from datetime import datetime
from enum import Enum
from typing import Optional
from pydantic import BaseModel, Field, field_validator


class Priority(str, Enum):
    HIGH = "high"
    MEDIUM = "medium"
    LOW = "low"


# === Request 스키마 ===


class TodoCreate(BaseModel):
    """할일 생성 요청 (F-001)"""
    title: str = Field(..., min_length=1, max_length=200)
    content: Optional[str] = Field(None, max_length=2000)
    category_id: Optional[str] = None
    tags: list[str] = Field(default_factory=list, max_length=10)
    priority: Priority = Priority.MEDIUM
    start_date: Optional[datetime] = None
    due_date: Optional[datetime] = None

    @field_validator("title")
    @classmethod
    def title_not_blank(cls, v: str) -> str:
        v = v.strip()
        if not v:
            raise ValueError("제목은 공백만으로 구성할 수 없습니다")
        return v

    @field_validator("tags")
    @classmethod
    def normalize_tags(cls, v: list[str]) -> list[str]:
        """소문자 정규화, 중복 제거, 공백 trim"""
        seen: set[str] = set()
        result: list[str] = []
        for tag in v:
            tag = tag.strip().lower()
            if tag and len(tag) <= 30 and tag not in seen:
                seen.add(tag)
                result.append(tag)
        return result

    @field_validator("category_id")
    @classmethod
    def validate_category_id(cls, v: Optional[str]) -> Optional[str]:
        from bson import ObjectId
        if v is not None and not ObjectId.is_valid(v):
            raise ValueError("유효하지 않은 카테고리 ID 형식입니다")
        return v


class TodoUpdate(BaseModel):
    """할일 수정 요청 (F-004) - Partial Update"""
    title: Optional[str] = Field(None, min_length=1, max_length=200)
    content: Optional[str] = Field(None, max_length=2000)
    completed: Optional[bool] = None
    category_id: Optional[str] = None
    tags: Optional[list[str]] = None
    priority: Optional[Priority] = None
    start_date: Optional[datetime] = None
    due_date: Optional[datetime] = None

    @field_validator("title")
    @classmethod
    def title_not_blank(cls, v: Optional[str]) -> Optional[str]:
        if v is not None:
            v = v.strip()
            if not v:
                raise ValueError("제목은 공백만으로 구성할 수 없습니다")
        return v

    @field_validator("tags")
    @classmethod
    def normalize_tags(cls, v: Optional[list[str]]) -> Optional[list[str]]:
        if v is None:
            return None
        seen: set[str] = set()
        result: list[str] = []
        for tag in v:
            tag = tag.strip().lower()
            if tag and len(tag) <= 30 and tag not in seen:
                seen.add(tag)
                result.append(tag)
        return result

    @field_validator("category_id")
    @classmethod
    def validate_category_id(cls, v: Optional[str]) -> Optional[str]:
        from bson import ObjectId
        if v is not None and not ObjectId.is_valid(v):
            raise ValueError("유효하지 않은 카테고리 ID 형식입니다")
        return v


class BatchRequest(BaseModel):
    """일괄 작업 요청 (F-019, F-020, F-021)"""
    action: str = Field(..., pattern="^(complete|delete|move_category)$")
    ids: list[str] = Field(..., min_length=1)
    category_id: Optional[str] = None  # move_category 시에만 사용

    @field_validator("ids")
    @classmethod
    def validate_ids(cls, v: list[str]) -> list[str]:
        from bson import ObjectId
        for id_str in v:
            if not ObjectId.is_valid(id_str):
                raise ValueError(f"유효하지 않은 ID 형식: {id_str}")
        return v


# === Attachment 스키마 ===


class Attachment(BaseModel):
    """첨부파일 메타데이터"""
    id: str
    filename: str
    stored_filename: str
    content_type: str
    size: int
    uploaded_at: datetime


# === Response 스키마 ===


class TodoResponse(BaseModel):
    """할일 응답 (카테고리 정보 포함 가능)"""
    id: str
    title: str
    content: Optional[str] = None
    completed: bool
    priority: Priority
    category_id: Optional[str] = None
    category_name: Optional[str] = None
    category_color: Optional[str] = None
    tags: list[str] = []
    start_date: Optional[datetime] = None
    due_date: Optional[datetime] = None
    attachments: list[Attachment] = []
    created_at: datetime
    updated_at: datetime


class TodoListResponse(BaseModel):
    """할일 목록 페이지네이션 응답 (F-002)"""
    items: list[TodoResponse]
    total: int
    page: int
    limit: int
    total_pages: int


class ToggleResponse(BaseModel):
    """완료 토글 응답 (F-006)"""
    id: str
    completed: bool


class BatchResponse(BaseModel):
    """일괄 작업 응답 (F-019, F-020, F-021)"""
    action: str
    processed: int
    failed: int


class TagInfo(BaseModel):
    """태그 정보 (F-013)"""
    name: str
    count: int


class SearchResponse(BaseModel):
    """검색 응답 (F-017)"""
    items: list[TodoResponse]
    total: int
    query: str
    page: int
    limit: int


# === 대시보드 통계 모델 ===


class OverviewStats(BaseModel):
    total: int
    completed: int
    incomplete: int
    completion_rate: float


class CategoryStats(BaseModel):
    category_id: Optional[str] = None
    name: str
    color: str
    count: int


class PriorityStats(BaseModel):
    high: int
    medium: int
    low: int


class UpcomingDeadline(BaseModel):
    id: str
    title: str
    due_date: datetime
    priority: Priority


class DashboardStats(BaseModel):
    """대시보드 통계 응답 (F-018)"""
    overview: OverviewStats
    by_category: list[CategoryStats]
    by_priority: PriorityStats
    upcoming_deadlines: list[UpcomingDeadline]