lightspeed

//// Typestate lifecycle for Lightspeed session agents.

/// Marker type for a disconnected agent.
pub type Disconnected {
  Disconnected
}

/// Marker type for an agent performing protocol handshake.
pub type Handshaking {
  Handshaking
}

/// Marker type for an agent whose component has mounted.
pub type Mounted {
  Mounted
}

/// Marker type for an active live agent.
pub type Live {
  Live
}

/// Marker type for an agent draining before shutdown.
pub type Draining {
  Draining
}

/// Marker type for a terminated agent.
pub type Terminated {
  Terminated
}

/// Lifecycle labels useful for logs and protocol diagnostics.
pub type Lifecycle {
  DisconnectedLabel
  HandshakingLabel
  MountedLabel
  LiveLabel
  DrainingLabel
  TerminatedLabel
}

/// A session agent parameterized by lifecycle state.
pub opaque type Agent(state) {
  Agent(id: String, label: Lifecycle)
}

/// Create a disconnected agent.
pub fn new(id: String) -> Agent(Disconnected) {
  Agent(id: id, label: DisconnectedLabel)
}

/// Transition from disconnected to handshaking.
pub fn handshake(agent: Agent(Disconnected)) -> Agent(Handshaking) {
  Agent(id: agent.id, label: HandshakingLabel)
}

/// Transition from handshaking to mounted.
pub fn mount(agent: Agent(Handshaking)) -> Agent(Mounted) {
  Agent(id: agent.id, label: MountedLabel)
}

/// Transition from mounted to live.
pub fn go_live(agent: Agent(Mounted)) -> Agent(Live) {
  Agent(id: agent.id, label: LiveLabel)
}

/// Transition from live to draining.
pub fn drain(agent: Agent(Live)) -> Agent(Draining) {
  Agent(id: agent.id, label: DrainingLabel)
}

/// Transition from draining to terminated.
pub fn terminate(agent: Agent(Draining)) -> Agent(Terminated) {
  Agent(id: agent.id, label: TerminatedLabel)
}

/// Return the agent id.
pub fn id(agent: Agent(state)) -> String {
  agent.id
}

/// Return the lifecycle label.
pub fn lifecycle(agent: Agent(state)) -> Lifecycle {
  agent.label
}

/// Convert a lifecycle label to a stable string.
pub fn lifecycle_to_string(lifecycle: Lifecycle) -> String {
  case lifecycle {
    DisconnectedLabel -> "disconnected"
    HandshakingLabel -> "handshaking"
    MountedLabel -> "mounted"
    LiveLabel -> "live"
    DrainingLabel -> "draining"
    TerminatedLabel -> "terminated"
  }
}