from django.db import transaction
from rest_framework import serializers

from .models import (
    Account,
    CompanySettings,
    Employee,
    Invoice,
    InvoiceLine,
    Party,
    Payslip,
    Product,
    TreasuryTxn,
    Voucher,
    VoucherLine,
)


class AccountSerializer(serializers.ModelSerializer):
    parentId = serializers.PrimaryKeyRelatedField(
        source='parent', queryset=Account.objects.all(), allow_null=True, required=False
    )
    isGroup = serializers.BooleanField(source='is_group', required=False)
    openingBalance = serializers.FloatField(source='opening_balance', required=False)

    class Meta:
        model = Account
        fields = ['id', 'code', 'name', 'type', 'parentId', 'isGroup', 'openingBalance']


class PartySerializer(serializers.ModelSerializer):
    economicCode = serializers.CharField(source='economic_code', required=False, allow_blank=True)
    openingBalance = serializers.FloatField(source='opening_balance', required=False)

    class Meta:
        model = Party
        fields = ['id', 'kind', 'name', 'phone', 'economicCode', 'address', 'openingBalance']


class ProductSerializer(serializers.ModelSerializer):
    salePrice = serializers.FloatField(source='sale_price', required=False)
    purchasePrice = serializers.FloatField(source='purchase_price', required=False)
    reorderLevel = serializers.FloatField(source='reorder_level', required=False)

    class Meta:
        model = Product
        fields = ['id', 'code', 'name', 'unit', 'salePrice', 'purchasePrice', 'stock', 'reorderLevel']


class VoucherLineSerializer(serializers.ModelSerializer):
    # Lenient: accepts client-generated ids (ignored on write, recreated server-side).
    id = serializers.CharField(required=False)
    accountId = serializers.PrimaryKeyRelatedField(source='account', queryset=Account.objects.all())

    class Meta:
        model = VoucherLine
        fields = ['id', 'accountId', 'description', 'debit', 'credit']


class VoucherSerializer(serializers.ModelSerializer):
    lines = VoucherLineSerializer(many=True)

    class Meta:
        model = Voucher
        fields = ['id', 'number', 'date', 'description', 'status', 'source', 'lines']

    @transaction.atomic
    def create(self, validated_data):
        lines = validated_data.pop('lines', [])
        voucher = Voucher.objects.create(**validated_data)
        for line in lines:
            line.pop('id', None)
            VoucherLine.objects.create(voucher=voucher, **line)
        return voucher

    @transaction.atomic
    def update(self, instance, validated_data):
        lines = validated_data.pop('lines', None)
        for attr, value in validated_data.items():
            setattr(instance, attr, value)
        instance.save()
        if lines is not None:
            instance.lines.all().delete()
            for line in lines:
                line.pop('id', None)
                VoucherLine.objects.create(voucher=instance, **line)
        return instance


class InvoiceLineSerializer(serializers.ModelSerializer):
    # Lenient: accepts client-generated ids (ignored on write, recreated server-side).
    id = serializers.CharField(required=False)
    productId = serializers.PrimaryKeyRelatedField(
        source='product', queryset=Product.objects.all(), allow_null=True, required=False
    )
    unitPrice = serializers.FloatField(source='unit_price', required=False)
    taxRate = serializers.FloatField(source='tax_rate', required=False)

    class Meta:
        model = InvoiceLine
        fields = ['id', 'productId', 'quantity', 'unitPrice', 'discount', 'taxRate']


class InvoiceSerializer(serializers.ModelSerializer):
    partyId = serializers.PrimaryKeyRelatedField(
        source='party', queryset=Party.objects.all(), allow_null=True, required=False
    )
    lines = InvoiceLineSerializer(many=True)

    class Meta:
        model = Invoice
        fields = ['id', 'kind', 'number', 'partyId', 'date', 'status', 'note', 'lines']

