from __future__ import unicode_literals

import hashlib

from django.apps import apps
from django.db import models
from django.template import loader
from django.template.response import TemplateResponse
from django.urls import reverse
from django.utils.encoding import force_text, python_2_unicode_compatible
from django.utils.translation import ugettext

from .settings import setting_home_view


@python_2_unicode_compatible
class Collection(object):
    _registry = []

    @classmethod
    def get_all(cls):
        return sorted(cls._registry, key=lambda entry: entry._order)

    def __init__(self, label, icon=None, icon_class=None, link=None, queryset=None, model=None, order=None):
        self._label = label
        self._icon = icon
        self._icon_class = icon_class
        self._link = link
        self._queryset = queryset
        self._model = model
        self._order = order or 99
        self.__class__._registry.append(self)

    def __str__(self):
        return force_text(self.label)

    def resolve(self):
        self.children = self._get_children()
        self.icon = self._icon
        self.label = self._label
        self.url = None
        if self._link:
            self.icon = getattr(self._link, 'icon', self._icon)
            self.icon_class = getattr(self._link, 'icon_class', self._icon_class)
            self.url = reverse(viewname=self._link.view, args=self._link.args)
        return ''

    def _get_children(self):
        if self._queryset:
            return self._queryset
        else:
            if self._model:
                return self._model.objects.all()


class Dashboard(object):
    _registry = {}

    @classmethod
    def get(cls, name):
        return cls._registry[name]

    def __init__(self, name, label):
        self.name = name
        self.label = label
        self.widgets = {}
        self.removed_widgets = []
        self.__class__._registry[name] = self

    def add_widget(self, widget, order=0):
        self.widgets[widget] = {'widget': widget, 'order': order}

    def get_widgets(self):
        """
        Returns a list of widgets sorted by their 'order'.
        If two or more widgets have the same 'order', sort by label.
        """
        return map(
            lambda x: x['widget'],
            filter(
                lambda x: x['widget'] not in self.removed_widgets,
                sorted(
                    self.widgets.values(),
                    key=lambda x: (x['order'], x['widget'].label)
                )
            )
        )

    def remove_widget(self, widget):
        self.removed_widgets.append(widget)

    def render(self, request):
        rendered_widgets = [widget().render(request=request) for widget in self.get_widgets()]

        return loader.render_to_string(
            template_name='dashboard/dashboard.html', context={
                'widgets': rendered_widgets
            }
        )


class BaseDashboardWidget(object):
    _registry = {}
    context = {}
    template_name = None

    @classmethod
    def get(cls, name):
        return cls._registry[name]

    @classmethod
    def get_all(cls):
        return cls._registry.items()

    @classmethod
    def register(cls, klass):
        cls._registry[klass.name] = klass

    def get_context(self):
        return self.context

    def render(self, request):
        if self.template_name:
            return loader.render_to_string(
                template_name=self.template_name, context=self.get_context(),
            )


class DashboardWidgetNumeric(BaseDashboardWidget):
    count = 0
    icon_class = None
    label = None
    link = None
    template_name = 'dashboard/numeric_widget.html'

    def get_context(self):
        return {
            'count': self.count,
            'icon_class': self.icon_class,
            'label': self.label,
            'link': self.link,
        }


@python_2_unicode_compatible
class ErrorLogNamespace(object):
    def __init__(self, name, label=None):
        self.name = name
        self.label = label or name

    def __str__(self):
        return force_text(self.label)

    def create(self, obj, result):
        obj.error_logs.create(namespace=self.name, result=result)

    def all(self):
        ErrorLogEntry = apps.get_model(
            app_label='common', model_name='ErrorLogEntry'
        )

        return ErrorLogEntry.objects.filter(namespace=self.name)


class MissingItem(object):
    _registry = []

    @classmethod
    def get_all(cls):
        return cls._registry

    def __init__(self, label, condition, description, view):
        self.label = label
        self.condition = condition
        self.description = description
        self.view = view
        self.__class__._registry.append(self)


@python_2_unicode_compatible
class ModelAttribute(object):
    _registry = {}

    @classmethod
    def get_for(cls, model):
        try:
            return cls._registry[model]
        except KeyError:
            # We were passed a model instance, try again using the model of
            # the instance

            # If we are already in the model class, exit with an error
            if model.__class__ == models.base.ModelBase:
                raise

            return cls.get_for(model=type(model))

    @classmethod
    def get_choices_for(cls, model):
        return [
            (attribute.name, attribute) for attribute in cls.get_for(model)
        ]

