from rest_framework import serializers

from .models import UserCheckpointProgress, UserProgress


class UserProgressSerializer(serializers.ModelSerializer):
    resource_title = serializers.CharField(source='resource.title', read_only=True)
    has_checkpoints = serializers.SerializerMethodField()
    in_current_plan = serializers.SerializerMethodField()

    class Meta:
        model = UserProgress
        fields = ['id', 'resource', 'resource_title', 'status', 'progress',
                  'started_at', 'completed_at', 'has_checkpoints',
                  'in_current_plan']
        read_only_fields = ['status', 'started_at', 'completed_at',
                            'resource_title', 'has_checkpoints',
                            'in_current_plan']

    def get_has_checkpoints(self, obj) -> bool:
        # Prefer the annotated value from the list view's queryset; fall back
        # to a direct count on single-object endpoints.
        annotated = getattr(obj, 'resource_has_checkpoints', None)
        if annotated is not None:
            return annotated
        # ResourceProgressView (detail) sets no prefetch_related, so this is
        # one extra query on a single object — not an N+1, fine off the list.
        return len(obj.resource.checkpoints.all()) > 0

    def get_in_current_plan(self, obj) -> bool:
        # Annotated by UserProgressListView.get_queryset. Single-object
        # endpoints (ResourceProgressView) don't annotate it; default False —
        # the frontend only consumes this flag on the list to disable
        # out-of-plan rows, so a conservative False off the detail path is safe.
        annotated = getattr(obj, 'in_current_plan_annot', None)
        return bool(annotated) if annotated is not None else False


class UserCheckpointProgressSerializer(serializers.ModelSerializer):
    class Meta:
        model = UserCheckpointProgress
        fields = ['id', 'checkpoint', 'completed_at']
        read_only_fields = ['completed_at']