"""批次 D4 · 税率测试。

覆盖：价内税拆分数学、行税率解析优先级、开单落税率与税额、凭证销项/进项拆分、
抹零在税后、报表口径（收入为不含税）、税率 0 时完全兼容老行为。
"""

import pytest
from datetime import date
from decimal import Decimal
from model_bakery import baker

from apps.catalog.models import Product
from apps.inventory.models import Warehouse
from apps.partner.models import Customer, Supplier
from apps.core.services import compute_tax, resolve_tax_rate
from apps.sales import services as sales_services
from apps.sales.models import SalesBill
from apps.purchase import services as purchase_services
from apps.finance.models import Account, Voucher
from apps.finance import services as fin_services


@pytest.fixture
def warehouse(db, tenant):
    return baker.make(Warehouse, tenant=tenant, code="WH01", name="主仓")


@pytest.fixture
def customer(db, tenant):
    return baker.make(Customer, tenant=tenant, code="C001", name="张三便利店",
                      credit_limit=Decimal("100000"))


@pytest.fixture
def supplier(db, tenant):
    return baker.make(Supplier, tenant=tenant, code="S001", name="上游厂")


@pytest.fixture
def chart(db, tenant):
    """初始化会计科目（凭证测试需要）。"""
    fin_services.init_chart_of_accounts(tenant)
    return True


# ============================================================
# 价内税拆分
# ============================================================


def test_compute_tax_exact_13pct():
    """113 含税 @13% → 100 + 13（整除，无尾差）。"""
    out = compute_tax(Decimal("113"), Decimal("0.13"))
    assert out["net"] == Decimal("100.0000")
    assert out["tax"] == Decimal("13.0000")
    assert out["net"] + out["tax"] == out["gross"]


def test_compute_tax_zero_rate():
    out = compute_tax(Decimal("100"), Decimal("0"))
    assert out["net"] == Decimal("100.0000")
    assert out["tax"] == Decimal("0.0000")


def test_compute_tax_none_rate():
    out = compute_tax(Decimal("50"), None)
    assert out["tax"] == Decimal("0.0000")
    assert out["net"] == Decimal("50.0000")


@pytest.mark.parametrize("amount,rate,expect_tax", [
    ("100", "0.13", "11.5044"),     # 100/1.13 → 净 88.4956
    ("50.5", "0.06", "2.8585"),
    ("1000", "0.09", "82.5688"),
    ("9.9", "0.03", "0.2883"),
])
def test_compute_tax_various_rates(amount, rate, expect_tax):
    out = compute_tax(Decimal(amount), Decimal(rate))
    assert out["tax"] == Decimal(expect_tax)
    # 不留尾差：净 + 税 = 含税
    assert out["net"] + out["tax"] == out["gross"]


def test_compute_tax_never_negative_or_over():
    """税额必须落在 [0, 含税额] 区间。"""
    for amt in ("0.01", "1", "100"):
        for rate in ("0", "0.01", "0.13", "0.5"):
            out = compute_tax(Decimal(amt), Decimal(rate))
            assert Decimal("0") <= out["tax"] <= out["gross"]


# ============================================================
# 税率解析优先级
# ============================================================


def test_resolve_tax_rate_line_overrides_product(db, tenant):
    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   tax_rate=Decimal("0.13"))
    assert resolve_tax_rate(p, {"tax_rate": "0.06"}) == Decimal("0.06")


def test_resolve_tax_rate_falls_back_to_product(db, tenant):
    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   tax_rate=Decimal("0.09"))
    assert resolve_tax_rate(p, {}) == Decimal("0.09")


def test_resolve_tax_rate_default_zero_when_unset(db, tenant):
    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   tax_rate=Decimal("0"))
    assert resolve_tax_rate(p, {}) == Decimal("0")


# ============================================================
# 开单落税率/税额
# ============================================================


def test_sales_bill_lines_carry_tax(db, tenant, warehouse, customer):
    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   sale_price=Decimal("113"), tax_rate=Decimal("0.13"))
    bill = sales_services.create_sales_bill(
        tenant=tenant, customer=customer, warehouse=warehouse,
        lines=[{"product": p, "quantity": 1, "unit_price": "113"}],
    )
    line = bill.lines.first()
    assert line.tax_rate == Decimal("0.1300")
    assert line.tax_amount == Decimal("13.0000")
    # 单据总额是含税金额（价内口径不变）
    assert bill.total_amount == Decimal("113.0000")


def test_sales_bill_line_tax_override(db, tenant, warehouse, customer):
    p = baker.make(Product, tenant=tenant, code="P001", name="农产品",
                   sale_price=Decimal("106"), tax_rate=Decimal("0.13"))
    bill = sales_services.create_sales_bill(
        tenant=tenant, customer=customer, warehouse=warehouse,
        lines=[{"product": p, "quantity": 1, "unit_price": "106",
                "tax_rate": "0.06"}],
    )
    assert bill.lines.first().tax_amount == Decimal("6.0000")   # 106/1.06


