from rest_framework import serializers

from .models import Document


class DocumentListSerializer(serializers.ModelSerializer[Document]):
    cover_url = serializers.SerializerMethodField()

    class Meta:
        model = Document
        fields = [
            "id", "title", "author", "cover_url", "description",
            "file_type", "file_size", "page_count", "tags",
            "is_public", "uploaded_at", "updated_at",
        ]
        read_only_fields = ["id", "uploaded_at", "updated_at"]

    def get_cover_url(self, obj: Document) -> str | None:
        return obj.cover_url


class DocumentDetailSerializer(DocumentListSerializer):
    owner = serializers.PrimaryKeyRelatedField(read_only=True)

    class Meta(DocumentListSerializer.Meta):
        fields = DocumentListSerializer.Meta.fields + ["owner", "file"]


class DocumentUploadSerializer(serializers.ModelSerializer[Document]):
    class Meta:
        model = Document
        fields = [
            "title", "author", "description", "cover", "file",
            "file_type", "file_size", "page_count", "tags", "is_public",
        ]

    def validate_file_size(self, value: int) -> int:
        max_size = 100 * 1024 * 1024  # 100 MB
        if value > max_size:
            raise serializers.ValidationError("File size must not exceed 100 MB.")
        return value