from rest_framework import serializers
from .models import Fertilizer, FertilizationPlan, FertilizationEntry


class FertilizerSerializer(serializers.ModelSerializer):
    class Meta:
        model = Fertilizer
        fields = '__all__'


class FertilizationEntrySerializer(serializers.ModelSerializer):
    field_name = serializers.CharField(source='field.name', read_only=True)
    field_area_tan = serializers.DecimalField(
        source='field.area_tan', max_digits=6, decimal_places=4, read_only=True
    )
    fertilizer_name = serializers.CharField(source='fertilizer.name', read_only=True)

    class Meta:
        model = FertilizationEntry
        fields = ['id', 'field', 'field_name', 'field_area_tan', 'fertilizer', 'fertilizer_name', 'bags']


class FertilizationPlanSerializer(serializers.ModelSerializer):
    variety_name = serializers.SerializerMethodField()
    crop_name = serializers.SerializerMethodField()
    entries = FertilizationEntrySerializer(many=True, read_only=True)
    field_count = serializers.SerializerMethodField()
    fertilizer_count = serializers.SerializerMethodField()

    class Meta:
        model = FertilizationPlan
        fields = [
            'id', 'name', 'year', 'variety', 'variety_name', 'crop_name',
            'entries', 'field_count', 'fertilizer_count', 'created_at', 'updated_at'
        ]

    def get_variety_name(self, obj):
        return obj.variety.name

    def get_crop_name(self, obj):
        return obj.variety.crop.name

    def get_field_count(self, obj):
        return obj.entries.values('field').distinct().count()

    def get_fertilizer_count(self, obj):
        return obj.entries.values('fertilizer').distinct().count()


class FertilizationPlanWriteSerializer(serializers.ModelSerializer):
    """保存用（entries を一括で受け取る）"""
    entries = serializers.ListField(child=serializers.DictField(), write_only=True, required=False)

    class Meta:
        model = FertilizationPlan
        fields = ['id', 'name', 'year', 'variety', 'entries']

    def create(self, validated_data):
        entries_data = validated_data.pop('entries', [])
        plan = FertilizationPlan.objects.create(**validated_data)
        self._save_entries(plan, entries_data)
        return plan

    def update(self, instance, validated_data):
        entries_data = validated_data.pop('entries', None)
        for attr, value in validated_data.items():
            setattr(instance, attr, value)
        instance.save()
        if entries_data is not None:
            instance.entries.all().delete()
            self._save_entries(instance, entries_data)
        return instance

    def _save_entries(self, plan, entries_data):
        for entry in entries_data:
            FertilizationEntry.objects.create(
                plan=plan,
                field_id=entry['field_id'],
                fertilizer_id=entry['fertilizer_id'],
                bags=entry['bags'],
            )