package park

import (
	"github.com/carlosframework/platform/internal/regionname"
	"time"
)

// HomePlacementCode is the console door's home-name rule. It consumes a
// roster/API name, not an engine region; @home is never a placement code.
func HomePlacementCode(home, region string) string { return regionname.HomePlacementCode(home, region) }

// SameRegion compares nonempty engine identities under the verified home binding.
func SameRegion(home, a, b string) bool { return regionname.SameRegion(home, a, b) }

func QuietUntil(bounds map[string]time.Time, home, region string) time.Time {
	var latest time.Time
	for r, until := range bounds {
		if SameRegion(home, r, region) && latest.Before(until) {
			latest = until
		}
	}
	return latest
}

func (e Engine) OwnsRegion(region string) bool {
	return SameRegion(e.HomeRegion, e.Region, region)
}

func (v View) sameRegion(a, b string) bool { return SameRegion(v.HomeRegion, a, b) }

// PlacementMatches compares a record code with a nonempty engine identity.
func PlacementMatches(home, code, engine string) bool {
	return SameRegion(home, PlacementRegion(code), engine)
}

// BoundHome joins the verified local binding and the admitted operation's
// binding for history reads. It never changes an engine's ownership.
func BoundHome(local, operation string) (string, error) {
	for _, home := range []string{local, operation} {
		if home != "" && PlacementRegion(home) != home {
			return "", ErrUnsafe
		}
	}
	if local != "" && operation != "" && local != operation {
		return "", ErrUnsafe
	}
	if local != "" {
		return local, nil
	}
	return operation, nil
}

// EnginePlacement projects a verified engine identity into record vocabulary.
func EnginePlacement(home, engine string) (string, bool) {
	if engine == "" {
		return "", false
	}
	if SameRegion(home, engine, HomeRegion) {
		return "", true
	}
	return engine, PlacementRegion(engine) == engine
}

func VerifiedHome(fleet, local, region, operation string) (string, error) {
	if (fleet != "" && PlacementRegion(fleet) != fleet) || (operation != "" && operation != fleet) || (local != "" && (local != fleet || local != region)) || (local == "" && operation != "" && operation == region) {
		return "", ErrUnsafe
	}
	return BoundHome(local, operation)
}