"""
Demo platform for the Device tracker component.

For more details about this platform, please refer to the documentation
https://home-assistant.io/components/demo/
"""
import random

from homeassistant.components.device_tracker import DOMAIN


def setup_scanner(hass, config, see, discovery_info=None):
    """Set up the demo tracker."""
    def offset():
        """Return random offset."""
        return (random.randrange(500, 2000)) / 2e5 * random.choice((-1, 1))

    def random_see(dev_id, name):
        """Randomize a sighting."""
        see(
            dev_id=dev_id,
            host_name=name,
            gps=(hass.config.latitude + offset(),
                 hass.config.longitude + offset()),
            gps_accuracy=random.randrange(50, 150),
            battery=random.randrange(10, 90)
        )

    def observe(call=None):
        """Observe three entities."""
        random_see('demo_paulus', 'Paulus')
        random_see('demo_anne_therese', 'Anne Therese')

    observe()

    see(
        dev_id='demo_home_boy',
        host_name='Home Boy',
        gps=[hass.config.latitude - 0.00002, hass.config.longitude + 0.00002],
        gps_accuracy=20,
        battery=53
    )

    hass.services.register(DOMAIN, 'demo', observe)

    return True