"""Template helper methods for rendering strings with Home Assistant data."""
from datetime import datetime
import json
import logging
import random
import re

import jinja2
from jinja2 import contextfilter
from jinja2.sandbox import ImmutableSandboxedEnvironment

from homeassistant.const import (
    STATE_UNKNOWN, ATTR_LATITUDE, ATTR_LONGITUDE, MATCH_ALL,
    ATTR_UNIT_OF_MEASUREMENT)
from homeassistant.core import State
from homeassistant.exceptions import TemplateError
from homeassistant.helpers import location as loc_helper
from homeassistant.loader import get_component, bind_hass
from homeassistant.util import convert, dt as dt_util, location as loc_util
from homeassistant.util.async import run_callback_threadsafe

_LOGGER = logging.getLogger(__name__)
_SENTINEL = object()
DATE_STR_FORMAT = "%Y-%m-%d %H:%M:%S"

_RE_NONE_ENTITIES = re.compile(r"distance\(|closest\(", re.I | re.M)
_RE_GET_ENTITIES = re.compile(
    r"(?:(?:states\.|(?:is_state|is_state_attr|states)"
    r"\((?:[\ \'\"]?))([\w]+\.[\w]+)|([\w]+))", re.I | re.M
)


@bind_hass
def attach(hass, obj):
    """Recursively attach hass to all template instances in list and dict."""
    if isinstance(obj, list):
        for child in obj:
            attach(hass, child)
    elif isinstance(obj, dict):
        for child in obj.values():
            attach(hass, child)
    elif isinstance(obj, Template):
        obj.hass = hass


def extract_entities(template, variables=None):
    """Extract all entities for state_changed listener from template string."""
    if template is None or _RE_NONE_ENTITIES.search(template):
        return MATCH_ALL

    extraction = _RE_GET_ENTITIES.findall(template)
    extraction_final = []

    for result in extraction:
        if result[0] == 'trigger.entity_id' and 'trigger' in variables and \
           'entity_id' in variables['trigger']:
            extraction_final.append(variables['trigger']['entity_id'])
        elif result[0]:
            extraction_final.append(result[0])

        if variables and result[1] in variables and \
           isinstance(variables[result[1]], str):
            extraction_final.append(variables[result[1]])

    if extraction_final:
        return list(set(extraction_final))
    return MATCH_ALL


class Template(object):
    """Class to hold a template and manage caching and rendering."""

    def __init__(self, template, hass=None):
        """Instantiate a template."""
        if not isinstance(template, str):
            raise TypeError('Expected template to be a string')

        self.template = template
        self._compiled_code = None
        self._compiled = None
        self.hass = hass

    def ensure_valid(self):
        """Return if template is valid."""
        if self._compiled_code is not None:
            return

        try:
            self._compiled_code = ENV.compile(self.template)
        except jinja2.exceptions.TemplateSyntaxError as err:
            raise TemplateError(err)

    def extract_entities(self, variables=None):
        """Extract all entities for state_changed listener."""
        return extract_entities(self.template, variables)

    def render(self, variables=None, **kwargs):
        """Render given template."""
        if variables is not None:
            kwargs.update(variables)

        return run_callback_threadsafe(
            self.hass.loop, self.async_render, kwargs).result()

    def async_render(self, variables=None, **kwargs):
        """Render given template.

        This method must be run in the event loop.
        """
        self._ensure_compiled()

        if variables is not None:
            kwargs.update(variables)

        try:
            return self._compiled.render(kwargs).strip()
        except jinja2.TemplateError as err:
            raise TemplateError(err)

    def render_with_possible_json_value(self, value, error_value=_SENTINEL):
        """Render template with value exposed.

        If valid JSON will expose value_json too.
        """
        return run_callback_threadsafe(
            self.hass.loop, self.async_render_with_possible_json_value, value,
            error_value).result()

    # pylint: disable=invalid-name
    def async_render_with_possible_json_value(self, value,
                                              error_value=_SENTINEL):
        """Render template with value exposed.

        If valid JSON will expose value_json too.

        This method must be run in the event loop.
        """
        self._ensure_compiled()

        variables = {
            'value': value
        }
        try:
            variables['value_json'] = json.loads(value)
        except ValueError:
            pass

        try:
            return self._compiled.render(variables).strip()
        except jinja2.TemplateError as ex:
            _LOGGER.error("Error parsing value: %s (value: %s, template: %s)",
                          ex, value, self.template)
            return value if error_value is _SENTINEL else error_value

    def _ensure_compiled(self):
        """Bind a template to a specific hass instance."""
        if self._compiled is not None:
            return

        self.ensure_valid()

        assert self.hass is not None, 'hass variable not set on template'

        location_methods = LocationMethods(self.hass)

        global_vars = ENV.make_globals({
            'closest': location_methods.closest,
            'distance': location_methods.distance,
            'is_state': self.hass.states.is_state,
            'is_state_attr': self.hass.states.is_state_attr,
            'states': AllStates(self.hass),
        })

        self._compiled = jinja2.Template.from_code(
            ENV, self._compiled_code, global_vars, None)

        return self._compiled

    def __eq__(self, other):
        """Compare template with another."""
        return (self.__class__ == other.__class__ and
                self.template == other.template and
                self.hass == other.hass)


class AllStates(object):
    """Class to expose all HA states as attributes."""

