from datetime import datetime

import django
from django import forms
from django.conf import settings
from django.conf.urls import url
from django.contrib import admin, messages
from django.contrib.admin.models import ADDITION, CHANGE, DELETION, LogEntry
from django.contrib.auth import get_permission_codename
from django.contrib.contenttypes.models import ContentType
from django.core.exceptions import PermissionDenied
from django.http import HttpResponse, HttpResponseRedirect
from django.template.response import TemplateResponse
from django.urls import reverse
from django.utils.decorators import method_decorator
from django.utils.encoding import force_str
from django.utils.module_loading import import_string
from django.utils.translation import gettext_lazy as _
from django.views.decorators.http import require_POST

from .formats.base_formats import DEFAULT_FORMATS
from .forms import ConfirmImportForm, ExportForm, ImportForm, export_action_form_factory
from .resources import modelresource_factory
from .results import RowResult
from .signals import post_export, post_import
from .tmp_storages import TempFolderStorage

SKIP_ADMIN_LOG = getattr(settings, 'IMPORT_EXPORT_SKIP_ADMIN_LOG', False)
TMP_STORAGE_CLASS = getattr(settings, 'IMPORT_EXPORT_TMP_STORAGE_CLASS',
                            TempFolderStorage)


if isinstance(TMP_STORAGE_CLASS, str):
    TMP_STORAGE_CLASS = import_string(TMP_STORAGE_CLASS)


class ImportExportMixinBase:
    def get_model_info(self):
        app_label = self.model._meta.app_label
        return (app_label, self.model._meta.model_name)


class ImportMixin(ImportExportMixinBase):
    """
    Import mixin.

    This is intended to be mixed with django.contrib.admin.ModelAdmin
    https://docs.djangoproject.com/en/2.1/ref/contrib/admin/#modeladmin-objects
    """

    #: template for change_list view
    change_list_template = 'admin/import_export/change_list_import.html'
    #: template for import view
    import_template_name = 'admin/import_export/import.html'
    #: resource class
    resource_class = None
    #: available import formats
    formats = DEFAULT_FORMATS
    #: import data encoding
    from_encoding = "utf-8"
    skip_admin_log = None
    # storage class for saving temporary files
    tmp_storage_class = None

    def get_skip_admin_log(self):
        if self.skip_admin_log is None:
            return SKIP_ADMIN_LOG
        else:
            return self.skip_admin_log

    def get_tmp_storage_class(self):
        if self.tmp_storage_class is None:
            return TMP_STORAGE_CLASS
        else:
            return self.tmp_storage_class

    def has_import_permission(self, request):
        """
        Returns whether a request has import permission.
        """
        IMPORT_PERMISSION_CODE = getattr(settings, 'IMPORT_EXPORT_IMPORT_PERMISSION_CODE', None)
        if IMPORT_PERMISSION_CODE is None:
            return True

        opts = self.opts
        codename = get_permission_codename(IMPORT_PERMISSION_CODE, opts)
        return request.user.has_perm("%s.%s" % (opts.app_label, codename))

    def get_urls(self):
        urls = super().get_urls()
        info = self.get_model_info()
        my_urls = [
            url(r'^process_import/$',
                self.admin_site.admin_view(self.process_import),
                name='%s_%s_process_import' % info),
            url(r'^import/$',
                self.admin_site.admin_view(self.import_action),
                name='%s_%s_import' % info),
        ]
        return my_urls + urls

    def get_resource_kwargs(self, request, *args, **kwargs):
        return {}

    def get_import_resource_kwargs(self, request, *args, **kwargs):
        """Prepares/returns kwargs used when initializing Resource"""
        return self.get_resource_kwargs(request, *args, **kwargs)

    def get_resource_class(self):
        """Returns ResourceClass"""
        if not self.resource_class:
            return modelresource_factory(self.model)
        else:
            return self.resource_class

    def get_import_resource_class(self):
        """
        Returns ResourceClass to use for import.
        """
        return self.get_resource_class()

    def get_import_formats(self):
        """
        Returns available import formats.
        """
        return [f for f in self.formats if f().can_import()]

