"""
Form classes
"""

import copy

from django.utils.datastructures import SortedDict
from django.utils.html import escape
from django.utils.encoding import StrAndUnicode, smart_unicode, force_unicode

from fields import Field
from widgets import TextInput, Textarea
from util import flatatt, ErrorDict, ErrorList, ValidationError

__all__ = ('BaseForm', 'Form')

NON_FIELD_ERRORS = '__all__'

def pretty_name(name):
    "Converts 'first_name' to 'First name'"
    name = name[0].upper() + name[1:]
    return name.replace('_', ' ')

class SortedDictFromList(SortedDict):
    "A dictionary that keeps its keys in the order in which they're inserted."
    # This is different than django.utils.datastructures.SortedDict, because
    # this takes a list/tuple as the argument to __init__().
    def __init__(self, data=None):
        if data is None: data = []
        self.keyOrder = [d[0] for d in data]
        dict.__init__(self, dict(data))

    def copy(self):
        return SortedDictFromList([(k, copy.copy(v)) for k, v in self.items()])

class DeclarativeFieldsMetaclass(type):
    """
    Metaclass that converts Field attributes to a dictionary called
    'base_fields', taking into account parent class 'base_fields' as well.
    """
    def __new__(cls, name, bases, attrs):
        fields = [(field_name, attrs.pop(field_name)) for field_name, obj in attrs.items() if isinstance(obj, Field)]
        fields.sort(lambda x, y: cmp(x[1].creation_counter, y[1].creation_counter))

        # If this class is subclassing another Form, add that Form's fields.
        # Note that we loop over the bases in *reverse*. This is necessary in
        # order to preserve the correct order of fields.
        for base in bases[::-1]:
            if hasattr(base, 'base_fields'):
                fields = base.base_fields.items() + fields

        attrs['base_fields'] = SortedDictFromList(fields)
        return type.__new__(cls, name, bases, attrs)

class BaseForm(StrAndUnicode):
    # This is the main implementation of all the Form logic. Note that this
    # class is different than Form. See the comments by the Form class for more
    # information. Any improvements to the form API should be made to *this*
    # class, not to the Form class.
    def __init__(self, data=None, auto_id='id_%s', prefix=None, initial=None):
        self.is_bound = data is not None
        self.data = data or {}
        self.auto_id = auto_id
        self.prefix = prefix
        self.initial = initial or {}
        self._errors = None # Stores the errors after clean() has been called.

        # The base_fields class attribute is the *class-wide* definition of
        # fields. Because a particular *instance* of the class might want to
        # alter self.fields, we create self.fields here by copying base_fields.
        # Instances should always modify self.fields; they should not modify
        # self.base_fields.
        self.fields = self.base_fields.copy()

    def __unicode__(self):
        return self.as_table()

    def __iter__(self):
        for name, field in self.fields.items():
            yield BoundField(self, field, name)

    def __getitem__(self, name):
        "Returns a BoundField with the given name."
        try:
            field = self.fields[name]
        except KeyError:
            raise KeyError('Key %r not found in Form' % name)
        return BoundField(self, field, name)

    def _get_errors(self):
        "Returns an ErrorDict for self.data"
        if self._errors is None:
            self.full_clean()
        return self._errors
    errors = property(_get_errors)

    def is_valid(self):
        """
        Returns True if the form has no errors. Otherwise, False. If errors are
        being ignored, returns False.
        """
        return self.is_bound and not bool(self.errors)

    def add_prefix(self, field_name):
        """
        Returns the field name with a prefix appended, if this Form has a
        prefix set.

        Subclasses may wish to override.
        """
        return self.prefix and ('%s-%s' % (self.prefix, field_name)) or field_name

    def _html_output(self, normal_row, error_row, row_ender, help_text_html, errors_on_separate_row):
        "Helper function for outputting HTML. Used by as_table(), as_ul(), as_p()."
        top_errors = self.non_field_errors() # Errors that should be displayed above all fields.
        output, hidden_fields = [], []
        for name, field in self.fields.items():
            bf = BoundField(self, field, name)
            bf_errors = ErrorList([escape(error) for error in bf.errors]) # Escape and cache in local variable.
            if bf.is_hidden:
                if bf_errors:
                    top_errors.extend(['(Hidden field %s) %s' % (name, force_unicode(e)) for e in bf_errors])
                hidden_fields.append(unicode(bf))
            else:
                if errors_on_separate_row and bf_errors:
                    output.append(error_row % force_unicode(bf_errors))
                if bf.label:
                    label = escape(force_unicode(bf.label))
                    # Only add a colon if the label does not end in punctuation.
                    if label[-1] not in ':?.!':
                        label += ':'
                    label = bf.label_tag(label) or ''
                else:
                    label = ''
                if field.help_text:
                    help_text = help_text_html % force_unicode(field.help_text)
                else:
                    help_text = u''
                output.append(normal_row % {'errors': force_unicode(bf_errors), 'label': force_unicode(label), 'field': unicode(bf), 'help_text': help_text})
        if top_errors:
            output.insert(0, error_row % top_errors)
        if hidden_fields: # Insert any hidden fields in the last row.
            str_hidden = u''.join(hidden_fields)
            if output:
                last_row = output[-1]
                # Chop off the trailing row_ender (e.g. '</td></tr>') and insert the hidden fields.
                output[-1] = last_row[:-len(row_ender)] + str_hidden + row_ender
            else: # If there aren't any rows in the output, just append the hidden fields.
                output.append(str_hidden)
        return u'\n'.join(output)