    def __init__(self, hass):
        """Initialize all states."""
        self._hass = hass

    def __getattr__(self, name):
        """Return the domain state."""
        return DomainStates(self._hass, name)

    def __iter__(self):
        """Return all states."""
        return iter(
            _wrap_state(state) for state in
            sorted(self._hass.states.async_all(),
                   key=lambda state: state.entity_id))

    def __len__(self):
        """Return number of states."""
        return len(self._hass.states.async_entity_ids())

    def __call__(self, entity_id):
        """Return the states."""
        state = self._hass.states.get(entity_id)
        return STATE_UNKNOWN if state is None else state.state


class DomainStates(object):
    """Class to expose a specific HA domain as attributes."""

    def __init__(self, hass, domain):
        """Initialize the domain states."""
        self._hass = hass
        self._domain = domain

    def __getattr__(self, name):
        """Return the states."""
        return _wrap_state(
            self._hass.states.get('{}.{}'.format(self._domain, name)))

    def __iter__(self):
        """Return the iteration over all the states."""
        return iter(sorted(
            (_wrap_state(state) for state in self._hass.states.async_all()
             if state.domain == self._domain),
            key=lambda state: state.entity_id))

    def __len__(self):
        """Return number of states."""
        return len(self._hass.states.async_entity_ids(self._domain))


class TemplateState(State):
    """Class to represent a state object in a template."""

    # Inheritance is done so functions that check against State keep working
    # pylint: disable=super-init-not-called
    def __init__(self, state):
        """Initialize template state."""
        self._state = state

    @property
    def state_with_unit(self):
        """Return the state concatenated with the unit if available."""
        state = object.__getattribute__(self, '_state')
        unit = state.attributes.get(ATTR_UNIT_OF_MEASUREMENT)
        if unit is None:
            return state.state
        return "{} {}".format(state.state, unit)

    def __getattribute__(self, name):
        """Return an attribute of the state."""
        if name in TemplateState.__dict__:
            return object.__getattribute__(self, name)
        else:
            return getattr(object.__getattribute__(self, '_state'), name)

    def __repr__(self):
        """Representation of Template State."""
        rep = object.__getattribute__(self, '_state').__repr__()
        return '<template ' + rep[1:]


def _wrap_state(state):
    """Helper function to wrap a state."""
    return None if state is None else TemplateState(state)


class LocationMethods(object):
    """Class to expose distance helpers to templates."""

    def __init__(self, hass):
        """Initialize the distance helpers."""
        self._hass = hass

    def closest(self, *args):
        """Find closest entity.

        Closest to home:
          closest(states)
          closest(states.device_tracker)
          closest('group.children')
          closest(states.group.children)

        Closest to a point:
          closest(23.456, 23.456, 'group.children')
          closest('zone.school', 'group.children')
          closest(states.zone.school, 'group.children')
        """
        if len(args) == 1:
            latitude = self._hass.config.latitude
            longitude = self._hass.config.longitude
            entities = args[0]

        elif len(args) == 2:
            point_state = self._resolve_state(args[0])

            if point_state is None:
                _LOGGER.warning("Closest:Unable to find state %s", args[0])
                return None
            elif not loc_helper.has_location(point_state):
                _LOGGER.warning(
                    "Closest:State does not contain valid location: %s",
                    point_state)
                return None

            latitude = point_state.attributes.get(ATTR_LATITUDE)
            longitude = point_state.attributes.get(ATTR_LONGITUDE)

            entities = args[1]

        else:
            latitude = convert(args[0], float)
            longitude = convert(args[1], float)

            if latitude is None or longitude is None:
                _LOGGER.warning(
                    "Closest:Received invalid coordinates: %s, %s",
                    args[0], args[1])
                return None

            entities = args[2]

        if isinstance(entities, (AllStates, DomainStates)):
            states = list(entities)
        else:
            if isinstance(entities, State):
                gr_entity_id = entities.entity_id
            else:
                gr_entity_id = str(entities)

            group = get_component('group')

            states = [self._hass.states.get(entity_id) for entity_id
                      in group.expand_entity_ids(self._hass, [gr_entity_id])]

        return _wrap_state(loc_helper.closest(latitude, longitude, states))

    def distance(self, *args):
        """Calculate distance.

