from apps.utils.serializers import CustomModelSerializer
from rest_framework import serializers
from .models import Paper


class PaperListSerializer(CustomModelSerializer):
    abstract = serializers.SerializerMethodField()
    pdf_url = serializers.SerializerMethodField()
    xml_url = serializers.SerializerMethodField()

    class Meta:
        model = Paper
        fields = '__all__'

    def get_abstract(self, obj) -> str:
        # PaperAbstract 是 O2O,related_name="abstract";无行 / has_abstract=False 时返空串
        abs_obj = getattr(obj, "abstract", None)
        if abs_obj is None:
            return ""
        return abs_obj.abstract or ""

    def _media_url(self, obj, ext: str) -> str:
        """拼 /media/papers/<Y>/<M>/<D>/<safe_doi>.<ext> 静态直链。

        date 缺失(unknown 目录)/ doi 缺失返空串 —— LLM 拿到空串就知道没法直链下,
        改走 get_paper / paper_pdf_view。
        """
        if obj.publication_date is None or not obj.doi:
            return ""
        safe_doi = obj.doi.replace("/", "_")
        d = obj.publication_date
        path = f"/media/papers/{d.year}/{d.month}/{d.day}/{safe_doi}.{ext}"
        request = self.context.get("request")
        return request.build_absolute_uri(path) if request else path

    def get_pdf_url(self, obj) -> str:
        return self._media_url(obj, "pdf") if obj.has_fulltext_pdf else ""

    def get_xml_url(self, obj) -> str:
        return self._media_url(obj, "xml") if obj.has_fulltext_xml else ""