import csv
import itertools
import re

from django import forms
from django.conf import settings
from django.core.urlresolvers import reverse_lazy
from django.core.validators import URLValidator
from django.utils.encoding import force_text
from django.utils.html import format_html
from django.utils.safestring import mark_safe


COLOR_CHOICES = (
    ('aa1409', 'Dark red'),
    ('f44336', 'Red'),
    ('e91e63', 'Pink'),
    ('ff66ff', 'Fuschia'),
    ('9c27b0', 'Purple'),
    ('673ab7', 'Dark purple'),
    ('3f51b5', 'Indigo'),
    ('2196f3', 'Blue'),
    ('03a9f4', 'Light blue'),
    ('00bcd4', 'Cyan'),
    ('009688', 'Teal'),
    ('2f6a31', 'Dark green'),
    ('4caf50', 'Green'),
    ('8bc34a', 'Light green'),
    ('cddc39', 'Lime'),
    ('ffeb3b', 'Yellow'),
    ('ffc107', 'Amber'),
    ('ff9800', 'Orange'),
    ('ff5722', 'Dark orange'),
    ('795548', 'Brown'),
    ('c0c0c0', 'Light grey'),
    ('9e9e9e', 'Grey'),
    ('607d8b', 'Dark grey'),
    ('111111', 'Black'),
)
NUMERIC_EXPANSION_PATTERN = '\[((?:\d+[?:,-])+\d+)\]'
IP4_EXPANSION_PATTERN = '\[((?:[0-9]{1,3}[?:,-])+[0-9]{1,3})\]'
IP6_EXPANSION_PATTERN = '\[((?:[0-9a-f]{1,4}[?:,-])+[0-9a-f]{1,4})\]'


def parse_numeric_range(string, base=10):
    """
    Expand a numeric range (continuous or not) into a decimal or
    hexadecimal list, as specified by the base parameter
      '0-3,5' => [0, 1, 2, 3, 5]
      '2,8-b,d,f' => [2, 8, 9, a, b, d, f]
    """
    values = list()
    for dash_range in string.split(','):
        try:
            begin, end = dash_range.split('-')
        except ValueError:
            begin, end = dash_range, dash_range
        begin, end = int(begin.strip()), int(end.strip(), base=base) + 1
        values.extend(range(begin, end))
    return list(set(values))


def expand_numeric_pattern(string):
    """
    Expand a numeric pattern into a list of strings. Examples:
      'ge-0/0/[0-3,5]' => ['ge-0/0/0', 'ge-0/0/1', 'ge-0/0/2', 'ge-0/0/3', 'ge-0/0/5']
      'xe-0/[0,2-3]/[0-7]' => ['xe-0/0/0', 'xe-0/0/1', 'xe-0/0/2', ... 'xe-0/3/5', 'xe-0/3/6', 'xe-0/3/7']
    """
    lead, pattern, remnant = re.split(NUMERIC_EXPANSION_PATTERN, string, maxsplit=1)
    parsed_range = parse_numeric_range(pattern)
    for i in parsed_range:
        if re.search(NUMERIC_EXPANSION_PATTERN, remnant):
            for string in expand_numeric_pattern(remnant):
                yield "{}{}{}".format(lead, i, string)
        else:
            yield "{}{}{}".format(lead, i, remnant)


def expand_ipaddress_pattern(string, family):
    """
    Expand an IP address pattern into a list of strings. Examples:
      '192.0.2.[1,2,100-250,254]/24' => ['192.0.2.1/24', '192.0.2.2/24', '192.0.2.100/24' ... '192.0.2.250/24', '192.0.2.254/24']
      '2001:db8:0:[0,fd-ff]::/64' => ['2001:db8:0:0::/64', '2001:db8:0:fd::/64', ... '2001:db8:0:ff::/64']
    """
    if family not in [4, 6]:
        raise Exception("Invalid IP address family: {}".format(family))
    if family == 4:
        regex = IP4_EXPANSION_PATTERN
        base = 10
    else:
        regex = IP6_EXPANSION_PATTERN
        base = 16
    lead, pattern, remnant = re.split(regex, string, maxsplit=1)
    parsed_range = parse_numeric_range(pattern, base)
    for i in parsed_range:
        if re.search(regex, remnant):
            for string in expand_ipaddress_pattern(remnant, family):
                yield ''.join([lead, format(i, 'x' if family == 6 else 'd'), string])
        else:
            yield ''.join([lead, format(i, 'x' if family == 6 else 'd'), remnant])


def add_blank_choice(choices):
    """
    Add a blank choice to the beginning of a choices list.
    """
    return ((None, '---------'),) + tuple(choices)