    @transaction.atomic
    def create(self, validated_data):
        lines = validated_data.pop('lines', [])
        invoice = Invoice.objects.create(**validated_data)
        for line in lines:
            line.pop('id', None)
            InvoiceLine.objects.create(invoice=invoice, **line)
        return invoice

    @transaction.atomic
    def update(self, instance, validated_data):
        lines = validated_data.pop('lines', None)
        for attr, value in validated_data.items():
            setattr(instance, attr, value)
        instance.save()
        if lines is not None:
            instance.lines.all().delete()
            for line in lines:
                line.pop('id', None)
                InvoiceLine.objects.create(invoice=instance, **line)
        return instance


class TreasuryTxnSerializer(serializers.ModelSerializer):
    partyId = serializers.PrimaryKeyRelatedField(
        source='party', queryset=Party.objects.all(), allow_null=True, required=False
    )

    class Meta:
        model = TreasuryTxn
        fields = ['id', 'number', 'kind', 'method', 'date', 'partyId', 'amount', 'reference', 'description']


class EmployeeSerializer(serializers.ModelSerializer):
    baseSalary = serializers.FloatField(source='base_salary', required=False)
    insuranceNo = serializers.CharField(source='insurance_no', required=False, allow_blank=True)
    hireDate = serializers.DateField(source='hire_date', required=False, allow_null=True)

    class Meta:
        model = Employee
        fields = ['id', 'code', 'name', 'position', 'baseSalary', 'insuranceNo', 'hireDate', 'active']


class PayslipSerializer(serializers.ModelSerializer):
    employeeId = serializers.PrimaryKeyRelatedField(source='employee', queryset=Employee.objects.all())
    baseSalary = serializers.FloatField(source='base_salary', required=False)

    class Meta:
        model = Payslip
        fields = [
            'id', 'employeeId', 'period', 'baseSalary', 'overtime', 'bonus',
            'deductions', 'insurance', 'tax',
        ]


class CompanySettingsSerializer(serializers.ModelSerializer):
    economicCode = serializers.CharField(source='economic_code', required=False, allow_blank=True)
    fiscalYear = serializers.CharField(source='fiscal_year', required=False, allow_blank=True)
    baseCurrency = serializers.CharField(source='base_currency', required=False, allow_blank=True)
    taxRate = serializers.FloatField(source='tax_rate', required=False)
    voucherAccounts = serializers.SerializerMethodField()

    _MAPPING_FIELDS = {
        'bankAccountId': 'bank_account_id',
        'ownerPayableAccountId': 'owner_payable_account_id',
        'customerPayableAccountId': 'customer_payable_account_id',
        'ownerShareAccountId': 'owner_share_account_id',
        'salesIncomeAccountId': 'sales_income_account_id',
    }

    class Meta:
        model = CompanySettings
        fields = [
            'name', 'economicCode', 'fiscalYear', 'baseCurrency',
            'taxRate', 'address', 'phone', 'voucherAccounts',
        ]

    def get_voucherAccounts(self, obj):
        def to_id(value):
            return str(value) if value else ''

        return {
            'bankAccountId': to_id(obj.bank_account_id),
            'ownerPayableAccountId': to_id(obj.owner_payable_account_id),
            'customerPayableAccountId': to_id(obj.customer_payable_account_id),
            'ownerShareAccountId': to_id(obj.owner_share_account_id),
            'salesIncomeAccountId': to_id(obj.sales_income_account_id),
        }

    def _apply_voucher_accounts(self, instance):
        mapping = self.initial_data.get('voucherAccounts')
        if not isinstance(mapping, dict):
            return
        valid_ids = {str(v) for v in Account.objects.values_list('id', flat=True)}
        for camel_key, model_attr in self._MAPPING_FIELDS.items():
            if camel_key not in mapping:
                continue
            raw = mapping.get(camel_key)
            setattr(instance, model_attr, raw if raw in valid_ids else None)

    @transaction.atomic
    def update(self, instance, validated_data):
        for attr, value in validated_data.items():
            setattr(instance, attr, value)
        self._apply_voucher_accounts(instance)
        instance.save()
        return instance