import json

from charms.reactive import when, when_not
from charms.reactive import set_flag, clear_flag
from charms.reactive import Endpoint


class HttpRequires(Endpoint):

    @when('endpoint.{endpoint_name}.changed')
    def changed(self):
        if any(unit.received_raw['port'] for unit in self.all_joined_units):
            set_flag(self.expand_name('{endpoint_name}.available'))

    @when_not('endpoint.{endpoint_name}.joined')
    def broken(self):
        clear_flag(self.expand_name('{endpoint_name}.available'))

    def services(self):
        """
        Returns a list of available HTTP services and their associated hosts
        and ports.

        The return value is a list of dicts of the following form::

            [
                {
                    'service_name': name_of_service,
                    'hosts': [
                        {
                            'hostname': address_of_host,
                            'private-address': private_address_of_host,
                            'port': port_for_host,
                        },
                        # ...
                    ],
                },
                # ...
            ]
        """
        def build_service_host(data):
            private_address = data['private-address']
            host = data['hostname'] or private_address
            if host and data['port']:
                return (host, private_address, data['port'])
            else:
                return None

        services = {}
        for relation in self.relations:
            service_name = relation.application_name
            service = services.setdefault(service_name, {
                'service_name': service_name,
                'hosts': [],
            })
            host_set = set()
            for unit in relation.joined_units:
                data = unit.received_raw
                host = build_service_host(data)
                if host:
                    host_set.add(host)

                # if we have extended data, add it
                if 'extended_data' in data:
                    for ed in json.loads(data['extended_data']):
                        host = build_service_host(ed)
                        if host:
                            host_set.add(host)

            service['hosts'] = [
                {'hostname': h, 'private-address': pa, 'port': p}
                for h, pa, p in sorted(host_set)
            ]

        ret = [s for s in services.values() if s['hosts']]
        return ret