"""Deep-merge overrides (a JSON file, path in argv[1]) into config.yaml.

Run inside the hermes container as the hermes user. Only keys present in the
overrides are touched. Prints CHANGED when the file was rewritten.
"""
import json
import os
import sys

import yaml

PATH = "/opt/data/config.yaml"
with open(sys.argv[1]) as fh:
    overrides = json.load(fh)

if os.path.exists(PATH):
    with open(PATH) as fh:
        current = yaml.safe_load(fh) or {}
else:
    current = {}


def merge(dst, src):
    changed = False
    for key, val in src.items():
        if isinstance(val, dict) and isinstance(dst.get(key), dict):
            changed |= merge(dst[key], val)
        elif dst.get(key) != val:
            dst[key] = val
            changed = True
    return changed


if merge(current, overrides):
    with open(PATH, "w") as fh:
        yaml.safe_dump(current, fh, sort_keys=False)
    print("CHANGED")
else:
    print("UNCHANGED")
sys.exit(0)