#!/usr/bin/env python
# License: GPLv3 Copyright: 2024, Kovid Goyal <kovid at kovidgoyal.net>

import atexit
import io
import json
import os
import re
import sys
from collections import deque
from contextlib import suppress
from dataclasses import dataclass
from functools import lru_cache
from itertools import count
from time import monotonic
from typing import BinaryIO, Iterable, Iterator

from qt.core import (
    QAudio,
    QAudioFormat,
    QAudioSink,
    QByteArray,
    QIODevice,
    QIODeviceBase,
    QMediaDevices,
    QObject,
    QProcess,
    Qt,
    QTextToSpeech,
    QWidget,
    pyqtSignal,
    sip,
)

from calibre.constants import cache_dir, is_debugging, iswindows, piper_cmdline
from calibre.gui2 import error_dialog
from calibre.gui2.tts.types import TTS_EMBEDED_CONFIG, EngineSpecificSettings, Quality, TTSBackend, Voice, widget_parent
from calibre.spell.break_iterator import PARAGRAPH_SEPARATOR, split_into_sentences_for_tts
from calibre.utils.filenames import ascii_text
from calibre.utils.localization import canonicalize_lang, get_lang
from calibre.utils.resources import get_path as P

HIGH_QUALITY_SAMPLE_RATE = 22050


def debug(*a, **kw):
    if is_debugging():
        if not hasattr(debug, 'first'):
            debug.first = monotonic()
        kw['end'] = kw.get('end', '\r\n')
        print(f'[{monotonic() - debug.first:.2f}]', *a, **kw)


def audio_format(audio_rate: int = HIGH_QUALITY_SAMPLE_RATE) -> QAudioFormat:
    fmt = QAudioFormat()
    fmt.setSampleFormat(QAudioFormat.SampleFormat.Int16)
    fmt.setSampleRate(audio_rate)
    fmt.setChannelConfig(QAudioFormat.ChannelConfig.ChannelConfigMono)
    return fmt


def piper_process_metadata(model_path, config_path, s: EngineSpecificSettings, voice: Voice) -> tuple[int, list[str]]:
    if not model_path:
        raise Exception('Could not download voice data')
    if 'metadata' not in voice.engine_data:
        with open(config_path) as f:
            voice.engine_data['metadata'] = json.load(f)
    audio_rate = voice.engine_data['metadata']['audio']['sample_rate']
    length_scale = max(0.1, 1 + -1 * s.rate)  # maps -1 to 1 to 2 to 0.1
    cmdline = list(piper_cmdline()) + [
        '--model', model_path, '--config', config_path, '--output-raw', '--json-input',
        '--sentence-silence', str(s.sentence_delay), '--length_scale', str(length_scale)]
    if is_debugging():
        cmdline.append('--debug')
    return audio_rate, cmdline


def piper_cache_dir() -> str:
    return os.path.join(cache_dir(), 'piper-voices')


def paths_for_voice(voice: Voice) -> tuple[str, str]:
    fname = voice.engine_data['model_filename']
    model_path = os.path.join(piper_cache_dir(), fname)
    config_path = os.path.join(os.path.dirname(model_path), fname + '.json')
    return model_path, config_path