        Will calculate distance from home to a point or between points.
        Points can be passed in using state objects or lat/lng coordinates.
        """
        locations = []

        to_process = list(args)

        while to_process:
            value = to_process.pop(0)

            if isinstance(value, State):
                latitude = value.attributes.get(ATTR_LATITUDE)
                longitude = value.attributes.get(ATTR_LONGITUDE)

                if latitude is None or longitude is None:
                    _LOGGER.warning(
                        "Distance:State does not contains a location: %s",
                        value)
                    return None

            else:
                # We expect this and next value to be lat&lng
                if not to_process:
                    _LOGGER.warning(
                        "Distance:Expected latitude and longitude, got %s",
                        value)
                    return None

                value_2 = to_process.pop(0)
                latitude = convert(value, float)
                longitude = convert(value_2, float)

                if latitude is None or longitude is None:
                    _LOGGER.warning("Distance:Unable to process latitude and "
                                    "longitude: %s, %s", value, value_2)
                    return None

            locations.append((latitude, longitude))

        if len(locations) == 1:
            return self._hass.config.distance(*locations[0])

        return self._hass.config.units.length(
            loc_util.distance(*locations[0] + locations[1]), 'm')

    def _resolve_state(self, entity_id_or_state):
        """Return state or entity_id if given."""
        if isinstance(entity_id_or_state, State):
            return entity_id_or_state
        elif isinstance(entity_id_or_state, str):
            return self._hass.states.get(entity_id_or_state)
        return None


def forgiving_round(value, precision=0):
    """Round accepted strings."""
    try:
        value = round(float(value), precision)
        return int(value) if precision == 0 else value
    except (ValueError, TypeError):
        # If value can't be converted to float
        return value


def multiply(value, amount):
    """Filter to convert value to float and multiply it."""
    try:
        return float(value) * amount
    except (ValueError, TypeError):
        # If value can't be converted to float
        return value


def timestamp_custom(value, date_format=DATE_STR_FORMAT, local=True):
    """Filter to convert given timestamp to format."""
    try:
        date = dt_util.utc_from_timestamp(value)

        if local:
            date = dt_util.as_local(date)

        return date.strftime(date_format)
    except (ValueError, TypeError):
        # If timestamp can't be converted
        return value


def timestamp_local(value):
    """Filter to convert given timestamp to local date/time."""
    try:
        return dt_util.as_local(
            dt_util.utc_from_timestamp(value)).strftime(DATE_STR_FORMAT)
    except (ValueError, TypeError):
        # If timestamp can't be converted
        return value


def timestamp_utc(value):
    """Filter to convert given timestamp to UTC date/time."""
    try:
        return dt_util.utc_from_timestamp(value).strftime(DATE_STR_FORMAT)
    except (ValueError, TypeError):
        # If timestamp can't be converted
        return value


def forgiving_as_timestamp(value):
    """Try to convert value to timestamp."""
    try:
        return dt_util.as_timestamp(value)
    except (ValueError, TypeError):
        return None


def strptime(string, fmt):
    """Parse a time string to datetime."""
    try:
        return datetime.strptime(string, fmt)
    except (ValueError, AttributeError):
        return string


def fail_when_undefined(value):
    """Filter to force a failure when the value is undefined."""
    if isinstance(value, jinja2.Undefined):
        value()
    return value


def forgiving_float(value):
    """Try to convert value to a float."""
    try:
        return float(value)
    except (ValueError, TypeError):
        return value


@contextfilter
def random_every_time(context, values):
    """Choose a random value.

    Unlike Jinja's random filter,
    this is context-dependent to avoid caching the chosen value.
    """
    return random.choice(values)


class TemplateEnvironment(ImmutableSandboxedEnvironment):
    """The Home Assistant template environment."""

    def is_safe_callable(self, obj):
        """Test if callback is safe."""
        return isinstance(obj, AllStates) or super().is_safe_callable(obj)


ENV = TemplateEnvironment()
ENV.filters['round'] = forgiving_round
ENV.filters['multiply'] = multiply
ENV.filters['timestamp_custom'] = timestamp_custom
ENV.filters['timestamp_local'] = timestamp_local
ENV.filters['timestamp_utc'] = timestamp_utc
ENV.filters['is_defined'] = fail_when_undefined
ENV.filters['max'] = max
ENV.filters['min'] = min
ENV.filters['random'] = random_every_time
ENV.globals['float'] = forgiving_float
ENV.globals['now'] = dt_util.now
ENV.globals['utcnow'] = dt_util.utcnow
ENV.globals['as_timestamp'] = forgiving_as_timestamp
ENV.globals['relative_time'] = dt_util.get_age
ENV.globals['strptime'] = strptime
