"""Utterance detection: adaptive energy VAD with hangover.

Deliberately simple and dependency-free; swap for silero/webrtcvad later if the
Phase-0 PoC shows it is needed. Operates on 20 ms SLIN frames.
"""

from __future__ import annotations

from dataclasses import dataclass, field

from gogo.voice.audio import FRAME_MS, rms


@dataclass
class VadConfig:
    # energy threshold = max(min_threshold, noise_floor * ratio)
    min_threshold: int = 500
    noise_ratio: float = 3.0
    start_ms: int = 120  # this much voiced audio starts an utterance
    end_ms: int = 700  # this much silence ends it
    max_utterance_ms: int = 15000  # hard cap
    pre_roll_ms: int = 200  # audio kept from before the trigger


@dataclass
class UtteranceCollector:
    """Feed 20 ms frames; returns the full utterance PCM when one completes."""

    config: VadConfig = field(default_factory=VadConfig)
    _noise_floor: float = 200.0
    _voiced_ms: int = 0
    _silence_ms: int = 0
    _in_utterance: bool = False
    _buffer: bytearray = field(default_factory=bytearray)
    _pre_roll: bytearray = field(default_factory=bytearray)

    def is_speech(self, frame: bytes) -> bool:
        energy = rms(frame)
        threshold = max(self.config.min_threshold, self._noise_floor * self.config.noise_ratio)
        speech = energy > threshold
        if not speech:
            # slowly track the noise floor on non-speech frames
            self._noise_floor = 0.95 * self._noise_floor + 0.05 * energy
        return speech

    def feed(self, frame: bytes) -> bytes | None:
        """Returns utterance PCM when a complete utterance is detected, else None."""
        speech = self.is_speech(frame)

        if not self._in_utterance:
            self._pre_roll.extend(frame)
            max_pre = self.config.pre_roll_ms * len(frame) // FRAME_MS
            if len(self._pre_roll) > max_pre:
                del self._pre_roll[: len(self._pre_roll) - max_pre]
            if speech:
                self._voiced_ms += FRAME_MS
                if self._voiced_ms >= self.config.start_ms:
                    self._in_utterance = True
                    self._buffer = bytearray(self._pre_roll)
                    self._silence_ms = 0
            else:
                self._voiced_ms = 0
            return None

        self._buffer.extend(frame)
        if speech:
            self._silence_ms = 0
        else:
            self._silence_ms += FRAME_MS

        utterance_ms = len(self._buffer) * FRAME_MS // len(frame)
        if self._silence_ms >= self.config.end_ms or utterance_ms >= self.config.max_utterance_ms:
            utterance = bytes(self._buffer)
            self.reset()
            return utterance
        return None

    def reset(self) -> None:
        self._in_utterance = False
        self._voiced_ms = 0
        self._silence_ms = 0
        self._buffer = bytearray()
        self._pre_roll = bytearray()