package main

// A question an agent session asks the operator, answered on a channel that proves who answered (novox/hq ADR 0332,
// issue 589).
//
// A session that needs a yes, a no or a choice asks it with claude_code_ask instead of waiting at a terminal the
// operator may not be watching. The ask is published under this module's name on the operator channel (ADR 0259):
// the bus grants that subject to this module alone, so the asker is proven by the bus, and the router stays the judge
// of answers, never an asker for others. Every option is at the level approve, so only a channel that proves who
// answered (Telegram, today) carries it, and each option binds the digest of the question and of itself.
//
// The session reads the answer by the question's key with claude_code_answer: from the router's own record of the
// ask, which only the router writes and only this module reads, held to the question as the `questions` state keeps
// it (asks.Warrant.For and asks.Option.Performs). A record that does not hold is said as not proven, never as a
// choice. An answer informs the session; it authorises nothing (ADR 0286 stays the way to an approved call).

import (
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	stdio "git.novox.be/novox/mesh-sdk/go"
	"git.novox.be/novox/mesh-sdk/go/asks"
)

// QuestionsState is the module's state the questions are kept in.
const QuestionsState = "questions"

// QuestionPrefix starts every question's key, so the router's word on one is never taken for a proposal's.
const QuestionPrefix = "q-"

// MostQuestions is how many questions may wait at once, mesh-wide: the router allows an asker three open asks
// (asks.MostOpen), and questions alone never fill them, so one is left for a proposed instruction section (ADR 0274)
// while two questions are open. Each open question holds one slot key in the `questions` state (slotKey), taken by
// create or by compare-and-set, so two nodes asking at once cannot both take the last one.
const MostQuestions = asks.MostOpen - 1

// A question the router holds no record of, and whose refusal was not heard here, keeps its slot until it expires:
// the router may still have it in its queue (down, or backlogged), and neither the queue's order nor a cancel can
// take it back — the queue offers a piece of work again after an error, so a cancel may be taken before the ask it
// cancels, and a cancel of an ask not yet recorded is dropped. Once the question has expired the router refuses it
// when it is taken (asks.Ask.Check), so the slot is free and the question has ended.

// slotKey is the key of one of the MostQuestions slots: not a question's key, so no question is ever read from it.
func slotKey(n int) string { return fmt.Sprintf("slot-%d", n) }

// slot is what a slot key holds: the question holding it.
type slot struct {
	Question string    `json:"question"`
	At       time.Time `json:"at"`
}

// The bounds of a question's life (ADR 0332 §2): at least five minutes, at most a day less ten minutes (the
// router's bound for an approval, with the margin a proposal keeps), an hour when none is given.
const (
	QuestionShortest = 5 * time.Minute
	QuestionLongest  = ProposalLasts
	QuestionDefault  = time.Hour
)

// The bounds of what a question says.
const (
	FewestQuestionOptions = 2
	MostContextBytes      = asks.SummaryLength
	MostMeansBytes        = 200
	MostWhyBytes          = 120
	MostOnExpiryBytes     = 200
)

// How long one claude_code_answer call may wait for the answer, and how often it looks meanwhile.
var (
	AnswerWaitsAtMost = 60 * time.Second
	AnswerLooksEvery  = 2 * time.Second
)

// QuestionOption is one answer a session offers.
type QuestionOption struct {
	ID          string `json:"id"`
	Label       string `json:"label"`
	Means       string `json:"means"`
	Recommended bool   `json:"recommended,omitempty"`
}

// QuestionStore is the `questions` state: a value with its revision, created only when absent, updated only at the
// revision read.
type QuestionStore interface {
	Get(key string) (json.RawMessage, uint64, bool, error)
	Create(key string, value any) error
	Update(key string, value any, revision uint64) error
	Put(key string, value any) error
}