def test_purchase_bill_lines_carry_tax(db, tenant, warehouse, supplier):
    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   tax_rate=Decimal("0.13"))
    bill = purchase_services.create_purchase_bill(
        tenant=tenant, supplier=supplier, warehouse=warehouse,
        lines=[{"product": p, "quantity": 10, "unit_price": "11.3"}],
    )
    line = bill.lines.first()
    assert line.tax_rate == Decimal("0.1300")
    assert line.tax_amount == Decimal("13.0000")     # 113 / 1.13
    assert bill.total_amount == Decimal("113.0000")


def test_zero_rate_bill_has_zero_tax(db, tenant, warehouse, customer):
    """税率 0（默认商品）：行为与 D4 之前完全一致。"""
    p = baker.make(Product, tenant=tenant, code="P001", name="免税品",
                   sale_price=Decimal("100"), tax_rate=Decimal("0"))
    bill = sales_services.create_sales_bill(
        tenant=tenant, customer=customer, warehouse=warehouse,
        lines=[{"product": p, "quantity": 1, "unit_price": "100"}],
    )
    assert bill.lines.first().tax_amount == Decimal("0.0000")
    assert bill.total_amount == Decimal("100.0000")


def test_round_off_applied_after_tax(db, tenant, warehouse, customer):
    """抹零在税后：行金额含税 → 合计 → 抹零 → 应收净额。"""
    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   sale_price=Decimal("113.6"), tax_rate=Decimal("0.13"))
    bill = sales_services.create_sales_bill(
        tenant=tenant, customer=customer, warehouse=warehouse,
        lines=[{"product": p, "quantity": 1, "unit_price": "113.6"}],
        round_to="1",
    )
    assert bill.total_amount == Decimal("113")       # 113.6 抹到 113
    assert bill.round_off == Decimal("0.6")
    # 行税额仍按未抹零的含税金额计算
    assert bill.lines.first().tax_amount == Decimal("13.0690")


# ============================================================
# 凭证：销项税 / 进项税拆分
# ============================================================


def test_receivable_voucher_splits_output_tax(db, tenant, warehouse, customer, chart):
    from apps.inventory import services as inv

    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   sale_price=Decimal("113"), tax_rate=Decimal("0.13"))
    inv.inbound(tenant=tenant, warehouse=warehouse, product=p,
                quantity=Decimal("10"), unit_cost=Decimal("50"))
    bill = sales_services.create_sales_bill(
        tenant=tenant, customer=customer, warehouse=warehouse,
        lines=[{"product": p, "quantity": 1, "unit_price": "113"}],
    )
    sales_services.confirm_sales_bill(bill)

    v = Voucher.objects.filter(tenant=tenant, source_type="sale").first()
    assert v is not None
    codes = {e.account.code: e for e in v.entries.select_related("account")}
    assert Decimal(codes["1122"].debit) == Decimal("113.0000")     # 应收全额
    assert Decimal(codes["6001"].credit) == Decimal("100.0000")    # 收入不含税
    assert Decimal(codes["2221"].credit) == Decimal("13.0000")     # 销项税
    # 借贷平衡
    total_debit = sum(Decimal(e.debit) for e in v.entries.all())
    total_credit = sum(Decimal(e.credit) for e in v.entries.all())
    assert total_debit == total_credit


def test_payable_voucher_splits_input_tax(db, tenant, warehouse, supplier, chart):
    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   tax_rate=Decimal("0.13"))
    bill = purchase_services.create_purchase_bill(
        tenant=tenant, supplier=supplier, warehouse=warehouse,
        lines=[{"product": p, "quantity": 10, "unit_price": "11.3"}],
    )
    purchase_services.confirm_purchase_bill(bill)

    v = Voucher.objects.filter(tenant=tenant, source_type="purchase").first()
    assert v is not None
    codes = {e.account.code: e for e in v.entries.select_related("account")}
    assert Decimal(codes["1403"].debit) == Decimal("100.0000")     # 存货不含税
    assert Decimal(codes["2222"].debit) == Decimal("13.0000")      # 进项税
    assert Decimal(codes["2202"].credit) == Decimal("113.0000")    # 应付全额
    total_debit = sum(Decimal(e.debit) for e in v.entries.all())
    total_credit = sum(Decimal(e.credit) for e in v.entries.all())
    assert total_debit == total_credit


def test_voucher_without_tax_keeps_two_entries(db, tenant, warehouse, customer, chart):
    """税率 0 时不产生税费分录（老行为不变）。"""
    from apps.inventory import services as inv

    p = baker.make(Product, tenant=tenant, code="P001", name="免税品",
                   sale_price=Decimal("100"), tax_rate=Decimal("0"))
    inv.inbound(tenant=tenant, warehouse=warehouse, product=p,
                quantity=Decimal("10"), unit_cost=Decimal("50"))
    bill = sales_services.create_sales_bill(
        tenant=tenant, customer=customer, warehouse=warehouse,
        lines=[{"product": p, "quantity": 1, "unit_price": "100"}],
    )
    sales_services.confirm_sales_bill(bill)

    v = Voucher.objects.filter(tenant=tenant, source_type="sale").first()
    codes = {e.account.code for e in v.entries.select_related("account")}
    assert "2221" not in codes
    assert codes == {"1122", "6001"}