    @classmethod
    def get_help_text_for(cls, model, show_name=False):
        result = []
        for count, attribute in enumerate(cls.get_for(model=model), 1):
            result.append(
                '{}) {}'.format(
                    count, force_text(attribute.get_display(show_name=show_name))
                )
            )

        return ' '.join(
            [ugettext('Available attributes: \n'), '\n'.join(result)]
        )

    def __init__(self, model, name, label=None, description=None):
        self.model = model
        self.label = label
        self.name = name
        self.description = description
        self._registry.setdefault(model, [])
        self._registry[model].append(self)

    def __str__(self):
        return self.get_display()

    def get_display(self, show_name=False):
        if self.description:
            return '{} - {}'.format(
                self.name if show_name else self.label, self.description
            )
        else:
            return force_text(self.name if show_name else self.label)


class ModelField(ModelAttribute):
    """Subclass to handle model database fields"""
    _registry = {}

    @classmethod
    def get_help_text_for(cls, model, show_name=False):
        result = []
        for count, model_field in enumerate(cls.get_for(model=model), 1):
            result.append(
                '{}) {} - {}'.format(
                    count,
                    model_field.name if show_name else model_field.label,
                    model_field.description
                )
            )

        return ' '.join(
            [ugettext('Available fields: \n'), '\n'.join(result)]
        )

    def __init__(self, *args, **kwargs):
        super(ModelField, self).__init__(*args, **kwargs)
        self._final_model_verbose_name = None

        if not self.label:
            self.label = self.get_field_attribute(
                attribute='verbose_name'
            )
            if self.label != self._final_model_verbose_name:
                self.label = '{} {}'.format(
                    self._final_model_verbose_name, self.label
                )

        if not self.description:
            self.description = self.get_field_attribute(
                attribute='help_text'
            )

    def get_field_attribute(self, attribute, model=None, field_name=None):
        if not model:
            model = self.model

        if not field_name:
            field_name = self.name

        parts = field_name.split('__')
        if len(parts) > 1:
            return self.get_field_attribute(
                model=model._meta.get_field(parts[0]).related_model,
                field_name='__'.join(parts[1:]), attribute=attribute
            )
        else:
            self._final_model_verbose_name = model._meta.verbose_name
            return getattr(
                model._meta.get_field(field_name=field_name),
                attribute
            )


class ModelProperty(object):
    _registry = []

    @classmethod
    def get_for(cls, model):
        result = []

        for klass in cls._registry:
            result.extend(klass.get_for(model=model))

        return result

    @classmethod
    def get_choices_for(cls, model):
        result = []

        for klass in cls._registry:
            result.extend(klass.get_choices_for(model=model))

        return result

    @classmethod
    def get_help_text_for(cls, model, show_name=False):
        result = []

        for klass in cls._registry:
            result.append(
                klass.get_help_text_for(model=model, show_name=show_name)
            )

        return '\n'.join(result)

    @classmethod
    def register(cls, klass):
        cls._registry.append(klass)


class Package(object):
    _registry = []

    @classmethod
    def get_all(cls):
        return cls._registry

    def __init__(self, label, license_text):
        self.label = label
        self.license_text = license_text
        self.__class__._registry.append(self)


class PropertyHelper(object):
    """
    Makes adding fields using __class__.add_to_class easier.
    Each subclass must implement the `constructor` and the `get_result`
    method.
    """
    @staticmethod
    @property
    def constructor(source_object):
        return PropertyHelper(source_object)

    def __init__(self, instance):
        self.instance = instance

    def __getattr__(self, name):
        return self.get_result(name=name)

    def get_result(self, name):
        """
        The method that produces the actual result. Must be implemented
        by each subclass.
        """
        raise NotImplementedError


class Template(object):
    _registry = {}

    @classmethod
    def all(cls, rendered=False, request=None):
        if not rendered:
            return cls._registry.values()
        else:
            result = []
            for template in cls._registry.values():
                result.append(template.render(request=request))
            return result

    @classmethod
    def get(cls, name):
        return cls._registry[name]

    def __init__(self, name, template_name):
        self.name = name
        self.template_name = template_name
        self.__class__._registry[name] = self

    def get_absolute_url(self):
        return reverse(
            kwargs={'name': self.name}, viewname='rest_api:template-detail'
        )

    def render(self, request):
        context = {
            'home_view': setting_home_view.value,
        }
        result = TemplateResponse(
            request=request,
            template=self.template_name,
            context=context,
        ).render()

        # Calculate the hash of the bytes version but return the unicode
        # version
        self.html = result.rendered_content.replace('\n', '')
        self.hex_hash = hashlib.sha256(result.content).hexdigest()
        return self


ModelProperty.register(ModelAttribute)
ModelProperty.register(ModelField)