package domain

import (
	"fmt"

	rvboxv1 "github.com/rvbox/rvbox/gen/go/rvbox/v1"
)

// CanTransition reports whether a public lifecycle change is legal. Duplicate
// events are handled by sequence validation and are not state transitions.
func CanTransition(from, to rvboxv1.CommandLifecycle) bool {
	switch from {
	case rvboxv1.CommandLifecycle_COMMAND_QUEUED:
		return to == rvboxv1.CommandLifecycle_COMMAND_DISPATCHED ||
			to == rvboxv1.CommandLifecycle_COMMAND_CANCELLED ||
			to == rvboxv1.CommandLifecycle_COMMAND_EXPIRED
	case rvboxv1.CommandLifecycle_COMMAND_DISPATCHED:
		return to == rvboxv1.CommandLifecycle_COMMAND_QUEUED ||
			to == rvboxv1.CommandLifecycle_COMMAND_ACCEPTED ||
			to == rvboxv1.CommandLifecycle_COMMAND_REJECTED ||
			to == rvboxv1.CommandLifecycle_COMMAND_CANCELLED ||
			to == rvboxv1.CommandLifecycle_COMMAND_INTERRUPTED
	case rvboxv1.CommandLifecycle_COMMAND_ACCEPTED:
		return to == rvboxv1.CommandLifecycle_COMMAND_RUNNING ||
			to == rvboxv1.CommandLifecycle_COMMAND_REJECTED ||
			to == rvboxv1.CommandLifecycle_COMMAND_CANCELLED ||
			to == rvboxv1.CommandLifecycle_COMMAND_INTERRUPTED
	case rvboxv1.CommandLifecycle_COMMAND_RUNNING:
		return to == rvboxv1.CommandLifecycle_COMMAND_SUCCEEDED ||
			to == rvboxv1.CommandLifecycle_COMMAND_FAILED ||
			to == rvboxv1.CommandLifecycle_COMMAND_TERMINATED ||
			to == rvboxv1.CommandLifecycle_COMMAND_INTERRUPTED
	default:
		return false
	}
}

// ValidateTransition rejects unspecified, repeated, terminal-origin, and
// otherwise impossible public lifecycle changes.
func ValidateTransition(from, to rvboxv1.CommandLifecycle) error {
	if CanTransition(from, to) {
		return nil
	}
	return NewError(
		rvboxv1.ControlError_PROTOCOL_ERROR,
		fmt.Sprintf("illegal command lifecycle transition %s -> %s", from, to),
		"",
	)
}

// IsTerminal reports whether no further public lifecycle transition is legal.
func IsTerminal(state rvboxv1.CommandLifecycle) bool {
	switch state {
	case rvboxv1.CommandLifecycle_COMMAND_SUCCEEDED,
		rvboxv1.CommandLifecycle_COMMAND_FAILED,
		rvboxv1.CommandLifecycle_COMMAND_TERMINATED,
		rvboxv1.CommandLifecycle_COMMAND_CANCELLED,
		rvboxv1.CommandLifecycle_COMMAND_INTERRUPTED,
		rvboxv1.CommandLifecycle_COMMAND_EXPIRED,
		rvboxv1.CommandLifecycle_COMMAND_REJECTED:
		return true
	default:
		return false
	}
}

// LaunchPhase is durable client-only state between accepted and running.
type LaunchPhase uint8

const (
	LaunchPhaseNone LaunchPhase = iota
	LaunchPhasePrepared
	LaunchPhaseAuthorized
)

// CanAdvanceLaunchPhase permits only the one-way launch barrier.
func CanAdvanceLaunchPhase(from, to LaunchPhase) bool {
	return (from == LaunchPhaseNone && to == LaunchPhasePrepared) ||
		(from == LaunchPhasePrepared && to == LaunchPhaseAuthorized)
}

// MayRedispatch is false once command code may have been released.
func MayRedispatch(phase LaunchPhase) bool {
	return phase == LaunchPhaseNone || phase == LaunchPhasePrepared
}