from __future__ import unicode_literals

import datetime

from django.forms.utils import flatatt, pretty_name
from django.forms.widgets import Textarea, TextInput
from django.utils import six
from django.utils.encoding import (
    force_text, python_2_unicode_compatible, smart_text,
)
from django.utils.functional import cached_property
from django.utils.html import conditional_escape, format_html, html_safe
from django.utils.safestring import mark_safe
from django.utils.translation import ugettext_lazy as _

__all__ = ('BoundField',)


UNSET = object()


@html_safe
@python_2_unicode_compatible
class BoundField(object):
    "A Field plus data"
    def __init__(self, form, field, name):
        self.form = form
        self.field = field
        self.name = name
        self.html_name = form.add_prefix(name)
        self.html_initial_name = form.add_initial_prefix(name)
        self.html_initial_id = form.add_initial_prefix(self.auto_id)
        if self.field.label is None:
            self.label = pretty_name(name)
        else:
            self.label = self.field.label
        self.help_text = field.help_text or ''
        self._initial_value = UNSET

    def __str__(self):
        """Renders this field as an HTML widget."""
        if self.field.show_hidden_initial:
            return self.as_widget() + self.as_hidden(only_initial=True)
        return self.as_widget()

    @cached_property
    def subwidgets(self):
        """
        Most widgets yield a single subwidget, but others like RadioSelect and
        CheckboxSelectMultiple produce one subwidget for each choice.

        This property is cached so that only one database query occurs when
        rendering ModelChoiceFields.
        """
        id_ = self.field.widget.attrs.get('id') or self.auto_id
        attrs = {'id': id_} if id_ else {}
        attrs = self.build_widget_attrs(attrs)
        return list(self.field.widget.subwidgets(self.html_name, self.value(), attrs))

    def __iter__(self):
        return iter(self.subwidgets)

    def __len__(self):
        return len(self.subwidgets)

    def __getitem__(self, idx):
        # Prevent unnecessary reevaluation when accessing BoundField's attrs
        # from templates.
        if not isinstance(idx, six.integer_types + (slice,)):
            raise TypeError
        return self.subwidgets[idx]

    @property
    def errors(self):
        """
        Returns an ErrorList for this field. Returns an empty ErrorList
        if there are none.
        """
        return self.form.errors.get(self.name, self.form.error_class())

    def as_widget(self, widget=None, attrs=None, only_initial=False):
        """
        Renders the field by rendering the passed widget, adding any HTML
        attributes passed as attrs.  If no widget is specified, then the
        field's default widget will be used.
        """
        if not widget:
            widget = self.field.widget

        if self.field.localize:
            widget.is_localized = True

        attrs = attrs or {}
        attrs = self.build_widget_attrs(attrs, widget)
        auto_id = self.auto_id
        if auto_id and 'id' not in attrs and 'id' not in widget.attrs:
            if not only_initial:
                attrs['id'] = auto_id
            else:
                attrs['id'] = self.html_initial_id

        if not only_initial:
            name = self.html_name
        else:
            name = self.html_initial_name
        return force_text(widget.render(name, self.value(), attrs=attrs))

    def as_text(self, attrs=None, **kwargs):
        """
        Returns a string of HTML for representing this as an <input type="text">.
        """
        return self.as_widget(TextInput(), attrs, **kwargs)

    def as_textarea(self, attrs=None, **kwargs):
        "Returns a string of HTML for representing this as a <textarea>."
        return self.as_widget(Textarea(), attrs, **kwargs)

    def as_hidden(self, attrs=None, **kwargs):
        """
        Returns a string of HTML for representing this as an <input type="hidden">.
        """
        return self.as_widget(self.field.hidden_widget(), attrs, **kwargs)

