"""
Provides a JSON API for the Part app
"""

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

from django_filters.rest_framework import DjangoFilterBackend
from django.conf import settings

from django.db.models import Q, F, Sum, Count
from django.db.models.functions import Coalesce

from rest_framework import status
from rest_framework.response import Response
from rest_framework import filters, serializers
from rest_framework import generics, permissions

from django.conf.urls import url, include
from django.urls import reverse

import os
from decimal import Decimal

from .models import Part, PartCategory, BomItem, PartStar
from .models import PartParameter, PartParameterTemplate

from . import serializers as part_serializers

from InvenTree.status_codes import OrderStatus, StockStatus, BuildStatus
from InvenTree.views import TreeSerializer
from InvenTree.helpers import str2bool, isNull


class PartCategoryTree(TreeSerializer):

    title = "Parts"
    model = PartCategory
    
    @property
    def root_url(self):
        return reverse('part-index')

    def get_items(self):
        return PartCategory.objects.all().prefetch_related('parts', 'children')


class CategoryList(generics.ListCreateAPIView):
    """ API endpoint for accessing a list of PartCategory objects.

    - GET: Return a list of PartCategory objects
    - POST: Create a new PartCategory object
    """

    queryset = PartCategory.objects.all()
    serializer_class = part_serializers.CategorySerializer

    permission_classes = [
        permissions.IsAuthenticated,
    ]

    def get_queryset(self):
        """
        Custom filtering:
        - Allow filtering by "null" parent to retrieve top-level part categories
        """

        cat_id = self.request.query_params.get('parent', None)

        queryset = super().get_queryset()

        if cat_id is not None:
            
            # Look for top-level categories
            if isNull(cat_id):
                queryset = queryset.filter(parent=None)
            
            else:
                try:
                    cat_id = int(cat_id)
                    queryset = queryset.filter(parent=cat_id)
                except ValueError:
                    pass

        return queryset

    filter_backends = [
        DjangoFilterBackend,
        filters.SearchFilter,
        filters.OrderingFilter,
    ]

    filter_fields = [
    ]

    ordering_fields = [
        'name',
    ]

    ordering = 'name'

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


class CategoryDetail(generics.RetrieveUpdateDestroyAPIView):
    """ API endpoint for detail view of a single PartCategory object """
    serializer_class = part_serializers.CategorySerializer
    queryset = PartCategory.objects.all()


class PartThumbs(generics.ListAPIView):
    """ API endpoint for retrieving information on available Part thumbnails """

    serializer_class = part_serializers.PartThumbSerializer

    def list(self, reguest, *args, **kwargs):
        """
        Serialize the available Part images.
        - Images may be used for multiple parts!
        """

        # Get all Parts which have an associated image
        queryset = Part.objects.all().exclude(image='')

        # Return the most popular parts first
        data = queryset.values(
            'image',
        ).annotate(count=Count('image')).order_by('-count')

        return Response(data)


class PartDetail(generics.RetrieveUpdateAPIView):
    """ API endpoint for detail view of a single Part object """

    queryset = Part.objects.all()
    serializer_class = part_serializers.PartSerializer

    permission_classes = [
        permissions.IsAuthenticated,
    ]


class PartList(generics.ListCreateAPIView):
    """ API endpoint for accessing a list of Part objects

    - GET: Return list of objects
    - POST: Create a new Part object

    The Part object list can be filtered by:
        - category: Filter by PartCategory reference
        - cascade: If true, include parts from sub-categories
        - starred: Is the part "starred" by the current user?
        - is_template: Is the part a template part?
        - variant_of: Filter by variant_of Part reference
        - assembly: Filter by assembly field
        - component: Filter by component field
        - trackable: Filter by trackable field
        - purchaseable: Filter by purcahseable field
        - salable: Filter by salable field
        - active: Filter by active field
    """

    serializer_class = part_serializers.PartSerializer

    queryset = Part.objects.all()

    starred_parts = None

    def get_serializer(self, *args, **kwargs):

        try:
            cat_detail = str2bool(self.request.query_params.get('category_detail', False))
        except AttributeError:
            cat_detail = None

        # Ensure the request context is passed through
        kwargs['context'] = self.get_serializer_context()

        kwargs['category_detail'] = cat_detail

        # Pass a list of "starred" parts fo the current user to the serializer
        # We do this to reduce the number of database queries required!
        if self.starred_parts is None:
            self.starred_parts = [star.part for star in self.request.user.starred_parts.all()]

        kwargs['starred_parts'] = self.starred_parts

        return self.serializer_class(*args, **kwargs)

    def create(self, request, *args, **kwargs):
        """ Override the default 'create' behaviour:
        We wish to save the user who created this part!

