from rest_framework import serializers

from apps.bizapps.models import (
    Account,
    Customer,
    Invoice,
    InvoiceItem,
    LedgerBook,
    LedgerEntry,
    LedgerInstallment,
    Product,
    StockMovement,
    Transaction,
)


class AccountSerializer(serializers.ModelSerializer):
    full_path = serializers.CharField(read_only=True)
    level_display = serializers.CharField(source="get_level_display", read_only=True)
    account_type_display = serializers.CharField(source="get_account_type_display", read_only=True)

    class Meta:
        model = Account
        fields = [
            "id", "code", "name", "level", "level_display", "account_type",
            "account_type_display", "parent", "full_path", "is_system", "is_active",
        ]
        read_only_fields = ["is_system"]


class CustomerSerializer(serializers.ModelSerializer):
    account_code = serializers.CharField(source="account.code", read_only=True, default="")

    class Meta:
        model = Customer
        fields = [
            "id", "name", "phone", "social_platform", "social_handle",
            "email", "address", "notes",
            "total_purchases_count", "total_purchase_amount", "last_purchase_date",
            "outstanding_balance", "account_code", "updated_at",
        ]
        # این‌ها را سرویس‌ها محاسبه می‌کنند، نه کلاینت — وگرنه مانده‌ی بدهی
        # از سمت اپ قابل‌دستکاری می‌شد.
        read_only_fields = [
            "total_purchases_count", "total_purchase_amount", "last_purchase_date",
            "outstanding_balance", "account_code", "updated_at",
        ]


class LedgerInstallmentSerializer(serializers.ModelSerializer):
    class Meta:
        model = LedgerInstallment
        fields = ["id", "amount", "paid_date", "reference", "created_at"]
        # برخلافِ بقیه‌ی مدل‌ها (که UUID را خودِ اپ فلاتر می‌سازد و می‌فرستد)،
        # id قسط را ویو تولید می‌کند — پس نباید از کلاینت الزامی باشد.
        read_only_fields = ["id", "created_at"]

    def validate_amount(self, value):
        if value <= 0:
            raise serializers.ValidationError("مبلغ قسط باید بزرگ‌تر از صفر باشد.")
        return value

    def validate(self, attrs):
        entry: LedgerEntry = self.context["ledger_entry"]
        if not entry.is_debt:
            raise serializers.ValidationError("فقط برای ردیف‌های بدهی‌دار می‌توان قسط ثبت کرد.")
        amount = attrs.get("amount", 0)
        # epsilon کوچک تا خطای گرد‌کردنِ اعشارِ شناور باعثِ ردِ یک قسطِ
        # تسویه‌ی دقیق نشود.
        if amount > entry.remaining_amount + 1:
            raise serializers.ValidationError("مبلغ قسط از مانده‌ی بدهی بیشتر است.")
        return attrs


class LedgerEntrySerializer(serializers.ModelSerializer):
    installments = LedgerInstallmentSerializer(many=True, read_only=True)
    is_debt = serializers.BooleanField(read_only=True)
    professional_type = serializers.CharField(read_only=True)
    paid_amount = serializers.FloatField(read_only=True)
    remaining_amount = serializers.FloatField(read_only=True)
    category_display = serializers.CharField(source="get_category_display", read_only=True)
    account_name = serializers.CharField(source="account.name", read_only=True, default="")
    account_code = serializers.CharField(source="account.code", read_only=True, default="")
    discount_amount = serializers.FloatField(read_only=True)
    tax_amount = serializers.FloatField(read_only=True)
    computed_amount = serializers.FloatField(read_only=True)

    class Meta:
        model = LedgerEntry
        fields = [
            "id", "entry_type", "title", "amount", "category", "category_display",
            "entry_date", "note", "total_amount", "counterparty_name", "counterparty_phone",
            "linked_invoice", "account_name", "account_code",
            "base_amount", "discount_percent", "tax_percent",
            "discount_amount", "tax_amount", "computed_amount",
            "is_debt", "professional_type", "paid_amount", "remaining_amount",
            "installments", "updated_at",
        ]
        read_only_fields = ["linked_invoice", "account_name", "account_code", "updated_at"]

