#!/usr/bin/env python

"""
invirt-getconf [-f FILE] KEY prints the configuration the option named KEY from
the invirt configuration file FILE.  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 authn.0.type
"""

from invirt.config import load
from sys import argv, exit, stderr
from optparse import OptionParser

class invirt_exception(Exception): pass

def main(argv):
    try:
        parser = OptionParser(usage = '%prog [options] key',
                description = __doc__.strip().split('\n\n')[0])
        parser.add_option('-s', '--src',
                default = '/etc/invirt/master.yaml',
                help = 'the source YAML configuration file to read from')
        parser.add_option('-c', '--cache',
                default = '/var/lib/invirt/invirt.json',
                help = 'path to the JSON cache')
        parser.add_option('-r', '--refresh',
                action = 'store_true',
                help = 'force the cache to be regenerated')
        opts, args = parser.parse_args()

        try: [key] = args
        except: raise invirt_exception(__doc__.strip())

        conf = load(opts.src, opts.cache, opts.refresh)
        components = key.split('.')
        for i, component in enumerate(components):
            progress = '.'.join(components[:i])
            if type(conf) not in [dict, list]:
                raise invirt_exception(
                        '%s: node has no children (atomic datum)' % progress)
            if type(conf) == list:
                try: component = int(component)
                except: raise invirt_exception(
                        '%s: node a list; integer path component required, '
                        'but got "%s"' % (progress, component))
            try: conf = conf[component]
            except KeyError: raise invirt_exception(
                    '%s: key "%s" not found' % (progress, component))
            except IndexError: raise invirt_exception(
                    '%s: index %s out of range' % (progress, component))
        print conf
    except (invirt_exception, OSError), ex:
        print >> stderr, ex
        return 1

if __name__ == '__main__':
    exit(main(argv))

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