import platform
import sys
from collections import OrderedDict

import yaml as pyyaml


_items = "viewitems" if sys.version_info < (3,) else "items"
_std_dict_is_order_preserving = sys.version_info >= (3, 7) or (
    sys.version_info >= (3, 6) and platform.python_implementation() == "CPython"
)


def map_representer(dumper, data):
    return dumper.represent_dict(getattr(data, _items)())


def map_constructor(loader, node):
    loader.flatten_mapping(node)
    pairs = loader.construct_pairs(node)
    try:
        return OrderedDict(pairs)
    except TypeError:
        loader.construct_mapping(node)  # trigger any contextual error
        raise


if pyyaml.safe_dump is pyyaml.dump:
    # PyYAML v4.x
    SafeDumper = pyyaml.dumper.Dumper
    DangerDumper = pyyaml.dumper.DangerDumper
else:
    SafeDumper = pyyaml.dumper.SafeDumper
    DangerDumper = pyyaml.dumper.Dumper

pyyaml.add_representer(dict, map_representer, Dumper=SafeDumper)
pyyaml.add_representer(OrderedDict, map_representer, Dumper=SafeDumper)
pyyaml.add_representer(dict, map_representer, Dumper=DangerDumper)
pyyaml.add_representer(OrderedDict, map_representer, Dumper=DangerDumper)


Loader = None
if not _std_dict_is_order_preserving:
    for loader_name in pyyaml.loader.__all__:
        Loader = getattr(pyyaml.loader, loader_name)
        pyyaml.add_constructor("tag:yaml.org,2002:map", map_constructor, Loader=Loader)


# Merge PyYAML namespace into ours.
# This allows users a drop-in replacement:
#   import oyaml as yaml
del map_constructor, map_representer, SafeDumper, DangerDumper, Loader
from yaml import *