#!/usr/bin/env python
import os
import sys
import yaml


def os_family(distro):
    """Given a distribution, returns a operating system family."""
    family = None
    if distro in ['centos', 'fedora', 'rhel', 'rhel7']:
        family = 'redhat'
    elif distro in ['debian', 'ubuntu']:
        family = 'debian'
    elif distro == 'opensuse':
        family = 'suse'
    return family


def merge_data(source, destination, distro):
    """Merges two dictionaries and filters on distro, family, or default
    (in order)."""
    result = dict()
    result.update(destination)
    family = os_family(distro)
    for servicename, mapping in source.iteritems():
        if servicename in result:
            raise Exception("%s already found in services list" % servicename)
        if distro in mapping:
            result[servicename] = mapping.get(distro)
        elif family in mapping:
            result[servicename] = mapping.get(family)
        elif 'default' in mapping:
            result[servicename] = mapping.get('default')
        else:
            result[servicename] = servicename

    return result


def write_data_to_file(data, service_file_path):
    """Writes yaml data to a specified path."""
    with open(service_file_path, 'w') as destination:
        yaml.dump(data, destination, default_flow_style=False)


def main():
    elements = os.environ.get("IMAGE_ELEMENT").split(' ')
    element_paths = os.environ.get("ELEMENTS_PATH").split(':')
    service_names = dict()
    for element in elements:
        for element_path in element_paths:
            data_path = os.path.join(element_path, element, "svc-map")
            if os.path.exists(data_path):
                with open(data_path, 'r') as dataFile:
                    data = yaml.load(dataFile.read())
                    try:
                        service_names = merge_data(
                            data,
                            service_names,
                            os.environ.get("DISTRO_NAME"))
                    except Exception as err:
                        print("%s.  Check %s for duplicate \
                            service name." % (err, element))
                        sys.exit(1)

    write_data_to_file(service_names, os.path.join("/tmp", 'svc-map-services'))


if __name__ == "__main__":
    main()