def load_voice_metadata() -> tuple[dict[str, Voice], tuple[Voice, ...], dict[str, Voice]]:
    d = json.loads(P('piper-voices.json', data=True))
    ans = []
    lang_voices_map = {}
    _voice_name_map = {}
    downloaded = set()
    with suppress(OSError):
        downloaded = set(os.listdir(piper_cache_dir()))
    for bcp_code, voice_map in d['lang_map'].items():
        lang, sep, country = bcp_code.partition('_')
        lang = canonicalize_lang(lang) or lang
        voices_for_lang = lang_voices_map.setdefault(lang, [])
        for voice_name, qual_map in voice_map.items():
            best_qual = voice = None
            for qual, e in qual_map.items():
                q = Quality.from_piper_quality(qual)
                if best_qual is None or q.value < best_qual.value:
                    best_qual = q
                    mf = f'{bcp_code}-{ascii_text(voice_name)}-{qual}.onnx'
                    voice = Voice(bcp_code + ':' + voice_name, lang, country, human_name=voice_name, quality=q, engine_data={
                        'model_url': e['model'], 'config_url': e['config'],
                        'model_filename': mf, 'is_downloaded': mf in downloaded,
                    })
            if voice:
                ans.append(voice)
                _voice_name_map[voice.name] = voice
                voices_for_lang.append(voice)
    _voices = tuple(ans)
    _voice_for_lang = {}
    for lang, voices in lang_voices_map.items():
        voices.sort(key=lambda v: v.quality.value)
        _voice_for_lang[lang] = voices[0]
        if lang == 'eng':
            for v in voices:
                if v.human_name == 'libritts':
                    _voice_for_lang[lang] = v
                    break
    return _voice_name_map, _voices, _voice_for_lang


def download_voice(voice: Voice, download_even_if_exists: bool = False, parent: QObject | None = None, headless: bool = False) -> tuple[str, str]:
    model_path, config_path = paths_for_voice(voice)
    if os.path.exists(model_path) and os.path.exists(config_path):
        if not download_even_if_exists:
            return model_path, config_path
    os.makedirs(os.path.dirname(model_path), exist_ok=True)
    from calibre.gui2.tts.download import download_resources
    ok = download_resources(_('Downloading voice for Read aloud'), _('Downloading neural network for the {} voice').format(voice.human_name), {
            voice.engine_data['model_url']: (model_path, _('Neural network data')),
            voice.engine_data['config_url']: (config_path, _('Neural network metadata')),
        }, parent=widget_parent(parent), headless=headless,
    )
    voice.engine_data['is_downloaded'] = bool(ok)
    return (model_path, config_path) if ok else ('', '')


@dataclass
class Utterance:
    id: int
    start: int
    length: int
    payload_size: int
    left_to_write: QByteArray
    audio_data: QByteArray

    started: bool = False
    synthesized: bool = False


UTTERANCE_SEPARATOR = b'\n'


class UtteranceAudioQueue(QIODevice):

    saying = pyqtSignal(int, int)
    update_status = pyqtSignal()

    def __init__(self, parent: QObject | None = None):
        super().__init__(parent)
        self.utterances: deque[Utterance] = deque()
        self.current_audio_data = QByteArray()
        self.audio_state = QAudio.State.IdleState
        self.utterance_being_played: Utterance | None = None
        self.open(QIODeviceBase.OpenModeFlag.ReadOnly)

    def audio_state_changed(self, s: QAudio.State) -> None:
        debug('Audio state:', s)
        prev_state, self.audio_state = self.audio_state, s
        if s == prev_state:
            return
        if s == QAudio.State.IdleState and prev_state == QAudio.State.ActiveState:
            if self.utterance_being_played:
                debug(f'Utterance {self.utterance_being_played.id} audio output finished')
            self.utterance_being_played = None
            self.start_utterance()
        self.update_status.emit()

    def add_utterance(self, u: Utterance) -> None:
        self.utterances.append(u)
        if not self.utterance_being_played:
            self.start_utterance()

    def start_utterance(self):
        if self.utterances:
            u = self.utterances.popleft()
            self.current_audio_data = u.audio_data
            self.utterance_being_played = u
            self.readyRead.emit()
            self.saying.emit(u.start, u.length)

    def close(self):
        self.utterances.clear()
        self.current_audio_data = QByteArray()
        self.utterance_being_played = None
        return super().close()

    def clear(self):
        self.utterances.clear()
        self.utterance_being_played = None
        self.current_audio_data = QByteArray()
        self.audio_state = QAudio.State.IdleState

    def atEnd(self) -> bool:
        return not len(self.current_audio_data)

