from rest_framework import status
from rest_framework.response import Response
from rest_framework.views import APIView

from app.expenses.models import Category, Subcategory

from .authentication import HasValidToken, TokenEnvAuthentication
from .serializers import (
	CategorySerializer,
	ExpenseReadSerializer,
	ExpenseWriteSerializer,
	SubcategorySerializer,
)


class RootView(APIView):
	authentication_classes = [TokenEnvAuthentication]
	permission_classes = [HasValidToken]

	def get(self, request):
		return Response(
			{
				"type": "Success",
				"_links": {
					"categories": {"href": "/api/categories/", "method": "GET"},
					"expenses": {"href": "/api/expenses/", "method": "POST"},
				},
			}
		)


class BaseAPIView(APIView):
	authentication_classes = [TokenEnvAuthentication]
	permission_classes = [HasValidToken]

	def _success(self, data, meta=None, links=None, status_code=status.HTTP_200_OK):
		response = {"type": "Success", "data": data}
		if meta:
			response["meta"] = meta
		if links:
			response["_links"] = links
		return Response(response, status=status_code)

	def _error(
		self,
		errors,
		error_type="ParametersError",
		status_code=status.HTTP_400_BAD_REQUEST,
	):
		formatted = []
		if isinstance(errors, dict):
			for field, messages in errors.items():
				for msg in messages if isinstance(messages, list) else [messages]:
					formatted.append({"field": field, "message": str(msg)})
		else:
			formatted.append({"field": None, "message": str(errors)})
		return Response(
			{"type": error_type, "errors": formatted},
			status=status_code,
		)


class CategoriesView(BaseAPIView):
	def get(self, request):
		categories = Category.objects.prefetch_related("subcategories").all()
		serializer = CategorySerializer(categories, many=True)
		return self._success(
			serializer.data,
			links={
				"self": {"href": "/api/categories/", "method": "GET"},
			},
		)


class SubcategoriesView(BaseAPIView):
	def get(self, request, category_id):
		try:
			category = Category.objects.get(id=category_id)
		except Category.DoesNotExist:
			return self._error(
				"Category not found.",
				error_type="ResourceError",
				status_code=status.HTTP_404_NOT_FOUND,
			)
		subcategories = Subcategory.objects.filter(category=category)
		serializer = SubcategorySerializer(subcategories, many=True)
		return self._success(
			serializer.data,
			links={
				"self": {
					"href": f"/api/categories/{category_id}/subcategories/",
					"method": "GET",
				},
				"category": {
					"href": "/api/categories/",
					"method": "GET",
				},
			},
		)


class ExpensesView(BaseAPIView):
	def post(self, request):
		serializer = ExpenseWriteSerializer(data=request.data)
		if not serializer.is_valid():
			return self._error(serializer.errors)

		expense = serializer.save()
		read_serializer = ExpenseReadSerializer(expense)
		return self._success(
			read_serializer.data,
			links={
				"self": {"href": "/api/expenses/", "method": "POST"},
				"categories": {"href": "/api/categories/", "method": "GET"},
			},
			status_code=status.HTTP_201_CREATED,
		)