import re

# Some models occasionally leave literal backslash-u escape sequences un-decoded inside
# tool-call argument strings (a known JSON-generation quirk) — e.g. the string ends up
# containing the six characters ü instead of the character ü. json.loads() alone
# doesn't catch this because the escaping happened *inside* an already-valid JSON string,
# not at the JSON structural level.
_DOUBLE_ESCAPED_UNICODE_RE = re.compile(r"\\u([0-9a-fA-F]{4})")


def _fix_string(text: str) -> str:
    if "\\u" not in text:
        return text
    return _DOUBLE_ESCAPED_UNICODE_RE.sub(lambda m: chr(int(m.group(1), 16)), text)


def fix_double_escaped_unicode(value):
    """Recursively repair double-escaped unicode in a parsed JSON value (dict/list/str)."""
    if isinstance(value, str):
        return _fix_string(value)
    if isinstance(value, list):
        return [fix_double_escaped_unicode(v) for v in value]
    if isinstance(value, dict):
        return {k: fix_double_escaped_unicode(v) for k, v in value.items()}
    return value