// Package rollout is the box's rollout scheduler (zero-downtime deploys spec
// §6, §8, §10). It decides which instance moves to which build, when, in which
// swap mode, and what happens when a build fails. It is armed only by
// CARLOS_SWAP=overlap. With the flag unset nothing in this package runs, and
// the box keeps today's stop-then-wake paths.
package rollout

import "strings"

// SwapEnv is the box flag (spec §15).
const SwapEnv = "CARLOS_SWAP"

// Enabled reports whether the box flag arms the scheduler. Only the exact
// word "overlap" does: a typo must leave the box on today's paths, not on a
// half-understood new one.
func Enabled(getenv func(string) string) bool {
	return strings.TrimSpace(getenv(SwapEnv)) == "overlap"
}