package activator

import "context"

// BuildStateLocation is where an instance's build-state.json lives (settings
// spec §4.2): the bucket and the prefix of the lease's lock.json. With host
// claims off that is Config.Bucket and HibernatePrefix(Config.Prefix, host);
// with them on, the claim actor's bucket and Holder.Location (never a
// g-<gen>/ generation prefix). The wake knows which lease it holds, so it
// puts the location on the context it hands BeforeExec, and the agent's hook
// writes there rather than guessing.
type BuildStateLocation struct{ Bucket, Prefix string }

type buildStateLocationKey struct{}

// WithBuildStateLocation returns ctx carrying l. A location with either part
// empty reads back as none, so a caller can mask a location it inherited.
func WithBuildStateLocation(ctx context.Context, l BuildStateLocation) context.Context {
	return context.WithValue(ctx, buildStateLocationKey{}, l)
}

// BuildStateLocationFrom is the location ctx carries, if a whole one.
func BuildStateLocationFrom(ctx context.Context) (BuildStateLocation, bool) {
	l, ok := ctx.Value(buildStateLocationKey{}).(BuildStateLocation)
	if !ok || l.Bucket == "" || l.Prefix == "" {
		return BuildStateLocation{}, false
	}
	return l, true
}