from __future__ import annotations

import hashlib
import json
import math
from typing import Any

from pydantic import BaseModel


def _jcs(value: Any) -> str:
    """Deterministic JSON close to RFC 8785 for this integer/string DTO domain."""
    if value is None:
        return "null"
    if value is True:
        return "true"
    if value is False:
        return "false"
    if isinstance(value, str):
        return json.dumps(value, ensure_ascii=False, separators=(",", ":"))
    if isinstance(value, int):
        return str(value)
    if isinstance(value, float):
        if not math.isfinite(value):
            raise ValueError("non-finite numbers are not JSON canonicalizable")
        raise TypeError("floating point values are forbidden in safety fingerprints")
    if isinstance(value, list):
        return "[" + ",".join(_jcs(item) for item in value) + "]"
    if isinstance(value, dict):
        keys = sorted(value, key=lambda key: key.encode("utf-16be"))
        return "{" + ",".join(f"{_jcs(key)}:{_jcs(value[key])}" for key in keys) + "}"
    raise TypeError(f"unsupported fingerprint type: {type(value).__name__}")


def canonical_json(model: BaseModel | dict[str, Any]) -> bytes:
    value = model.model_dump(mode="json") if isinstance(model, BaseModel) else model
    return _jcs(value).encode("utf-8")


def fingerprint(model: BaseModel | dict[str, Any]) -> bytes:
    return hashlib.sha256(canonical_json(model)).digest()