// keptQuestions is the `questions` state on the bus.
type keptQuestions struct{ s stdio.KeptState }

func (k keptQuestions) Get(key string) (json.RawMessage, uint64, bool, error) {
	e, err := k.s.Get(key)
	if err != nil || e == nil {
		return nil, 0, false, err
	}
	return e.Value, e.Revision, true, nil
}
func (k keptQuestions) Create(key string, value any) error {
	_, err := k.s.Create(key, value)
	return err
}
func (k keptQuestions) Update(key string, value any, revision uint64) error {
	_, err := k.s.Update(key, value, revision)
	return err
}
func (k keptQuestions) Put(key string, value any) error { _, err := k.s.Put(key, value); return err }

// Question is one question, as the `questions` state keeps it. Every field the ask is composed from is here, so the
// answer is held to exactly the question asked.
type Question struct {
	ID       string           `json:"id"`
	Headline string           `json:"headline"`
	Context  string           `json:"context"`
	Options  []QuestionOption `json:"options"`
	Why      string           `json:"why"`
	OnExpiry string           `json:"on-expiry"`
	By       string           `json:"by"`
	From     string           `json:"from"`
	At       time.Time        `json:"at"`
	Expires  time.Time        `json:"expires"`
	// Form is how its ask is composed (AskGlance since novox/hq issue 639), so the answer is held to the ask asked.
	Form int `json:"form,omitempty"`
	// Asked is empty once the ask was published, or says why it was not; nothing composes from it.
	Asked string `json:"asked,omitempty"`
	// Ended is the router's word that the ask ended without a choice, as heard on the decided subject: a refused ask
	// leaves no record of the router's to read it from. It never makes a choice.
	Ended string `json:"ended,omitempty"`
}

// recommended is the option marked as recommended.
func (q Question) recommended() (QuestionOption, bool) {
	for _, o := range q.Options {
		if o.Recommended {
			return o, true
		}
	}
	return QuestionOption{}, false
}

// Act is what an answer binds: this question, whole, and the option chosen.
func (q Question) Act(option string) asks.Act {
	act := asks.Act{"verb": Module + ".question", "option": option, "question": q.ID, "headline": q.Headline,
		"context": q.Context, "why": q.Why, "on-expiry": q.OnExpiry, "by": q.By, "from": q.From,
		"at": q.At.UTC().Format(time.RFC3339Nano), "expires": q.Expires.UTC().Format(time.RFC3339Nano),
		"options": strconv.Itoa(len(q.Options))}
	for i, o := range q.Options {
		act[fmt.Sprintf("option.%d", i)] = o.ID + "\n" + o.Label + "\n" + o.Means + "\n" + strconv.FormatBool(o.Recommended)
	}
	return act
}

// Ask is the ask for a question, composed from it alone, in the form it was asked in.
func (q Question) Ask() asks.Ask {
	if q.Form == AskGlance {
		return q.glanceAsk()
	}
	return q.listedAsk()
}

// glanceAsk is the question read at a glance on the phone (novox/hq issue 639): its context, then the recommended
// answer and why as its one point; who asked and what the answer does are its Details.
func (q Question) glanceAsk() asks.Ask {
	explanation := strings.TrimSpace(q.Context)
	if rec, ok := q.recommended(); ok {
		explanation += fmt.Sprintf("\n• Recommended: %s, because %s.", rec.Label, strings.TrimRight(strings.TrimSpace(q.Why), "."))
	}
	details := fmt.Sprintf("Asked by the agent session %s on %s through the claude-code module, at %s UTC. Your answer is told "+
		"to that session; it performs nothing by itself.", q.By, q.From, q.At.UTC().Format("15:04 on 2 Jan"))
	return q.withOptions(asks.Ask{ID: q.ID, Headline: q.Headline, Explanation: explanation, Details: details})
}

func (q Question) withOptions(a asks.Ask) asks.Ask {
	a.Who, a.Expires, a.OnExpiry = asks.Operator, q.Expires, q.OnExpiry
	for _, o := range q.Options {
		does := o.Means
		if o.Recommended {
			does = "Recommended. " + does
		}
		binds, _ := asks.ActDigest(q.Act(o.ID))
		a.Options = append(a.Options, asks.Option{ID: o.ID, Label: o.Label, Does: does, Level: asks.Approve, Binds: binds})
	}
	return a
}

