from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select
from typing import List

from app.core.database import get_db
from app.core.security import get_password_hash
from app.models.models import User
from app.schemas.schemas import UserResponse, UserCreate, UserUpdate
from app.api.deps import get_current_user, require_admin

router = APIRouter(prefix="/users", tags=["Users Management"], dependencies=[Depends(require_admin)])

@router.get("", response_model=List[UserResponse])
async def list_users(db: AsyncSession = Depends(get_db)):
    """Lists all user accounts in the database."""
    result = await db.execute(select(User).order_by(User.id.asc()))
    users = result.scalars().all()
    return users

@router.post("", response_model=UserResponse)
async def create_user(payload: UserCreate, db: AsyncSession = Depends(get_db)):
    """Creates a new user account (Local or RADIUS)."""
    # Check if email already registered
    email_clean = payload.email.strip().lower()
    result = await db.execute(select(User).where(User.email == email_clean))
    existing = result.scalar_one_or_none()
    if existing:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Email address is already registered."
        )

    user = User(
        email=email_clean,
        hashed_password=get_password_hash(payload.password),
        full_name=payload.full_name,
        role=payload.role,
        auth_source=payload.auth_source,
        is_active=payload.is_active
    )
    db.add(user)
    await db.commit()
    await db.refresh(user)
    return user

@router.put("/{user_id}", response_model=UserResponse)
async def update_user(user_id: int, payload: UserUpdate, db: AsyncSession = Depends(get_db)):
    """Updates an existing user account."""
    result = await db.execute(select(User).where(User.id == user_id))
    user = result.scalar_one_or_none()
    if not user:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="User not found."
        )

    # Prevent changing email of default admin
    if user.email == "admin@oneverdrive.local" and payload.email and payload.email.strip().lower() != user.email:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Email address of the default system administrator cannot be changed."
        )

    if payload.email is not None:
        email_clean = payload.email.strip().lower()
        if email_clean != user.email:
            existing_res = await db.execute(select(User).where(User.email == email_clean))
            if existing_res.scalar_one_or_none():
                raise HTTPException(
                    status_code=status.HTTP_400_BAD_REQUEST,
                    detail="Target email address is already in use."
                )
            user.email = email_clean

    if payload.password is not None and payload.password != "":
        user.hashed_password = get_password_hash(payload.password)

    if payload.full_name is not None:
        user.full_name = payload.full_name

    if payload.role is not None:
        # Prevent demoting the main admin
        if user.email == "admin@oneverdrive.local" and payload.role != "ADMIN":
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Default system administrator role cannot be demoted."
            )
        user.role = payload.role

    if payload.is_active is not None:
        # Prevent deactivating the main admin
        if user.email == "admin@oneverdrive.local" and not payload.is_active:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Default system administrator account cannot be deactivated."
            )
        user.is_active = payload.is_active

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

@router.delete("/{user_id}")
async def delete_user(user_id: int, db: AsyncSession = Depends(get_db), current_user: User = Depends(get_current_user)):
    """Deletes a user account from the system."""
    if user_id == current_user.id:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="You cannot delete your own account."
        )

    result = await db.execute(select(User).where(User.id == user_id))
    user = result.scalar_one_or_none()
    if not user:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="User not found."
        )

    if user.email == "admin@oneverdrive.local":
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="The default system administrator account cannot be deleted."
        )

    await db.delete(user)
    await db.commit()
    return {"message": f"User account '{user.email}' deleted successfully."}