from pydantic import BaseModel, Field, field_validator
from datetime import date, datetime, timezone
from typing import Optional, List


def parse_date(value):
    """解析日期字符串"""
    if value is None or value == '':
        return None
    if isinstance(value, date):
        return value
    if isinstance(value, datetime):
        return value.date()
    formats = [
        '%Y-%m-%d',
        '%Y-%m-%dT%H:%M:%S',
        '%Y-%m-%d %H:%M:%S',
        '%Y-%m-%dT%H:%M:%S.%f',
    ]
    for fmt in formats:
        try:
            return datetime.strptime(value, fmt).date()
        except ValueError:
            continue
    try:
        return date.fromisoformat(value)
    except ValueError:
        raise ValueError(f"无法解析日期: {value}")


# ============ 纪念日分类 Schema ============

class AnniversaryCategoryBase(BaseModel):
    """纪念日分类基础模型"""
    name: str = Field(..., max_length=50)
    icon: str = Field(default="calendar", max_length=50)
    color: str = Field(default="#FFB7C5", max_length=20)
    sort_order: int = Field(default=0)


class AnniversaryCategoryCreate(AnniversaryCategoryBase):
    """创建纪念日分类请求模型"""
    pass


class AnniversaryCategoryUpdate(BaseModel):
    """更新纪念日分类请求模型"""
    name: Optional[str] = Field(None, max_length=50)
    icon: Optional[str] = Field(None, max_length=50)
    color: Optional[str] = Field(None, max_length=20)
    sort_order: Optional[int] = None


class AnniversaryCategoryResponse(AnniversaryCategoryBase):
    """纪念日分类响应模型"""
    id: int

    class Config:
        from_attributes = True


# ============ 纪念日 Schema ============

class AnniversaryBase(BaseModel):
    """纪念日基础模型"""
    title: str = Field(..., max_length=200)
    date: date
    year: Optional[int] = None
    category_id: Optional[int] = None
    description: Optional[str] = None
    is_recurring: bool = Field(default=True)
    remind_days_before: int = Field(default=3)

    @field_validator('date', mode='before')
    @classmethod
    def parse_anniversary_date(cls, v):
        result = parse_date(v)
        if result is None:
            raise ValueError("纪念日日期不能为空")
        return result


class AnniversaryCreate(AnniversaryBase):
    """创建纪念日请求模型"""
    pass


class AnniversaryUpdate(BaseModel):
    """更新纪念日请求模型"""
    title: Optional[str] = Field(None, max_length=200)
    date: Optional[date] = None
    year: Optional[int] = None
    category_id: Optional[int] = None
    description: Optional[str] = None
    is_recurring: Optional[bool] = None
    remind_days_before: Optional[int] = None

    @field_validator('date', mode='before')
    @classmethod
    def parse_anniversary_date(cls, v):
        if v is None:
            return None
        return parse_date(v)

    @property
    def clearable_fields(self) -> set:
        """允许被显式清空（设为 None）的字段集合"""
        return {'description', 'category_id', 'year'}


class AnniversaryResponse(AnniversaryBase):
    """纪念日响应模型"""
    id: int
    created_at: datetime
    updated_at: datetime
    category: Optional[AnniversaryCategoryResponse] = None
    next_date: Optional[date] = None
    days_until: Optional[int] = None
    year_count: Optional[int] = None

    class Config:
        from_attributes = True