package main

// The wake word, "Мэйвен" (V-487 stage two).
//
// Silero answers "is this frame speech". It does not answer "was this said to
// her", and until this file existed nothing did: every utterance near the
// microphone became a turn. What made that safe rather than expensive was
// SurfaceVoice capping acts at L0, and L0 does not cap reading, so the room
// could still hear his facts read back.
//
// This file owns the 80ms cadence and the three rings of state between the
// models. wakefeatures.go owns the tensors.
//
// Nil is a working value, and it is the CLOSED gate rather than the open one.
// Feed on a nil receiver reports no keyword; session.go asks separately
// whether a gate exists at all. That split is deliberate: a nil that answers
// "yes, keyword" reads as a working wake word in every log line it produces.

import (
	"log"
	"sync"
)

// defaultWakeThreshold — score above which the keyword was said.
//
// Picked from the false-accept rate on held-out Russian speech, not from
// accuracy: a miss costs him a repeat, a false accept costs a turn nobody
// asked for. Over 65 minutes of Common Voice, 0.99 woke her three times and
// 0.999 once, and the difference in recall was one render out of 126. So the
// default is the strict one. `docs/evals/2026-08-09-wake-word.md` has both
// tables.
const defaultWakeThreshold = 0.999

// wakeWord is the streaming state around wakeModels. It is fed the same
// capture frames the VAD sees and answers whether the keyword has just been
// spoken.
type wakeWord struct {
	mu sync.Mutex
	m  *wakeModels

	threshold float64

	// pending holds captured samples not yet part of a full 80ms chunk, and
	// history holds the melContext samples before them.
	pending []float32
	history []float32

	// mels is the newest embedFrames mel frames, oldest first.
	mels [][melBins]float32
	// embeds is the newest headWindow embeddings, oldest first.
	embeds [][embedDim]float32

	last float64 // most recent score, held between chunks
}

// newWakeWord loads the models and wraps them in the streaming gate.
func newWakeWord(melPath, embedPath, headPath, libPath string, threshold float64) (*wakeWord, error) {
	m, err := newWakeModels(melPath, embedPath, headPath, libPath)
	if err != nil {
		return nil, err
	}
	if threshold <= 0 {
		threshold = defaultWakeThreshold
	}
	return &wakeWord{m: m, threshold: threshold}, nil
}

// Close releases the models.
func (w *wakeWord) Close() {
	if w == nil {
		return
	}
	w.mu.Lock()
	defer w.mu.Unlock()
	w.m.Close()
	w.m = nil
}

// Feed takes one capture frame and reports whether the keyword was heard on
// it. A nil wakeWord hears nothing.
func (w *wakeWord) Feed(frame []int16) bool {
	if w == nil {
		return false
	}
	w.mu.Lock()
	defer w.mu.Unlock()

	for _, v := range frame {
		w.pending = append(w.pending, float32(v)/32768.0)
	}
	fired := false
	for len(w.pending) >= chunkSamples {
		chunk := w.pending[:chunkSamples]
		if w.step(chunk) {
			fired = true
		}
		w.history = append(w.history[:0], tailFloat32(append(w.history, chunk...), melContext)...)
		// Slide the remainder to the front rather than reslicing. This runs
		// every 80ms for as long as the daemon lives.
		w.pending = append(w.pending[:0], w.pending[chunkSamples:]...)
	}
	return fired
}

// Reset drops the streaming state, so a fresh utterance is not judged on audio
// from before it. Called after every dispatch and after barge-in, for the same
// reason silero is: echo-era history must not score the next sentence, and her
// own voice saying the keyword must not wake her.
func (w *wakeWord) Reset() {
	if w == nil {
		return
	}
	w.mu.Lock()
	defer w.mu.Unlock()
	w.pending, w.history = w.pending[:0], w.history[:0]
	w.mels, w.embeds = nil, nil
	w.last = 0
}

// Score returns the most recent score, for the operator to read out of the
// journal when picking a threshold for his room.
func (w *wakeWord) Score() float64 {
	if w == nil {
		return 0
	}
	w.mu.Lock()
	defer w.mu.Unlock()
	return w.last
}

// step runs one 80ms chunk through all three models. It returns true when the
// score crosses the threshold on this chunk.
func (w *wakeWord) step(chunk []float32) bool {
	buf := make([]float32, 0, melContext+len(chunk))
	if pad := melContext - len(w.history); pad > 0 {
		buf = append(buf, make([]float32, pad)...)
	}
	buf = append(buf, tailFloat32(w.history, melContext)...)
	buf = append(buf, chunk...)

	frames, err := w.m.melFrames(buf)
	if err != nil {
		// A failed inference must not silence the microphone. Hold the last
		// score and let the next chunk try again.
		log.Printf("mavwaked: wake word: mel: %v", err)
		return false
	}
	w.mels = tailMel(append(w.mels, frames...), embedFrames)
	if len(w.mels) < embedFrames {
		return false
	}
	e, err := w.m.embedding(w.mels)
	if err != nil {
		log.Printf("mavwaked: wake word: embedding: %v", err)
		return false
	}
	w.embeds = tailEmbed(append(w.embeds, e), headWindow)
	if len(w.embeds) < headWindow {
		return false
	}
	score, err := w.m.score(w.embeds)
	if err != nil {
		log.Printf("mavwaked: wake word: head: %v", err)
		return false
	}
	// Report the crossing, not the state. A keyword held above the threshold
	// for a second is one wake, and firing on every chunk of it would make the
	// gate look open when it is merely slow to fall.
	crossed := score >= w.threshold && w.last < w.threshold
	w.last = score
	return crossed
}

// The three rings. Each keeps the newest n entries and nothing older.

func tailFloat32(s []float32, n int) []float32 {
	if len(s) <= n {
		return s
	}
	return s[len(s)-n:]
}

func tailMel(s [][melBins]float32, n int) [][melBins]float32 {
	if len(s) <= n {
		return s
	}
	return append(s[:0], s[len(s)-n:]...)
}

func tailEmbed(s [][embedDim]float32, n int) [][embedDim]float32 {
	if len(s) <= n {
		return s
	}
	return append(s[:0], s[len(s)-n:]...)
}