import dataclasses
import datetime
import enum
import hashlib
import json
import logging
import re
import threading
from typing import Any, Dict, Optional, Union

import paho.mqtt.client as mqtt
import pint

from . import Device, Publisher

logger = logging.getLogger('janet.mqtt')
_ureg = pint.get_application_registry()

_DEVICE_CLASSES = {
    _ureg.amp: 'current',
    _ureg.volt: 'voltage',
    _ureg.watt: 'power',
    _ureg.degC: 'temperature',
    _ureg.watt_hour: 'energy',
}

_UNITS = {
    _ureg.amp: 'A',
    _ureg.volt: 'V',
    _ureg.watt: 'W',
    _ureg.degC: '°C',
    _ureg.watt_hour: 'Wh',
    _ureg.second: 's',
    _ureg.hertz: 'Hz',
    _ureg.hour: 'h',
}


def _to_state(value: Any) -> Union[float, str, None]:
    if isinstance(value, pint.Quantity):
        return round(value.m, 6)
    elif isinstance(value, datetime.datetime):
        return value.isoformat()
    elif isinstance(value, enum.IntEnum):
        return value.name
    elif isinstance(value, bool):
        return 'ON' if value else 'OFF'
    elif isinstance(value, str):
        return value
    elif isinstance(value, int):
        return value
    elif isinstance(value, float):
        return round(value, 6)
    else:
        return None


def _to_device_class(value) -> Optional[str]:
    if isinstance(value, pint.Quantity):
        for unit, klass in _DEVICE_CLASSES.items():
            if unit == value.units:
                return klass
        logger.debug(f'No device class for units {value.units}')
        return None
    elif isinstance(value, datetime.datetime):
        return 'timestamp'
    else:
        return None


def _to_units(value) -> Optional[str]:
    if isinstance(value, pint.Quantity):
        for unit, klass in _UNITS.items():
            if unit == value.units:
                return klass
        logger.info(f'Unrecognised units {value.units}')
        return None
    elif isinstance(value, datetime.datetime):
        return 's'
    else:
        return None


def _uid(entity, device: Device) -> str:
    cls = entity.__class__
    kind = device.kind if device else None
    kind = kind or cls.__module__
    id0 = device.identifiers[0] if len(device.identifiers) >= 1 else None
    if id0 and re.match(r'^\w+$', id0):
        uid = id0
    else:
        uid = hashlib.sha1(str(device.identifiers).encode()).hexdigest()[:13]

    if entity == device:
        return f'{kind}_{uid}'
    else:
        return f'{kind}_{uid}/{cls.__name__}'.lower().replace('.', '_')


def _device(device: Device) -> dict:
    dev = {
        'identifiers': device.identifiers,
        'name': device.name,
    }
    if device.manufacturer:
        dev['manufacturer'] = device.manufacturer
    if device.model:
        dev['model'] = device.model
    if device.sw_version:
        dev['sw_version'] = device.sw_version

    return dev


@dataclasses.dataclass
class Setter:
    field: dataclasses.Field
    callback: Any


class Client(Publisher):
    def __init__(self, host: str, port: int = 1883):
        self._lock = threading.Lock()
        self._setters: Dict[str, Setter] = {}

        self._client = mqtt.Client()
        self._client.on_message = self._on_message

        self._client.connect_async(host, port, 60)
        self._client.loop_start()

    def _on_message(self, unused_client, unused_userdata,
                    message: mqtt.MQTTMessage):
        with self._lock:
            setter = self._setters.get(message.topic, None)
        if setter is not None:
            setter.callback(setter.field, message.payload)

    def publish(self, device: Device, entity: Any, setter=None):
        uid = _uid(entity, device)
        base = f'janet/{uid}'
        state_topic = f'{base}/state'
        states = {
            name: _to_state(value)
            for name, value in dataclasses.asdict(entity).items()
            if _to_state(value) is not None
        }
        self._client.publish(state_topic, json.dumps(states))

        available = getattr(device, 'available', None)
        if available is not None:
            self._client.publish(f'{base}/power',
                                 'ON' if available else 'OFF',
                                 retain=True)

        for field in dataclasses.fields(entity):
            value = getattr(entity, field.name)
            if value is None:
                continue
            state = _to_state(value)
            if state is None:
                logger.warning(
                    f'Ignoring field {field.name} type {field.type}')
                continue

            topic = f'{base}/{field.name}'
            if field.type in (bool, Optional[bool]):
                config_topic = (
                    f'homeassistant/binary_sensor/{uid}_{field.name}/config')
            else:
                config_topic = (
                    f'homeassistant/sensor/{uid}_{field.name}/config')

            dev = _device(device)
            kind = entity.__class__.__name__
            name = field.name.replace('_', ' ')

            config = {
                'name': f'{kind} {name}',
                'state_topic': state_topic,
                'value_template': f'{{{{value_json.{field.name}}}}}',
                'unique_id': f'{uid}_{field.name}',
                'device': dev,
                'expire_after': 600,
            }
            device_class = _to_device_class(value)
            if device_class:
                config['device_class'] = device_class

            units = _to_units(value)
            if units:
                config['unit_of_measurement'] = units

            if setter:
                command = f'{topic}/set'
                with self._lock:
                    if command not in self._setters:
                        self._client.subscribe(command)
                    self._setters[command] = Setter(field, setter)
            self._client.publish(config_topic, json.dumps(config))