"""VM backend implementations.

The :class:`~ci_orchestrator.backends.protocol.VmBackend` Protocol defines
the neutral interface every backend must satisfy. Phase A ships only the
:class:`~ci_orchestrator.backends.workstation.WorkstationVmrunBackend`;
Phase C will add an ESXi backend behind the same interface.
"""

from __future__ import annotations

from ci_orchestrator.backends.protocol import VmBackend, VmHandle, VmState
from ci_orchestrator.backends.workstation import WorkstationVmrunBackend

__all__ = ["VmBackend", "VmHandle", "VmState", "WorkstationVmrunBackend", "load_backend"]


def load_backend(config: object) -> VmBackend:
    """Factory: pick a backend implementation from ``config.backend.type``.

    Phase C hook: when the ESXi backend lands, this function will dispatch
    on ``config.backend.type``. For now only ``workstation`` is supported.
    """
    backend_type = getattr(getattr(config, "backend", None), "type", "workstation")
    if backend_type != "workstation":
        raise NotImplementedError(
            f"Backend type '{backend_type}' is not implemented. "
            "Only 'workstation' is available in Phase A."
        )
    vmrun_path = getattr(config, "vmrun_path", None)
    return WorkstationVmrunBackend(vmrun_path=vmrun_path)