    def bytesAvailable(self) -> int:
        return len(self.current_audio_data)

    def __bool__(self) -> bool:
        return bool(self.utterances) or self.utterance_being_played is not None

    def isSequential(self) -> bool:
        return True

    def seek(self, pos):
        return False

    def readData(self, maxlen: int) -> QByteArray:
        if maxlen < 1:
            debug(f'Audio data sent to output: {maxlen=}')
            return QByteArray()
        if maxlen >= len(self.current_audio_data):
            ans = self.current_audio_data
            self.current_audio_data = QByteArray()
        else:
            ans = self.current_audio_data.first(maxlen)
            self.current_audio_data = self.current_audio_data.last(len(self.current_audio_data) - maxlen)
            if len(self.current_audio_data):
                self.readyRead.emit()
        debug(f'Audio sent to output: {maxlen=} {len(ans)=}')
        return ans


def split_into_utterances(text: str, counter: count, lang: str = 'en'):
    for start, sentence in split_into_sentences_for_tts(text, lang):
        payload = json.dumps({'text': sentence}).encode('utf-8')
        ba = QByteArray()
        ba.reserve(len(payload) + 1)
        ba.append(payload)
        ba.append(UTTERANCE_SEPARATOR)
        u = Utterance(id=next(counter), payload_size=len(ba), audio_data=QByteArray(),
                        left_to_write=ba, start=start, length=len(sentence))
        debug(f'Utterance created {u.id} {start=}: {sentence!r}')
        yield u


@lru_cache(2)
def stderr_pat():
    return re.compile(rb'\[piper\] \[([a-zA-Z0-9_]+?)\] (.+)')


def detect_end_of_data(data: bytes, callback):
    lines = data.split(b'\n')
    for line in lines[:-1]:
        if m := stderr_pat().search(line):
            which, payload = m.group(1), m.group(2)
            if which == b'info':
                debug(f'[piper-info] {payload.decode("utf-8", "replace")}')
                if payload.startswith(b'Real-time factor:'):
                    callback(True, None)
            elif which == b'error':
                callback(False, payload.decode('utf-8', 'replace'))
            elif which == b'debug':
                debug(f'[piper-debug] {payload.decode("utf-8", "replace")}')
    return lines[-1]


class Piper(TTSBackend):

    engine_name: str = 'piper'
    filler_char: str = PARAGRAPH_SEPARATOR
    _synthesis_done = pyqtSignal()

    def __init__(self, engine_name: str = '', parent: QObject | None = None):
        super().__init__(parent)
        self._process: QProcess | None = None
        self._audio_sink: QAudioSink | None = None

        self._current_voice: Voice | None = None
        self._utterances_being_synthesized: deque[Utterance] = deque()
        self._utterance_counter = count(start=1)
        self._utterances_being_spoken = UtteranceAudioQueue()
        self._utterances_being_spoken.saying.connect(self.saying)
        self._utterances_being_spoken.update_status.connect(self._update_status, type=Qt.ConnectionType.QueuedConnection)
        self._state = QTextToSpeech.State.Ready
        self._voices = self._voice_for_lang = None
        self._last_error = ''
        self._errors_from_piper: list[str] = []
        self._pending_stderr_data = b''

        self._synthesis_done.connect(self._utterance_synthesized, type=Qt.ConnectionType.QueuedConnection)
        atexit.register(self.shutdown)

