package dialogue

import (
	"sync"
	"time"
)

// Slot names one field of Slots. Named type, not a free string, so a missing
// slot cannot be misspelled — the question phrasing switches on these.
type Slot string

const (
	SlotTime  Slot = "time"  // Slots.Time / HasTime
	SlotKey   Slot = "key"   // Slots.Key / HasKey
	SlotValue Slot = "value" // Slots.Value (paired with Key)
	SlotFn    Slot = "fn"    // Slots.Fn / HasFn
	SlotText  Slot = "text"  // Slots.Text
)

// MaxAttempts is 1 because Maven is not a nag (DESIGN.md § Non-goals). She asks
// one clarifying question. If the answer still leaves the slot empty she drops
// the request instead of asking again.
const MaxAttempts = 1

// PendingQuestion is what Maven holds while she waits for an answer to an open
// question. Unlike the yes/no confirms in cmd/mavend/voice.go, the answer here
// is free text that fills a missing slot rather than a verdict.
type PendingQuestion struct {
	Intent    Intent // what the router already guessed
	Slots     Slots  // what it already filled
	Missing   []Slot // what is still empty, in the order to ask about
	Utterance string // the user's original raw words
	Asked     time.Time
	TTL       time.Duration
	Attempts  int // questions already asked; capped by MaxAttempts
}

func (q *PendingQuestion) IsExpired(now time.Time) bool {
	return now.After(q.Asked.Add(q.TTL))
}

// CanAsk reports whether Maven may ask another question about this request.
func (q *PendingQuestion) CanAsk() bool {
	return q.Attempts < MaxAttempts
}

// TODO: the daemon will phrase the question text from Missing (one short ru
// question per Slot, feminine self-reference) and speak it here.

// ClarifyStore holds the parked questions. Same shape and locking as
// SessionStore: keyed by dialogue id, expired entries dropped on read.
type ClarifyStore struct {
	mu         sync.RWMutex
	questions  map[string]*PendingQuestion
	defaultTTL time.Duration
}

func NewClarifyStore(defaultTTL time.Duration) *ClarifyStore {
	if defaultTTL <= 0 {
		// Short, like confirmTTL in voice.go: a clarifying question is a
		// same-breath gesture, a stale one should not eat a later utterance.
		defaultTTL = 90 * time.Second
	}
	return &ClarifyStore{
		questions:  make(map[string]*PendingQuestion),
		defaultTTL: defaultTTL,
	}
}

// TODO: the daemon will Put a question here when Decision.Clarify fires, in
// place of the flat "не разобрала" reply (cmd/mavend/voice.go).
func (s *ClarifyStore) Put(id string, q *PendingQuestion) {
	if q.TTL <= 0 {
		q.TTL = s.defaultTTL
	}
	s.mu.Lock()
	s.questions[id] = q
	s.mu.Unlock()
}

// TODO: the daemon will Get on the next turn, parse that turn into Slots, call
// Answer, and Delete — the open-question twin of resolveConfirm.
func (s *ClarifyStore) Get(id string, now time.Time) *PendingQuestion {
	s.mu.RLock()
	q, ok := s.questions[id]
	s.mu.RUnlock()
	if !ok {
		return nil
	}
	if q.IsExpired(now) {
		s.Delete(id)
		return nil
	}
	return q
}

func (s *ClarifyStore) Delete(id string) {
	s.mu.Lock()
	delete(s.questions, id)
	s.mu.Unlock()
}

// Answer merges the slots parsed from the user's answer into the parked ones.
// Only the slots listed in Missing are filled, and an already filled slot is
// never overwritten — the answer completes the original request, it does not
// restate it. Parsing the answer text into `answer` is the caller's job; this
// package must stay free of internal/router.
func (q *PendingQuestion) Answer(text string, answer Slots) Slots {
	out := q.Slots
	for _, slot := range q.Missing {
		switch slot {
		case SlotTime:
			if !out.HasTime && answer.HasTime {
				out.Time = answer.Time
				out.HasTime = true
			}
		case SlotKey:
			if !out.HasKey && answer.HasKey {
				out.Key = answer.Key
				out.HasKey = true
			}
		case SlotValue:
			if out.Value == "" && answer.Value != "" {
				out.Value = answer.Value
			}
		case SlotFn:
			if !out.HasFn && answer.HasFn {
				out.Fn = answer.Fn
				out.HasFn = true
				if len(out.Args) == 0 {
					out.Args = append([]string(nil), answer.Args...)
				}
			}
		case SlotText:
			if out.Text == "" {
				if answer.Text != "" {
					out.Text = answer.Text
				} else {
					// No parse for a text slot — the raw answer IS the text.
					out.Text = text
				}
			}
		}
	}
	return out
}

// StillMissing lists the slots that are empty in s, out of the ones asked for.
// The caller uses it to decide between acting and dropping the request.
func StillMissing(want []Slot, s Slots) []Slot {
	var out []Slot
	for _, slot := range want {
		empty := false
		switch slot {
		case SlotTime:
			empty = !s.HasTime
		case SlotKey:
			empty = !s.HasKey
		case SlotValue:
			empty = s.Value == ""
		case SlotFn:
			empty = !s.HasFn
		case SlotText:
			empty = s.Text == ""
		}
		if empty {
			out = append(out, slot)
		}
	}
	return out
}