"""
M365 Tenant service layer for business logic and database operations.

This module handles all database operations for M365 tenants, providing a clean
separation between the API routes and data access layer.
"""

from typing import Optional
from uuid import UUID

from fastapi import HTTPException, status
from sqlalchemy.exc import IntegrityError
from sqlalchemy.orm import Session

from api.models.m365_tenant import M365Tenant
from api.models.client import Client
from api.schemas.m365_tenant import M365TenantCreate, M365TenantUpdate


def get_m365_tenants(db: Session, skip: int = 0, limit: int = 100) -> tuple[list[M365Tenant], int]:
    """
    Retrieve a paginated list of M365 tenants.

    Args:
        db: Database session
        skip: Number of records to skip (for pagination)
        limit: Maximum number of records to return

    Returns:
        tuple: (list of M365 tenants, total count)

    Example:
        ```python
        tenants, total = get_m365_tenants(db, skip=0, limit=50)
        print(f"Retrieved {len(tenants)} of {total} M365 tenants")
        ```
    """
    # Get total count
    total = db.query(M365Tenant).count()

    # Get paginated results, ordered by created_at descending (newest first)
    tenants = (
        db.query(M365Tenant)
        .order_by(M365Tenant.created_at.desc())
        .offset(skip)
        .limit(limit)
        .all()
    )

    return tenants, total


def get_m365_tenant_by_id(db: Session, tenant_id: UUID) -> M365Tenant:
    """
    Retrieve a single M365 tenant by its ID.

    Args:
        db: Database session
        tenant_id: UUID of the M365 tenant to retrieve

    Returns:
        M365Tenant: The M365 tenant object

    Raises:
        HTTPException: 404 if M365 tenant not found

    Example:
        ```python
        tenant = get_m365_tenant_by_id(db, tenant_id)
        print(f"Found tenant: {tenant.tenant_name}")
        ```
    """
    tenant = db.query(M365Tenant).filter(M365Tenant.id == str(tenant_id)).first()

    if not tenant:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"M365 tenant with ID {tenant_id} not found"
        )

    return tenant


def get_m365_tenant_by_tenant_id(db: Session, tenant_id: str) -> Optional[M365Tenant]:
    """
    Retrieve an M365 tenant by its Microsoft tenant ID.

    Args:
        db: Database session
        tenant_id: Microsoft tenant ID to search for

    Returns:
        Optional[M365Tenant]: The M365 tenant if found, None otherwise

    Example:
        ```python
        tenant = get_m365_tenant_by_tenant_id(db, "abc12345-6789-0def-1234-56789abcdef0")
        if tenant:
            print(f"Found tenant: {tenant.tenant_name}")
        ```
    """
    return db.query(M365Tenant).filter(M365Tenant.tenant_id == tenant_id).first()


def get_m365_tenants_by_client(db: Session, client_id: UUID, skip: int = 0, limit: int = 100) -> tuple[list[M365Tenant], int]:
    """
    Retrieve M365 tenants for a specific client.

    Args:
        db: Database session
        client_id: UUID of the client
        skip: Number of records to skip (for pagination)
        limit: Maximum number of records to return

    Returns:
        tuple: (list of M365 tenants, total count)

    Raises:
        HTTPException: 404 if client not found

    Example:
        ```python
        tenants, total = get_m365_tenants_by_client(db, client_id, skip=0, limit=50)
        print(f"Client has {total} M365 tenants")
        ```
    """
    # Verify client exists
    client = db.query(Client).filter(Client.id == str(client_id)).first()
    if not client:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"Client with ID {client_id} not found"
        )

    # Get total count for this client
    total = db.query(M365Tenant).filter(M365Tenant.client_id == str(client_id)).count()

    # Get paginated results
    tenants = (
        db.query(M365Tenant)
        .filter(M365Tenant.client_id == str(client_id))
        .order_by(M365Tenant.created_at.desc())
        .offset(skip)
        .limit(limit)
        .all()
    )

    return tenants, total


def create_m365_tenant(db: Session, tenant_data: M365TenantCreate) -> M365Tenant:
    """
    Create a new M365 tenant.

    Args:
        db: Database session
        tenant_data: M365 tenant creation data

    Returns:
        M365Tenant: The created M365 tenant object

    Raises:
        HTTPException: 404 if client_id provided and client doesn't exist
        HTTPException: 409 if M365 tenant with tenant_id already exists
        HTTPException: 500 if database error occurs

    Example:
        ```python
        tenant_data = M365TenantCreate(
            tenant_id="abc12345-6789-0def-1234-56789abcdef0",
            tenant_name="dataforth.com",
            client_id="123e4567-e89b-12d3-a456-426614174000"
        )
        tenant = create_m365_tenant(db, tenant_data)
        print(f"Created M365 tenant: {tenant.id}")
        ```
    """
    # Validate client exists if client_id provided
    if tenant_data.client_id:
        client = db.query(Client).filter(Client.id == str(tenant_data.client_id)).first()
        if not client:
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail=f"Client with ID {tenant_data.client_id} not found"
            )

