import warnings
from itertools import groupby
from operator import itemgetter

from django import forms
from django.conf import settings
from django.contrib.auth import get_user_model
from django.contrib.auth.models import Group, Permission
from django.contrib.auth.password_validation import (
    password_validators_help_text_html, validate_password)
from django.db import transaction
from django.db.models.fields import BLANK_CHOICE_DASH
from django.template.loader import render_to_string
from django.utils.html import mark_safe
from django.utils.translation import ugettext_lazy as _

from wagtail.admin.utils import get_available_admin_languages, get_available_admin_time_zones
from wagtail.admin.widgets import AdminPageChooser
from wagtail.core import hooks
from wagtail.core.models import (
    PAGE_PERMISSION_TYPE_CHOICES, PAGE_PERMISSION_TYPES, GroupPagePermission, Page,
    UserPagePermissionsProxy)
from wagtail.users.models import UserProfile
from wagtail.utils import l18n

User = get_user_model()

# The standard fields each user model is expected to have, as a minimum.
standard_fields = set(['email', 'first_name', 'last_name', 'is_superuser', 'groups'])
# Custom fields
if hasattr(settings, 'WAGTAIL_USER_CUSTOM_FIELDS'):
    custom_fields = set(settings.WAGTAIL_USER_CUSTOM_FIELDS)
else:
    custom_fields = set()


class UsernameForm(forms.ModelForm):
    """
    Intelligently sets up the username field if it is in fact a username. If the
    User model has been swapped out, and the username field is an email or
    something else, don't touch it.
    """
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        if User.USERNAME_FIELD == 'username':
            field = self.fields['username']
            field.regex = r"^[\w.@+-]+$"
            field.help_text = _("Required. 30 characters or fewer. Letters, "
                                "digits and @/./+/-/_ only.")
            field.error_messages = field.error_messages.copy()
            field.error_messages.update({
                'invalid': _("This value may contain only letters, numbers "
                             "and @/./+/-/_ characters.")})

    @property
    def username_field(self):
        return self[User.USERNAME_FIELD]

    def separate_username_field(self):
        return User.USERNAME_FIELD not in standard_fields


class UserForm(UsernameForm):
    required_css_class = "required"

    @property
    def password_required(self):
        return getattr(settings, 'WAGTAILUSERS_PASSWORD_REQUIRED', True)

    @property
    def password_enabled(self):
        return getattr(settings, 'WAGTAILUSERS_PASSWORD_ENABLED', True)

    error_messages = {
        'duplicate_username': _("A user with that username already exists."),
        'password_mismatch': _("The two password fields didn't match."),
    }

    email = forms.EmailField(required=True, label=_('Email'))
    first_name = forms.CharField(required=True, label=_('First Name'))
    last_name = forms.CharField(required=True, label=_('Last Name'))

    password1 = forms.CharField(
        label=_('Password'), required=False,
        widget=forms.PasswordInput,
        help_text=_("Leave blank if not changing."))
    password2 = forms.CharField(
        label=_("Password confirmation"), required=False,
        widget=forms.PasswordInput,
        help_text=_("Enter the same password as above, for verification."))

    is_superuser = forms.BooleanField(
        label=_("Administrator"), required=False,
        help_text=_('Administrators have full access to manage any object '
                    'or setting.'))

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        if self.password_enabled:
            if self.password_required:
                self.fields['password1'].help_text = mark_safe(password_validators_help_text_html())
                self.fields['password1'].required = True
                self.fields['password2'].required = True
        else:
            del self.fields['password1']
            del self.fields['password2']

    # We cannot call this method clean_username since this the name of the
    # username field may be different, so clean_username would not be reliably
    # called. We therefore call _clean_username explicitly in _clean_fields.
    def _clean_username(self):
        username_field = User.USERNAME_FIELD
        # This method is called even if username if empty, contrary to clean_*
        # methods, so we have to check again here that data is defined.
        if username_field not in self.cleaned_data:
            return
        username = self.cleaned_data[username_field]

        users = User._default_manager.all()
        if self.instance.pk is not None:
            users = users.exclude(pk=self.instance.pk)
        if users.filter(**{username_field: username}).exists():
            self.add_error(User.USERNAME_FIELD, forms.ValidationError(
                self.error_messages['duplicate_username'],
                code='duplicate_username',
            ))
        return username

    def clean_password2(self):
        password1 = self.cleaned_data.get("password1")
        password2 = self.cleaned_data.get("password2")
        if password2 != password1:
            self.add_error('password2', forms.ValidationError(
                self.error_messages['password_mismatch'],
                code='password_mismatch',
            ))

