# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from django.conf.urls import url, include

from django_filters.rest_framework import DjangoFilterBackend

from rest_framework import generics, filters

import InvenTree.helpers

from stock.models import StockItem, StockLocation

from .models import StockItemLabel, StockLocationLabel
from .serializers import StockItemLabelSerializer, StockLocationLabelSerializer


class LabelListView(generics.ListAPIView):
    """
    Generic API class for label templates
    """

    filter_backends = [
        DjangoFilterBackend,
        filters.SearchFilter
    ]

    filter_fields = [
        'enabled',
    ]

    search_fields = [
        'name',
        'description',
    ]


class StockItemLabelList(LabelListView):
    """
    API endpoint for viewing list of StockItemLabel objects.

    Filterable by:

    - enabled: Filter by enabled / disabled status
    - item: Filter by single stock item
    - items: Filter by list of stock items

    """

    queryset = StockItemLabel.objects.all()
    serializer_class = StockItemLabelSerializer

    def get_items(self):
        """
        Return a list of requested stock items
        """

        items = []

        params = self.request.query_params

        if 'items' in params:
            items = params.getlist('items', [])
        elif 'item' in params:
            items = [params.get('item', None)]

        if type(items) not in [list, tuple]:
            items = [items]

        valid_ids = []

        for item in items:
            try:
                valid_ids.append(int(item))
            except (ValueError):
                pass

        # List of StockItems which match provided values
        valid_items = StockItem.objects.filter(pk__in=valid_ids)

        return valid_items

    def filter_queryset(self, queryset):
        """
        Filter the StockItem label queryset.
        """
        
        queryset = super().filter_queryset(queryset)

        # List of StockItem objects to match against
        items = self.get_items()

        # We wish to filter by stock items
        if len(items) > 0:
            """
            At this point, we are basically forced to be inefficient,
            as we need to compare the 'filters' string of each label,
            and see if it matches against each of the requested items.

            TODO: In the future, if this becomes excessively slow, it
                  will need to be readdressed.
            """

            # Keep track of which labels match every specified stockitem
            valid_label_ids = set()
            
            for label in queryset.all():

                matches = True

                # Filter string defined for the StockItemLabel object
                filters = InvenTree.helpers.validateFilterString(label.filters)

                for item in items:

                    item_query = StockItem.objects.filter(pk=item.pk)

                    if not item_query.filter(**filters).exists():
                        matches = False
                        break

                # Matched all items
                if matches:
                    valid_label_ids.add(label.pk)
                else:
                    continue

            # Reduce queryset to only valid matches
            queryset = queryset.filter(pk__in=[pk for pk in valid_label_ids])

        return queryset


class StockLocationLabelList(LabelListView):
    """
    API endpoint for viewiing list of StockLocationLabel objects.

    Filterable by:

    - enabled: Filter by enabled / disabled status
    - location: Filter by a single stock location
    - locations: Filter by list of stock locations
    """

    queryset = StockLocationLabel.objects.all()
    serializer_class = StockLocationLabelSerializer

    def get_locations(self):
        """
        Return a list of requested stock locations
        """

        locations = []

        params = self.request.query_params

        if 'locations' in params:
            locations = params.getlist('locations', [])
        elif 'location' in params:
            locations = [params.get('location', None)]

        if type(locations) not in [list, tuple]:
            locations = [locations]

        valid_ids = []

        for loc in locations:
            try:
                valid_ids.append(int(item))
            except (ValueError):
                pass

        # List of StockLocation objects which match provided values
        valid_locations = StockLocation.objects.filter(pk__in=valid_ids)

        return valid_locations

    def filter_queryset(self, queryset):
        """
        Filter the StockLocationLabel queryset
        """

        queryset = super().filter_queryset(queryset)
        
        # List of StockLocation objects to match against
        locations = self.get_locations()

        # We wish to filter by stock location(s)
        if len(locations) > 0:
            """
            At this point, we are basically forced to be inefficient,
            as we need to compare the 'filters' string of each label,
            and see if it matches against each of the requested items.

            TODO: In the future, if this becomes excessively slow, it
                  will need to be readdressed.
            """

            valid_label_ids = set()

            for label in queryset.all():

                matches = True

                # Filter string defined for the StockLocationLabel object
                filters = InvenTree.helpers.validateFilterString(label.filters)

                for loc in locations:

                    loc_query = StockLocation.objects.filter(pk=loc.pk)

                    if not loc_query.filter(**filters).exists():
                        matches = False
                        break

                # Matched all items
                if matches:
                    valid_label_ids.add(label.pk)
                else:
                    continue

            # Reduce queryset to only valid matches
            queryset = queryset.filter(pk__in=[pk for pk in valid_label_ids])

        return queryset


label_api_urls = [

    # Stock item labels
    url(r'stock/', include([
        url(r'^.*$', StockItemLabelList.as_view(), name='api-stockitem-label-list'),
    ])),

    # Stock location labels
    url(r'location/', include([
        url(r'^.*$', StockLocationLabelList.as_view(), name='api-stocklocation-label-list'),
    ])),
]