    def validate(self, attrs):
        category = attrs.get("category", getattr(self.instance, "category", ""))
        if category in LedgerEntry.DEBT_CATEGORIES:
            total = attrs.get("total_amount", getattr(self.instance, "total_amount", 0))
            if not total or total <= 0:
                raise serializers.ValidationError(
                    {"total_amount": "برای فروش قسطی/خرید نسیه، مبلغ کل تعهد الزامی است."}
                )
        return attrs


class ProductSerializer(serializers.ModelSerializer):
    is_low_stock = serializers.BooleanField(read_only=True)

    class Meta:
        model = Product
        fields = [
            "id", "name", "sku", "category", "unit", "quantity",
            "unit_price", "purchase_price", "total_purchase_value",
            "low_stock_threshold", "is_low_stock", "is_active",
            "production_date", "expiry_date", "notes", "updated_at",
        ]
        read_only_fields = ["total_purchase_value", "is_low_stock", "updated_at"]


class StockMovementSerializer(serializers.ModelSerializer):
    class Meta:
        model = StockMovement
        fields = ["id", "delta", "quantity_after", "note", "created_at"]
        read_only_fields = fields


class AdjustStockSerializer(serializers.Serializer):
    delta = serializers.FloatField()
    note = serializers.CharField(max_length=255, required=False, allow_blank=True, default="")

    def validate_delta(self, value):
        if value == 0:
            raise serializers.ValidationError("مقدار تغییر نمی‌تواند صفر باشد.")
        return value


class InvoiceItemSerializer(serializers.ModelSerializer):
    class Meta:
        model = InvoiceItem
        fields = ["id", "product", "description", "quantity", "unit_price", "discount_percent", "total_price"]
        read_only_fields = ["total_price"]


class InvoiceSerializer(serializers.ModelSerializer):
    items = InvoiceItemSerializer(many=True, read_only=True)
    payment_type_display = serializers.CharField(source="get_payment_type_display", read_only=True)
    payment_status_display = serializers.CharField(source="get_payment_status_display", read_only=True)
    order_status_display = serializers.CharField(source="get_order_status_display", read_only=True)

    class Meta:
        model = Invoice
        fields = [
            "id", "invoice_number", "invoice_date", "customer",
            "buyer_name", "buyer_phone", "buyer_address",
            "seller_name", "seller_phone", "seller_address",
            "total_amount", "discount_percent", "discount_amount",
            "extra_discount_label", "extra_discount_percent", "extra_discount_amount",
            "tax_lines", "final_amount",
            "payment_type", "payment_type_display",
            "payment_status", "payment_status_display",
            "order_status", "order_status_display",
            "shipping_method", "tracking_code", "notes", "paid_at",
            "items", "created_at", "updated_at",
        ]
        read_only_fields = [
            "invoice_number", "total_amount", "final_amount", "paid_at", "created_at", "updated_at",
        ]


class CreateInvoiceItemSerializer(serializers.Serializer):
    product = serializers.PrimaryKeyRelatedField(queryset=Product.objects.all(), required=False, allow_null=True)
    description = serializers.CharField(max_length=255, required=False, allow_blank=True, default="")
    quantity = serializers.FloatField(min_value=0.0001)
    unit_price = serializers.FloatField(required=False, default=0)
    discount_percent = serializers.FloatField(required=False, default=0, min_value=0, max_value=100)

    def validate(self, attrs):
        if attrs.get("product") is None and not attrs.get("description"):
            raise serializers.ValidationError("برای ردیف بدون کالا، شرح الزامی است.")
        return attrs