        Note: Implementation coped from DRF class CreateModelMixin
        """

        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        
        # Record the user who created this Part object
        part = serializer.save()
        part.creation_user = request.user
        part.save()

        headers = self.get_success_headers(serializer.data)
        return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers)


    def filter_queryset(self, queryset):
        """
        Perform custom filtering of the queryset
        """

        # Perform basic filtering
        queryset = super().filter_queryset(queryset)

        # Filter by 'starred' parts?
        starred = str2bool(self.request.query_params.get('starred', None))

        if starred is not None:
            starred_parts = [star.part.pk for star in self.request.user.starred_parts.all()]

            if starred:
                queryset = queryset.filter(pk__in=starred_parts)
            else:
                queryset = queryset.exclude(pk__in=starred_parts)

        # Cascade?
        cascade = str2bool(self.request.query_params.get('cascade', None))

        # Does the user wish to filter by category?
        cat_id = self.request.query_params.get('category', None)

        if cat_id is None:
            # No category filtering if category is not specified
            pass
        
        else:
            # Category has been specified!
            if isNull(cat_id):
                # A 'null' category is the top-level category
                if cascade is False:
                    # Do not cascade, only list parts in the top-level category
                    queryset = queryset.filter(category=None)

            else:
                try:
                    category = PartCategory.objects.get(pk=cat_id)

                    # If '?cascade=true' then include parts which exist in sub-categories
                    if cascade:
                        queryset = queryset.filter(category__in=category.getUniqueChildren())
                    # Just return parts directly in the requested category
                    else:
                        queryset = queryset.filter(category=cat_id)
                except (ValueError, PartCategory.DoesNotExist):
                    pass

        # Annotate calculated data to the queryset
        # (This will be used for further filtering)
        queryset = part_serializers.PartSerializer.annotate_queryset(queryset)

        # Filter by whether the part has stock
        has_stock = self.request.query_params.get("has_stock", None)
        if has_stock is not None:
            has_stock = str2bool(has_stock)

            if has_stock:
                queryset = queryset.filter(Q(in_stock__gt=0))
            else:
                queryset = queryset.filter(Q(in_stock__lte=0))

        # If we are filtering by 'low_stock' status
        low_stock = self.request.query_params.get('low_stock', None)

        if low_stock is not None:
            low_stock = str2bool(low_stock)

            if low_stock:
                # Ignore any parts which do not have a specified 'minimum_stock' level
                queryset = queryset.exclude(minimum_stock=0)
                # Filter items which have an 'in_stock' level lower than 'minimum_stock'
                queryset = queryset.filter(Q(in_stock__lt=F('minimum_stock')))
            else:
                # Filter items which have an 'in_stock' level higher than 'minimum_stock'
                queryset = queryset.filter(Q(in_stock__gte=F('minimum_stock')))

        return queryset

    permission_classes = [
        permissions.IsAuthenticated,
    ]

    filter_backends = [
        DjangoFilterBackend,
        filters.SearchFilter,
        filters.OrderingFilter,
    ]

    filter_fields = [
        'is_template',
        'variant_of',
        'assembly',
        'component',
        'trackable',
        'purchaseable',
        'salable',
        'active',
    ]

    ordering_fields = [
        'name',
    ]

    # Default ordering
    ordering = 'name'

    search_fields = [
        '$name',
        'description',
        '$IPN',
        'keywords',
    ]


class PartStarDetail(generics.RetrieveDestroyAPIView):
    """ API endpoint for viewing or removing a PartStar object """

    queryset = PartStar.objects.all()
    serializer_class = part_serializers.PartStarSerializer


class PartStarList(generics.ListCreateAPIView):
    """ API endpoint for accessing a list of PartStar objects.

    - GET: Return list of PartStar objects
    - POST: Create a new PartStar object
    """

    queryset = PartStar.objects.all()
    serializer_class = part_serializers.PartStarSerializer

    def create(self, request, *args, **kwargs):

        # Override the user field (with the logged-in user)
        data = request.data.copy()
        data['user'] = str(request.user.id)

        serializer = self.get_serializer(data=data)

        serializer.is_valid(raise_exception=True)
        self.perform_create(serializer)
        headers = self.get_success_headers(serializer.data)
        return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers)

    permission_classes = [
        permissions.IsAuthenticated,
    ]

    filter_backends = [
        DjangoFilterBackend,
        filters.SearchFilter
    ]

    filter_fields = [
        'part',
        'user',
    ]

    search_fields = [
        'partname'
    ]


class PartParameterTemplateList(generics.ListCreateAPIView):
    """ API endpoint for accessing a list of PartParameterTemplate objects.