// listedAsk is the ask as it was composed before issue 639: composed only to hold the answer to a question asked then.
func (q Question) listedAsk() asks.Ask {
	var b strings.Builder
	b.WriteString(strings.TrimSpace(q.Context))
	if rec, ok := q.recommended(); ok {
		fmt.Fprintf(&b, "\n\nRecommended: %s, because %s", rec.Label, strings.TrimRight(strings.TrimSpace(q.Why), "."))
		b.WriteString(".")
	}
	fmt.Fprintf(&b, "\n\nAsked by the agent session %s on %s through the claude-code module, at %s UTC. "+
		"Your answer is told to that session; it performs nothing by itself.", q.By, q.From, q.At.UTC().Format("15:04 on 2 Jan"))
	a := asks.Ask{ID: q.ID, Headline: q.Headline, Explanation: b.String(), Who: asks.Operator, Expires: q.Expires,
		OnExpiry: q.OnExpiry}
	for _, o := range q.Options {
		does := o.Means
		if o.Recommended {
			does = "Recommended. " + does
		}
		binds, _ := asks.ActDigest(q.Act(o.ID))
		a.Options = append(a.Options, asks.Option{ID: o.ID, Label: o.Label, Does: does, Level: asks.Approve, Binds: binds})
	}
	return a
}

var sessionName = regexp.MustCompile(`^[A-Za-z0-9][A-Za-z0-9_-]{0,47}$`)

// QuestionProblem says why a question cannot be asked, or "": every bound of ADR 0332 §2 that this module holds
// itself. The words are held to the content rule by the router, which says its refusal back.
func QuestionProblem(q Question) string {
	var problems []string
	add := func(format string, args ...any) { problems = append(problems, fmt.Sprintf(format, args...)) }
	switch {
	case strings.TrimSpace(q.Headline) == "":
		add("it has no headline")
	case len([]rune(q.Headline)) > asks.HeadlineLength:
		add("its headline is %d characters, more than %d", len([]rune(q.Headline)), asks.HeadlineLength)
	}
	switch {
	case strings.TrimSpace(q.Context) == "":
		add("it gives no context: say in plain words what the operator decides and why it matters")
	case len([]rune(q.Context)) > MostContextBytes:
		add("its context is %d characters, more than the %d a phone shows in one glance", len([]rune(q.Context)), MostContextBytes)
	case strings.Contains(strings.TrimSpace(q.Context), "\n"):
		add("its context is more than one line: a phone shows it at a glance as one short paragraph")
	}
	if n := len(q.Options); n < FewestQuestionOptions || n > asks.MostOptions {
		add("it offers %d options; a question offers %d to %d", n, FewestQuestionOptions, asks.MostOptions)
	}
	recommended, labels := 0, map[string]bool{}
	for i, o := range q.Options {
		switch {
		case strings.TrimSpace(o.Label) == "":
			add("option %d has no label", i+1)
		case len([]rune(o.Label)) > asks.LabelLength:
			add("option %d's label is longer than %d characters", i+1, asks.LabelLength)
		case labels[strings.ToLower(o.Label)]:
			add("two options are labelled %q", o.Label)
		}
		labels[strings.ToLower(o.Label)] = true
		if strings.TrimSpace(o.Means) == "" {
			add("option %d does not say what choosing it means", i+1)
		} else if len(o.Means) > MostMeansBytes {
			add("what option %d means is longer than %d bytes", i+1, MostMeansBytes)
		}
		if !asks.UsableID(o.ID) {
			add("option %d's id is not one", i+1)
		}
		if o.Recommended {
			recommended++
		}
	}
	if recommended != 1 {
		add("%d options are marked recommended; exactly one is", recommended)
	}
	switch {
	case strings.TrimSpace(q.Why) == "":
		add("it does not say why the recommended option is recommended")
	case len(q.Why) > MostWhyBytes:
		add("why the option is recommended is longer than %d bytes", MostWhyBytes)
	}
	switch {
	case strings.TrimSpace(q.OnExpiry) == "":
		add("it does not say what the session does if nobody answers")
	case len(q.OnExpiry) > MostOnExpiryBytes:
		add("what happens if nobody answers is longer than %d bytes", MostOnExpiryBytes)
	}
	if !sessionName.MatchString(q.By) {
		add("who asks is not a session's name: letters, digits, - and _, such as fix-589")
	}
	if !nodeName.MatchString(q.From) {
		add("where it comes from is not a node's name")
	}
	if life := q.Expires.Sub(q.At); life < QuestionShortest || life > QuestionLongest {
		add("it lasts %s; a question lasts %s to %s", life.Round(time.Minute), QuestionShortest, QuestionLongest)
	}
	if problem := questionWordsProblem(q); problem != "" {
		add("%s", problem)
	}
	if len(problems) == 0 {
		return ""
	}
	return strings.Join(problems, "; ")
}

