// Package supervisor runs and watches engine processes (plan §5.4).
package supervisor

import "fmt"

// State is where a shard is in its lifecycle.
//
// Loading is separate from Starting because model loading dominates startup:
// a 70B model takes minutes, and an operator watching a shard sit in one state
// for ten minutes needs to know whether that is normal.
type State int

const (
	// Pending means the shard is known but not started.
	Pending State = iota
	// Starting means the process has been launched but has not opened its port.
	Starting
	// Loading means the port is open but the model is not ready.
	Loading
	// Ready means health checks pass and the model is served.
	Ready
	// Draining means no new work; existing requests finish.
	Draining
	// Stopped means the process exited as intended.
	Stopped
	// Failed means the process exited unexpectedly or never became ready.
	Failed
)

func (s State) String() string {
	switch s {
	case Pending:
		return "pending"
	case Starting:
		return "starting"
	case Loading:
		return "loading"
	case Ready:
		return "ready"
	case Draining:
		return "draining"
	case Stopped:
		return "stopped"
	case Failed:
		return "failed"
	default:
		return fmt.Sprintf("unknown(%d)", int(s))
	}
}

// Terminal reports whether the shard has finished for good.
func (s State) Terminal() bool { return s == Stopped || s == Failed }

// Live reports whether a process should be running in this state.
func (s State) Live() bool {
	return s == Starting || s == Loading || s == Ready || s == Draining
}