    - GET: Return list of PartParameterTemplate objects
    - POST: Create a new PartParameterTemplate object
    """

    queryset = PartParameterTemplate.objects.all()
    serializer_class = part_serializers.PartParameterTemplateSerializer

    permission_classes = [
        permissions.IsAuthenticated,
    ]

    filter_backends = [
        filters.OrderingFilter,
    ]

    filter_fields = [
        'name',
    ]


class PartParameterList(generics.ListCreateAPIView):
    """ API endpoint for accessing a list of PartParameter objects

    - GET: Return list of PartParameter objects
    - POST: Create a new PartParameter object
    """

    queryset = PartParameter.objects.all()
    serializer_class = part_serializers.PartParameterSerializer

    permission_classes = [
        permissions.IsAuthenticated,
    ]

    filter_backends = [
        DjangoFilterBackend
    ]

    filter_fields = [
        'part',
        'template',
    ]


class BomList(generics.ListCreateAPIView):
    """ API endpoint for accessing a list of BomItem objects.

    - GET: Return list of BomItem objects
    - POST: Create a new BomItem object
    """

    serializer_class = part_serializers.BomItemSerializer
    
    def get_serializer(self, *args, **kwargs):

        # Do we wish to include extra detail?
        try:
            part_detail = str2bool(self.request.GET.get('part_detail', None))
            sub_part_detail = str2bool(self.request.GET.get('sub_part_detail', None))
        except AttributeError:
            part_detail = None
            sub_part_detail = None

        kwargs['part_detail'] = part_detail
        kwargs['sub_part_detail'] = sub_part_detail

        # Ensure the request context is passed through!
        kwargs['context'] = self.get_serializer_context()
        
        return self.serializer_class(*args, **kwargs)

    def get_queryset(self):
        queryset = BomItem.objects.all()
        queryset = self.get_serializer_class().setup_eager_loading(queryset)

        # Filter by part?
        part = self.request.query_params.get('part', None)

        if part is not None:
            queryset = queryset.filter(part=part)
        
        # Filter by sub-part?
        sub_part = self.request.query_params.get('sub_part', None)

        if sub_part is not None:
            queryset = queryset.filter(sub_part=sub_part)

        return queryset

    permission_classes = [
        permissions.IsAuthenticated,
    ]

    filter_backends = [
        DjangoFilterBackend,
        filters.SearchFilter,
        filters.OrderingFilter,
    ]

    filter_fields = [
    ]


class BomDetail(generics.RetrieveUpdateDestroyAPIView):
    """ API endpoint for detail view of a single BomItem object """

    queryset = BomItem.objects.all()
    serializer_class = part_serializers.BomItemSerializer

    permission_classes = [
        permissions.IsAuthenticated,
    ]


class BomItemValidate(generics.UpdateAPIView):
    """ API endpoint for validating a BomItem """

    # Very simple serializers
    class BomItemValidationSerializer(serializers.Serializer):

        valid = serializers.BooleanField(default=False)

    queryset = BomItem.objects.all()
    serializer_class = BomItemValidationSerializer

    def update(self, request, *args, **kwargs):
        """ Perform update request """

        partial = kwargs.pop('partial', False)

        valid = request.data.get('valid', False)

        instance = self.get_object()
        
        serializer = self.get_serializer(instance, data=request.data, partial=partial)
        serializer.is_valid(raise_exception=True)

        if type(instance) == BomItem:
            instance.validate_hash(valid)

        return Response(serializer.data)


cat_api_urls = [

    url(r'^(?P<pk>\d+)/?', CategoryDetail.as_view(), name='api-part-category-detail'),

    url(r'^$', CategoryList.as_view(), name='api-part-category-list'),
]


part_star_api_urls = [
    url(r'^(?P<pk>\d+)/?', PartStarDetail.as_view(), name='api-part-star-detail'),

    # Catchall
    url(r'^.*$', PartStarList.as_view(), name='api-part-star-list'),
]

part_param_api_urls = [
    url(r'^template/$', PartParameterTemplateList.as_view(), name='api-part-param-template-list'),

    url(r'^.*$', PartParameterList.as_view(), name='api-part-param-list'),
]

part_api_urls = [
    url(r'^tree/?', PartCategoryTree.as_view(), name='api-part-tree'),

    url(r'^category/', include(cat_api_urls)),
    url(r'^star/', include(part_star_api_urls)),
    url(r'^parameter/', include(part_param_api_urls)),

    url(r'^thumbs/', PartThumbs.as_view(), name='api-part-thumbs'),

    url(r'^(?P<pk>\d+)/?', PartDetail.as_view(), name='api-part-detail'),

    url(r'^.*$', PartList.as_view(), name='api-part-list'),
]

bom_item_urls = [

    url(r'^validate/?', BomItemValidate.as_view(), name='api-bom-item-validate'),

    url(r'^.*$', BomDetail.as_view(), name='api-bom-item-detail'),
]

bom_api_urls = [
    # BOM Item Detail
    url(r'^(?P<pk>\d+)/', include(bom_item_urls)),

    # Catch-all
    url(r'^.*$', BomList.as_view(), name='api-bom-list'),
]