// Package witness is the node-engine watching a core build it placed — the node tools on every machine — and
// restoring the build before it when the new one is not healthy in bound (novox/hq to-be 45 §8, ADR 0227 rule 8: the
// component being replaced is never the only witness of its successor).
//
// **The contract is this file.** What the engine reads to call a build healthy, from where, in what
// shape, within which bound — said once, here, and held by contract_test.go.
package witness

import (
	"time"

	"github.com/novox/mesh-host/internal/link"
)

// The witnesses, as a process declares which watches it (`witness`). A process that says none is placed as ever; one
// that says nothing is judged by its name's default (Default).
const (
	// ByPing: healthy when this machine's runtime answers the services protocol's PING.
	ByPing = "ping"
	// ByNone: not judged.
	ByNone = "none"
)

// Bounds (to-be 45 §8). A build is given Within of time the witness could ask in; asked every Every.
const (
	// NodeToolsWithin: the runtime is announced and answering within sixty seconds of starting,
	// each PING answered within PingWithin.
	NodeToolsWithin = 60 * time.Second
	PingWithin      = 5 * time.Second
	Every           = 5 * time.Second
	// GiveUp is how long a witness goes on when it cannot ask at all before it says the build is
	// unwitnessed: the grant missing, the bus away the whole time.
	GiveUp = 30 * time.Minute
)

// NodeToolsService is the runtime's name on the services protocol, and its instance is this
// machine's node name: what `$SRV.PING.<service>.<node>` asks, so only this machine's runtime can
// answer (mesh-tools node-tools internal/runtime, announce.Service{Name: module, ID: node}).
const NodeToolsService = "node-tools"

// Default is the witness a process is judged by when it names none: the core process the mesh composes on every
// machine, by the name it composes it under, and nothing else.
func Default(process string) string {
	if process == NodeToolsService {
		return ByPing
	}
	return ByNone
}

// Within is the bound for a witness.
func Within(string) time.Duration { return NodeToolsWithin }

// Component names what a witness judges, as a rollback says it.
func Component(string) string { return link.ComponentNodeTools }