Update Orchestration & Rollback

"""Vehicle OTA update state machine."""
from enum import Enum, auto

class UpdateState(Enum):
    IDLE            = auto()  # no update pending
    DOWNLOADING     = auto()  # receiving update package
    VERIFYING       = auto()  # checking hash and signature
    READY_TO_APPLY  = auto()  # verified; waiting for safe window
    APPLYING        = auto()  # writing to B partition
    COMMITTING      = auto()  # switching boot partition
    REBOOTING       = auto()  # ECU restarting
    VALIDATING      = auto()  # post-reboot health check
    COMMITTED       = auto()  # update complete; B is now active
    ROLLING_BACK    = auto()  # health check failed; reverting
    FAILED          = auto()  # permanent failure

PRECONDITIONS = {
    "battery_level_pct":   20,    # minimum 20% before starting
    "vehicle_speed_kmh":   0,     # must be stationary
    "ignition_state":      "OFF_OR_ACC",
    "cellular_signal_dbm": -100,  # minimum signal
}

def check_preconditions(vehicle_state: dict) -> bool:
    """Verify all preconditions before committing update."""
    for key, minimum in PRECONDITIONS.items():
        actual = vehicle_state.get(key)
        if actual is None:
            return False
        if key == "ignition_state":
            if actual not in minimum.split("_OR_"):
                return False
        elif actual < minimum:
            return False
    return True

def decide_rollback(health_metrics: dict) -> bool:
    """Trigger rollback if post-update health check fails."""
    critical_failures = [
        health_metrics.get("can_bus_errors", 0) > 10,
        health_metrics.get("ecu_boot_failures", 0) > 0,
        health_metrics.get("safety_monitor_ok", True) == False,
    ]
    return any(critical_failures)