// questionWordsProblem says why a question's words may not be kept at all, or "": anything shaped like a secret, or a
// character a phone does not show, in any word the operator is shown — the headline, the context, why, what happens
// on expiry, and each option's label and meaning. Judged before anything is kept: the `questions` state is read by
// every node, and the router judges the content rule only after the question was kept.
func questionWordsProblem(q Question) string {
	fields := []struct{ name, text string }{{"the headline", q.Headline}, {"the context", q.Context}, {"why", q.Why},
		{"what happens on expiry", q.OnExpiry}}
	for i, o := range q.Options {
		fields = append(fields, struct{ name, text string }{fmt.Sprintf("option %d's label", i+1), o.Label},
			struct{ name, text string }{fmt.Sprintf("what option %d means", i+1), o.Means})
	}
	for _, f := range fields {
		for _, re := range secretShaped {
			if re.MatchString(f.text) {
				return f.name + " holds something shaped like a secret, which is never kept or shown on a phone"
			}
		}
		if what := invisible(f.text); what != "" {
			return f.name + " holds " + what + ", which a phone does not show"
		}
	}
	return ""
}

func newQuestionID() string {
	var b [8]byte
	_, _ = rand.Read(b[:])
	return QuestionPrefix + hex.EncodeToString(b[:])
}

// QuestionInput is what a session asks.
type QuestionInput struct {
	Headline string
	Context  string
	Options  []QuestionOption
	Why      string
	OnExpiry string
	By       string
	Expires  time.Duration
}

