"""
User API router.
Provides endpoints for user management and statistics.
"""
from typing import List, Optional
from fastapi import APIRouter, HTTPException, status, Query, Request
from database import get_db_connection
from schemas.user import (
    UserResponse,
    UserWithStatsResponse,
    UserListResponse,
    UserStatsResponse,
    AssignableUserResponse,
    TaskStats
)

router = APIRouter(
    prefix="/api/users",
    tags=["users"]
)


def require_admin(request: Request) -> dict:
    """
    验证当前用户是否为管理员。
    
    Args:
        request: FastAPI Request 对象
        
    Returns:
        当前用户信息
        
    Raises:
        HTTPException: 401 未认证或 403 权限不足
    """
    user = getattr(request.state, "user", None)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="未认证"
        )
    if user["role"] != "admin":
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="只有管理员可以访问此接口"
        )
    return user


def get_user_task_stats(cursor, user_id: str) -> TaskStats:
    """
    获取用户的任务统计信息。
    
    Args:
        cursor: 数据库游标
        user_id: 用户ID
        
    Returns:
        TaskStats 对象
    """
    # 查询任务统计
    cursor.execute("""
        SELECT 
            COUNT(*) as assigned_count,
            SUM(CASE WHEN status = 'completed' THEN 1 ELSE 0 END) as completed_count,
            SUM(CASE WHEN status = 'in_progress' THEN 1 ELSE 0 END) as in_progress_count,
            SUM(CASE WHEN status = 'pending' THEN 1 ELSE 0 END) as pending_count
        FROM tasks
        WHERE assigned_to = ?
    """, (user_id,))
    
    task_row = cursor.fetchone()
    
    assigned_count = task_row["assigned_count"] or 0
    completed_count = task_row["completed_count"] or 0
    in_progress_count = task_row["in_progress_count"] or 0
    pending_count = task_row["pending_count"] or 0
    
    # 查询标注数量
    cursor.execute("""
        SELECT COUNT(*) as annotation_count
        FROM annotations
        WHERE user_id = ?
    """, (user_id,))
    
    annotation_row = cursor.fetchone()
    annotation_count = annotation_row["annotation_count"] or 0
    
    # 计算完成率
    completion_rate = 0.0
    if assigned_count > 0:
        completion_rate = round(completed_count / assigned_count * 100, 2)
    
    return TaskStats(
        assigned_count=assigned_count,
        completed_count=completed_count,
        in_progress_count=in_progress_count,
        pending_count=pending_count,
        annotation_count=annotation_count,
        completion_rate=completion_rate
    )


@router.get("", response_model=UserListResponse)
async def list_users(
    request: Request,
    role: Optional[str] = Query(None, description="按角色筛选"),
    search: Optional[str] = Query(None, description="按用户名或邮箱搜索"),
    skip: int = Query(0, ge=0, description="跳过记录数"),
    limit: int = Query(50, ge=1, le=100, description="返回记录数")
):
    """
    获取用户列表（管理员权限）。
    
    支持按角色筛选和关键词搜索。
    
    Args:
        request: FastAPI Request 对象
        role: 角色筛选（admin/annotator/viewer）
        search: 搜索关键词（用户名或邮箱）
        skip: 分页偏移
        limit: 每页数量
        
    Returns:
        用户列表和总数
    """
    require_admin(request)
    
    with get_db_connection() as conn:
        cursor = conn.cursor()
        
        # 构建查询条件
        where_clauses = []
        params = []
        
        if role:
            where_clauses.append("role = ?")
            params.append(role)
        
        if search:
            where_clauses.append("(username LIKE ? OR email LIKE ?)")
            search_pattern = f"%{search}%"
            params.extend([search_pattern, search_pattern])
        
        where_sql = ""
        if where_clauses:
            where_sql = "WHERE " + " AND ".join(where_clauses)
        
        # 查询总数
        count_sql = f"SELECT COUNT(*) as total FROM users {where_sql}"
        cursor.execute(count_sql, tuple(params))
        total = cursor.fetchone()["total"]
        
        # 查询用户列表
        query_sql = f"""
            SELECT id, username, email, role, created_at
            FROM users
            {where_sql}
            ORDER BY created_at DESC
            LIMIT ? OFFSET ?
        """
        params.extend([limit, skip])
        cursor.execute(query_sql, tuple(params))
        rows = cursor.fetchall()
        
        users = []
        for row in rows:
            # 获取每个用户的任务统计
            task_stats = get_user_task_stats(cursor, row["id"])
            
            users.append(UserWithStatsResponse(
                id=row["id"],
                username=row["username"],
                email=row["email"],
                role=row["role"],
                created_at=row["created_at"],
                task_stats=task_stats
            ))
        
        return UserListResponse(users=users, total=total)


