#!/bin/env python3
#
# this is NOT a human-facing tool
#
# This is to replace the legacy data files being used to populate
# variables in a shell script and instead get them from the vars
# files even though that still feels weird.
#
# Example:
# azs=$(yamlpath.py roles/cassandra/vars/clusters.yml clusters/multitenant-us-east-1/availability_zones)
# echo $azs
# us-east-1b us-east-1c us-east-1a

import yaml
import sys
import os.path

# no fancy arg parsing, only simple checking because
# I expect the caller (my script) to get things right
yamlfile=sys.argv[1]
yamlpath=sys.argv[2]

if not os.path.isfile(yamlfile):
    sys.exit("the first arg must be a filename, got: '{}'".format(yamlfile))
if len(yamlpath) < 1:
    sys.exit("you must provide a yaml path to emit, got: '{}'".format(yamlpath))

def extract_path(yamlpath, data):
    parts = yamlpath.split("/")

    cursor = data
    for part in parts:
        if type(cursor) is list and part.isdigit():
            cursor = cursor[int(part)]
        elif type(cursor) is dict:
            cursor = cursor[part]

    if type(cursor) in (str,int,float):
        print(cursor)
    elif type(cursor) is list:
       print(" ".join(cursor))
    elif type(cursor) is dict:
        print(" ".join(cursor.keys()))
    else:
        sys.exit("cannot print node type '{}'".format(type(cursor)))

with open(yamlfile, 'r') as stream:
    try:
        data = yaml.load(stream)
        extract_path(yamlpath, data)
    except yaml.YAMLError as e:
        sys.exit("YAML parsing failed: {}".format(e))