    @property
    def available_voices(self) -> dict[str, tuple[Voice, ...]]:
        self._load_voice_metadata()
        return {'': self._voices}

    def _wait_for_process_to_start(self) -> bool:
        if not self.process.waitForStarted():
            cmdline = [self.process.program()] + self.process.arguments()
            if self.process.error() is QProcess.ProcessError.TimedOut:
                self._set_error(f'Timed out waiting for piper process {cmdline} to start')
            else:
                self._set_error(f'Failed to start piper process: {cmdline}')
            return False
        return True

    def say(self, text: str) -> None:
        if self._last_error:
            return
        self.stop()
        if not self._wait_for_process_to_start():
            return
        lang = 'en'
        if self._current_voice and self._current_voice.language_code:
            lang = self._current_voice.language_code
        self._utterances_being_synthesized.extend(split_into_utterances(text, self._utterance_counter, lang))
        self._write_current_utterance()

    def pause(self) -> None:
        if self._audio_sink is not None:
            self._audio_sink.suspend()

    def resume(self) -> None:
        if self._audio_sink is not None:
            self._audio_sink.resume()

    def stop(self) -> None:
        if self._process is not None:
            if self._state is not QTextToSpeech.State.Ready or self._utterances_being_synthesized or self._utterances_being_spoken:
                self.shutdown()
                # We cannot re-create self.process here as that will cause the
                # audio device to go to active state which will cause a
                # speaking event to be generated

    def shutdown(self) -> None:
        if self._process is not None:
            self._audio_sink.stateChanged.disconnect()
            self._process.readyReadStandardError.disconnect()
            self._process.bytesWritten.disconnect()
            self._process.readyReadStandardOutput.disconnect()
            self._process.stateChanged.disconnect()
            self._process.kill()
            self._process.waitForFinished(-1)
            # this dance is needed otherwise stop() is very slow on Linux
            self._audio_sink.suspend()
            self._audio_sink.reset()
            self._audio_sink.stop()
            sip.delete(self._audio_sink)
            sip.delete(self._process)
            self._process = self._audio_sink = None
            self._set_state(QTextToSpeech.State.Ready)

    def reload_after_configure(self) -> None:
        self.shutdown()

    @property
    def state(self) -> QTextToSpeech.State:
        return self._state

    def error_message(self) -> str:
        return self._last_error

    def _set_state(self, s: QTextToSpeech.State) -> None:
        if self._state is not s:
            self._state = s
            self.state_changed.emit(s)

    def _set_error(self, msg: str) -> None:
        self._last_error = msg
        self._set_state(QTextToSpeech.State.Error)

    @property
    def process(self) -> QProcess:
        if self._process is None:
            model_path = config_path = ''
            try:
                self._load_voice_metadata()
                s = EngineSpecificSettings.create_from_config(self.engine_name)
                voice = self._voice_name_map.get(s.voice_name) or self._default_voice
                model_path, config_path = self._ensure_voice_is_downloaded(voice)
            except AttributeError as e:
                raise Exception(str(e)) from e
            self._current_voice = voice
            self._utterances_being_spoken.clear()
            self._utterances_being_synthesized.clear()
            self._errors_from_piper.clear()
            self._process = QProcess(self)
            self._pending_stderr_data = b''
            self._set_state(QTextToSpeech.State.Ready)

            audio_rate, cmdline = piper_process_metadata(model_path, config_path, s, voice)
            self._process.setProgram(cmdline[0])
            self._process.setArguments(cmdline[1:])
            debug('Running piper:', cmdline)
            self._process.readyReadStandardError.connect(self.piper_stderr_available)
            self._process.readyReadStandardOutput.connect(self.piper_stdout_available)
            self._process.bytesWritten.connect(self.bytes_written)
            self._process.stateChanged.connect(self._update_status)
            fmt = audio_format(audio_rate)
            dev = None
            if s.audio_device_id:
                for q in QMediaDevices.audioOutputs():
                    if bytes(q.id()) == s.audio_device_id.id:
                        dev = q
                        break
            if dev:
                self._audio_sink = QAudioSink(dev, fmt, self)
            else:
                self._audio_sink = QAudioSink(fmt, self)
            if s.volume is not None:
                self._audio_sink.setVolume(s.volume)
            # On Windows, the buffer is zero causing data to be discarded.
            # Ensure we have a nice large buffer on all platforms.
            self._audio_sink.setBufferSize(2 * 1024 * 1024)
            self._audio_sink.stateChanged.connect(self._utterances_being_spoken.audio_state_changed)
            self._process.start()
            self._audio_sink.start(self._utterances_being_spoken)
        return self._process

