getenv

#!/usr/bin/env python3
DEFAULT_SYSTEM_NAME = "default"


def get_current_dir() -> str:
    import os
    return os.path.dirname(os.path.realpath(__file__))


def get_supported_systems() -> [str]:
    """Return a list of systems where support is availabl
    Scan the available env. files and filter the names with the pattern env.SYSTEMNAME.(compiler).(whatever).postfix
    """
    import os
    import re
    pattern = re.compile(r'\Aenv\.(?P<name>[\w\-._]+)\.((cray|gnu|gcc|pgi|clang)\.((\w-_)+\.)*)\w+$')
    ls = os.listdir(get_current_dir())
    filtered = set()
    for f in ls:
        m = pattern.match(f)
        if m:
            filtered.add(m.group('name'))
    return list(filtered)


def match_system(hostname: str) -> str:
    """"Match a hostname with the supported system.
    Fit the longest prefix with the supported system.

    A host with the name keschln-0001 should fit to keschln-0001 if available, otherwise it should fit to kesch.
    """
    import platform
    hostname = platform.node()
    systems = get_supported_systems()
    bestfit = ''
    for s in systems:
        if hostname.startswith(s):
            if len(s) > len(bestfit):
                bestfit = s
    if bestfit == '':
        return DEFAULT_SYSTEM_NAME
    return bestfit


def find_environment(system_name: str, environment: str) -> str:
    """Find the system with the associated environment. 
    If multiple environments are available, select the one with the least specifiers."""
    import os
    files = os.listdir(get_current_dir())

    if system_name == DEFAULT_SYSTEM_NAME:
        environment = ''

    prefix = "env.{system}".format(system=system_name)
    if environment != '':
        prefix = "{prefix}.{environment}".format(prefix=prefix, environment=environment)

    filtered = [x for x in files if x.startswith(prefix)]
    if len(filtered) == 0:
        raise ValueError("Environment with the prefix {} not found!".format(prefix))

    filtered.sort(key=len)
    return "{cd}/{file}".format(cd=get_current_dir(), file=filtered[0])


if __name__ == "__main__":
    import platform
    import argparse
    hostname = platform.node()
    system = match_system(hostname)

    parser = argparse.ArgumentParser(description="Get system environment")
    parser.add_argument("-l", "--list", action="store_true",
                        help="List supported systems.")
    parser.add_argument("-e", "--environment", type=str, default="gnu",
                        help="Environment (i.e. gnu, gnu.4.9.3, cray, etc...)")
    args = parser.parse_args()

    if args.list:
        print("Hostname: {}".format(hostname))
        print("Supported Systems:")
        for x in get_supported_systems():
            print("- {}".format(x))
        print("Matched with: {}".format(system))
        exit(0)

    print(find_environment(system, args.environment))