from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy.orm import Session
from typing import List, Optional
import uuid
import re

from database import get_db
from models.category import Category
from models.product import Product
from models.user import User
from schemas.category import CategoryResponse, CategoryCreate, CategoryUpdate, CategoryTreeResponse
from routers.auth import get_current_user, is_admin_user

router = APIRouter()

def generate_level_code() -> str:
    """生成6位字母数字组合编码"""
    # 使用UUID生成并截取前6位，确保包含字母和数字
    while True:
        code = uuid.uuid4().hex[:6].lower()
        # 检查是否同时包含字母和数字
        if re.search(r'[a-z]', code) and re.search(r'[0-9]', code):
            return code

def get_category_level_by_code(db: Session, category_code: str, company_code: str) -> int:
    """通过编码获取分类的层级，0为顶级"""
    if not category_code:
        return 0
    # 通过下划线数量判断层级
    return category_code.count('_')

def build_category_code(db: Session, parent_code: str, company_code: str) -> str:
    """构建级联编码"""
    if not parent_code:
        # 顶级分类，直接生成编码
        return generate_level_code()
    
    parent = db.query(Category).filter(
        Category.code == parent_code,
        Category.company_code == company_code
    ).first()
    if not parent:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Parent category not found"
        )
    
    # 生成当前层级编码，拼接父级编码
    level_code = generate_level_code()
    return f"{parent_code}_{level_code}"

def build_category_tree(categories: List[Category], parent_code: str = "") -> List[CategoryTreeResponse]:
    """构建分类树形结构"""
    tree = []
    for cat in categories:
        if cat.parent_code == parent_code:
            children = build_category_tree(categories, cat.code)
            tree.append(CategoryTreeResponse(
                **cat.__dict__,
                children=children
            ))
    return tree

@router.get("/", response_model=List[CategoryResponse])
async def get_categories(
    parent_code: Optional[str] = None,
    current_user: User = Depends(get_current_user),
    db: Session = Depends(get_db)
):
    """获取分类列表"""
    query = db.query(Category)
    if not is_admin_user(current_user):
        query = query.filter(Category.company_code == current_user.company_code)
    if parent_code is not None:
        query = query.filter(Category.parent_code == parent_code)
    categories = query.order_by(Category.sort_order, Category.id).all()
    
    # 计算每个分类的产品数量
    result = []
    for category in categories:
        product_count = db.query(Product).filter(
            Product.category_id == category.id
        )
        if not is_admin_user(current_user):
            product_count = product_count.filter(Product.company_code == current_user.company_code)
        result.append(CategoryResponse(
            **category.__dict__,
            product_count=product_count.count()
        ))
    return result

@router.get("/tree", response_model=List[CategoryTreeResponse])
async def get_category_tree(
    current_user: User = Depends(get_current_user),
    db: Session = Depends(get_db)
):
    """获取分类树形结构"""
    query = db.query(Category)
    if not is_admin_user(current_user):
        query = query.filter(Category.company_code == current_user.company_code)
    
    categories = query.order_by(Category.sort_order, Category.id).all()
    
    return build_category_tree(categories, "")

@router.get("/{category_id}", response_model=CategoryResponse)
async def get_category(
    category_id: int,
    current_user: User = Depends(get_current_user),
    db: Session = Depends(get_db)
):
    """获取单个分类详情"""
    query = db.query(Category).filter(Category.id == category_id)
    if not is_admin_user(current_user):
        query = query.filter(Category.company_code == current_user.company_code)
    
    category = query.first()
    if not category:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Category not found"
        )
    
    # 计算产品数量
    product_count = db.query(Product).filter(Product.category_id == category.id)
    if not is_admin_user(current_user):
        product_count = product_count.filter(Product.company_code == current_user.company_code)
    
    return CategoryResponse(
        **category.__dict__,
        product_count=product_count.count()
    )

