package viewstate

import (
	"fmt"
	"strings"

	"git.novox.be/novox/mesh-delivery/contracts/go/clients/meshdeliveryclient"
	"git.novox.be/novox/mesh-delivery/modules/mesh-delivery-assigner/asks"
)

const viewWord = "view"

// ViewAnswerKey is the key, in the state answers, of the view's answer to the ask at askKey: `<ask key>.view`. An ask that needs
// proof of who answered is refused with its reason: it is answered on the phone (issue 953).
func ViewAnswerKey(askKey string) (string, error) {
	ask, err := asks.ParseAnyAskKey(askKey)
	if err != nil {
		return "", err
	}
	if proof, _ := asks.AskNeedsProof(ask.Kind); proof {
		return "", fmt.Errorf("viewstate: the ask %s needs proof of who answered: answer it on the phone (issue 953)", askKey)
	}
	return askKey + "." + viewWord, nil
}

// ParseViewAnswerKey is the inverse of ViewAnswerKey: the ask's key. It refuses a key without `.view`, an ask key of a kind that
// needs proof, and a key of another state, naming it.
func ParseViewAnswerKey(key string) (askKey string, err error) {
	askKey, ok := strings.CutSuffix(key, "."+viewWord)
	if !ok {
		return "", fmt.Errorf("viewstate: %q is not a view answer key, <ask key>.view", key)
	}
	if _, err := ViewAnswerKey(askKey); err != nil {
		return "", fmt.Errorf("viewstate: %q is not a view answer key: %w", key, err)
	}
	return askKey, nil
}

// ViewAnswerFits says whether the view's answer a answers the ask at key as it stands now: it refuses an answer to another
// asking of the ask (a stale answer to an earlier writing of the same key), naming both. Whether the ask offers the option
// chosen, and at the level acknowledge only (an option that authorises is answered on a channel that proves who answered,
// never in the view, which proves nobody), the teller reads from the ask through operator-channel's client.
func ViewAnswerFits(a ViewAnswer, key string, ask asks.Ask) error {
	if want := meshdeliveryclient.AskingID(key, ask.Asking); a.Asking != want {
		return fmt.Errorf("viewstate: the view's answer is to the asking %s, and the ask stands at the asking %s", a.Asking, want)
	}
	return nil
}