// AskQuestion keeps a question and asks the operator. It answers within seconds, once the router has said whether it
// took the question, with the question's key; the answer is read with ReadAnswer.
func AskQuestion(p Paths, in QuestionInput, store QuestionStore, bus AskBus, now time.Time) (map[string]any, error) {
	refuse := func(why string) (map[string]any, error) { return nil, errors.New(why + ". Nothing was asked") }
	by := strings.TrimSpace(in.By)
	if who, node, found := strings.Cut(by, "@"); found {
		if node != p.Node {
			return refuse(fmt.Sprintf("who asks names the node %q, and this is %s: ask on the node the session runs on", node, p.Node))
		}
		by = who
	}
	if by == "" {
		return refuse("it does not say who asks: give by, your session's name as who@node, such as fix-589@g14")
	}
	life := in.Expires
	if life == 0 {
		life = QuestionDefault
	}
	q := Question{ID: newQuestionID(), Headline: strings.TrimSpace(in.Headline), Context: strings.TrimSpace(in.Context),
		Why: strings.TrimSpace(in.Why), OnExpiry: strings.TrimSpace(in.OnExpiry), By: by, From: p.Node, At: now.UTC(),
		Expires: now.UTC().Add(life), Form: AskGlance}
	for i, o := range in.Options {
		q.Options = append(q.Options, QuestionOption{ID: fmt.Sprintf("o%d", i+1), Label: strings.TrimSpace(o.Label),
			Means: strings.TrimSpace(o.Means), Recommended: o.Recommended})
	}
	if problem := QuestionProblem(q); problem != "" {
		return refuse(problem)
	}
	ask := q.Ask()
	if err := ask.Check(now); err != nil {
		return refuse(err.Error())
	}
	// The question is kept before its slot is taken, so a slot always names a question another node can judge.
	if err := store.Create(q.ID, q); err != nil {
		return nil, fmt.Errorf("the question could not be kept, so the operator was not asked: %w", err)
	}
	if open, err := takeSlot(store, bus, q, now); err != nil {
		_ = store.Put(q.ID, tombstone(q, "not asked: "+err.Error()))
		return refuse(err.Error())
	} else if open != nil {
		_ = store.Put(q.ID, tombstone(q, "not asked: two questions were open"))
		return refuse(fmt.Sprintf("%d questions already wait for the operator's answer (%s), and sessions hold at most %d "+
			"at once, so one of the router's three open asks is left for a proposed instruction section; read them with "+
			"claude_code_answer, or wait for one to end", len(open), strings.Join(open, ", "), MostQuestions))
	}
	if err := bus.Publish(asks.AskSubject(Module), ask, ask.ID); err != nil {
		_ = store.Put(q.ID, tombstone(q, "not asked: "+err.Error()))
		return nil, fmt.Errorf("the operator could not be asked: %v", err)
	}
	say("question %s from the session %s asked of the operator", q.ID, q.By)
	taken := "the router has not said yet whether it took the question; claude_code_answer says"
	defer forgetQuestionEnd(q.ID)
	for deadline := time.Now().Add(RouterAnswersWithin); time.Now().Before(deadline); {
		if w, ended := questionEnd(q.ID); ended {
			return nil, fmt.Errorf("the router did not ask the operator: the question %s (%s)", w.Outcome, w.Words)
		}
		if entry, err := bus.Record(q.ID); err == nil && entry != nil {
			taken = "the router took the question and shows it where who answers is proven (Telegram)"
			break
		}
		time.Sleep(RouterAnswersEvery)
	}
	return map[string]any{
		"key":     q.ID,
		"router":  taken,
		"asked":   "\"" + q.Headline + "\", with the answers " + labelsOf(q),
		"expires": q.Expires.Format(time.RFC3339),
		"next": "read the answer with claude_code_answer {\"key\": \"" + q.ID + "\"} (it may wait up to a minute); " +
			"keep working meanwhile, and if it expires do what you said: " + q.OnExpiry,
	}, nil
}

func labelsOf(q Question) string {
	var out []string
	for _, o := range q.Options {
		out = append(out, o.Label)
	}
	return strings.Join(out, ", ")
}

// questionOpen says whether a question still waits: kept, asked, not ended, not expired, and open in the router's
// record or not recorded yet. An unreadable record is open: a slot is never freed on a guess.
func questionOpen(store QuestionStore, bus AskBus, id string, now time.Time) (bool, error) {
	q, ok, err := readQuestionErr(store, id)
	if err != nil {
		return true, err
	}
	if !ok || q.Asked != "" || q.Ended != "" || !now.Before(q.Expires) {
		return false, nil
	}
	entry, err := bus.Record(q.ID)
	if err != nil {
		return true, err
	}
	if entry == nil {
		return true, nil
	}
	var rec routerRecord
	if json.Unmarshal(entry.Value, &rec) != nil {
		return true, nil
	}
	return rec.State == "" || rec.State == "open", nil
}