# ============================================================
# 报表口径
# ============================================================


def test_income_statement_revenue_is_net_of_tax(db, tenant, warehouse, customer, chart):
    """利润表营业收入取 6001 贷方发生额 = 不含税净额。"""
    from apps.inventory import services as inv
    from apps.finance import services as fin

    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   sale_price=Decimal("113"), tax_rate=Decimal("0.13"))
    inv.inbound(tenant=tenant, warehouse=warehouse, product=p,
                quantity=Decimal("10"), unit_cost=Decimal("50"))
    bill = sales_services.create_sales_bill(
        tenant=tenant, customer=customer, warehouse=warehouse,
        lines=[{"product": p, "quantity": 1, "unit_price": "113"}],
    )
    sales_services.confirm_sales_bill(bill)

    period = fin.current_period(tenant)
    data = fin.income_statement(tenant, period)
    assert Decimal(data["total_revenue"]) == Decimal("100.0000")   # 不含税


def test_tax_accounts_exist_in_chart(db, tenant, chart):
    codes = set(Account.objects.filter(tenant=tenant).values_list("code", flat=True))
    assert "2221" in codes     # 销项
    assert "2222" in codes     # 进项


def test_balance_sheet_stays_balanced_with_tax(db, tenant, warehouse, customer, chart):
    from apps.inventory import services as inv
    from apps.finance import services as fin

    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   sale_price=Decimal("113"), tax_rate=Decimal("0.13"))
    inv.inbound(tenant=tenant, warehouse=warehouse, product=p,
                quantity=Decimal("10"), unit_cost=Decimal("50"))
    bill = sales_services.create_sales_bill(
        tenant=tenant, customer=customer, warehouse=warehouse,
        lines=[{"product": p, "quantity": 1, "unit_price": "113"}],
    )
    sales_services.confirm_sales_bill(bill)

    period = fin.current_period(tenant)
    bs = fin.balance_sheet(tenant, period)
    assert bs["balanced"] is True


# ============================================================
# API 级：税率随开单接口落地
# ============================================================


@pytest.fixture
def auth_client(db, user, tenant):
    from rest_framework.test import APIClient
    from rest_framework_simplejwt.tokens import RefreshToken

    c = APIClient()
    refresh = RefreshToken.for_user(user)
    c.credentials(
        HTTP_AUTHORIZATION=f"Bearer {refresh.access_token}",
        HTTP_X_TENANT_ID=tenant.code,
    )
    return c


def test_units_api_exposes_tax_rate(db, auth_client, tenant):
    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   sale_price=Decimal("113"), tax_rate=Decimal("0.13"))
    resp = auth_client.get(f"/api/v1/catalog/products/{p.id}/units/")
    assert resp.status_code == 200, resp.content
    assert Decimal(resp.json()["tax_rate"]) == Decimal("0.13")


def test_create_bill_api_returns_tax_fields(db, auth_client, tenant, warehouse, customer):
    from apps.inventory import services as inv

    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   sale_price=Decimal("113"), tax_rate=Decimal("0.13"))
    inv.inbound(tenant=tenant, warehouse=warehouse, product=p,
                quantity=Decimal("10"), unit_cost=Decimal("50"))
    resp = auth_client.post("/api/v1/sales/bills/create-bill/", {
        "customer": customer.id, "warehouse": warehouse.id,
        "lines": [{"product": p.id, "quantity": 1, "unit_price": "113"}],
    }, format="json")
    assert resp.status_code == 201, resp.content
    body = resp.json()
    line = body["lines"][0]
    assert Decimal(line["tax_rate"]) == Decimal("0.13")
    assert Decimal(line["tax_amount"]) == Decimal("13.0000")
    assert Decimal(body["tax_total"]) == Decimal("13.0000")
    # 单据总额仍是含税（价内口径）
    assert Decimal(body["total_amount"]) == Decimal("113.0000")


def test_purchase_create_bill_api_tax_fields(db, auth_client, tenant, warehouse, supplier):
    p = baker.make(Product, tenant=tenant, code="P001", name="可乐",
                   tax_rate=Decimal("0.13"))
    resp = auth_client.post("/api/v1/purchase/bills/create-bill/", {
        "supplier": supplier.id, "warehouse": warehouse.id,
        "lines": [{"product": p.id, "quantity": 10, "unit_price": "11.3"}],
    }, format="json")
    assert resp.status_code == 201, resp.content
    line = resp.json()["lines"][0]
    assert Decimal(line["tax_amount"]) == Decimal("13.0000")