"""一维优化下料服务：首递减(FFD)装箱算法，输出切割方案与利用率。

对齐目标站 optimize1d 语义：输入订单型材需求 + 库存原料，输出每根原料的切割组合。
"""
from dataclasses import dataclass, field


@dataclass
class BarDemand:
    """一段型材需求。"""
    length: int      # 需求长度(mm)
    qty: int         # 数量
    label: str = ""  # 用途标签


@dataclass
class StockBar:
    """库存原料。"""
    length: int      # 原料长度(mm)
    qty: int         # 库存根数
    label: str = ""


@dataclass
class CutPiece:
    length: int
    label: str = ""


@dataclass
class CutPlan:
    """一根原料的切割方案。"""
    stock_length: int
    stock_label: str
    pieces: list[CutPiece] = field(default_factory=list)
    waste: int = 0   # 余料浪费


# 锯口损耗(mm)，每次切割损耗一段
KERF_DEFAULT = 5


def optimize_1d(demands: list[BarDemand], stocks: list[StockBar],
                kerf: int = KERF_DEFAULT) -> dict:
    """首递减装箱：长件优先装入可容纳的原料，输出方案与统计。"""
    # 展开需求并降序
    pieces: list[CutPiece] = []
    for d in demands:
        pieces.extend(CutPiece(length=d.length, label=d.label) for _ in range(max(0, d.qty)))
    pieces.sort(key=lambda p: p.length, reverse=True)

    # 展开库存（可切割长度 = 原料长）
    avail: list[dict] = []
    for s in stocks:
        for _ in range(max(0, s.qty)):
            avail.append({"length": s.length, "label": s.label, "pieces": [], "used": 0})

    unplaced: list[CutPiece] = []
    for piece in pieces:
        # 找第一根装得下的原料（剩余空间 >= 件长 + 锯口）
        placed = False
        for bar in avail:
            remain = bar["length"] - bar["used"]
            cost = piece.length + (kerf if bar["pieces"] else 0)
            if remain >= cost:
                bar["pieces"].append(piece)
                bar["used"] += cost
                placed = True
                break
        if not placed:
            unplaced.append(piece)

    plans = [
        CutPlan(
            stock_length=b["length"],
            stock_label=b["label"],
            pieces=b["pieces"],
            waste=b["length"] - b["used"],
        )
        for b in avail if b["pieces"]
    ]
    total_demand = sum(p.length for p in pieces)
    total_stock = sum(p.stock_length for p in plans)
    return {
        "plans": [
            {
                "stock_length": p.stock_length,
                "stock_label": p.stock_label,
                "pieces": [{"length": c.length, "label": c.label} for c in p.pieces],
                "waste": p.waste,
            }
            for p in plans
        ],
        "unplaced": [{"length": c.length, "label": c.label} for c in unplaced],
        "stats": {
            "total_pieces": len(pieces),
            "placed_pieces": len(pieces) - len(unplaced),
            "stock_bars_used": len(plans),
            "total_demand_mm": total_demand,
            "total_stock_mm": total_stock,
            "utilization": round(total_demand / total_stock, 4) if total_stock else 0,
            "kerf_mm": kerf,
        },
    }