resolver.py

from functools import partial
import re
import sys
import logging
import flatdict
import collections
import os
logger = logging.getLogger(__name__)

def resolve_yamls(yaml_templates, environ=os.environ):
    logger.debug("Merging following yaml_templates: %s" % yaml_templates)
    logger.debug("Using environ: %s" % environ)
    merged_yaml = _merge_dicts(reversed(yaml_templates + [environ]))
    flattened = flatdict.FlatDict(merged_yaml, delimiter=".")
    keep_resolving = True
    loops = 0
    while keep_resolving and loops < len(flattened):
        loops += 1
        keep_resolving = False
        for key, value in flattened.items():
            keys_to_resolve = re.findall("\$\{(.*?)\}", str(value))
            if len(keys_to_resolve) > 0: keep_resolving = True
            resolved_keys = _resolve_key_substition(flattened, keys_to_resolve)
            for sub_key, resolved_key in resolved_keys:
                flattened[key] = flattened[key].replace(
                            "${%s}" % sub_key, str(resolved_key))
    return flattened

def _resolve_key_substition(flattened, keys_to_resolve):
    #this function returns array of tuples to replace strings later
    resolved_keys = []
    if len(keys_to_resolve) > 0:
        for key_default in keys_to_resolve:
            key_default_split = key_default.split(":")
            sub_key = key_default_split[0]
            default = key_default_split[1] if len(key_default_split) == 2 else sub_key
            resolved = flattened.get(sub_key, default)
            resolved_keys.append((key_default,resolved))
        return resolved_keys
    else:
        return resolved_keys

def _merge_dicts(dicts):
    result = {}
    for dictionary in dicts:
        _merge_dict(result, dictionary)
    return result

def _merge_dict(dct, merge_dct):
    for k, v in merge_dct.items():
        if (k in dct and isinstance(dct[k], dict)
                and isinstance(merge_dct[k], collections.Mapping)):
            _merge_dict(dct[k], merge_dct[k])
        else:
            dct[k] = merge_dct[k]