// takeSlot takes one of the MostQuestions slots for q: a slot no key holds, by create, or one whose question no longer
// waits, by compare-and-set at the revision read. Of two nodes taking the same slot only one wins; the other tries
// the next. It answers the open questions when every slot is held, and an error — refusing, never guessing — when a
// slot or its question cannot be read.
func takeSlot(store QuestionStore, bus AskBus, q Question, now time.Time) ([]string, error) {
	mine := slot{Question: q.ID, At: q.At}
	var open []string
	for n := 1; n <= MostQuestions; n++ {
		key := slotKey(n)
		raw, rev, found, err := store.Get(key)
		if err != nil {
			return nil, fmt.Errorf("the open questions could not be counted (%v), so none more is asked", err)
		}
		if !found {
			if err := store.Create(key, mine); err == nil {
				return nil, nil
			} else if !errors.Is(err, stdio.ErrChanged) {
				return nil, fmt.Errorf("the open questions could not be counted (%v), so none more is asked", err)
			}
			if raw, rev, found, err = store.Get(key); err != nil || !found {
				return nil, fmt.Errorf("the open questions could not be counted, so none more is asked")
			}
		}
		var held slot
		if json.Unmarshal(raw, &held) == nil && held.Question != "" {
			waits, err := questionOpen(store, bus, held.Question, now)
			if err != nil {
				return nil, fmt.Errorf("the open questions could not be counted (%v), so none more is asked", err)
			}
			if waits {
				open = append(open, held.Question)
				continue
			}
		}
		if err := store.Update(key, mine, rev); err == nil {
			return nil, nil
		} else if !errors.Is(err, stdio.ErrChanged) {
			return nil, fmt.Errorf("the open questions could not be counted (%v), so none more is asked", err)
		}
		open = append(open, "one taken just now")
	}
	sort.Strings(open)
	return open, nil
}

// tombstone is what is kept of a question that was not asked or that the router refused: its key, who asked, when, and
// why it ended — none of its words, which the router judged unfit to leave the mesh or never saw.
func tombstone(q Question, ended string) Question {
	return Question{ID: q.ID, By: q.By, From: q.From, At: q.At, Expires: q.Expires, Ended: ended}
}

func readQuestion(store QuestionStore, key string) (Question, bool) {
	q, ok, _ := readQuestionErr(store, key)
	return q, ok
}

func readQuestionErr(store QuestionStore, key string) (Question, bool, error) {
	if !strings.HasPrefix(key, QuestionPrefix) {
		return Question{}, false, nil
	}
	raw, _, found, err := store.Get(key)
	if err != nil || !found {
		return Question{}, false, err
	}
	var q Question
	if json.Unmarshal(raw, &q) != nil || q.ID != key {
		return Question{}, false, nil
	}
	return q, true, nil
}

// The router's word that a question ended without a choice, as heard on the decided subject.
var (
	questionEndsMu sync.Mutex
	questionEnds   = map[string]asks.Warrant{}
)

func questionEnd(id string) (asks.Warrant, bool) {
	questionEndsMu.Lock()
	defer questionEndsMu.Unlock()
	w, ok := questionEnds[id]
	return w, ok
}

func forgetQuestionEnd(id string) {
	questionEndsMu.Lock()
	delete(questionEnds, id)
	questionEndsMu.Unlock()
}

// HeardQuestionEnd takes the router's word that a question ended without a choice — refused, expired, cancelled or
// replaced — and keeps it on the question, because a refused ask leaves no record of the router's. A refused question
// keeps none of its words (tombstone). A choice is never taken from this word: only from the router's record, held to
// the question (ReadAnswer).
func HeardQuestionEnd(store QuestionStore, w asks.Warrant) {
	if w.Asker != Module || w.Outcome == asks.OutcomeChosen || !strings.HasPrefix(w.Ask, QuestionPrefix) {
		return
	}
	q, known := readQuestion(store, w.Ask)
	if !known {
		return
	}
	if q.Ended == "" {
		ended := string(w.Outcome)
		if w.Words != "" {
			ended += ": " + w.Words
		}
		if w.Outcome == asks.OutcomeRefused {
			q = tombstone(q, ended)
		} else {
			q.Ended = ended
		}
		_ = store.Put(q.ID, q)
	}
	// Kept on the question first, then said to a session waiting on it: what it reads next is already there.
	questionEndsMu.Lock()
	questionEnds[w.Ask] = w
	questionEndsMu.Unlock()
}

// The answer's states, as claude_code_answer says them.
const (
	AnswerWaiting   = "waiting"
	AnswerChosen    = "chosen"
	AnswerEnded     = "ended"
	AnswerNotProven = "not proven"
)