#
# Widgets
#

class SmallTextarea(forms.Textarea):
    pass


class ColorSelect(forms.Select):

    def __init__(self, *args, **kwargs):
        kwargs['choices'] = COLOR_CHOICES
        super(ColorSelect, self).__init__(*args, **kwargs)

    def render_option(self, selected_choices, option_value, option_label):
        if option_value is None:
            option_value = ''
        option_value = force_text(option_value)
        if option_value in selected_choices:
            selected_html = mark_safe(' selected')
            if not self.allow_multiple_selected:
                # Only allow for a single selection.
                selected_choices.remove(option_value)
        else:
            selected_html = ''
        return format_html('<option value="{}"{} style="background-color: #{}">{}</option>',
                           option_value, selected_html, option_value, force_text(option_label))


class SelectWithDisabled(forms.Select):
    """
    Modified the stock Select widget to accept choices using a dict() for a label. The dict for each option must include
    'label' (string) and 'disabled' (boolean).
    """

    def render_option(self, selected_choices, option_value, option_label):

        # Determine if option has been selected
        option_value = force_text(option_value)
        if option_value in selected_choices:
            selected_html = mark_safe(' selected="selected"')
            if not self.allow_multiple_selected:
                # Only allow for a single selection.
                selected_choices.remove(option_value)
        else:
            selected_html = ''

        # Determine if option has been disabled
        option_disabled = False
        exempt_value = force_text(self.attrs.get('exempt', None))
        if isinstance(option_label, dict):
            option_disabled = option_label['disabled'] if option_value != exempt_value else False
            option_label = option_label['label']
        disabled_html = ' disabled="disabled"' if option_disabled else ''

        return format_html(u'<option value="{}"{}{}>{}</option>',
                           option_value,
                           selected_html,
                           disabled_html,
                           force_text(option_label))


class APISelect(SelectWithDisabled):
    """
    A select widget populated via an API call

    :param api_url: API URL
    :param display_field: (Optional) Field to display for child in selection list. Defaults to `name`.
    :param disabled_indicator: (Optional) Mark option as disabled if this field equates true.
    """

    def __init__(self, api_url, display_field=None, disabled_indicator=None, *args, **kwargs):

        super(APISelect, self).__init__(*args, **kwargs)

        self.attrs['class'] = 'api-select'
        self.attrs['api-url'] = '/{}{}'.format(settings.BASE_PATH, api_url.lstrip('/'))  # Inject BASE_PATH
        if display_field:
            self.attrs['display-field'] = display_field
        if disabled_indicator:
            self.attrs['disabled-indicator'] = disabled_indicator


class Livesearch(forms.TextInput):
    """
    A text widget that carries a few extra bits of data for use in AJAX-powered autocomplete search

    :param query_key: The name of the parameter to query against
    :param query_url: The name of the API URL to query
    :param field_to_update: The name of the "real" form field whose value is being set
    :param obj_label: The field to use as the option label (optional)
    """

    def __init__(self, query_key, query_url, field_to_update, obj_label=None, *args, **kwargs):

        super(Livesearch, self).__init__(*args, **kwargs)

        self.attrs = {
            'data-key': query_key,
            'data-source': reverse_lazy(query_url),
            'data-field': field_to_update,
        }

        if obj_label:
            self.attrs['data-label'] = obj_label


#
# Form fields
#

class CSVDataField(forms.CharField):
    """
    A field for comma-separated values (CSV). Values containing commas should be encased within double quotes. Example:
        '"New York, NY",new-york-ny,Other stuff' => ['New York, NY', 'new-york-ny', 'Other stuff']
    """
    csv_form = None
    widget = forms.Textarea

    def __init__(self, csv_form, *args, **kwargs):
        self.csv_form = csv_form
        self.columns = self.csv_form().fields.keys()
        super(CSVDataField, self).__init__(*args, **kwargs)
        self.strip = False
        if not self.label:
            self.label = 'CSV Data'
        if not self.help_text:
            self.help_text = 'Enter one line per record in CSV format.'