        return password2

    def validate_password(self):
        """
        Run the Django password validators against the new password. This must
        be called after the user instance in self.instance is populated with
        the new data from the form, as some validators rely on attributes on
        the user model.
        """
        password1 = self.cleaned_data.get("password1")
        password2 = self.cleaned_data.get("password2")
        if password1 and password2 and password1 == password2:
            validate_password(password1, user=self.instance)

    def _post_clean(self):
        super()._post_clean()
        try:
            self.validate_password()
        except forms.ValidationError as e:
            self.add_error('password2', e)

    def _clean_fields(self):
        super()._clean_fields()
        self._clean_username()

    def save(self, commit=True):
        user = super().save(commit=False)

        if self.password_enabled:
            password = self.cleaned_data['password1']
            if password:
                user.set_password(password)

        if commit:
            user.save()
            self.save_m2m()
        return user


class UserCreationForm(UserForm):
    class Meta:
        model = User
        fields = set([User.USERNAME_FIELD]) | standard_fields | custom_fields
        widgets = {
            'groups': forms.CheckboxSelectMultiple
        }


class UserEditForm(UserForm):
    password_required = False

    def __init__(self, *args, **kwargs):
        editing_self = kwargs.pop('editing_self', False)
        super().__init__(*args, **kwargs)

        if editing_self:
            del self.fields["is_active"]
            del self.fields["is_superuser"]

    class Meta:
        model = User
        fields = set([User.USERNAME_FIELD, "is_active"]) | standard_fields | custom_fields
        widgets = {
            'groups': forms.CheckboxSelectMultiple
        }


class GroupForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.registered_permissions = Permission.objects.none()
        for fn in hooks.get_hooks('register_permissions'):
            self.registered_permissions = self.registered_permissions | fn()
        self.fields['permissions'].queryset = self.registered_permissions.select_related('content_type')

    required_css_class = "required"

    error_messages = {
        'duplicate_name': _("A group with that name already exists."),
    }

    is_superuser = forms.BooleanField(
        label=_("Administrator"),
        required=False,
        help_text=_("Administrators have full access to manage any object or setting.")
    )

    class Meta:
        model = Group
        fields = ("name", "permissions", )
        widgets = {
            'permissions': forms.CheckboxSelectMultiple(),
        }

    def clean_name(self):
        # Since Group.name is unique, this check is redundant,
        # but it sets a nicer error message than the ORM. See #13147.
        name = self.cleaned_data["name"]
        try:
            Group._default_manager.exclude(pk=self.instance.pk).get(name=name)
        except Group.DoesNotExist:
            return name
        raise forms.ValidationError(self.error_messages['duplicate_name'])

    def save(self):
        # We go back to the object to read (in order to reapply) the
        # permissions which were set on this group, but which are not
        # accessible in the wagtail admin interface, as otherwise these would
        # be clobbered by this form.
        try:
            untouchable_permissions = self.instance.permissions.exclude(pk__in=self.registered_permissions)
            bool(untouchable_permissions)  # force this to be evaluated, as it's about to change
        except ValueError:
            # this form is not bound; we're probably creating a new group
            untouchable_permissions = []
        group = super().save()
        group.permissions.add(*untouchable_permissions)
        return group


class PagePermissionsForm(forms.Form):
    """
    Note 'Permissions' (plural). A single instance of this form defines the permissions
    that are assigned to an entity (i.e. group or user) for a specific page.
    """
    page = forms.ModelChoiceField(
        queryset=Page.objects.all(),
        widget=AdminPageChooser(show_edit_link=False, can_choose_root=True)
    )
    permission_types = forms.MultipleChoiceField(
        choices=PAGE_PERMISSION_TYPE_CHOICES,
        required=False,
        widget=forms.CheckboxSelectMultiple
    )


class BaseGroupPagePermissionFormSet(forms.BaseFormSet):
    permission_types = PAGE_PERMISSION_TYPES  # defined here for easy access from templates

    def __init__(self, data=None, files=None, instance=None, prefix='page_permissions'):
        if instance is None:
            instance = Group()

        self.instance = instance

        initial_data = []

        for page, page_permissions in groupby(
            instance.page_permissions.select_related('page').order_by('page'), lambda pp: pp.page
        ):
            initial_data.append({
                'page': page,
                'permission_types': [pp.permission_type for pp in page_permissions]
            })

        super().__init__(
            data, files, initial=initial_data, prefix=prefix
        )
        for form in self.forms:
            form.fields['DELETE'].widget = forms.HiddenInput()

    @property
    def empty_form(self):
        empty_form = super().empty_form
        empty_form.fields['DELETE'].widget = forms.HiddenInput()
        return empty_form

    def clean(self):
        """Checks that no two forms refer to the same page object"""
        if any(self.errors):
            # Don't bother validating the formset unless each form is valid on its own
            return

        pages = [
            form.cleaned_data['page']
            for form in self.forms
            # need to check for presence of 'page' in cleaned_data,
            # because a completely blank form passes validation
            if form not in self.deleted_forms and 'page' in form.cleaned_data
        ]
        if len(set(pages)) != len(pages):
            # pages list contains duplicates
            raise forms.ValidationError(_("You cannot have multiple permission records for the same page."))

