from rest_framework.exceptions import ValidationError
from apps.projects.models import ProjectMembership

def add_project_member(project, user_id, role):
    """
    Adds a user to a project. Ensures no duplicate active memberships exist.
    """
    if ProjectMembership.objects.filter(project=project, user_id=user_id, is_deleted=False).exists():
        raise ValidationError({"user_id": "This user is already a member of the project."})

    return ProjectMembership.objects.create(
        project=project,
        user_id=user_id,
        role=role,
        is_active=True
    )

def update_project_member(membership, **kwargs):
    """
    Updates a project membership (e.g., changing role or active status).
    """
    update_fields = []
    for field, value in kwargs.items():
        if hasattr(membership, field) and getattr(membership, field) != value:
            setattr(membership, field, value)
            update_fields.append(field)
            
    if update_fields:
        update_fields.append("updated_at")
        membership.save(update_fields=update_fields)
        
    return membership