"""
库存与利润核算 Service 层
- MWA 入库事务（悲观锁 FOR UPDATE + 零元隔离）
- 订单利润快照
- 利润报表聚合
"""

from __future__ import annotations

import uuid
from datetime import datetime

from sqlalchemy import func, select, update, text
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.exceptions import BizException, NotFoundException
from app.models.erp import ErpSkuInventory, InventoryFlow, ProductSku
from app.models.cost import ErpOrderItemCost
from app.models.order import ErpOrder, ErpOrderItem
from app.schemas.auth import CurrentUserPayload


# ── MWA 入库事务 ────────────────────────────────────────
async def process_inbound_with_mwa(
    db: AsyncSession,
    sku_id: uuid.UUID,
    company_id: uuid.UUID,
    qty: float,
    purchase_unit_price: float,
    operator_id: uuid.UUID | None = None,
    remark: str | None = None,
    is_special_zero_cost: bool = False,
) -> dict:
    """
    入库事务（悲观锁 + MWA）
    1. SELECT ... FOR UPDATE 锁定库存行
    2. 如果非零元特殊，计算新 MWA
    3. 更新库存 + 记录流水
    """
    # 悲观锁获取库存记录
    inv_stmt = (
        select(ErpSkuInventory)
        .where(
            ErpSkuInventory.sku_id == sku_id,
            ErpSkuInventory.company_id == company_id,
        )
        .with_for_update()
    )
    inv = (await db.execute(inv_stmt)).scalar_one_or_none()

    if inv is None:
        # 首次入库，创建库存记录
        inv = ErpSkuInventory(
            sku_id=sku_id,
            company_id=company_id,
            stock_qty=0,
            mwa_unit_cost=0,
        )
        db.add(inv)
        await db.flush()
        # 重新锁定
        inv = (await db.execute(inv_stmt)).scalar_one()

    old_qty = float(inv.stock_qty or 0)
    old_mwa = float(inv.mwa_unit_cost or 0)
    new_qty = old_qty + qty

    # MWA 计算（零元特殊入库不参与）
    if is_special_zero_cost or purchase_unit_price == 0:
        new_mwa = old_mwa  # 保持原有 MWA
    else:
        if new_qty > 0:
            new_mwa = (old_qty * old_mwa + qty * purchase_unit_price) / new_qty
        else:
            new_mwa = purchase_unit_price

    # 更新库存
    inv.stock_qty = new_qty
    inv.mwa_unit_cost = round(new_mwa, 4)
    inv.updated_at = datetime.utcnow()

    # 记录流水
    flow = InventoryFlow(
        sku_id=sku_id,
        company_id=company_id,
        flow_type="in",
        change_qty=qty,
        reason="purchase_in",
        purchase_unit_price=purchase_unit_price,
        is_special_zero_cost=is_special_zero_cost,
        operator_id=operator_id,
        remark=remark or f"入库 {qty} 件 @ ¥{purchase_unit_price}",
    )
    db.add(flow)

    await db.commit()

    return {
        "sku_id": str(sku_id),
        "old_qty": old_qty,
        "new_qty": new_qty,
        "old_mwa": old_mwa,
        "new_mwa": round(new_mwa, 4),
        "is_special_zero_cost": is_special_zero_cost,
    }


# ── 订单明细成本快照 ────────────────────────────────────
async def snapshot_order_item_costs(
    db: AsyncSession,
    order_id: uuid.UUID,
    company_id: uuid.UUID,
) -> list[dict]:
    """为订单的所有明细行锚定 MWA 成本快照"""
    items_stmt = select(ErpOrderItem).where(
        ErpOrderItem.order_id == order_id,
        ErpOrderItem.is_deleted.is_(False),
    )
    items = (await db.execute(items_stmt)).scalars().all()

    results = []
    for item in items:
        # 查当前 MWA
        inv = (await db.execute(
            select(ErpSkuInventory).where(
                ErpSkuInventory.sku_id == item.sku_id,
                ErpSkuInventory.company_id == company_id,
            )
        )).scalar_one_or_none()

        mwa_cost = float(inv.mwa_unit_cost or 0) if inv else 0
        sell_price = float(item.unit_price or 0)
        qty = float(item.qty or 0)
        profit = (sell_price - mwa_cost) * qty
        profit_rate = (sell_price - mwa_cost) / sell_price if sell_price > 0 else 0

        # 检查是否已有快照
        existing = (await db.execute(
            select(ErpOrderItemCost).where(
                ErpOrderItemCost.order_item_id == item.id
            )
        )).scalar_one_or_none()

        if existing:
            existing.purchase_unit_price = mwa_cost
            existing.profit_amount = round(profit, 2)
            existing.profit_rate = round(profit_rate, 4)
        else:
            cost_snap = ErpOrderItemCost(
                order_item_id=item.id,
                purchase_unit_price=mwa_cost,
                profit_amount=round(profit, 2),
                profit_rate=round(profit_rate, 4),
            )
            db.add(cost_snap)

        results.append({
            "sku_id": str(item.sku_id),
            "qty": qty,
            "sell_price": sell_price,
            "mwa_cost": mwa_cost,
            "profit": round(profit, 2),
            "profit_rate": round(profit_rate * 100, 2),
        })

    await db.commit()
    return results


# ── 利润报表 ────────────────────────────────────────────
async def get_profit_report(
    db: AsyncSession,
    company_id: uuid.UUID,
    start_date: str | None = None,
    end_date: str | None = None,
) -> dict:
    """聚合利润报表"""
    base_where = [
        ErpOrder.company_id == company_id,
        ErpOrder.is_deleted.is_(False),
    ]
    if start_date:
        base_where.append(ErpOrder.order_date >= start_date)
    if end_date:
        base_where.append(ErpOrder.order_date <= end_date)

    # 聚合：每笔订单的利润
    stmt = (
        select(
            ErpOrder.id.label("order_id"),
            ErpOrder.order_no,
            ErpOrder.order_date,
            ErpOrder.total_amount,
            func.sum(ErpOrderItemCost.profit_amount).label("total_profit"),
        )
        .join(ErpOrderItem, ErpOrderItem.order_id == ErpOrder.id)
        .join(ErpOrderItemCost, ErpOrderItemCost.order_item_id == ErpOrderItem.id)
        .where(*base_where)
        .group_by(ErpOrder.id, ErpOrder.order_no, ErpOrder.order_date, ErpOrder.total_amount)
        .order_by(ErpOrder.order_date.desc())
    )
    rows = (await db.execute(stmt)).all()

    orders = []
    total_revenue = 0
    total_profit = 0
    for r in rows:
        revenue = float(r.total_amount or 0)
        profit = float(r.total_profit or 0)
        total_revenue += revenue
        total_profit += profit
        orders.append({
            "order_id": str(r.order_id),
            "order_no": r.order_no,
            "order_date": r.order_date.isoformat() if r.order_date else None,
            "revenue": revenue,
            "profit": profit,
            "profit_rate": round(profit / revenue * 100, 2) if revenue > 0 else 0,
        })

    return {
        "total_revenue": round(total_revenue, 2),
        "total_profit": round(total_profit, 2),
        "overall_profit_rate": round(total_profit / total_revenue * 100, 2) if total_revenue > 0 else 0,
        "orders": orders,
    }