"""Support for alexa Smart Home Skill API."""
import asyncio
import logging
from uuid import uuid4

from homeassistant.const import (
    ATTR_SUPPORTED_FEATURES, ATTR_ENTITY_ID, SERVICE_TURN_ON, SERVICE_TURN_OFF)
from homeassistant.components import switch, light
from homeassistant.util.decorator import Registry

HANDLERS = Registry()
_LOGGER = logging.getLogger(__name__)

ATTR_HEADER = 'header'
ATTR_NAME = 'name'
ATTR_NAMESPACE = 'namespace'
ATTR_MESSAGE_ID = 'messageId'
ATTR_PAYLOAD = 'payload'
ATTR_PAYLOAD_VERSION = 'payloadVersion'


MAPPING_COMPONENT = {
    switch.DOMAIN: ['SWITCH', ('turnOff', 'turnOn'), None],
    light.DOMAIN: [
        'LIGHT', ('turnOff', 'turnOn'), {
            light.SUPPORT_BRIGHTNESS: 'setPercentage'
        }
    ],
}


@asyncio.coroutine
def async_handle_message(hass, message):
    """Handle incoming API messages."""
    assert int(message[ATTR_HEADER][ATTR_PAYLOAD_VERSION]) == 2

    # Do we support this API request?
    funct_ref = HANDLERS.get(message[ATTR_HEADER][ATTR_NAME])
    if not funct_ref:
        _LOGGER.warning(
            "Unsupported API request %s", message[ATTR_HEADER][ATTR_NAME])
        return api_error(message)

    return (yield from funct_ref(hass, message))


def api_message(name, namespace, payload=None):
    """Create a API formatted response message.

    Async friendly.
    """
    payload = payload or {}
    return {
        ATTR_HEADER: {
            ATTR_MESSAGE_ID: str(uuid4()),
            ATTR_NAME: name,
            ATTR_NAMESPACE: namespace,
            ATTR_PAYLOAD_VERSION: '2',
        },
        ATTR_PAYLOAD: payload,
    }


def api_error(request, exc='DriverInternalError'):
    """Create a API formatted error response.

    Async friendly.
    """
    return api_message(exc, request[ATTR_HEADER][ATTR_NAMESPACE])


@HANDLERS.register('DiscoverAppliancesRequest')
@asyncio.coroutine
def async_api_discovery(hass, request):
    """Create a API formatted discovery response.

    Async friendly.
    """
    discovered_appliances = []

    for entity in hass.states.async_all():
        class_data = MAPPING_COMPONENT.get(entity.domain)

        if not class_data:
            continue

        appliance = {
            'actions': [],
            'applianceTypes': [class_data[0]],
            'additionalApplianceDetails': {},
            'applianceId': entity.entity_id.replace('.', '#'),
            'friendlyDescription': '',
            'friendlyName': entity.name,
            'isReachable': True,
            'manufacturerName': 'Unknown',
            'modelName': 'Unknown',
            'version': 'Unknown',
        }

        # static actions
        if class_data[1]:
            appliance['actions'].extend(list(class_data[1]))

        # dynamic actions
        if class_data[2]:
            supported = entity.attributes.get(ATTR_SUPPORTED_FEATURES, 0)
            for feature, action_name in class_data[2].items():
                if feature & supported > 0:
                    appliance['actions'].append(action_name)

        discovered_appliances.append(appliance)

    return api_message(
        'DiscoverAppliancesResponse', 'Alexa.ConnectedHome.Discovery',
        payload={'discoveredAppliances': discovered_appliances})


def extract_entity(funct):
    """Decorator for extract entity object from request."""
    @asyncio.coroutine
    def async_api_entity_wrapper(hass, request):
        """Process a turn on request."""
        entity_id = \
            request[ATTR_PAYLOAD]['appliance']['applianceId'].replace('#', '.')

        # extract state object
        entity = hass.states.get(entity_id)
        if not entity:
            _LOGGER.error("Can't process %s for %s",
                          request[ATTR_HEADER][ATTR_NAME], entity_id)
            return api_error(request)

        return (yield from funct(hass, request, entity))

    return async_api_entity_wrapper


@HANDLERS.register('TurnOnRequest')
@extract_entity
@asyncio.coroutine
def async_api_turn_on(hass, request, entity):
    """Process a turn on request."""
    yield from hass.services.async_call(entity.domain, SERVICE_TURN_ON, {
        ATTR_ENTITY_ID: entity.entity_id
    }, blocking=True)

    return api_message('TurnOnConfirmation', 'Alexa.ConnectedHome.Control')


@HANDLERS.register('TurnOffRequest')
@extract_entity
@asyncio.coroutine
def async_api_turn_off(hass, request, entity):
    """Process a turn off request."""
    yield from hass.services.async_call(entity.domain, SERVICE_TURN_OFF, {
        ATTR_ENTITY_ID: entity.entity_id
    }, blocking=True)

    return api_message('TurnOffConfirmation', 'Alexa.ConnectedHome.Control')


@HANDLERS.register('SetPercentageRequest')
@extract_entity
@asyncio.coroutine
def async_api_set_percentage(hass, request, entity):
    """Process a set percentage request."""
    if entity.domain == light.DOMAIN:
        brightness = request[ATTR_PAYLOAD]['percentageState']['value']
        yield from hass.services.async_call(entity.domain, SERVICE_TURN_ON, {
            ATTR_ENTITY_ID: entity.entity_id,
            light.ATTR_BRIGHTNESS: brightness,
        }, blocking=True)
    else:
        return api_error(request)

    return api_message(
        'SetPercentageConfirmation', 'Alexa.ConnectedHome.Control')