from fastapi import APIRouter, Depends, HTTPException, status, Query, Request
from sqlalchemy.orm import Session
from sqlalchemy import or_
from typing import List

from app.core.database import get_db
from app.models.user import User
from app.models.role import Role
from app.models import AuditAction
from app.schemas.user import UserResponse, UserUpdate
from app.middleware.auth import (
    get_current_user,
    require_permission,
    require_system_admin,
    check_department_access,
)
from app.middleware.audit import get_audit_metadata
from app.services.audit_service import AuditService

router = APIRouter()


@router.get("/search", response_model=List[UserResponse])
async def search_users(
    q: str = Query(..., min_length=1, max_length=100, description="Search query"),
    limit: int = Query(10, ge=1, le=50, description="Max results"),
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """
    Search users by name or email. Used for @mention autocomplete.
    Returns users matching the query, limited to same department unless system admin.
    """
    query = db.query(User).filter(
        User.is_active == True,
        or_(
            User.name.ilike(f"%{q}%"),
            User.email.ilike(f"%{q}%"),
        )
    )

    # Filter by department if not system admin
    if not current_user.is_system_admin and current_user.department_id:
        query = query.filter(User.department_id == current_user.department_id)

    users = query.limit(limit).all()
    return users


@router.get("", response_model=List[UserResponse])
async def list_users(
    skip: int = 0,
    limit: int = 100,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_permission("users.read")),
):
    """
    List all users. Filtered by department if not system admin.
    """
    query = db.query(User)

    # Filter by department if not system admin
    if not current_user.is_system_admin and current_user.department_id:
        query = query.filter(User.department_id == current_user.department_id)

    users = query.offset(skip).limit(limit).all()
    return users


@router.get("/{user_id}", response_model=UserResponse)
async def get_user(
    user_id: str,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_permission("users.read")),
):
    """
    Get a specific user by ID.
    """
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="User not found",
        )

    # Check department access
    if not check_department_access(current_user, user.department_id):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Access denied to this user",
        )

    return user


@router.patch("/{user_id}", response_model=UserResponse)
async def update_user(
    user_id: str,
    user_update: UserUpdate,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_permission("users.write")),
):
    """
    Update user information.
    """
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="User not found",
        )

    # Check department access
    if not check_department_access(current_user, user.department_id):
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Access denied to this user",
        )

    # Prevent modification of system admin properties by non-system-admins
    if user.is_system_admin and not current_user.is_system_admin:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Cannot modify system administrator",
        )

    # Update fields
    update_data = user_update.model_dump(exclude_unset=True)
    for field, value in update_data.items():
        setattr(user, field, value)

    db.commit()
    db.refresh(user)
    return user


@router.patch("/{user_id}/role", response_model=UserResponse)
async def assign_role(
    user_id: str,
    role_id: str,
    request: Request,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_system_admin),
):
    """
    Assign a role to a user. Requires system admin.
    """
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="User not found",
        )

    # Prevent modification of system admin
    if user.is_system_admin:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Cannot modify system administrator role",
        )

    # Verify role exists
    role = db.query(Role).filter(Role.id == role_id).first()
    if not role:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Role not found",
        )

    # Prevent assigning system role to non-system-admin
    if role.is_system_role:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Cannot assign system role",
        )

    old_role_id = user.role_id
    user.role_id = role_id

    # Audit log for role change (high sensitivity)
    if old_role_id != role_id:
        AuditService.log_event(
            db=db,
            event_type="user.role_change",
            resource_type="user",
            action=AuditAction.UPDATE,
            user_id=current_user.id,
            resource_id=user.id,
            changes=[{"field": "role_id", "old_value": old_role_id, "new_value": role_id}],
            request_metadata=get_audit_metadata(request),
        )

    db.commit()
    db.refresh(user)
    return user


@router.patch("/{user_id}/admin", response_model=UserResponse)
async def set_admin_status(
    user_id: str,
    is_admin: bool,
    request: Request,
    db: Session = Depends(get_db),
    current_user: User = Depends(require_system_admin),
):
    """
    Set or revoke system administrator status. Requires system admin.
    """
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="User not found",
        )

    # Prevent self-modification
    if user.id == current_user.id:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Cannot modify your own admin status",
        )

    old_admin_status = user.is_system_admin
    user.is_system_admin = is_admin

    # Audit log for admin change (critical sensitivity, triggers alert)
    if old_admin_status != is_admin:
        AuditService.log_event(
            db=db,
            event_type="user.admin_change",
            resource_type="user",
            action=AuditAction.UPDATE,
            user_id=current_user.id,
            resource_id=user.id,
            changes=[{"field": "is_system_admin", "old_value": old_admin_status, "new_value": is_admin}],
            request_metadata=get_audit_metadata(request),
        )

    db.commit()
    db.refresh(user)
    return user