    # Check if M365 tenant with tenant_id already exists
    existing_tenant = get_m365_tenant_by_tenant_id(db, tenant_data.tenant_id)
    if existing_tenant:
        raise HTTPException(
            status_code=status.HTTP_409_CONFLICT,
            detail=f"M365 tenant with tenant_id '{tenant_data.tenant_id}' already exists"
        )

    try:
        # Create new M365 tenant instance
        db_tenant = M365Tenant(**tenant_data.model_dump())

        # Add to database
        db.add(db_tenant)
        db.commit()
        db.refresh(db_tenant)

        return db_tenant

    except IntegrityError as e:
        db.rollback()
        # Handle unique constraint violations
        if "tenant_id" in str(e.orig):
            raise HTTPException(
                status_code=status.HTTP_409_CONFLICT,
                detail=f"M365 tenant with tenant_id '{tenant_data.tenant_id}' already exists"
            )
        elif "client_id" in str(e.orig):
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail=f"Client with ID {tenant_data.client_id} not found"
            )
        else:
            raise HTTPException(
                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                detail=f"Database error: {str(e)}"
            )
    except Exception as e:
        db.rollback()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to create M365 tenant: {str(e)}"
        )


def update_m365_tenant(db: Session, tenant_id: UUID, tenant_data: M365TenantUpdate) -> M365Tenant:
    """
    Update an existing M365 tenant.

    Args:
        db: Database session
        tenant_id: UUID of the M365 tenant to update
        tenant_data: M365 tenant update data (only provided fields will be updated)

    Returns:
        M365Tenant: The updated M365 tenant object

    Raises:
        HTTPException: 404 if M365 tenant not found or client_id provided and client doesn't exist
        HTTPException: 409 if update would violate unique constraints
        HTTPException: 500 if database error occurs

    Example:
        ```python
        update_data = M365TenantUpdate(
            admin_email="admin@example.com",
            notes="Updated tenant information"
        )
        tenant = update_m365_tenant(db, tenant_id, update_data)
        print(f"Updated M365 tenant: {tenant.tenant_name}")
        ```
    """
    # Get existing M365 tenant
    tenant = get_m365_tenant_by_id(db, tenant_id)

    try:
        # Update only provided fields
        update_data = tenant_data.model_dump(exclude_unset=True)

        # If updating client_id, validate client exists
        if "client_id" in update_data and update_data["client_id"] is not None:
            client = db.query(Client).filter(Client.id == str(update_data["client_id"])).first()
            if not client:
                raise HTTPException(
                    status_code=status.HTTP_404_NOT_FOUND,
                    detail=f"Client with ID {update_data['client_id']} not found"
                )

        # If updating tenant_id, check if new tenant_id is already taken
        if "tenant_id" in update_data and update_data["tenant_id"] != tenant.tenant_id:
            existing = get_m365_tenant_by_tenant_id(db, update_data["tenant_id"])
            if existing:
                raise HTTPException(
                    status_code=status.HTTP_409_CONFLICT,
                    detail=f"M365 tenant with tenant_id '{update_data['tenant_id']}' already exists"
                )

        # Apply updates
        for field, value in update_data.items():
            setattr(tenant, field, value)

        db.commit()
        db.refresh(tenant)

        return tenant

    except HTTPException:
        db.rollback()
        raise
    except IntegrityError as e:
        db.rollback()
        if "tenant_id" in str(e.orig):
            raise HTTPException(
                status_code=status.HTTP_409_CONFLICT,
                detail="M365 tenant with this tenant_id already exists"
            )
        elif "client_id" in str(e.orig):
            raise HTTPException(
                status_code=status.HTTP_404_NOT_FOUND,
                detail="Client not found"
            )
        else:
            raise HTTPException(
                status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                detail=f"Database error: {str(e)}"
            )
    except Exception as e:
        db.rollback()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to update M365 tenant: {str(e)}"
        )


def delete_m365_tenant(db: Session, tenant_id: UUID) -> dict:
    """
    Delete an M365 tenant by its ID.

    Args:
        db: Database session
        tenant_id: UUID of the M365 tenant to delete

    Returns:
        dict: Success message

    Raises:
        HTTPException: 404 if M365 tenant not found
        HTTPException: 500 if database error occurs

    Example:
        ```python
        result = delete_m365_tenant(db, tenant_id)
        print(result["message"])  # "M365 tenant deleted successfully"
        ```
    """
    # Get existing M365 tenant (raises 404 if not found)
    tenant = get_m365_tenant_by_id(db, tenant_id)

    try:
        db.delete(tenant)
        db.commit()

        return {
            "message": "M365 tenant deleted successfully",
            "tenant_id": str(tenant_id)
        }

    except Exception as e:
        db.rollback()
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to delete M365 tenant: {str(e)}"
        )