    def piper_stdout_available(self) -> None:
        if self._utterances_being_synthesized:
            u = self._utterances_being_synthesized[0]
            while True:
                ba = self.process.readAll()
                if not len(ba):
                    break
                debug('Synthesized data read:', len(ba), 'bytes')
                u.audio_data.append(ba)

    def piper_stderr_available(self) -> None:
        if self._process is not None:
            def callback(ok, payload):
                if ok:
                    if self._utterances_being_synthesized:
                        self._synthesis_done.emit()
                else:
                    self._errors_from_piper.append(payload.decode('utf-8', 'replace'))
            data = self._pending_stderr_data + bytes(self._process.readAllStandardError())
            self._pending_stderr_data = detect_end_of_data(data, callback)

    def _utterance_synthesized(self):
        self.piper_stdout_available()  # just in case
        u = self._utterances_being_synthesized.popleft()
        u.synthesized = True
        debug(f'Utterance {u.id} got {len(u.audio_data)} bytes of audio data from piper')
        if len(u.audio_data):
            self._utterances_being_spoken.add_utterance(u)
        self._write_current_utterance()
        self._update_status()

    def _update_status(self):
        if self._process is not None and self._process.state() is QProcess.ProcessState.NotRunning:
            if self._process.exitStatus() is not QProcess.ExitStatus.NormalExit or self._process.exitCode():
                m = '\n'.join(self._errors_from_piper)
                self._set_error(f'piper process failed with exit code: {self._process.exitCode()} and error messages: {m}')
                return
        if self._state is QTextToSpeech.State.Error:
            return
        state = self._utterances_being_spoken.audio_state
        if state is QAudio.State.ActiveState:
            self._set_state(QTextToSpeech.State.Speaking)
        elif state is QAudio.State.SuspendedState:
            self._set_state(QTextToSpeech.State.Paused)
        elif state is QAudio.State.StoppedState:
            if self._audio_sink.error() not in (QAudio.Error.NoError, QAudio.Error.UnderrunError):
                self._set_error(f'Audio playback failed with error: {self._audio_sink.error()}')
            else:
                if self._state is not QTextToSpeech.State.Error:
                    self._set_state(QTextToSpeech.State.Ready)
        elif state is QAudio.State.IdleState:
            if not self._utterances_being_synthesized and not self._utterances_being_spoken:
                self._set_state(QTextToSpeech.State.Ready)

    def bytes_written(self, count: int) -> None:
        self._write_current_utterance()

    def _write_current_utterance(self) -> None:
        if self._utterances_being_synthesized:
            u = self._utterances_being_synthesized[0]
            while len(u.left_to_write):
                written = self.process.write(u.left_to_write)
                if written < 0:
                    self._set_error('Failed to write to piper process with error: {self.process.errorString()}')
                    break
                if not u.started and written:
                    u.started = True
                    debug(f'Utterance {u.id} synthesis started')
                u.left_to_write = u.left_to_write.last(len(u.left_to_write) - written)

    def audio_sink_state_changed(self, state: QAudio.State) -> None:
        self._update_status()

    def _load_voice_metadata(self) -> None:
        if self._voices is not None:
            return
        self._voice_name_map, self._voices, self._voice_for_lang = load_voice_metadata()

    @property
    def _default_voice(self) -> Voice:
        self._load_voice_metadata()
        lang = get_lang()
        lang = canonicalize_lang(lang) or lang
        return self._voice_for_lang.get(lang) or self._voice_for_lang['eng']

