package hostactors

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
)

// BoxBinding is the digest installed claim state on one box binds to: the
// deployment's binding facts and that box's row identity and state, read from
// one verified roster. It changes only when one of those facts changes. Holds,
// activations, enrollment attempts, consoles, regions, other boxes' rows, this
// box's role, label, group, loss ids and enrollment time, and the roster's
// write counter (Revision) never change it, so the console's per-operation
// roster writes no longer strand installed instances.
//
// The second result is false when ref names no row.
func BoxBinding(r Roster, ref string) (string, bool) {
	b, ok := r.Boxes[ref]
	if !ok {
		return "", false
	}
	sum := sha256.Sum256(boxBindingV1(r, b))
	return hex.EncodeToString(sum[:]), true
}

// ValidBinding reports whether s has BoxBinding's form: 64 lower-case hex
// digits. It says nothing about which roster or box it was computed from.
func ValidBinding(s string) bool {
	if len(s) != 2*sha256.Size {
		return false
	}
	for i := 0; i < len(s); i++ {
		if c := s[i]; (c < '0' || c > '9') && (c < 'a' || c > 'f') {
			return false
		}
	}
	return true
}

// boxBindingV1 freezes the binding facts in an ordered v1 tuple, encoded like
// the journal's request tuple (hostbox/journalservice.go). Never extend this
// tuple when Roster or Box grows: a new bound fact requires a new version tag
// and a separate encoder, and every installed stamp changes with it.
func boxBindingV1(r Roster, b Box) []byte {
	raw, _ := json.Marshal([]any{
		"carlos-box-binding-v1",
		r.DeploymentBucket, r.HomeRegion, r.RequestLimitNS, r.Publication, r.FloorSHA256,
		b.Enrollment, b.Namespace, b.BoxID, b.Region, b.Pool,
		[]any{b.Cloud.Provider, b.Cloud.Account, b.Cloud.Region, b.Cloud.InstanceID},
		b.EvidenceSHA256, b.State, b.QuarantineRevision, hex.EncodeToString(b.CensusPublicKey),
	})
	return raw
}