//// A small pure state machine, not a complete agent runtime.
//// Supply a fresh incarnation identifier whenever the owner is replaced.
//// This educational example was not compiler-verified in the research environment.
pub type RunId {
RunId(incarnation: String, sequence: Int)
}
pub type Reason {
UserRequested(prompt: String)
ScheduledWake(tag: String)
}
pub type Outcome {
Succeeded(value: String)
Failed(reason: String)
Stopped
}
pub type Phase {
Idle
Running(run_id: RunId)
Stopping(run_id: RunId)
}
pub opaque type Model {
Model(incarnation: String, next_sequence: Int, phase: Phase)
}
pub type Event {
RequestRun(reason: Reason)
RequestCancel
WorkEnded(run_id: RunId, outcome: Outcome)
}
pub type Effect {
StartJob(run_id: RunId, reason: Reason)
AskJobToStop(run_id: RunId)
ReportFinished(run_id: RunId, outcome: Outcome)
ReportAbandoned(run_id: RunId)
RejectBusy
}
pub fn new(incarnation: String) -> Model {
Model(incarnation:, next_sequence: 1, phase: Idle)
}
pub fn phase(model: Model) -> Phase {
model.phase
}
pub fn transition(model: Model, event: Event) -> #(Model, List(Effect)) {
case event {
RequestRun(reason) -> {
case model.phase {
Idle -> {
let run_id = RunId(model.incarnation, model.next_sequence)
#(
Model(
..model,
next_sequence: model.next_sequence + 1,
phase: Running(run_id),
),
[StartJob(run_id, reason)],
)
}
Running(_) | Stopping(_) -> #(model, [RejectBusy])
}
}
RequestCancel -> {
case model.phase {
Running(run_id) -> #(Model(..model, phase: Stopping(run_id)), [
AskJobToStop(run_id),
])
Idle | Stopping(_) -> #(model, [])
}
}
WorkEnded(run_id, outcome) -> {
case model.phase {
Running(active) if active == run_id -> #(Model(..model, phase: Idle), [
ReportFinished(run_id, outcome),
])
Stopping(active) if active == run_id -> #(Model(..model, phase: Idle), [
ReportAbandoned(run_id),
])
Idle | Running(_) | Stopping(_) -> #(model, [])
}
}
}
}