#!/usr/bin/env python3

"""
invirt-getconf loads an invirt configuration file (either the original YAML
source or the faster-to-load JSON cache) and prints the configuration option
with the given name (key).  Keys are dot-separated paths into the YAML
configuration tree.  List indexes (0-based) are also treated as path
components.

(Due to this path language, certain restrictions are placed on the keys used in
the YAML configuration; e.g., they cannot contain dots.)

Examples:

  invirt-getconf db.uri
  invirt-getconf hosts.0.ip
"""

import argparse
import sys
import yaml

import invirt.config


class PathResolutionException(Exception):
    pass


def main():
    parser = argparse.ArgumentParser(description='Get values from invirt configuration file')
    parser.add_argument('-r', '--refresh', action='store_true', help='Force regenerate the cache')
    parser.add_argument('-l', '--ls', action='store_true', help='List children of node')
    parser.add_argument('path', nargs='?', default='', help='Path of value to get')

    args = parser.parse_args()

    components = args.path.split('.')

    conf = invirt.config.load(args.refresh)
    for i, component in enumerate(components):
        progress = '.'.join(components[:i])

        if isinstance(conf, list):
            try:
                component = int(component)
            except ValueError:
                raise PathResolutionException(f'{progress}: node is a list; integer path component required, '
                                              'but got "{component}"')

            try:
                conf = conf[component]
            except IndexError:
                raise PathResolutionException(f'{progress}: index {component} out of range')
        elif isinstance(conf, dict):
            try:
                conf = conf[component]
            except KeyError:
                raise PathResolutionException(f'{progress}: key "{component}" not found')
        else:
            raise PathResolutionException(f'{progress}: node has no children (atomic datum)')

    if args.ls:
        if isinstance(conf, list):
            for i in range(len(conf)):
                print(i)
        elif isinstance(conf, dict):
            for k in conf:
                print(k)
        else:
            raise PathResolutionException(f'{".".join(components)}: node has no children (atomic datum)')
    else:
        if isinstance(conf, (dict, list)):
            print(conf)
        else:
            yaml.dump(conf, sys.stdout, Dumper=yaml.CSafeDumper, default_flow_style=False)


if __name__ == '__main__':
    main()