"""
余额相关 Schema

定义余额数据的验证和序列化规则。

设计说明：
- 内部存储使用整数单位（units），外部显示使用小数（display）
- 1.00 显示余额 = 1000 单位额度
"""

from datetime import datetime
from typing import Annotated

from pydantic import Field, field_validator, computed_field

from app.schemas.base import BaseSchema, PaginatedResponse
from app.models.balance import TransactionType, TransactionStatus


# ============================================================
# 余额单位转换工具
# ============================================================

UNITS_PER_DISPLAY = 1000  # 1.00 显示余额 = 1000 单位额度


def display_to_units(display_amount: float) -> int:
    """将显示金额转换为单位额度"""
    return int(round(display_amount * UNITS_PER_DISPLAY))


def units_to_display(units: int) -> float:
    """将单位额度转换为显示金额"""
    return units / UNITS_PER_DISPLAY


def format_display(units: int) -> str:
    """格式化显示金额（2 位小数）"""
    return f"{units / UNITS_PER_DISPLAY:.2f}"


# ============================================================
# 余额账户 Schema
# ============================================================

class BalanceResponse(BaseSchema):
    """余额信息响应"""
    
    user_id: str
    balance_units: Annotated[
        int,
        Field(description="当前余额（单位额度）"),
    ]
    frozen_units: Annotated[
        int,
        Field(description="冻结余额（单位额度）"),
    ]
    total_recharged_units: Annotated[
        int,
        Field(description="累计充值（单位额度）"),
    ]
    total_consumed_units: Annotated[
        int,
        Field(description="累计消费（单位额度）"),
    ]
    
    @computed_field
    @property
    def balance(self) -> str:
        """显示余额（2 位小数）"""
        return format_display(self.balance_units)
    
    @computed_field
    @property
    def available_balance(self) -> str:
        """显示可用余额（2 位小数）"""
        return format_display(self.balance_units - self.frozen_units)
    
    @computed_field
    @property
    def frozen_balance(self) -> str:
        """显示冻结余额（2 位小数）"""
        return format_display(self.frozen_units)
    
    @computed_field
    @property
    def total_recharged(self) -> str:
        """显示累计充值（2 位小数）"""
        return format_display(self.total_recharged_units)
    
    @computed_field
    @property
    def total_consumed(self) -> str:
        """显示累计消费（2 位小数）"""
        return format_display(self.total_consumed_units)


class BalanceSummaryResponse(BaseSchema):
    """余额简要信息响应（用于嵌入用户信息）"""
    
    balance: str = Field(description="当前余额")
    available_balance: str = Field(description="可用余额")


# ============================================================
# 交易记录 Schema
# ============================================================

class TransactionResponse(BaseSchema):
    """交易记录响应"""
    
    id: str
    transaction_type: TransactionType
    status: TransactionStatus
    amount_units: Annotated[
        int,
        Field(description="交易金额（单位额度，正数收入，负数支出）"),
    ]
    balance_before_units: Annotated[
        int,
        Field(description="交易前余额（单位额度）"),
    ]
    balance_after_units: Annotated[
        int,
        Field(description="交易后余额（单位额度）"),
    ]
    reference_type: str | None
    reference_id: str | None
    description: str | None
    created_at: datetime
    
    @computed_field
    @property
    def amount(self) -> str:
        """显示交易金额（带符号，2 位小数）"""
        return f"{self.amount_units / UNITS_PER_DISPLAY:+.2f}"
    
    @computed_field
    @property
    def balance_before(self) -> str:
        """显示交易前余额（2 位小数）"""
        return format_display(self.balance_before_units)
    
    @computed_field
    @property
    def balance_after(self) -> str:
        """显示交易后余额（2 位小数）"""
        return format_display(self.balance_after_units)


class TransactionListResponse(PaginatedResponse[TransactionResponse]):
    """交易记录列表响应"""
    pass


# ============================================================
# 扣款请求 Schema
# ============================================================

class DeductionRequest(BaseSchema):
    """扣款请求"""
    
    amount: Annotated[
        float,
        Field(
            gt=0,
            description="扣款金额（显示金额，如 1.00）",
            examples=[1.00, 0.50],
        ),
    ]
    reference_type: Annotated[
        str | None,
        Field(
            default=None,
            max_length=64,
            description="关联业务类型",
            examples=["api_call", "service_fee"],
        ),
    ]
    reference_id: Annotated[
        str | None,
        Field(
            default=None,
            max_length=64,
            description="关联业务 ID",
        ),
    ]
    description: Annotated[
        str | None,
        Field(
            default=None,
            max_length=255,
            description="交易描述",
        ),
    ]
    idempotency_key: Annotated[
        str | None,
        Field(
            default=None,
            max_length=64,
            description="幂等键（防止重复扣款）",
        ),
    ]
    
    @field_validator("amount")
    @classmethod
    def validate_amount(cls, v: float) -> float:
        """验证金额精度"""
        # 最小精度 0.001（即 1 单位额度）
        if round(v, 3) != v:
            raise ValueError("金额精度不能超过 3 位小数")
        return v
    
    @property
    def amount_units(self) -> int:
        """转换为单位额度"""
        return display_to_units(self.amount)


class DeductionResponse(BaseSchema):
    """扣款响应"""
    
    transaction_id: str
    amount: str = Field(description="扣款金额")
    balance_before: str = Field(description="扣款前余额")
    balance_after: str = Field(description="扣款后余额")


# ============================================================
# 管理员操作 Schema
# ============================================================

class AdminAdjustmentRequest(BaseSchema):
    """管理员余额调整请求"""
    
    user_id: Annotated[
        str,
        Field(description="目标用户 ID"),
    ]
    amount: Annotated[
        float,
        Field(
            description="调整金额（正数增加，负数减少）",
            examples=[10.00, -5.00],
        ),
    ]
    reason: Annotated[
        str,
        Field(
            min_length=1,
            max_length=255,
            description="调整原因",
        ),
    ]
    
    @field_validator("amount")
    @classmethod
    def validate_amount(cls, v: float) -> float:
        """验证金额精度"""
        if round(v, 3) != v:
            raise ValueError("金额精度不能超过 3 位小数")
        if v == 0:
            raise ValueError("调整金额不能为 0")
        return v
    
    @property
    def amount_units(self) -> int:
        """转换为单位额度"""
        return display_to_units(self.amount)


class AdminBalanceResponse(BaseSchema):
    """管理员查看的余额信息（包含更多细节）"""
    
    user_id: str
    username: str
    balance: str
    available_balance: str
    frozen_balance: str
    total_recharged: str
    total_consumed: str
    version: int
    created_at: datetime
    updated_at: datetime