"""
HTML Widget classes
"""

__all__ = (
    'Widget', 'TextInput', 'PasswordInput', 'HiddenInput', 'FileInput',
    'Textarea', 'CheckboxInput',
    'Select', 'SelectMultiple', 'RadioSelect',
)

from django.utils.html import escape
from itertools import chain

try:
    set # Only available in Python 2.4+
except NameError:
    from sets import Set as set # Python 2.3 fallback

# Converts a dictionary to a single string with key="value", XML-style with
# a leading space. Assumes keys do not need to be XML-escaped.
flatatt = lambda attrs: ''.join([' %s="%s"' % (k, escape(v)) for k, v in attrs.items()])

class Widget(object):
    requires_data_list = False # Determines whether render()'s 'value' argument should be a list.
    def __init__(self, attrs=None):
        self.attrs = attrs or {}

    def render(self, name, value):
        raise NotImplementedError

    def build_attrs(self, extra_attrs=None, **kwargs):
        attrs = dict(self.attrs, **kwargs)
        if extra_attrs:
            attrs.update(extra_attrs)
        return attrs

class Input(Widget):
    """
    Base class for all <input> widgets (except type='checkbox' and
    type='radio', which are special).
    """
    input_type = None # Subclasses must define this.
    def render(self, name, value, attrs=None):
        if value is None: value = ''
        final_attrs = self.build_attrs(attrs, type=self.input_type, name=name)
        if value != '': final_attrs['value'] = value # Only add the 'value' attribute if a value is non-empty.
        return u'<input%s />' % flatatt(final_attrs)

class TextInput(Input):
    input_type = 'text'

class PasswordInput(Input):
    input_type = 'password'

class HiddenInput(Input):
    input_type = 'hidden'

class FileInput(Input):
    input_type = 'file'

class Textarea(Widget):
    def render(self, name, value, attrs=None):
        if value is None: value = ''
        final_attrs = self.build_attrs(attrs, name=name)
        return u'<textarea%s>%s</textarea>' % (flatatt(final_attrs), escape(value))

class CheckboxInput(Widget):
    def render(self, name, value, attrs=None):
        final_attrs = self.build_attrs(attrs, type='checkbox', name=name)
        if value: final_attrs['checked'] = 'checked'
        return u'<input%s />' % flatatt(final_attrs)

class Select(Widget):
    def __init__(self, attrs=None, choices=()):
        # choices can be any iterable
        self.attrs = attrs or {}
        self.choices = choices

    def render(self, name, value, attrs=None, choices=()):
        if value is None: value = ''
        final_attrs = self.build_attrs(attrs, name=name)
        output = [u'<select%s>' % flatatt(final_attrs)]
        str_value = str(value) # Normalize to string.
        for option_value, option_label in chain(self.choices, choices):
            selected_html = (str(option_value) == str_value) and ' selected="selected"' or ''
            output.append(u'<option value="%s"%s>%s</option>' % (escape(option_value), selected_html, escape(option_label)))
        output.append(u'</select>')
        return u'\n'.join(output)

class SelectMultiple(Widget):
    requires_data_list = True
    def __init__(self, attrs=None, choices=()):
        # choices can be any iterable
        self.attrs = attrs or {}
        self.choices = choices

    def render(self, name, value, attrs=None, choices=()):
        if value is None: value = []
        final_attrs = self.build_attrs(attrs, name=name)
        output = [u'<select multiple="multiple"%s>' % flatatt(final_attrs)]
        str_values = set([str(v) for v in value]) # Normalize to strings.
        for option_value, option_label in chain(self.choices, choices):
            selected_html = (str(option_value) in str_values) and ' selected="selected"' or ''
            output.append(u'<option value="%s"%s>%s</option>' % (escape(option_value), selected_html, escape(option_label)))
        output.append(u'</select>')
        return u'\n'.join(output)

class RadioInput(object):
    "An object used by RadioFieldRenderer that represents a single <input type='radio'>."
    def __init__(self, name, value, attrs, choice):
        self.name, self.value = name, value
        self.attrs = attrs or {}
        self.choice_value, self.choice_label = choice

    def __str__(self):
        return u'<label>%s %s</label>' % (self.tag(), self.choice_label)

    def is_checked(self):
        return self.value == str(self.choice_value)

    def tag(self):
        final_attrs = dict(self.attrs, type='radio', name=self.name, value=self.choice_value)
        if self.is_checked():
            final_attrs['checked'] = 'checked'
        return u'<input%s />' % flatatt(final_attrs)

class RadioFieldRenderer(object):
    "An object used by RadioSelect to enable customization of radio widgets."
    def __init__(self, name, value, attrs, choices):
        self.name, self.value, self.attrs = name, value, attrs
        self.choices = choices

    def __iter__(self):
        for choice in self.choices:
            yield RadioInput(self.name, self.value, self.attrs, choice)

    def __str__(self):
        "Outputs a <ul> for this set of radio fields."
        return u'<ul>\n%s\n</ul>' % u'\n'.join([u'<li>%s</li>' % w for w in self])

class RadioSelect(Select):
    def render(self, name, value, attrs=None, choices=()):
        "Returns a RadioFieldRenderer instance rather than a Unicode string."
        if value is None: value = ''
        str_value = str(value) # Normalize to string.
        return RadioFieldRenderer(name, str_value, attrs, list(chain(self.choices, choices)))

class CheckboxSelectMultiple(Widget):
    pass