    @method_decorator(require_POST)
    def process_import(self, request, *args, **kwargs):
        """
        Perform the actual import action (after the user has confirmed the import)
        """
        if not self.has_import_permission(request):
            raise PermissionDenied

        form_type = self.get_confirm_import_form()
        confirm_form = form_type(request.POST)
        if confirm_form.is_valid():
            import_formats = self.get_import_formats()
            input_format = import_formats[
                int(confirm_form.cleaned_data['input_format'])
            ]()
            tmp_storage = self.get_tmp_storage_class()(name=confirm_form.cleaned_data['import_file_name'])
            data = tmp_storage.read(input_format.get_read_mode())
            if not input_format.is_binary() and self.from_encoding:
                data = force_str(data, self.from_encoding)
            dataset = input_format.create_dataset(data)

            result = self.process_dataset(dataset, confirm_form, request, *args, **kwargs)

            tmp_storage.remove()

            return self.process_result(result, request)

    def process_dataset(self, dataset, confirm_form, request, *args, **kwargs):

        res_kwargs = self.get_import_resource_kwargs(request, form=confirm_form, *args, **kwargs)
        resource = self.get_import_resource_class()(**res_kwargs)

        imp_kwargs = self.get_import_data_kwargs(request, form=confirm_form, *args, **kwargs)
        return resource.import_data(dataset,
                                    dry_run=False,
                                    raise_errors=True,
                                    file_name=confirm_form.cleaned_data['original_file_name'],
                                    user=request.user,
                                    **imp_kwargs)

    def process_result(self, result, request):
        self.generate_log_entries(result, request)
        self.add_success_message(result, request)
        post_import.send(sender=None, model=self.model)

        url = reverse('admin:%s_%s_changelist' % self.get_model_info(),
                      current_app=self.admin_site.name)
        return HttpResponseRedirect(url)

    def generate_log_entries(self, result, request):
        if not self.get_skip_admin_log():
            # Add imported objects to LogEntry
            logentry_map = {
                RowResult.IMPORT_TYPE_NEW: ADDITION,
                RowResult.IMPORT_TYPE_UPDATE: CHANGE,
                RowResult.IMPORT_TYPE_DELETE: DELETION,
            }
            content_type_id = ContentType.objects.get_for_model(self.model).pk
            for row in result:
                if row.import_type != row.IMPORT_TYPE_ERROR and row.import_type != row.IMPORT_TYPE_SKIP:
                    LogEntry.objects.log_action(
                        user_id=request.user.pk,
                        content_type_id=content_type_id,
                        object_id=row.object_id,
                        object_repr=row.object_repr,
                        action_flag=logentry_map[row.import_type],
                        change_message=_("%s through import_export" % row.import_type),
                    )

    def add_success_message(self, result, request):
        opts = self.model._meta

        success_message = _('Import finished, with {} new and ' \
                            '{} updated {}.').format(result.totals[RowResult.IMPORT_TYPE_NEW],
                                                      result.totals[RowResult.IMPORT_TYPE_UPDATE],
                                                      opts.verbose_name_plural)

        messages.success(request, success_message)

    def get_import_context_data(self, **kwargs):
        return self.get_context_data(**kwargs)

    def get_context_data(self, **kwargs):
        return {}

    def get_import_form(self):
        """
        Get the form type used to read the import format and file.
        """
        return ImportForm

    def get_confirm_import_form(self):
        """
        Get the form type (class) used to confirm the import.
        """
        return ConfirmImportForm

    def get_form_kwargs(self, form, *args, **kwargs):
        """
        Prepare/returns kwargs for the import form.

        To distinguish between import and confirm import forms,
        the following approach may be used:

            if isinstance(form, ImportForm):
                # your code here for the import form kwargs
                # e.g. update.kwargs({...})
            elif isinstance(form, ConfirmImportForm):
                # your code here for the confirm import form kwargs
                # e.g. update.kwargs({...})
            ...
        """
        return kwargs

    def get_import_data_kwargs(self, request, *args, **kwargs):
        """
        Prepare kwargs for import_data.
        """
        form = kwargs.get('form')
        if form:
            kwargs.pop('form')
            return kwargs
        return {}

    def write_to_tmp_storage(self, import_file, input_format):
        tmp_storage = self.get_tmp_storage_class()()
        data = bytes()
        for chunk in import_file.chunks():
            data += chunk

        tmp_storage.save(data, input_format.get_read_mode())
        return tmp_storage

    def import_action(self, request, *args, **kwargs):
        """
        Perform a dry_run of the import to make sure the import will not
        result in errors.  If there where no error, save the user
        uploaded file to a local temp file that will be used by
        'process_import' for the actual import.
        """
        if not self.has_import_permission(request):
            raise PermissionDenied

        context = self.get_import_context_data()

        import_formats = self.get_import_formats()
        form_type = self.get_import_form()
        form_kwargs = self.get_form_kwargs(form_type, *args, **kwargs)
        form = form_type(import_formats,
                         request.POST or None,
                         request.FILES or None,
                         **form_kwargs)

        if request.POST and form.is_valid():
            input_format = import_formats[
                int(form.cleaned_data['input_format'])
            ]()
            import_file = form.cleaned_data['import_file']
            # first always write the uploaded file to disk as it may be a
            # memory file or else based on settings upload handlers
            tmp_storage = self.write_to_tmp_storage(import_file, input_format)

