"""Service Discovery.

We rely on a simple convention to resolve services based on a name and
environment.

For resolving services in dev, we allow the specification of custom mappings
via an environment variable OWSREQUEST_SERVICE_MAP, which should be a JSON
dictionary mapping service names to urls.

"""

import json
import os

from owsrequest.constants.environment import PROD_ENVIRONMENT
from owsrequest.constants.environment import QA_ENVIRONMENT
from owsrequest.constants.environment import UAT_ENVIRONMENT

SERVICE_URL_SPEC = '{environment}-{service_name}.{domain}'
SERVICE_DEFAULT_DOMAIN = 'theorchard.io'
LEGACY_SERVICE_URL_SPEC = '{service_name}.{domain}'
LEGACY_SERVICE_DEFAULT_QA_DOMAIN = 'qaorch.com'
LEGACY_SERVICE_DEFAULT_PROD_DOMAIN = 'theorchard.com'


def get_owsrequest_service_map():
    """Load service map from environment."""
    injected_mappings = os.environ.get('OWSREQUEST_SERVICE_MAP')
    if injected_mappings:
        return json.loads(injected_mappings)
    else:
        return {}


owsrequest_service_mapping = get_owsrequest_service_map()


def discover(service_name, environment, islegacy=False):
    """Resolve the application name.

    In dev, services resolve by default to their qa versions.

    This behavior can be overridden by injecting a custom service
    mapping via the environment variable `OWSREQUEST_SERVICE_MAP`.
    Its value should be a JSON dictionary mapping service names
    to service urls.

    Args:
        service_name (str): the name of the service.
        environment (str): the environment.
        islegacy (bool): True for php legacy service.

    Returns:
        str: the service url.

    """
    environment = environment.lower()
    service_name = service_name.lower()

    LEGACY_SERVICE_DEFAULT_DOMAIN = LEGACY_SERVICE_DEFAULT_PROD_DOMAIN \
        if environment == PROD_ENVIRONMENT \
        else LEGACY_SERVICE_DEFAULT_QA_DOMAIN

    if environment in (QA_ENVIRONMENT, PROD_ENVIRONMENT):
        if islegacy:
            url = LEGACY_SERVICE_URL_SPEC.format(
                service_name=service_name,
                domain=LEGACY_SERVICE_DEFAULT_DOMAIN
            )
        else:
            url = SERVICE_URL_SPEC.format(
                environment=environment,
                service_name=service_name,
                domain=SERVICE_DEFAULT_DOMAIN
            )
        return environment, url

    if environment == UAT_ENVIRONMENT:
        if service_name in owsrequest_service_mapping:
            return environment, owsrequest_service_mapping.get(service_name)
        return environment, SERVICE_URL_SPEC.format(
            environment=environment,
            service_name=service_name,
            domain=SERVICE_DEFAULT_DOMAIN,
        )

    if environment == 'dev' and service_name in owsrequest_service_mapping:
        url = owsrequest_service_mapping.get(service_name)
        return environment, url
    else:
        # Default to qa
        if islegacy:
            url = LEGACY_SERVICE_URL_SPEC.format(
                service_name=service_name,
                domain=LEGACY_SERVICE_DEFAULT_DOMAIN
            )
        else:
            url = SERVICE_URL_SPEC.format(
                environment=QA_ENVIRONMENT,
                service_name=service_name,
                domain=SERVICE_DEFAULT_DOMAIN
            )
        return QA_ENVIRONMENT, url