PYRSS-Website/apps/api/serializers.py

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

import logging

from django.conf import settings
from rest_framework import serializers

from apps.home.models import (
    Server,
    ContentFilter,
    MessageMutator,
    MessageStyle,
    DiscordChannel,
    Subscription,
    Content,
)

log = logging.getLogger(__name__)


# region Dynamic Model

# This DynamicModelSerializer is from a StackOverflow user in an obscure thread.
# I wish that I could remember which thread, because god bless that man.

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


# region Servers

class ServerSerializer(DynamicModelSerializer):
    id = serializers.CharField()

    class Meta:
        model = Server
        fields = (
            "id",
            "name",
            "icon_hash",
            "is_bot_operational",
            "active"
        )


# region Filters

class ContentFilterSerializer(DynamicModelSerializer):
    class Meta:
        model = ContentFilter
        fields = (
            "id",
            "server",
            "name",
            "match",
            "matching_algorithm",
            "is_insensitive",
            "is_whitelist"
        )


# region Msg Mutators

class MessageMutatorSerializer(DynamicModelSerializer):
    class Meta:
        model = MessageMutator
        fields = ("id", "name", "value")


# region Msg Styles

class MessageStyleSerializer(DynamicModelSerializer):
    title_mutator_detail = serializers.SerializerMethodField()
    description_mutator_detail = serializers.SerializerMethodField()

    class Meta:
        model = MessageStyle
        fields = (
            "id",
            "server",
            "name",
            "is_embed",
            "colour",
            "is_hyperlinked",
            "show_author",
            "show_timestamp",
            "show_images",
            "fetch_images",
            "title_mutator",
            "title_mutator_detail",
            "description_mutator",
            "description_mutator_detail",
            "auto_created"
        )
        read_only_fields = ("auto_created",)

    def get_title_mutator_detail(self, obj: MessageStyle):
        request = self.context.get("request")
        if request and request.method == "GET":
            return MessageMutatorSerializer(obj.title_mutator).data
        return {}

    def get_description_mutator_detail(self, obj: MessageStyle):
        request = self.context.get("request")
        if request and request.method == "GET":
            return MessageMutatorSerializer(obj.description_mutator).data
        return {}


# region Subscriptions

class DiscordChannelField(serializers.PrimaryKeyRelatedField):
    def to_internal_value(self, data):
        try:
            data = int(data)
        except (TypeError, ValueError):
            self.fail("invalid", pk_value=data)

        return super().to_internal_value(data)

    def to_representation(self, value):
        return str(value.pk)


class NestedDiscordChannelSerializer(DynamicModelSerializer):

    class Meta:
        model = DiscordChannel
        fields = ("id", "name", "is_nsfw")


class SubscriptionSerializer(DynamicModelSerializer):
    filters = serializers.PrimaryKeyRelatedField(
        queryset=ContentFilter.objects.all(),
        many=True
    )
    channels =  DiscordChannelField(
        queryset=DiscordChannel.objects.all(),
        many=True,
        required=True,
        allow_empty=False
    )
    channels_detail = serializers.SerializerMethodField()
    filters_detail = serializers.SerializerMethodField()
    message_style = serializers.PrimaryKeyRelatedField(
        queryset=MessageStyle.objects.all(),
        required=True,
        allow_null=False
    )
    message_style_detail = serializers.SerializerMethodField()

    class Meta:
        model = Subscription
        fields = (
            "id",
            "server",
            "name",
            "url",
            "created_at",
            "updated_at",
            "extra_notes",
            "active",
            "publish_threshold",
            "channels",
            "channels_detail",
            "filters",
            "filters_detail",
            "message_style",
            "message_style_detail"
        )

    def get_channels_detail(self, obj: Subscription):
        request = self.context.get("request")
        if request.method == "GET":
            return NestedDiscordChannelSerializer(obj.channels.all(), many=True).data
        return []

    def get_filters_detail(self, obj: Subscription):
        request = self.context.get("request")
        if request.method == "GET":
            return ContentFilterSerializer(obj.filters.all(), many=True).data
        return []

    def get_message_style_detail(self, obj: Subscription):
        request = self.context.get("request")
        if request.method == "GET":
            return MessageStyleSerializer(obj.message_style).data
        return {}

    def validate(self, data):
        server = data.get("server") or self.context.get("server")
        if not server:
            return data

        # Enforce max subscriptions per server
        subscriptions_count = Subscription.objects.filter(server=server).count();
        if subscriptions_count >= settings.MAX_SUBSCRIPTIONS_PER_SERVER:
            raise serializers.ValidationError(
                f"Cannot create more than {settings.MAX_SUBSCRIPTIONS_PER_SERVER} subscriptions for this server."
            )

        # Prevent using filters from a different server
        selected_filters = data.get("filters", [])
        valid_filter_ids = ContentFilter.objects.filter(server=server).values_list("id", flat=True)
        if any(fltr.id not in valid_filter_ids for fltr in selected_filters):
            raise serializers.ValidationError(
                {"filters": "All filters must belong to the specified server."}
            )

        # Prevent using message styles from a different server
        message_style = data.get("message_style")
        if message_style and message_style.server != server:
            raise serializers.ValidationError(
                {"message_style": "Message style must belong to the specified server."}
            )

        # Prevent assigning more channels than permitted
        channels = data.get("channels")
        if len(channels) > settings.MAX_CHANNELS_PER_SUBSCRIPTION:
            raise serializers.ValidationError(
                {"channels": "Please select 5 channels or fewer."}
            )

        return data


# region Content

class ContentSerializer(DynamicModelSerializer):
    class Meta:
        model = Content
        fields = (
            "id",
            "subscription",
            "item_id",
            "item_guid",
            "item_url",
            "item_title",
            "item_description",
            "item_content_hash",
            "item_image_url",
            "item_thumbnail_url",
            "item_published",
            "item_author",
            "item_author_url",
            "item_feed_title",
            "item_feed_url",
            "blocked"
        )