    @property
    def cache_dir(self) -> str:
        return piper_cache_dir()

    def is_voice_downloaded(self, v: Voice) -> bool:
        if not v or not v.name:
            v = self._default_voice
        for path in paths_for_voice(v):
            if not os.path.exists(path):
                return False
        return True

    def delete_voice(self, v: Voice) -> None:
        if not v.name:
            v = self._default_voice
        for path in paths_for_voice(v):
            with suppress(FileNotFoundError):
                os.remove(path)
        v.engine_data['is_downloaded'] = False

    def _download_voice(self, voice: Voice, download_even_if_exists: bool = False) -> tuple[str, str]:
        return download_voice(voice, download_even_if_exists, parent=self, headless=False)

    def download_voice(self, v: Voice) -> None:
        if not v.name:
            v = self._default_voice
        self._download_voice(v, download_even_if_exists=True)

    def _ensure_voice_is_downloaded(self, voice: Voice) -> tuple[str, str]:
        return self._download_voice(voice)

    def validate_settings(self, s: EngineSpecificSettings, parent: QWidget | None) -> bool:
        self._load_voice_metadata()
        voice = self._voice_name_map.get(s.voice_name) or self._default_voice
        try:
            m, c = self._ensure_voice_is_downloaded(voice)
            if not m:
                error_dialog(parent, _('Failed to download voice'), _('Failed to download the voice: {}').format(voice.human_name), show=True)
                return False
        except Exception:
            import traceback
            error_dialog(parent, _('Failed to download voice'), _('Failed to download the voice: {}').format(voice.human_name),
                         det_msg=traceback.format_exc(), show=True)
            return False
        return True


class PiperEmbedded:

    def __init__(self):
        self._embedded_settings = EngineSpecificSettings.create_from_config('piper', TTS_EMBEDED_CONFIG)
        self._voice_name_map, self._voices, self._voice_for_lang = load_voice_metadata()
        lang = get_lang()
        lang = canonicalize_lang(lang) or lang
        self._default_voice = self._voice_for_lang.get(lang) or self._voice_for_lang['eng']
        self._current_voice = self._process = self._pipe_reader = None
        self._current_audio_rate = 0

    def resolve_voice(self, lang: str, voice_name: str) -> Voice:
        from calibre.utils.localization import canonicalize_lang, get_lang
        lang = canonicalize_lang(lang or get_lang() or 'en')
        pv = self._embedded_settings.preferred_voices or {}
        if voice_name and voice_name in self._voice_name_map:
            voice = self._voice_name_map[voice_name]
        elif (voice_name := pv.get(lang, '')) and voice_name in self._voice_name_map:
            voice = self._voice_name_map[voice_name]
        else:
            voice = self._voice_for_lang.get(lang) or self._default_voice
        return voice

    def text_to_raw_audio_data(
        self, texts: Iterable[str], lang: str = '', voice_name: str = '', sample_rate: int = HIGH_QUALITY_SAMPLE_RATE, timeout: float = 10.,
    ) -> Iterator[tuple[bytes, float]]:
        voice = self.resolve_voice(lang, voice_name)
        if voice is not self._current_voice:
            self._current_voice = voice
            self.shutdown()
        self.ensure_process_started()
        piper_done, errors_from_piper = [], []
        needs_conversion = sample_rate != self._current_audio_rate
        if needs_conversion:
            from calibre_extensions.ffmpeg import resample_raw_audio_16bit

        def callback(ok, payload):
            if ok:
                piper_done.append(True)
            else:
                errors_from_piper.append(payload.decode('utf-8', 'replace'))

        for text in texts:
            text = text.strip()
            if not text:
                yield b'', 0.
                continue
            payload = json.dumps({'text': text}).encode('utf-8')
            self._process.stdin.write(payload)
            self._process.stdin.write(UTTERANCE_SEPARATOR)
            self._process.stdin.flush()
            stderr_data = b''
            buf = io.BytesIO()
            piper_done, errors_from_piper = [], []

            def stderr_callback(data: bytes) -> bool:
                nonlocal stderr_data
                stderr_data = detect_end_of_data(stderr_data + data, callback)
                return not piper_done