class CreateInvoiceSerializer(serializers.Serializer):
    items = CreateInvoiceItemSerializer(many=True)
    customer = serializers.PrimaryKeyRelatedField(queryset=Customer.objects.all(), required=False, allow_null=True)
    invoice_date = serializers.DateTimeField(required=False)
    buyer_name = serializers.CharField(max_length=150, required=False, allow_blank=True, default="")
    buyer_phone = serializers.CharField(max_length=20, required=False, allow_blank=True, default="")
    buyer_address = serializers.CharField(max_length=255, required=False, allow_blank=True, default="")
    seller_name = serializers.CharField(max_length=150, required=False, allow_blank=True, default="")
    seller_phone = serializers.CharField(max_length=20, required=False, allow_blank=True, default="")
    seller_address = serializers.CharField(max_length=255, required=False, allow_blank=True, default="")
    # درصد اولویت دارد: اگر discount_percent مثبت باشد، discount_amount از
    # روی همان محاسبه می‌شود (هم‌الگو با تخفیفِ درصدیِ هر قلم فاکتور)؛
    # discount_amount خامْ فقط برای سازگاری با کلاینت‌های قدیمی نگه داشته
    # شده — اگر درصد صفر باشد همان مقدار مستقیم استفاده می‌شود.
    discount_percent = serializers.FloatField(required=False, default=0, min_value=0, max_value=100)
    discount_amount = serializers.FloatField(required=False, default=0, min_value=0)
    # تخفیفِ ویژه/دوره‌ای — جدا از تخفیفِ بالا، روی مبلغِ بعد از آن اعمال
    # می‌شود. یا با درصد یا با مبلغِ ثابت پر می‌شود.
    extra_discount_label = serializers.CharField(max_length=100, required=False, allow_blank=True, default="")
    extra_discount_percent = serializers.FloatField(required=False, default=0, min_value=0, max_value=100)
    extra_discount_amount = serializers.FloatField(required=False, default=0, min_value=0)
    tax_lines = serializers.ListField(child=serializers.DictField(), required=False, default=list)
    payment_type = serializers.ChoiceField(choices=Invoice.PaymentType.choices, required=False)
    shipping_method = serializers.ChoiceField(choices=Invoice.ShippingMethod.choices, required=False)
    tracking_code = serializers.CharField(max_length=100, required=False, allow_blank=True, default="")
    notes = serializers.CharField(required=False, allow_blank=True, default="")
    send_sms = serializers.BooleanField(required=False, default=False)

    def validate_items(self, value):
        if not value:
            raise serializers.ValidationError("فاکتور باید حداقل یک قلم کالا داشته باشد.")
        return value


class UpdateInvoiceStatusSerializer(serializers.Serializer):
    order_status = serializers.ChoiceField(choices=Invoice.OrderStatus.choices, required=False)
    payment_status = serializers.ChoiceField(choices=Invoice.PaymentStatus.choices, required=False)
    tracking_code = serializers.CharField(max_length=100, required=False, allow_blank=True)

    def validate(self, attrs):
        if not attrs:
            raise serializers.ValidationError("حداقل یکی از فیلدهای وضعیت باید ارسال شود.")
        return attrs


class TransactionSerializer(serializers.ModelSerializer):
    transaction_type_display = serializers.CharField(source="get_transaction_type_display", read_only=True)
    debit_account_name = serializers.CharField(source="debit_account_ref.name", read_only=True, default="")
    credit_account_name = serializers.CharField(source="credit_account_ref.name", read_only=True, default="")

    class Meta:
        model = Transaction
        fields = [
            "id", "transaction_number", "transaction_date", "reference_invoice",
            "transaction_type", "transaction_type_display",
            "debit_account", "credit_account", "debit_account_name", "credit_account_name",
            "amount", "description", "created_at",
        ]
        read_only_fields = fields


class LedgerBookSerializer(serializers.ModelSerializer):
    class Meta:
        model = LedgerBook
        fields = [
            "id", "name", "start_date", "end_date", "opening_balance",
            "is_active", "is_closed", "closed_at", "created_at",
        ]
        read_only_fields = ["id", "is_active", "is_closed", "closed_at", "created_at"]


class OpenLedgerBookSerializer(serializers.Serializer):
    name = serializers.CharField(max_length=120)
    start_date = serializers.DateField()
    end_date = serializers.DateField(required=False, allow_null=True)
    # پیش‌فرض true: انتقالِ مانده سرِ سال مالی کارِ استاندارد است.
    carry_balance = serializers.BooleanField(required=False, default=True)

    def validate(self, attrs):
        end = attrs.get("end_date")
        if end and end <= attrs["start_date"]:
            raise serializers.ValidationError(
                {"end_date": "تاریخ پایان باید بعد از تاریخ شروع باشد."}
            )
        return attrs