@router.post("/", response_model=CategoryResponse, status_code=status.HTTP_201_CREATED)
async def create_category(
    category: CategoryCreate,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """创建新分类"""
    # 检查层级限制（最多三级）
    level = get_category_level_by_code(db, category.parent_code, current_user.company_code)
    if level >= 3:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Maximum category level is 3"
        )
    
    # 检查同级分类名称是否已存在
    existing = db.query(Category).filter(
        Category.name == category.name,
        Category.parent_code == category.parent_code,
        Category.company_code == current_user.company_code
    ).first()
    if existing:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Category name already exists in the same level"
        )
    
    # 构建编码
    code = build_category_code(db, category.parent_code, current_user.company_code)
    
    # 创建分类
    category_data = category.model_dump()
    if not is_admin_user(current_user):
        category_data['company_code'] = current_user.company_code
    category_data['code'] = code
    db_category = Category(**category_data)
    db.add(db_category)
    db.commit()
    db.refresh(db_category)
    
    return CategoryResponse(
        **db_category.__dict__,
        product_count=0
    )

@router.put("/{category_id}", response_model=CategoryResponse)
async def update_category(
    category_id: int,
    category_update: CategoryUpdate,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """更新分类"""
    query = db.query(Category).filter(Category.id == category_id)
    if not is_admin_user(current_user):
        query = query.filter(Category.company_code == current_user.company_code)
    
    db_category = query.first()
    if not db_category:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Category not found"
        )
    
    update_data = category_update.model_dump(exclude_unset=True)
    
    # 检查是否需要更新父分类
    new_parent_code = update_data.get('parent_code', db_category.parent_code)
    if new_parent_code != db_category.parent_code:
        # 检查层级限制（最多三级）
        level = get_category_level_by_code(db, new_parent_code, current_user.company_code)
        if level >= 3:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Maximum category level is 3"
            )
        
        # 检查是否有子分类，如果有则不能改变父分类
        child_count = db.query(Category).filter(
            Category.parent_code == db_category.code,
            Category.company_code == current_user.company_code
        ).count()
        if child_count > 0:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Cannot change parent category of category with children"
            )
        
        # 重新构建编码
        new_code = build_category_code(db, new_parent_code, current_user.company_code)
        update_data['code'] = new_code
    
    # 检查新名称是否与同级分类冲突
    new_name = update_data.get('name', db_category.name)
    if new_name != db_category.name or new_parent_code != db_category.parent_code:
        existing = db.query(Category).filter(
            Category.name == new_name,
            Category.parent_code == new_parent_code,
            Category.company_code == current_user.company_code,
            Category.id != category_id
        ).first()
        if existing:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Category name already exists in the same level"
            )
    
    # 更新分类
    for field, value in update_data.items():
        setattr(db_category, field, value)
    db.commit()
    db.refresh(db_category)
    
    # 计算产品数量
    product_count = db.query(Product).filter(Product.category_id == db_category.id)
    if not is_admin_user(current_user):
        product_count = product_count.filter(Product.company_code == current_user.company_code)
    
    return CategoryResponse(
        **db_category.__dict__,
        product_count=product_count.count()
    )

@router.delete("/{category_id}", status_code=status.HTTP_204_NO_CONTENT)
async def delete_category(
    category_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user)
):
    """删除分类"""
    query = db.query(Category).filter(Category.id == category_id)
    if not is_admin_user(current_user):
        query = query.filter(Category.company_code == current_user.company_code)
    
    db_category = query.first()
    if not db_category:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Category not found"
        )
    
    # 检查是否有子分类
    child_count = db.query(Category).filter(
        Category.parent_code == db_category.code,
        Category.company_code == current_user.company_code
    ).count()
    if child_count > 0:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail=f"Cannot delete category with {child_count} child categories"
        )
    
    # 检查是否有产品属于该分类
    product_count = db.query(Product).filter(
        Product.category_id == category_id,
        Product.company_code == current_user.company_code
    ).count()
    if product_count > 0:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail=f"Cannot delete category with {product_count} products"
        )
    
    db.delete(db_category)
    db.commit()
    return None