            try:
                self._pipe_reader(buf.write, stderr_callback)
            except Exception as e:
                raise Exception(f'Reading output from piper process failed with error: {e} and STDERR: ' + '\n'.join(errors_from_piper))

            raw_data = buf.getvalue()
            if needs_conversion:
                raw_data = resample_raw_audio_16bit(raw_data, self._current_audio_rate, sample_rate)
            yield raw_data, duration_of_raw_audio_data(raw_data, sample_rate)

    def ensure_voices_downloaded(self, specs: Iterable[tuple[str, str]], parent: QObject = None) -> bool:
        for lang, voice_name in specs:
            voice = self.resolve_voice(lang, voice_name)
            m, c = download_voice(voice, parent=parent, headless=parent is None)
            if not m:
                return False
        return True

    def shutdown(self):
        if self._process is not None:
            self._pipe_reader.close()
            self._pipe_reader = None
            self._process.stdin.close()
            self._process.stdout.close()
            self._process.stderr.close()
            self._process.kill()
            self._process.wait()
            self._process = None
    __del__ = shutdown

    def ensure_process_started(self):
        if self._process is not None:
            return
        model_path, config_path = download_voice(self._current_voice, headless=True)
        self._current_audio_rate, cmdline = piper_process_metadata(model_path, config_path, self._embedded_settings, self._current_voice)
        import subprocess
        self._process = subprocess.Popen(cmdline, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
        self._pipe_reader = (ThreadedPipeReader if iswindows else PipeReader)(self._process.stdout, self._process.stderr)


class PipeReader:

    TIMEOUT = 10.  # seconds

    def __init__(self, stdout: BinaryIO, stderr: BinaryIO):
        self.stdout_fd = stdout.fileno()
        self.stderr_fd = stderr.fileno()
        os.set_blocking(self.stdout_fd, False)
        os.set_blocking(self.stderr_fd, False)

    def close(self):
        self.stderr_fd = self.stdout_fd = -1

    def __call__(self, stdout_callback, stderr_callback):
        from select import select
        out, err = self.stdout_fd, self.stderr_fd
        readers = out, err
        buf = memoryview(bytearray(io.DEFAULT_BUFFER_SIZE))

        def readall(fd: int) -> bytes:
            output = io.BytesIO()
            while True:
                try:
                    num = os.readv(fd, (buf,))
                except BlockingIOError:
                    break
                else:
                    output.write(buf[:num])
            return output.getvalue()

        def readinto(fd: int, callback) -> None:
            while True:
                try:
                    num = os.readv(fd, (buf,))
                except BlockingIOError:
                    break
                else:
                    callback(buf[:num])

        while True:
            r, _, _ = select(readers, (), (), self.TIMEOUT)
            if not r:
                raise TimeoutError('Timed out waiting for output from piper process')
            if out in r:
                readinto(out, stdout_callback)
            if err in r:
                data = readall(err)
                if not stderr_callback(data):
                    # In case there is new data written to stdout
                    readinto(out, stdout_callback)
                    break


class ThreadedPipeReader(PipeReader):

    def __init__(self, stdout: BinaryIO, stderr: BinaryIO):
        from queue import Queue
        from threading import Event, Thread
        self.shutting_down = Event()
        self.queue = Queue()
        Thread(target=self._reader, args=(stdout.fileno(), True), daemon=True).start()
        Thread(target=self._reader, args=(stderr.fileno(), False), daemon=True).start()

    def close(self):
        self.shutting_down.set()

    def __call__(self, stdout_callback, stderr_callback):
        from queue import Empty
        while True:
            data, is_stdout, err = self.queue.get(True, self.TIMEOUT)
            if err is not None:
                raise err
            if data:
                if is_stdout:
                    stdout_callback(data)
                else:
                    if not stderr_callback(data):
                        # in case more data was written to stdout
                        while True:
                            try:
                                data, is_stdout, err = self.queue.get_nowait()
                            except Empty:
                                break
                            if err is not None:
                                raise err
                            if is_stdout:
                                stdout_callback(data)
                        break