@router.get("/annotators", response_model=List[AssignableUserResponse])
async def list_annotators(
    request: Request,
    search: Optional[str] = Query(None, description="按用户名或邮箱搜索")
):
    """
    获取可分配任务的用户列表。
    
    返回所有标注人员（annotator 角色）及其当前工作量。
    
    Args:
        request: FastAPI Request 对象
        search: 搜索关键词
        
    Returns:
        可分配用户列表
    """
    # 验证用户已登录
    user = getattr(request.state, "user", None)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="未认证"
        )
    
    with get_db_connection() as conn:
        cursor = conn.cursor()
        
        # 构建查询
        where_clauses = ["role = 'annotator'"]
        params = []
        
        if search:
            where_clauses.append("(username LIKE ? OR email LIKE ?)")
            search_pattern = f"%{search}%"
            params.extend([search_pattern, search_pattern])
        
        where_sql = "WHERE " + " AND ".join(where_clauses)
        
        # 查询用户及其任务统计
        query_sql = f"""
            SELECT 
                u.id,
                u.username,
                u.email,
                COUNT(CASE WHEN t.status != 'completed' THEN 1 END) as current_task_count,
                COUNT(CASE WHEN t.status = 'completed' THEN 1 END) as completed_task_count
            FROM users u
            LEFT JOIN tasks t ON u.id = t.assigned_to
            {where_sql}
            GROUP BY u.id, u.username, u.email
            ORDER BY u.username
        """
        
        cursor.execute(query_sql, tuple(params))
        rows = cursor.fetchall()
        
        annotators = []
        for row in rows:
            annotators.append(AssignableUserResponse(
                id=row["id"],
                username=row["username"],
                email=row["email"],
                current_task_count=row["current_task_count"] or 0,
                completed_task_count=row["completed_task_count"] or 0
            ))
        
        return annotators


@router.get("/{user_id}", response_model=UserWithStatsResponse)
async def get_user(request: Request, user_id: str):
    """
    获取用户详情（管理员权限）。
    
    Args:
        request: FastAPI Request 对象
        user_id: 用户ID
        
    Returns:
        用户详情及统计信息
    """
    require_admin(request)
    
    with get_db_connection() as conn:
        cursor = conn.cursor()
        
        cursor.execute("""
            SELECT id, username, email, role, created_at
            FROM users
            WHERE id = ?
        """, (user_id,))
        
        row = cursor.fetchone()
        
        if not row:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail=f"用户 '{user_id}' 不存在"
            )
        
        task_stats = get_user_task_stats(cursor, user_id)
        
        return UserWithStatsResponse(
            id=row["id"],
            username=row["username"],
            email=row["email"],
            role=row["role"],
            created_at=row["created_at"],
            task_stats=task_stats
        )


@router.get("/{user_id}/stats", response_model=UserStatsResponse)
async def get_user_stats(request: Request, user_id: str):
    """
    获取用户详细统计信息（管理员权限）。
    
    包含用户基本信息、任务统计和最近任务列表。
    
    Args:
        request: FastAPI Request 对象
        user_id: 用户ID
        
    Returns:
        用户详细统计信息
    """
    require_admin(request)
    
    with get_db_connection() as conn:
        cursor = conn.cursor()
        
        # 查询用户信息
        cursor.execute("""
            SELECT id, username, email, role, created_at
            FROM users
            WHERE id = ?
        """, (user_id,))
        
        row = cursor.fetchone()
        
        if not row:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail=f"用户 '{user_id}' 不存在"
            )
        
        user = UserResponse(
            id=row["id"],
            username=row["username"],
            email=row["email"],
            role=row["role"],
            created_at=row["created_at"]
        )
        
        # 获取任务统计
        task_stats = get_user_task_stats(cursor, user_id)
        
        # 获取最近任务
        cursor.execute("""
            SELECT 
                t.id,
                t.name,
                t.status,
                t.created_at,
                p.name as project_name
            FROM tasks t
            LEFT JOIN projects p ON t.project_id = p.id
            WHERE t.assigned_to = ?
            ORDER BY t.created_at DESC
            LIMIT 10
        """, (user_id,))
        
        recent_tasks = []
        for task_row in cursor.fetchall():
            recent_tasks.append({
                "id": task_row["id"],
                "name": task_row["name"],
                "status": task_row["status"],
                "created_at": str(task_row["created_at"]),
                "project_name": task_row["project_name"]
            })
        
        return UserStatsResponse(
            user=user,
            task_stats=task_stats,
            recent_tasks=recent_tasks
        )