    def to_python(self, value):
        """
        Return a list of dictionaries, each representing an individual record
        """
        # Python 2's csv module has problems with Unicode
        if not isinstance(value, str):
            value = value.encode('utf-8')
        records = []
        reader = csv.reader(value.splitlines())
        for i, row in enumerate(reader, start=1):
            if row:
                if len(row) < len(self.columns):
                    raise forms.ValidationError("Line {}: Field(s) missing (found {}; expected {})"
                                                .format(i, len(row), len(self.columns)))
                elif len(row) > len(self.columns):
                    raise forms.ValidationError("Line {}: Too many fields (found {}; expected {})"
                                                .format(i, len(row), len(self.columns)))
                row = [col.strip() for col in row]
                record = dict(zip(self.columns, row))
                records.append(record)
        return records


class ExpandableNameField(forms.CharField):
    """
    A field which allows for numeric range expansion
      Example: 'Gi0/[1-3]' => ['Gi0/1', 'Gi0/2', 'Gi0/3']
    """
    def __init__(self, *args, **kwargs):
        super(ExpandableNameField, self).__init__(*args, **kwargs)
        if not self.help_text:
            self.help_text = 'Numeric ranges are supported for bulk creation.<br />'\
                             'Example: <code>ge-0/0/[0-23,25,30]</code>'

    def to_python(self, value):
        if re.search(NUMERIC_EXPANSION_PATTERN, value):
            return list(expand_numeric_pattern(value))
        return [value]


class ExpandableIPAddressField(forms.CharField):
    """
    A field which allows for expansion of IP address ranges
      Example: '192.0.2.[1-254]/24' => ['192.0.2.1/24', '192.0.2.2/24', '192.0.2.3/24' ... '192.0.2.254/24']
    """
    def __init__(self, *args, **kwargs):
        super(ExpandableIPAddressField, self).__init__(*args, **kwargs)
        if not self.help_text:
            self.help_text = 'Specify a numeric range to create multiple IPs.<br />'\
                             'Example: <code>192.0.2.[1,5,100-254]/24</code>'

    def to_python(self, value):
        # Hackish address family detection but it's all we have to work with
        if '.' in value and re.search(IP4_EXPANSION_PATTERN, value):
            return list(expand_ipaddress_pattern(value, 4))
        elif ':' in value and re.search(IP6_EXPANSION_PATTERN, value):
            return list(expand_ipaddress_pattern(value, 6))
        return [value]


class CommentField(forms.CharField):
    """
    A textarea with support for GitHub-Flavored Markdown. Exists mostly just to add a standard help_text.
    """
    widget = forms.Textarea
    default_label = 'Comments'
    # TODO: Port GFM syntax cheat sheet to internal documentation
    default_helptext = '<i class="fa fa-info-circle"></i> '\
                       '<a href="https://github.com/adam-p/markdown-here/wiki/Markdown-Cheatsheet" target="_blank">'\
                       'GitHub-Flavored Markdown</a> syntax is supported'

    def __init__(self, *args, **kwargs):
        required = kwargs.pop('required', False)
        label = kwargs.pop('label', self.default_label)
        help_text = kwargs.pop('help_text', self.default_helptext)
        super(CommentField, self).__init__(required=required, label=label, help_text=help_text, *args, **kwargs)


class FlexibleModelChoiceField(forms.ModelChoiceField):
    """
    Allow a model to be reference by either '{ID}' or the field specified by `to_field_name`.
    """
    def to_python(self, value):
        if value in self.empty_values:
            return None
        try:
            if not self.to_field_name:
                key = 'pk'
            elif re.match('^\{\d+\}$', value):
                key = 'pk'
                value = value.strip('{}')
            else:
                key = self.to_field_name
            value = self.queryset.get(**{key: value})
        except (ValueError, TypeError, self.queryset.model.DoesNotExist):
            raise forms.ValidationError(self.error_messages['invalid_choice'], code='invalid_choice')
        return value


