#!/usr/bin/env python
import argparse
import importlib
import pkgutil
# Create an argparser for the service name.
parser = argparse.ArgumentParser(
    description="Generate a commented yaml file from the policy in code rules"
    " extracted from a given OpenStack Service")
# Create argument for the service name, this should be the name of the
# python module to import. It will import <service_name>.policies to get
# the python files where the policies are defined
parser.add_argument("service", type=str,
                    help="The name of the openstack services's python module"
                    " to import for policy extraction")
# Parse user supplied arguments
args = parser.parse_args()
# Import the <service_name>.policies module, which should contain
# submodules that contain the actual policy logic
try:
    policies = importlib.import_module(args.service + ".policies")
except Exception as e:
    policies = importlib.import_module(args.service + ".policy")
# Policy_files should be the list of all the python submodules defined
# inside the policy module. These contain the rule logic that is enforced
# by the service
policy_files = [submod.name for submod in pkgutil.walk_packages(
    path=policies.__path__)]
# "Base", if it's defined, will contain the base rule logic that other policy
# rules use for enforcement, for easy of use, move this to the front
if any("base" in value for value in policy_files):
    policy_files.insert(0, policy_files.pop(policy_files.index("base")))
# Iterate through the list of policy files, extract and print the actual rules
for f in policy_files:
    # Get the actual policy file from the policies module with getattr
    policy_file = getattr(policies, f)
    # Print the name of the module this was defined in
    print("### Policy Rules defined in {}".format(policy_file.__name__))
    # Newline for formatting
    print("")
    # The list containing the policy objects should be either
    # "<name>_policies" or "rules", try both, if neither exist, this is
    # probably not what we want, so continue on to next file
    try:
        # Attempt to get <policy_file_name>_policies via getattr
        policy_objects = getattr(policy_file, "{}_policies".format(f))
    except Exception as e:
        try:
            # Failing that, as it will in "Base" files, get the field "rules",
            # which should contain the role:rule mappings
            policy_objects = getattr(policy_file, "rules")
        except Exception as e2:
            continue
    # Now that we have our policy objects, iterate through them and print the
    # useful fields
    for policy in policy_objects:
        # Description is one of the most important, if it exists, print it,
        # commented
        if policy.description is not None:
            # Since the description can be a multi-line string, split it into
            # several commented lines
            desc = policy.description.splitlines()
            for line in desc:
                # Print commented either way
                print("# {}".format(line))
        # Get the operations this policy may have associated with it, this will
        # be in the form of stuff like GET and a url like /servers/{id}
        try:
            # If there's an operations field in the policy, it'll be a list,
            # for each element, print the URLs and verbs it is associated with
            for operation in policy.operations:
                # Print in the format VERB /url/path/
                print("# {} {}".format(operation["method"], operation["path"]))
        except Exception as e:
            # If we don't have anything here, just print a blank line
            print("#")
        # Finally print the policy rule and its default check_str, this will
        # turn into something of the form:
        # "rule_name": "rule:context_is_admin"
        # or something similar
        print('# "{}": "{}"'.format(policy.name, policy.check_str))
        # Finally print a newline to separate the block
        print("")