# -*- encoding: utf-8 -*-

import logging

from django.apps import apps
from django.conf import settings
from rest_framework import serializers

from apps.home.models import RSSFeed, FeedChannel

log = logging.getLogger(__name__)


class DynamicModelSerializer(serializers.ModelSerializer):
    """For use with GET requests, to specify which fields to include or exclude
    Mimics some graphql functionality.

    Usage: Inherit your ModelSerializer with this class. Add "only_fields" or
    "exclude_fields" to the query parameters of your GET request.

    This also works with nested foreign keys, for example:
    ?only_fields=name,age&company__only_fields=id,name

    Some more examples:

    ?only_fields=company,name&company__exclude_fields=name
    ?exclude_fields=name&company__only_fields=id
    ?company__exclude_fields=name

    Note: the Foreign Key serializer must also inherit from this class
    """

    def only_keep_fields(self, fields_to_keep):
        fields_to_keep = set(fields_to_keep.split(","))
        all_fields = set(self.fields.keys())
        for field in all_fields - fields_to_keep:
            self.fields.pop(field, None)

    def exclude_fields(self, fields_to_exclude):
        fields_to_exclude = fields_to_exclude.split(",")
        for field in fields_to_exclude:
            self.fields.pop(field, None)

    def remove_unwanted_fields(self, dynamic_params):
        if fields_to_keep := dynamic_params.pop("only_fields", None):
            self.only_keep_fields(fields_to_keep)

        if fields_to_exclude := dynamic_params.pop("exclude_fields", None):
            self.exclude_fields(fields_to_exclude)

    def get_or_create_dynamic_params(self, child):
        if "dynamic_params" not in self.fields[child]._context:
            self.fields[child]._context.update({"dynamic_params": {}})
        return self.fields[child]._context["dynamic_params"]

    @staticmethod
    def split_param(dynamic_param):
        crumbs = dynamic_param.split("__")
        return crumbs[0], "__".join(crumbs[1:]) if len(crumbs) > 1 else None

    def set_dynamic_params_for_children(self, dynamic_params):
        for param, fields in dynamic_params.items():
            child, child_dynamic_param = self.split_param(param)
            if child in set(self.fields.keys()):
                dynamic_params = self.get_or_create_dynamic_params(child)
                dynamic_params.update({child_dynamic_param: fields})

    @staticmethod
    def is_param_dynamic(p):
        return p.endswith("only_fields") or p.endswith("exclude_fields")

    def get_dynamic_params_for_root(self, request):
        query_params = request.query_params.items()
        return {k: v for k, v in query_params if self.is_param_dynamic(k)}

    def get_dynamic_params(self):
        """
        When dynamic params get passed down in set_context_for_children
        If the child is a subclass of ListSerializer (has many=True)
        The context must be fetched from ListSerializer Class
        """
        if isinstance(self.parent, serializers.ListSerializer):
            return self.parent._context.get("dynamic_params", {})
        return self._context.get("dynamic_params", {})

    def __init__(self, *args, **kwargs):
        request = kwargs.get("context", {}).get("request")
        super().__init__(*args, **kwargs)
        is_root = bool(request)

        if is_root:
            if request.method != "GET":
                return

            dynamic_params = self.get_dynamic_params_for_root(request)
            self._context.update({"dynamic_params": dynamic_params})

    def to_representation(self, *args, **kwargs):
        if dynamic_params := self.get_dynamic_params().copy():
            self.remove_unwanted_fields(dynamic_params)
            self.set_dynamic_params_for_children(dynamic_params)

        return super().to_representation(*args, **kwargs)

    class Meta:
        abstract = True


class RssFeedSerializer(DynamicModelSerializer):

    class Meta:
        model = RSSFeed
        fields = (
            "uuid", "name", "url", "image", "created_at"
        )


class FeedChannelSerializer(DynamicModelSerializer):
    feeds = RssFeedSerializer(many=True)

    class Meta:
        model = FeedChannel
        fields = (
            "uuid", "channel_id", "feeds", "created_at"
        )