class SlugField(forms.SlugField):

    def __init__(self, slug_source='name', *args, **kwargs):
        label = kwargs.pop('label', "Slug")
        help_text = kwargs.pop('help_text', "URL-friendly unique shorthand")
        super(SlugField, self).__init__(label=label, help_text=help_text, *args, **kwargs)
        self.widget.attrs['slug-source'] = slug_source


class FilterChoiceField(forms.ModelMultipleChoiceField):
    iterator = forms.models.ModelChoiceIterator

    def __init__(self, null_option=None, *args, **kwargs):
        self.null_option = null_option
        if 'required' not in kwargs:
            kwargs['required'] = False
        if 'widget' not in kwargs:
            kwargs['widget'] = forms.SelectMultiple(attrs={'size': 6})
        super(FilterChoiceField, self).__init__(*args, **kwargs)

    def label_from_instance(self, obj):
        if hasattr(obj, 'filter_count'):
            return u'{} ({})'.format(obj, obj.filter_count)
        return force_text(obj)

    def _get_choices(self):
        if hasattr(self, '_choices'):
            return self._choices
        if self.null_option is not None:
            return itertools.chain([self.null_option], self.iterator(self))
        return self.iterator(self)

    choices = property(_get_choices, forms.ChoiceField._set_choices)


class LaxURLField(forms.URLField):
    """
    Custom URLField which allows any valid URL scheme
    """

    class AnyURLScheme(object):
        # A fake URL list which "contains" all scheme names abiding by the syntax defined in RFC 3986 section 3.1
        def __contains__(self, item):
            if not item or not re.match('^[a-z][0-9a-z+\-.]*$', item.lower()):
                return False
            return True

    default_validators = [URLValidator(schemes=AnyURLScheme())]


#
# Forms
#

class BootstrapMixin(forms.BaseForm):

    def __init__(self, *args, **kwargs):
        super(BootstrapMixin, self).__init__(*args, **kwargs)
        for field_name, field in self.fields.items():
            if type(field.widget) not in [type(forms.CheckboxInput()), type(forms.RadioSelect())]:
                try:
                    field.widget.attrs['class'] += ' form-control'
                except KeyError:
                    field.widget.attrs['class'] = 'form-control'
            if field.required:
                field.widget.attrs['required'] = 'required'
            if 'placeholder' not in field.widget.attrs:
                field.widget.attrs['placeholder'] = field.label


class ConfirmationForm(BootstrapMixin, forms.Form):
    """
    A generic confirmation form. The form is not valid unless the confirm field is checked. An optional return_url can
    be specified to direct the user to a specific URL after the action has been taken.
    """
    confirm = forms.BooleanField(required=True)
    return_url = forms.CharField(required=False, widget=forms.HiddenInput())


class BulkEditForm(forms.Form):

    def __init__(self, model, *args, **kwargs):
        super(BulkEditForm, self).__init__(*args, **kwargs)
        self.model = model
        # Copy any nullable fields defined in Meta
        if hasattr(self.Meta, 'nullable_fields'):
            self.nullable_fields = [field for field in self.Meta.nullable_fields]
        else:
            self.nullable_fields = []


class BulkImportForm(forms.Form):

    def clean(self):
        records = self.cleaned_data.get('csv')
        if not records:
            return

        obj_list = []

        for i, record in enumerate(records, start=1):
            obj_form = self.fields['csv'].csv_form(data=record)
            if obj_form.is_valid():
                obj = obj_form.save(commit=False)
                obj_list.append(obj)
            else:
                for field, errors in obj_form.errors.items():
                    for e in errors:
                        if field == '__all__':
                            self.add_error('csv', "Record {}: {}".format(i, e))
                        else:
                            self.add_error('csv', "Record {} ({}): {}".format(i, field, e))

        self.cleaned_data['csv'] = obj_list