"""
Offer template automation rules.

For more details about this automation rule, please refer to the documentation
at https://home-assistant.io/docs/automation/trigger/#template-trigger
"""
import asyncio
import logging

import voluptuous as vol

from homeassistant.core import callback
from homeassistant.const import CONF_VALUE_TEMPLATE, CONF_PLATFORM
from homeassistant.helpers.event import async_track_template
import homeassistant.helpers.config_validation as cv


_LOGGER = logging.getLogger(__name__)

TRIGGER_SCHEMA = IF_ACTION_SCHEMA = vol.Schema(
    {
        vol.Required(CONF_PLATFORM): "template",
        vol.Required(CONF_VALUE_TEMPLATE): cv.template,
    }
)


@asyncio.coroutine
def async_trigger(hass, config, action):
    """Listen for state changes based on configuration."""
    value_template = config.get(CONF_VALUE_TEMPLATE)
    value_template.hass = hass

    @callback
    def template_listener(entity_id, from_s, to_s):
        """Listen for state changes and calls action."""
        hass.async_run_job(
            action(
                {
                    "trigger": {
                        "platform": "template",
                        "entity_id": entity_id,
                        "from_state": from_s,
                        "to_state": to_s,
                    }
                },
                context=to_s.context,
            )
        )

    return async_track_template(hass, value_template, template_listener)