            # then read the file, using the proper format-specific mode
            # warning, big files may exceed memory
            try:
                data = tmp_storage.read(input_format.get_read_mode())
                if not input_format.is_binary() and self.from_encoding:
                    data = force_str(data, self.from_encoding)
                dataset = input_format.create_dataset(data)
            except UnicodeDecodeError as e:
                return HttpResponse(_(u"<h1>Imported file has a wrong encoding: %s</h1>" % e))
            except Exception as e:
                return HttpResponse(_(u"<h1>%s encountered while trying to read file: %s</h1>" % (type(e).__name__, import_file.name)))

            # prepare kwargs for import data, if needed
            res_kwargs = self.get_import_resource_kwargs(request, form=form, *args, **kwargs)
            resource = self.get_import_resource_class()(**res_kwargs)

            # prepare additional kwargs for import_data, if needed
            imp_kwargs = self.get_import_data_kwargs(request, form=form, *args, **kwargs)
            result = resource.import_data(dataset, dry_run=True,
                                          raise_errors=False,
                                          file_name=import_file.name,
                                          user=request.user,
                                          **imp_kwargs)

            context['result'] = result

            if not result.has_errors() and not result.has_validation_errors():
                initial = {
                    'import_file_name': tmp_storage.name,
                    'original_file_name': import_file.name,
                    'input_format': form.cleaned_data['input_format'],
                }
                confirm_form = self.get_confirm_import_form()
                initial = self.get_form_kwargs(form=form, **initial)
                context['confirm_form'] = confirm_form(initial=initial)
        else:
            res_kwargs = self.get_import_resource_kwargs(request, form=form, *args, **kwargs)
            resource = self.get_import_resource_class()(**res_kwargs)

        context.update(self.admin_site.each_context(request))

        context['title'] = _("Import")
        context['form'] = form
        context['opts'] = self.model._meta
        context['fields'] = [f.column_name for f in resource.get_user_visible_fields()]

        request.current_app = self.admin_site.name
        return TemplateResponse(request, [self.import_template_name],
                                context)

    def changelist_view(self, request, extra_context=None):
        if extra_context is None:
            extra_context = {}
        extra_context['has_import_permission'] = self.has_import_permission(request)
        return super().changelist_view(request, extra_context)


class ExportMixin(ImportExportMixinBase):
    """
    Export mixin.

    This is intended to be mixed with django.contrib.admin.ModelAdmin
    https://docs.djangoproject.com/en/2.1/ref/contrib/admin/#modeladmin-objects
    """
    #: resource class
    resource_class = None
    #: template for change_list view
    change_list_template = 'admin/import_export/change_list_export.html'
    #: template for export view
    export_template_name = 'admin/import_export/export.html'
    #: available export formats
    formats = DEFAULT_FORMATS
    #: export data encoding
    to_encoding = "utf-8"

    def get_urls(self):
        urls = super().get_urls()
        my_urls = [
            url(r'^export/$',
                self.admin_site.admin_view(self.export_action),
                name='%s_%s_export' % self.get_model_info()),
        ]
        return my_urls + urls

    def has_export_permission(self, request):
        """
        Returns whether a request has export permission.
        """
        EXPORT_PERMISSION_CODE = getattr(settings, 'IMPORT_EXPORT_EXPORT_PERMISSION_CODE', None)
        if EXPORT_PERMISSION_CODE is None:
            return True

        opts = self.opts
        codename = get_permission_codename(EXPORT_PERMISSION_CODE, opts)
        return request.user.has_perm("%s.%s" % (opts.app_label, codename))

    def get_resource_kwargs(self, request, *args, **kwargs):
        return {}

    def get_export_resource_kwargs(self, request, *args, **kwargs):
        return self.get_resource_kwargs(request, *args, **kwargs)

    def get_resource_class(self):
        if not self.resource_class:
            return modelresource_factory(self.model)
        else:
            return self.resource_class

    def get_export_resource_class(self):
        """
        Returns ResourceClass to use for export.
        """
        return self.get_resource_class()

    def get_export_formats(self):
        """
        Returns available export formats.
        """
        return [f for f in self.formats if f().can_export()]

    def get_export_filename(self, request, queryset, file_format):
        date_str = datetime.now().strftime('%Y-%m-%d')
        filename = "%s-%s.%s" % (self.model.__name__,
                                 date_str,
                                 file_format.get_extension())
        return filename

    def get_export_queryset(self, request):
        """
        Returns export queryset.

