"""设备模型

管理设备基础信息和折旧计算
"""

from typing import Optional
from datetime import date

from sqlalchemy import String, Boolean, Integer, Date, DECIMAL
from sqlalchemy.orm import Mapped, mapped_column

from app.models.base import BaseModel


class Equipment(BaseModel):
    """设备表"""
    
    __tablename__ = "equipments"
    
    equipment_code: Mapped[str] = mapped_column(
        String(50),
        unique=True,
        nullable=False,
        index=True,
        comment="设备编码"
    )
    equipment_name: Mapped[str] = mapped_column(
        String(100),
        nullable=False,
        comment="设备名称"
    )
    original_value: Mapped[float] = mapped_column(
        DECIMAL(12, 2),
        nullable=False,
        comment="设备原值"
    )
    residual_rate: Mapped[float] = mapped_column(
        DECIMAL(5, 2),
        nullable=False,
        default=5.00,
        comment="残值率(%)"
    )
    service_years: Mapped[int] = mapped_column(
        Integer,
        nullable=False,
        comment="预计使用年限"
    )
    estimated_uses: Mapped[int] = mapped_column(
        Integer,
        nullable=False,
        comment="预计使用次数"
    )
    depreciation_per_use: Mapped[float] = mapped_column(
        DECIMAL(12, 4),
        nullable=False,
        comment="单次折旧成本 = (原值 - 残值) / 总次数"
    )
    purchase_date: Mapped[Optional[date]] = mapped_column(
        Date,
        nullable=True,
        comment="购入日期"
    )
    is_active: Mapped[bool] = mapped_column(
        Boolean,
        nullable=False,
        default=True,
        comment="是否启用"
    )
    
    def calculate_depreciation(self) -> float:
        """计算单次折旧成本"""
        if self.estimated_uses <= 0:
            return 0
        residual_value = float(self.original_value) * float(self.residual_rate) / 100
        return (float(self.original_value) - residual_value) / self.estimated_uses