from __future__ import annotations

from dataclasses import dataclass
from decimal import Decimal
from typing import Optional


@dataclass(frozen=True)
class ThreeStatus:
    order_status: str
    delivery_status: str
    pay_status: str


def _to_decimal(v) -> Decimal:
    try:
        if v is None:
            return Decimal("0")
        if isinstance(v, Decimal):
            return v
        return Decimal(str(v))
    except Exception:
        return Decimal("0")


def derive_three_status_from_legacy(
    legacy_status: Optional[str],
    *,
    paid_amount=None,
) -> ThreeStatus:
    """
    阶段A兼容：从旧 status 推导三字段。
    约束：旧 status 本身混合了支付/配送/订单生命周期，因此只能尽力推断；
    若业务侧已有更精确来源（例如配送任务表/结算表），后续阶段再增强。
    """
    s = (legacy_status or "").strip() or "pending_payment"
    paid = _to_decimal(paid_amount)

    # 默认：仅保留新主状态模型
    order_status = "pending_confirm" if paid > 0 else "pending_payment"
    delivery_status = "pending_dispatch"
    pay_status = "paid" if paid > 0 else "pending_payment"

    if s == "cancelled":
        order_status = "cancelled"
    elif s == "completed":
        order_status = "completed"
        delivery_status = "delivered"
    elif s == "pending_payment":
        order_status = "pending_payment"
        pay_status = "pending_payment"
        delivery_status = "pending_dispatch"
    elif s == "delivering":
        order_status = "pending_confirm"
        delivery_status = "delivering"
    elif s == "pending_confirm":
        order_status = "pending_confirm"
        delivery_status = "delivered"
    elif s == "pending_review_cancel":
        order_status = "pending_confirm"
        delivery_status = "pending_dispatch"
        pass
    elif s == "refunding":
        pay_status = "refunding"

    return ThreeStatus(order_status=order_status, delivery_status=delivery_status, pay_status=pay_status)


def derive_legacy_status_from_three(
    *,
    order_status: Optional[str],
    delivery_status: Optional[str],
    pay_status: Optional[str],
) -> str:
    """
    阶段A兼容：从三字段反推旧 status（用于旧前端/旧筛选参数兼容）。
    """
    o = (order_status or "").strip()
    d = (delivery_status or "").strip()
    p = (pay_status or "").strip()

    if o == "cancelled":
        return "cancelled"
    if p == "refunding":
        return "refunding"
    if o == "completed":
        return "completed"

    if o == "pending_payment":
        return "pending_payment"
    if d == "pending_dispatch":
        return "pending_confirm"
    if d == "delivering":
        return "delivering"
    if d == "delivered":
        return "pending_confirm"

    return "pending_payment"