from rest_framework import serializers

from .models import Shipment


class ShipmentSerializer(serializers.ModelSerializer):
    """Mirror the ops form's rules, so the API cannot accept what the portal refuses.

    The model tolerates a blank vessel or container and a missing date, because
    records also arrive through this API. But a shipment is what the buyer's page
    shows, so the fields the buyer reads are required here too, and a departure
    after the arrival is refused. The bill of lading and the forwarder stay
    optional; the ports keep their model defaults.
    """

    class Meta:
        model = Shipment
        fields = "__all__"
        read_only_fields = ["id", "created_at"]
        extra_kwargs = {
            "status": {"required": True},
            "vessel_name": {"required": True, "allow_blank": False},
            "container_ref": {"required": True, "allow_blank": False},
            "etd_nigeria": {"required": True, "allow_null": False},
            "eta_uk": {"required": True, "allow_null": False},
        }

    def validate(self, attrs):
        etd = attrs.get("etd_nigeria", getattr(self.instance, "etd_nigeria", None))
        eta = attrs.get("eta_uk", getattr(self.instance, "eta_uk", None))
        if etd and eta and etd > eta:
            raise serializers.ValidationError(
                {"eta_uk": "The ETA cannot be before the ETD. Check the two dates."}
            )
        return attrs