    def as_table(self):
        "Returns this form rendered as HTML <tr>s -- excluding the <table></table>."
        return self._html_output(u'<tr><th>%(label)s</th><td>%(errors)s%(field)s%(help_text)s</td></tr>', u'<tr><td colspan="2">%s</td></tr>', '</td></tr>', u'<br />%s', False)

    def as_ul(self):
        "Returns this form rendered as HTML <li>s -- excluding the <ul></ul>."
        return self._html_output(u'<li>%(errors)s%(label)s %(field)s%(help_text)s</li>', u'<li>%s</li>', '</li>', u' %s', False)

    def as_p(self):
        "Returns this form rendered as HTML <p>s."
        return self._html_output(u'<p>%(label)s %(field)s%(help_text)s</p>', u'%s', '</p>', u' %s', True)

    def non_field_errors(self):
        """
        Returns an ErrorList of errors that aren't associated with a particular
        field -- i.e., from Form.clean(). Returns an empty ErrorList if there
        are none.
        """
        return self.errors.get(NON_FIELD_ERRORS, ErrorList())

    def full_clean(self):
        """
        Cleans all of self.data and populates self._errors and
        self.cleaned_data.
        """
        self._errors = ErrorDict()
        if not self.is_bound: # Stop further processing.
            return
        self.cleaned_data = {}
        for name, field in self.fields.items():
            # value_from_datadict() gets the data from the dictionary.
            # Each widget type knows how to retrieve its own data, because some
            # widgets split data over several HTML fields.
            value = field.widget.value_from_datadict(self.data, self.add_prefix(name))
            try:
                value = field.clean(value)
                self.cleaned_data[name] = value
                if hasattr(self, 'clean_%s' % name):
                    value = getattr(self, 'clean_%s' % name)()
                    self.cleaned_data[name] = value
            except ValidationError, e:
                self._errors[name] = e.messages
                if name in self.cleaned_data:
                    del self.cleaned_data[name]
        try:
            self.cleaned_data = self.clean()
        except ValidationError, e:
            self._errors[NON_FIELD_ERRORS] = e.messages
        if self._errors:
            delattr(self, 'cleaned_data')

    def clean(self):
        """
        Hook for doing any extra form-wide cleaning after Field.clean() been
        called on every field. Any ValidationError raised by this method will
        not be associated with a particular field; it will have a special-case
        association with the field named '__all__'.
        """
        return self.cleaned_data

class Form(BaseForm):
    "A collection of Fields, plus their associated data."
    # This is a separate class from BaseForm in order to abstract the way
    # self.fields is specified. This class (Form) is the one that does the
    # fancy metaclass stuff purely for the semantic sugar -- it allows one
    # to define a form using declarative syntax.
    # BaseForm itself has no way of designating self.fields.
    __metaclass__ = DeclarativeFieldsMetaclass

class BoundField(StrAndUnicode):
    "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)
        if self.field.label is None:
            self.label = pretty_name(name)
        else:
            self.label = self.field.label
        self.help_text = field.help_text or ''

    def __unicode__(self):
        "Renders this field as an HTML widget."
        # Use the 'widget' attribute on the field to determine which type
        # of HTML widget to use.
        value = self.as_widget(self.field.widget)
        if not isinstance(value, basestring):
            # Some Widget render() methods -- notably RadioSelect -- return a
            # "special" object rather than a string. Call __unicode__() on that
            # object to get its rendered value.
            value = unicode(value)
        return value

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

    def as_widget(self, widget, attrs=None):
        attrs = attrs or {}
        auto_id = self.auto_id
        if auto_id and 'id' not in attrs and 'id' not in widget.attrs:
            attrs['id'] = auto_id
        if not self.form.is_bound:
            data = self.form.initial.get(self.name, self.field.initial)
            if callable(data):
                data = data()
        else:
            data = self.data
        return widget.render(self.html_name, data, attrs=attrs)

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

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

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

    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.html_name)
    data = property(_data)

    def label_tag(self, contents=None, attrs=None):
        """
        Wraps the given contents in a <label>, if the field has an ID attribute.
        Does not HTML-escape the contents. 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.
        """
        contents = contents or escape(self.label)
        widget = self.field.widget
        id_ = widget.attrs.get('id') or self.auto_id
        if id_:
            attrs = attrs and flatatt(attrs) or ''
            contents = '<label for="%s"%s>%s</label>' % (widget.id_for_label(id_), attrs, contents)
        return contents

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

    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_unicode(auto_id):
            return smart_unicode(auto_id) % self.html_name
        elif auto_id:
            return self.html_name
        return ''
    auto_id = property(_auto_id)