// ReadAnswer is where a question stands: waiting, chosen (and what), ended without a choice, or not proven.
func ReadAnswer(store QuestionStore, bus AskBus, key string, now time.Time) (map[string]any, error) {
	q, ok := readQuestion(store, strings.TrimSpace(key))
	if !ok {
		return nil, fmt.Errorf("no question %q is kept: the key is the one claude_code_ask gave", key)
	}
	out := map[string]any{"key": q.ID, "headline": q.Headline, "asked": q.At.Format(time.RFC3339),
		"expires": q.Expires.Format(time.RFC3339)}
	if q.Asked != "" {
		out["state"], out["words"] = AnswerEnded, q.Asked
		return out, nil
	}
	entry, err := bus.Record(q.ID)
	if err != nil {
		return nil, fmt.Errorf("the router's record of the question could not be read now (%v); ask again", err)
	}
	var rec routerRecord
	if entry != nil {
		if err := json.Unmarshal(entry.Value, &rec); err != nil {
			out["state"], out["words"] = AnswerNotProven, "the router's record of it cannot be read: "+err.Error()
			return out, nil
		}
	}
	switch {
	case entry == nil && q.Ended != "":
		out["state"], out["words"] = AnswerEnded, q.Ended
	case entry == nil && !now.Before(q.Expires):
		out["state"], out["words"] = AnswerEnded, "expired without the router recording it: refused (its refusal was not "+
			"heard here) or never taken; the router refuses it now if it is taken late"
		out["now"] = "do what you said: " + q.OnExpiry
	case entry == nil:
		out["state"] = AnswerWaiting
		out["words"] = "not yet recorded by the router: it may still be in the router's queue, or was refused without the " +
			"refusal being heard here. It holds its slot, and the operator may still be asked, until it expires at " +
			q.Expires.Format(time.RFC3339)
	case entry == nil, rec.State == "open", rec.Warrant == nil:
		out["state"] = AnswerWaiting
		if q.Ended != "" {
			out["words"] = "the router said it ended (" + q.Ended + "), and its record says it is open; read again"
		}
	default:
		w := *rec.Warrant
		if w.Outcome != asks.OutcomeChosen {
			out["state"], out["words"] = AnswerEnded, string(w.Outcome)
			if w.Words != "" {
				out["words"] = string(w.Outcome) + ": " + w.Words
			}
			if w.Outcome == asks.OutcomeExpired {
				out["now"] = "do what you said: " + q.OnExpiry
			}
			return out, nil
		}
		if problem := QuestionProblem(q); problem != "" {
			out["state"], out["words"] = AnswerNotProven, "the question kept is not one this module asks: "+problem
			return out, nil
		}
		option, err := w.For(Module, q.Ask())
		if err == nil {
			err = option.Performs(q.Act(option.ID))
		}
		if err != nil {
			say("REFUSED the answer to question %s: %v", q.ID, err)
			out["state"], out["words"] = AnswerNotProven, "the router's record does not hold to the question asked: "+err.Error()
			return out, nil
		}
		chosen := map[string]any{"id": option.ID, "label": option.Label}
		for _, o := range q.Options {
			if o.ID == option.ID {
				chosen["means"], chosen["recommended"] = o.Means, o.Recommended
			}
		}
		out["state"], out["chosen"], out["by"], out["channel"], out["at"] = AnswerChosen, chosen, w.Says(), w.Channel,
			w.At.Format(time.RFC3339)
		out["note"] = "the operator's word to this session; it authorises no call that needs the operator's approval"
	}
	return out, nil
}

// WaitForAnswer reads the answer, and while it is waiting reads it again until wait has passed.
func WaitForAnswer(store QuestionStore, bus AskBus, key string, wait time.Duration, now func() time.Time) (map[string]any, error) {
	if wait > AnswerWaitsAtMost {
		wait = AnswerWaitsAtMost
	}
	deadline := time.Now().Add(wait)
	for {
		out, err := ReadAnswer(store, bus, key, now())
		if err != nil || out["state"] != AnswerWaiting || !time.Now().Before(deadline) {
			return out, err
		}
		time.Sleep(AnswerLooksEvery)
	}
}