    def _reader(self, pipe_fd: int, is_stdout: bool):
        while not self.shutting_down.is_set():
            try:
                data = os.read(pipe_fd, io.DEFAULT_BUFFER_SIZE)
            except OSError as e:
                if not self.shutting_down.is_set():
                    self.queue.put((b'', is_stdout, e))
                break
            else:
                self.queue.put((data, is_stdout, None))



def duration_of_raw_audio_data(data: bytes, sample_rate: int = HIGH_QUALITY_SAMPLE_RATE, bytes_per_sample: int = 2, num_channels: int = 1) -> float:
    total_num_of_samples = len(data) / bytes_per_sample
    num_of_samples_per_channel = total_num_of_samples / num_channels
    return num_of_samples_per_channel / sample_rate


# develop {{{
def develop_embedded():
    import subprocess

    from calibre.utils.speedups import ReadOnlyFileBuffer
    from calibre_extensions.ffmpeg import transcode_single_audio_stream, wav_header_for_pcm_data
    p = PiperEmbedded()
    all_data = [b'']
    sz = 0
    for data, duration in p.text_to_raw_audio_data((
        'Hello, good day to you.', 'This is the second sentence.', 'This is the final sentence.'
    )):
        print(f'{duration=} {len(data)=}')
        all_data.append(data)
        sz += len(data)
    all_data[0] = wav_header_for_pcm_data(sz, HIGH_QUALITY_SAMPLE_RATE)
    wav = ReadOnlyFileBuffer(b''.join(all_data), name='tts.wav')
    m4a = io.BytesIO()
    m4a.name = 'tts.m4a'
    transcode_single_audio_stream(wav, m4a)
    subprocess.run(['mpv', '-'], input=m4a.getvalue())


def develop():

    from qt.core import QSocketNotifier

    from calibre.gui2 import Application
    app = Application([])
    p = Piper()
    play_started = False
    def state_changed(s):
        nonlocal play_started
        debug('TTS State:', s)
        if s is QTextToSpeech.State.Error:
            debug(p.error_message(), file=sys.stderr)
            app.exit(1)
        elif s is QTextToSpeech.State.Speaking:
            play_started = True
        elif s is QTextToSpeech.State.Ready:
            if play_started:
                debug('Quitting on completion')
                app.quit()

    def input_ready():
        nonlocal play_started
        q = sys.stdin.buffer.read()
        if q in (b'\x03', b'\x1b'):
            app.exit(1)
        elif q == b' ':
            if p.state is QTextToSpeech.State.Speaking:
                p.pause()
            elif p.state is QTextToSpeech.State.Paused:
                p.resume()
        elif q == b'r':
            debug('Stopping')
            play_started = False
            p.stop()
            p.say(text)

    text = (
        'First, relatively short sentence. '
        'Second, much longer sentence which hopefully finishes synthesizing before the first finishes speaking. '
        'Third, and final short sentence.'
    )
    # text = f'Hello world{PARAGRAPH_SEPARATOR}.{PARAGRAPH_SEPARATOR}Bye world'

    def saying(offset, length):
        debug('Saying:', repr(text[offset:offset+length]))

    p.state_changed.connect(state_changed)
    p.saying.connect(saying)
    if not iswindows:
        import tty
        attr = tty.setraw(sys.stdin.fileno())
        os.set_blocking(sys.stdin.fileno(), False)
    sn = QSocketNotifier(sys.stdin.fileno(), QSocketNotifier.Type.Read, p)
    sn.activated.connect(input_ready)
    try:
        p.say(text)
        app.exec()
    finally:
        if not iswindows:
            import termios
            termios.tcsetattr(sys.stdout.fileno(), termios.TCSANOW, attr)


if __name__ == '__main__':
    develop()
# }}}
