"""
Offer state listening automation rules.

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

from homeassistant.core import callback
from homeassistant.const import MATCH_ALL, CONF_PLATFORM, CONF_FOR
from homeassistant.helpers.event import async_track_state_change, async_track_same_state
import homeassistant.helpers.config_validation as cv

CONF_ENTITY_ID = "entity_id"
CONF_FROM = "from"
CONF_TO = "to"

TRIGGER_SCHEMA = vol.All(
    vol.Schema(
        {
            vol.Required(CONF_PLATFORM): "state",
            vol.Required(CONF_ENTITY_ID): cv.entity_ids,
            # These are str on purpose. Want to catch YAML conversions
            vol.Optional(CONF_FROM): str,
            vol.Optional(CONF_TO): str,
            vol.Optional(CONF_FOR): vol.All(cv.time_period, cv.positive_timedelta),
        }
    ),
    cv.key_dependency(CONF_FOR, CONF_TO),
)


@asyncio.coroutine
def async_trigger(hass, config, action):
    """Listen for state changes based on configuration."""
    entity_id = config.get(CONF_ENTITY_ID)
    from_state = config.get(CONF_FROM, MATCH_ALL)
    to_state = config.get(CONF_TO, MATCH_ALL)
    time_delta = config.get(CONF_FOR)
    match_all = from_state == MATCH_ALL and to_state == MATCH_ALL
    unsub_track_same = {}

    @callback
    def state_automation_listener(entity, from_s, to_s):
        """Listen for state changes and calls action."""

        @callback
        def call_action():
            """Call action with right context."""
            hass.async_run_job(
                action(
                    {
                        "trigger": {
                            "platform": "state",
                            "entity_id": entity,
                            "from_state": from_s,
                            "to_state": to_s,
                            "for": time_delta,
                        }
                    },
                    context=to_s.context,
                )
            )

        # Ignore changes to state attributes if from/to is in use
        if (
            not match_all
            and from_s is not None
            and to_s is not None
            and from_s.state == to_s.state
        ):
            return

        if not time_delta:
            call_action()
            return

        unsub_track_same[entity] = async_track_same_state(
            hass,
            time_delta,
            call_action,
            lambda _, _2, to_state: to_state.state == to_s.state,
            entity_ids=entity_id,
        )

    unsub = async_track_state_change(
        hass, entity_id, state_automation_listener, from_state, to_state
    )

    @callback
    def async_remove():
        """Remove state listeners async."""
        unsub()
        for async_remove in unsub_track_same.values():
            async_remove()
        unsub_track_same.clear()

    return async_remove