    @transaction.atomic
    def save(self):
        if self.instance.pk is None:
            raise Exception(
                "Cannot save a GroupPagePermissionFormSet for an unsaved group instance"
            )

        # get a set of (page, permission_type) tuples for all ticked permissions
        forms_to_save = [
            form for form in self.forms
            if form not in self.deleted_forms and 'page' in form.cleaned_data
        ]

        final_permission_records = set()
        for form in forms_to_save:
            for permission_type in form.cleaned_data['permission_types']:
                final_permission_records.add((form.cleaned_data['page'], permission_type))

        # fetch the group's existing page permission records, and from that, build a list
        # of records to be created / deleted
        permission_ids_to_delete = []
        permission_records_to_keep = set()

        for pp in self.instance.page_permissions.all():
            if (pp.page, pp.permission_type) in final_permission_records:
                permission_records_to_keep.add((pp.page, pp.permission_type))
            else:
                permission_ids_to_delete.append(pp.pk)

        self.instance.page_permissions.filter(pk__in=permission_ids_to_delete).delete()

        permissions_to_add = final_permission_records - permission_records_to_keep
        GroupPagePermission.objects.bulk_create([
            GroupPagePermission(
                group=self.instance, page=page, permission_type=permission_type
            )
            for (page, permission_type) in permissions_to_add
        ])

    def as_admin_panel(self):
        return render_to_string('wagtailusers/groups/includes/page_permissions_formset.html', {
            'formset': self
        })


GroupPagePermissionFormSet = forms.formset_factory(
    PagePermissionsForm, formset=BaseGroupPagePermissionFormSet, extra=0, can_delete=True
)


class NotificationPreferencesForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        user_perms = UserPagePermissionsProxy(self.instance.user)
        if not user_perms.can_publish_pages():
            del self.fields['submitted_notifications']
        if not user_perms.can_edit_pages():
            del self.fields['approved_notifications']
            del self.fields['rejected_notifications']

    class Meta:
        model = UserProfile
        fields = ("submitted_notifications", "approved_notifications", "rejected_notifications")


def _get_language_choices():
    return sorted(BLANK_CHOICE_DASH + get_available_admin_languages(),
                  key=lambda l: l[1].lower())


class PreferredLanguageForm(forms.ModelForm):
    preferred_language = forms.ChoiceField(
        required=False, choices=_get_language_choices,
        label=_('Preferred language')
    )

    class Meta:
        model = UserProfile
        fields = ("preferred_language",)


class EmailForm(forms.ModelForm):
    email = forms.EmailField(required=True, label=_('Email'))

    class Meta:
        model = User
        fields = ("email",)


def _get_time_zone_choices():
    time_zones = [(tz, str(l18n.tz_fullnames.get(tz, tz)))
                  for tz in get_available_admin_time_zones()]
    time_zones.sort(key=itemgetter(1))
    return BLANK_CHOICE_DASH + time_zones


class CurrentTimeZoneForm(forms.ModelForm):
    current_time_zone = forms.ChoiceField(
        required=False, choices=_get_time_zone_choices,
        label=_('Current time zone')
    )

    class Meta:
        model = UserProfile
        fields = ("current_time_zone",)


class AvatarPreferencesForm(forms.ModelForm):
    avatar = forms.ImageField(
        label=_("Upload a profile picture"), required=True
    )

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._original_avatar = self.instance.avatar

    def save(self, commit=True):
        if commit and self._original_avatar and (self._original_avatar != self.cleaned_data['avatar']):
            # Call delete() on the storage backend directly, as calling self._original_avatar.delete()
            # will clear the now-updated field on self.instance too
            try:
                self._original_avatar.storage.delete(self._original_avatar.name)
            except IOError:
                # failure to delete the old avatar shouldn't prevent us from continuing
                warnings.warn("Failed to delete old avatar file: %s" % self._original_avatar.name)
        super().save(commit=commit)

    class Meta:
        model = UserProfile
        fields = ["avatar"]
