from rest_framework import serializers
from .models import ProcessingBatch


class ProcessingBatchListSerializer(serializers.ModelSerializer):
    qc_status = serializers.SerializerMethodField()
    shipment_status = serializers.SerializerMethodField()

    class Meta:
        model = ProcessingBatch
        fields = ["id", "batch_reference", "origin_facility", "grade", "weight_kg", "harvest_date", "status", "qc_status", "shipment_status", "created_at"]

    def get_qc_status(self, obj):
        qc = obj.qc_results.first()
        if qc:
            return "pass" if qc.overall_pass else "fail"
        return "pending"

    def get_shipment_status(self, obj):
        shipment = obj.shipments.first()
        return shipment.status if shipment else None


class ProcessingBatchDetailSerializer(serializers.ModelSerializer):
    created_by_name = serializers.CharField(source="created_by.full_name", read_only=True)
    qc_results = serializers.SerializerMethodField()
    shipments = serializers.SerializerMethodField()
    documents = serializers.SerializerMethodField()

    class Meta:
        model = ProcessingBatch
        fields = "__all__"

    def get_qc_results(self, obj):
        qc = obj.qc_results.first()
        if not qc:
            return None
        from apps.qc.serializers import QCResultSerializer
        return QCResultSerializer(qc).data

    def get_shipments(self, obj):
        shipments = obj.shipments.all()
        from apps.shipments.serializers import ShipmentSerializer
        return ShipmentSerializer(shipments, many=True).data

    def get_documents(self, obj):
        docs = obj.documents.all()
        from apps.documents.serializers import DocumentSerializer
        return DocumentSerializer(docs, many=True).data


# Mirrors apps/ops/forms.py: a QC status is set by recording a QC result, not by
# hand, and a failed batch is sticky — only a new result moves it. The portal
# enforces this in BatchForm; without the same rule here the write serializer is
# a way around the screen.
QC_SET_STATUSES = {
    ProcessingBatch.Status.QC_PASS,
    ProcessingBatch.Status.QC_FAIL,
}


class ProcessingBatchWriteSerializer(serializers.ModelSerializer):
    class Meta:
        model = ProcessingBatch
        fields = ["id", "batch_reference", "harvest_date", "weight_kg", "grade", "origin_facility", "notes", "status"]
        read_only_fields = ["id"]

    def validate_status(self, status):
        instance = self.instance
        unchanged = instance is not None and status == instance.status
        if status in QC_SET_STATUSES and not unchanged:
            raise serializers.ValidationError(
                f"Batch status {ProcessingBatch.Status(status).label} is set by the "
                "QC result, not by hand."
            )
        if (
            instance is not None
            and instance.status == ProcessingBatch.Status.QC_FAIL
            and status != ProcessingBatch.Status.QC_FAIL
        ):
            raise serializers.ValidationError(
                "A batch that has failed QC cannot be moved by hand; a new QC "
                "result is what moves it."
            )
        return status