from rest_framework import serializers
from rest_framework_gis.fields import GeometryField
from rest_framework_gis.serializers import GeoFeatureModelSerializer

from apps.utils.storage import preview_url
from .models import Challenge, ChallengeParticipant


class ChallengeCreateSerializer(serializers.ModelSerializer):
    # Accepts GeoJSON Polygon from the client
    region = GeometryField(precision=6)

    class Meta:
        model = Challenge
        fields = ["title", "description", "region", "max_submissions", "expires_at"]

    def validate_region(self, value):
        if value.geom_type != "Polygon":
            raise serializers.ValidationError("region must be a GeoJSON Polygon.")
        return value


class ChallengeUpdateSerializer(serializers.ModelSerializer):
    class Meta:
        model = Challenge
        fields = ["title", "description", "expires_at", "status"]


class ChallengeMapSerializer(GeoFeatureModelSerializer):
    """
    GeoJSON FeatureCollection using region_centroid as geometry.
    Used for the map pin list — does not include the full region polygon.
    """
    coaster_count = serializers.SerializerMethodField()

    class Meta:
        model = Challenge
        geo_field = "region_centroid"
        fields = [
            "id", "title", "status",
            "submission_count", "max_submissions",
            "coaster_count",
            "expires_at", "created_at",
        ]

    def get_coaster_count(self, obj):
        return obj.coasters.count()


class ChallengeSplatPreviewSerializer(serializers.Serializer):
    id = serializers.UUIDField()
    preview_url = serializers.SerializerMethodField()
    created_at = serializers.DateTimeField()

    def get_preview_url(self, obj):
        return preview_url(obj.preview_key)


class ChallengeDetailSerializer(serializers.ModelSerializer):
    region = serializers.SerializerMethodField()
    region_centroid = serializers.SerializerMethodField()
    creator_username = serializers.CharField(source="creator.username", read_only=True)
    participant_count = serializers.SerializerMethodField()
    is_participating = serializers.SerializerMethodField()
    preview_splats = serializers.SerializerMethodField()
    coaster_count = serializers.SerializerMethodField()

    class Meta:
        model = Challenge
        fields = [
            "id", "title", "description", "status",
            "creator_username",
            "region", "region_centroid",
            "max_submissions", "submission_count",
            "participant_count", "is_participating",
            "coaster_count",
            "preview_splats",
            "expires_at", "created_at", "updated_at",
        ]

    def get_region(self, obj):
        import json
        return json.loads(obj.region.geojson) if obj.region else None

    def get_region_centroid(self, obj):
        import json
        return json.loads(obj.region_centroid.geojson) if obj.region_centroid else None

    def get_participant_count(self, obj):
        return obj.participants.count()

    def get_is_participating(self, obj):
        request = self.context.get("request")
        if not request or not request.user.is_authenticated:
            return False
        return obj.participants.filter(user=request.user).exists()

    def get_coaster_count(self, obj):
        return obj.coasters.count()

    def get_preview_splats(self, obj):
        from apps.splats.models import Splat
        qs = (
            Splat.objects.filter(challenge=obj, is_published=True)
            .order_by("-created_at")[:5]
        )
        return ChallengeSplatPreviewSerializer(qs, many=True).data


class ChallengeParticipantSerializer(serializers.ModelSerializer):
    class Meta:
        model = ChallengeParticipant
        fields = ["id", "joined_at"]
        read_only_fields = fields