        Default implementation respects applied search and filters.
        """
        list_display = self.get_list_display(request)
        list_display_links = self.get_list_display_links(request, list_display)
        list_filter = self.get_list_filter(request)
        search_fields = self.get_search_fields(request)
        if self.get_actions(request):
            list_display = ['action_checkbox'] + list(list_display)

        ChangeList = self.get_changelist(request)
        changelist_kwargs = {
            'request': request,
            'model': self.model,
            'list_display': list_display,
            'list_display_links': list_display_links,
            'list_filter': list_filter,
            'date_hierarchy': self.date_hierarchy,
            'search_fields': search_fields,
            'list_select_related': self.list_select_related,
            'list_per_page': self.list_per_page,
            'list_max_show_all': self.list_max_show_all,
            'list_editable': self.list_editable,
            'model_admin': self,
        }
        if django.VERSION >= (2, 1):
            changelist_kwargs['sortable_by'] = self.sortable_by
        cl = ChangeList(**changelist_kwargs)

        return cl.get_queryset(request)

    def get_export_data(self, file_format, queryset, *args, **kwargs):
        """
        Returns file_format representation for given queryset.
        """
        request = kwargs.pop("request")
        if not self.has_export_permission(request):
            raise PermissionDenied

        resource_class = self.get_export_resource_class()
        data = resource_class(**self.get_export_resource_kwargs(request)).export(queryset, *args, **kwargs)
        export_data = file_format.export_data(data)
        return export_data

    def get_export_context_data(self, **kwargs):
        return self.get_context_data(**kwargs)

    def get_context_data(self, **kwargs):
        return {}

    def export_action(self, request, *args, **kwargs):
        if not self.has_export_permission(request):
            raise PermissionDenied

        formats = self.get_export_formats()
        form = ExportForm(formats, request.POST or None)
        if form.is_valid():
            file_format = formats[
                int(form.cleaned_data['file_format'])
            ]()

            queryset = self.get_export_queryset(request)
            export_data = self.get_export_data(file_format, queryset, request=request)
            content_type = file_format.get_content_type()
            response = HttpResponse(export_data, content_type=content_type)
            response['Content-Disposition'] = 'attachment; filename="%s"' % (
                self.get_export_filename(request, queryset, file_format),
            )

            post_export.send(sender=None, model=self.model)
            return response

        context = self.get_export_context_data()

        context.update(self.admin_site.each_context(request))

        context['title'] = _("Export")
        context['form'] = form
        context['opts'] = self.model._meta
        request.current_app = self.admin_site.name
        return TemplateResponse(request, [self.export_template_name],
                                context)

    def changelist_view(self, request, extra_context=None):
        if extra_context is None:
            extra_context = {}
        extra_context['has_export_permission'] = self.has_export_permission(request)
        return super().changelist_view(request, extra_context)


class ImportExportMixin(ImportMixin, ExportMixin):
    """
    Import and export mixin.
    """
    #: template for change_list view
    change_list_template = 'admin/import_export/change_list_import_export.html'


class ImportExportModelAdmin(ImportExportMixin, admin.ModelAdmin):
    """
    Subclass of ModelAdmin with import/export functionality.
    """


class ExportActionMixin(ExportMixin):
    """
    Mixin with export functionality implemented as an admin action.
    """

    # Don't use custom change list template.
    change_list_template = None

    def __init__(self, *args, **kwargs):
        """
        Adds a custom action form initialized with the available export
        formats.
        """
        choices = []
        formats = self.get_export_formats()
        if formats:
            choices.append(('', '---'))
            for i, f in enumerate(formats):
                choices.append((str(i), f().get_title()))

        self.action_form = export_action_form_factory(choices)
        super().__init__(*args, **kwargs)

    def export_admin_action(self, request, queryset):
        """
        Exports the selected rows using file_format.
        """
        export_format = request.POST.get('file_format')

        if not export_format:
            messages.warning(request, _('You must select an export format.'))
        else:
            formats = self.get_export_formats()
            file_format = formats[int(export_format)]()

            export_data = self.get_export_data(file_format, queryset, request=request)
            content_type = file_format.get_content_type()
            response = HttpResponse(export_data, content_type=content_type)
            response['Content-Disposition'] = 'attachment; filename="%s"' % (
                self.get_export_filename(request, queryset, file_format),
            )
            return response
    export_admin_action.short_description = _(
        'Export selected %(verbose_name_plural)s')

    actions = admin.ModelAdmin.actions + [export_admin_action]

    @property
    def media(self):
        super_media = super().media
        return forms.Media(js=super_media._js + ['import_export/action_formats.js'], css=super_media._css)


class ExportActionModelAdmin(ExportActionMixin, admin.ModelAdmin):
    """
    Subclass of ModelAdmin with export functionality implemented as an
    admin action.
    """


class ImportExportActionModelAdmin(ImportMixin, ExportActionModelAdmin):
    """
    Subclass of ExportActionModelAdmin with import/export functionality.
    Export functionality is implemented as an admin action.
    """