    @property
    def data(self):
        """
        Returns the data for this BoundField, or None if it wasn't given.
        """
        return self.field.widget.value_from_datadict(self.form.data, self.form.files, self.html_name)

    def value(self):
        """
        Returns the value for this BoundField, using the initial value if
        the form is not bound or the data otherwise.
        """
        if not self.form.is_bound:
            data = self.form.initial.get(self.name, self.field.initial)
            if callable(data):
                if self._initial_value is not UNSET:
                    data = self._initial_value
                else:
                    data = data()
                    # If this is an auto-generated default date, nix the
                    # microseconds for standardized handling. See #22502.
                    if (isinstance(data, (datetime.datetime, datetime.time)) and
                            not self.field.widget.supports_microseconds):
                        data = data.replace(microsecond=0)
                    self._initial_value = data
        else:
            data = self.field.bound_data(
                self.data, self.form.initial.get(self.name, self.field.initial)
            )
        return self.field.prepare_value(data)

    def label_tag(self, contents=None, attrs=None, label_suffix=None):
        """
        Wraps the given contents in a <label>, if the field has an ID attribute.
        contents should be 'mark_safe'd to avoid HTML escaping. If contents
        aren't given, uses the field's HTML-escaped label.

        If attrs are given, they're used as HTML attributes on the <label> tag.

        label_suffix allows overriding the form's label_suffix.
        """
        contents = contents or self.label
        if label_suffix is None:
            label_suffix = (self.field.label_suffix if self.field.label_suffix is not None
                            else self.form.label_suffix)
        # Only add the suffix if the label does not end in punctuation.
        # Translators: If found as last label character, these punctuation
        # characters will prevent the default label_suffix to be appended to the label
        if label_suffix and contents and contents[-1] not in _(':?.!'):
            contents = format_html('{}{}', contents, label_suffix)
        widget = self.field.widget
        id_ = widget.attrs.get('id') or self.auto_id
        if id_:
            id_for_label = widget.id_for_label(id_)
            if id_for_label:
                attrs = dict(attrs or {}, **{'for': id_for_label})
            if self.field.required and hasattr(self.form, 'required_css_class'):
                attrs = attrs or {}
                if 'class' in attrs:
                    attrs['class'] += ' ' + self.form.required_css_class
                else:
                    attrs['class'] = self.form.required_css_class
            attrs = flatatt(attrs) if attrs else ''
            contents = format_html('<label{}>{}</label>', attrs, contents)
        else:
            contents = conditional_escape(contents)
        return mark_safe(contents)

    def css_classes(self, extra_classes=None):
        """
        Returns a string of space-separated CSS classes for this field.
        """
        if hasattr(extra_classes, 'split'):
            extra_classes = extra_classes.split()
        extra_classes = set(extra_classes or [])
        if self.errors and hasattr(self.form, 'error_css_class'):
            extra_classes.add(self.form.error_css_class)
        if self.field.required and hasattr(self.form, 'required_css_class'):
            extra_classes.add(self.form.required_css_class)
        return ' '.join(extra_classes)

    @property
    def is_hidden(self):
        "Returns True if this BoundField's widget is hidden."
        return self.field.widget.is_hidden

    @property
    def auto_id(self):
        """
        Calculates and returns the ID attribute for this BoundField, if the
        associated Form has specified auto_id. Returns an empty string otherwise.
        """
        auto_id = self.form.auto_id
        if auto_id and '%s' in smart_text(auto_id):
            return smart_text(auto_id) % self.html_name
        elif auto_id:
            return self.html_name
        return ''

    @property
    def id_for_label(self):
        """
        Wrapper around the field widget's `id_for_label` method.
        Useful, for example, for focusing on this field regardless of whether
        it has a single widget or a MultiWidget.
        """
        widget = self.field.widget
        id_ = widget.attrs.get('id') or self.auto_id
        return widget.id_for_label(id_)

    def build_widget_attrs(self, attrs, widget=None):
        if not widget:
            widget = self.field.widget
        attrs = dict(attrs)  # Copy attrs to avoid modifying the argument.
        if not widget.is_hidden and self.field.required and self.form.use_required_attribute:
            attrs['required'] = True
        if self.field.disabled:
            attrs['disabled'] = True
        return attrs