from drf_spectacular.utils import extend_schema_field
from rest_framework import serializers

from apps.skills.serializers import SkillSerializer

from .models import Resource, ResourceCheckpoint, SkillResource


class ResourceCheckpointSerializer(serializers.ModelSerializer):
    # Populated when the serializer context carries a `completed_checkpoint_ids`
    # set — e.g. ResourceDetailView preloads the current user's completed
    # checkpoint IDs for the fetched resource. Absent in contexts without a
    # user (schema generation, seed scripts) — falls back to False.
    is_completed = serializers.SerializerMethodField()

    class Meta:
        model = ResourceCheckpoint
        fields = ['id', 'order_index', 'title', 'url_fragment',
                  'estimated_minutes', 'source', 'is_completed']

    def get_is_completed(self, obj) -> bool:
        completed = self.context.get('completed_checkpoint_ids') or set()
        return obj.id in completed


class SkillResourceSerializer(serializers.ModelSerializer):
    skill = SkillSerializer(read_only=True)

    class Meta:
        model = SkillResource
        fields = ['skill', 'relevance_score']


class ResourceListSerializer(serializers.ModelSerializer):
    # Populated by an Exists() annotation on the view's queryset — see
    # ResourceListView. Keep as BooleanField so it fails loud if the view
    # ever forgets the annotation.
    has_checkpoints = serializers.BooleanField(read_only=True)

    class Meta:
        model = Resource
        fields = ['id', 'title', 'provider', 'url', 'difficulty_level',
                  'duration', 'type', 'rating', 'has_checkpoints']


class ResourceDetailSerializer(serializers.ModelSerializer):
    checkpoints = ResourceCheckpointSerializer(many=True, read_only=True)
    skill_mappings = serializers.SerializerMethodField()

    class Meta:
        model = Resource
        fields = ['id', 'title', 'provider', 'url', 'difficulty_level',
                  'duration', 'type', 'rating', 'checkpoints', 'skill_mappings']

    @extend_schema_field(SkillResourceSerializer(many=True))
    def get_skill_mappings(self, obj):
        return SkillResourceSerializer(
            SkillResource.objects.filter(resource=obj).select_related('skill'),
            many=True,
        ).data


class ResourceAdminSerializer(serializers.ModelSerializer):
    """Full-field writable Resource serializer for admin CRUD.

    Linked skills and checkpoints are managed via separate endpoints
    (SkillResourceAdminViewSet, ResourceCheckpointAdminViewSet) so that each
    concern has its own CRUD surface — matches the existing Django admin UX.
    """
    class Meta:
        model = Resource
        fields = ['id', 'title', 'provider', 'url', 'difficulty_level',
                  'duration', 'type', 'rating', 'created_at']
        read_only_fields = ['created_at']


class ResourceCheckpointAdminSerializer(serializers.ModelSerializer):
    class Meta:
        model = ResourceCheckpoint
        fields = ['id', 'resource', 'order_index', 'title', 'url_fragment',
                  'estimated_minutes', 'source', 'extracted_at']


class SkillResourceAdminSerializer(serializers.ModelSerializer):
    skill_detail = SkillSerializer(source='skill', read_only=True)

    class Meta:
        model = SkillResource
        fields = ['id', 'skill', 'skill_detail', 'resource', 'relevance_score']