolve(context) if self.name_var else '',
            'type': button_type,
        })

    @classmethod
    def handle(cls, parser, token):
        name = cls.TAG_NAME

        bits = token.split_contents()[1:]
        # This is typically taken from getargspec, but we are doing funky things...

        # All the possible arguments
        params = ['type', 'class', 'icon', 'name']
        # Everything has an empty default
        defaults = [(arg, None) for arg in params]
        # No *args or **kwargs
        varargs, varkw = None

        args, kwargs = parse_bits(
            parser, bits, params, varargs, varkw, defaults,
            takes_context=False, function_name=name)

        # Get the contents till {% endbutton %}
        inner = parser.parse(['end' + name])
        parser.delete_first_token()

        return cls(inner, *args, **kwargs)
register.tag(Button.TAG_NAME, Button.handle)