"""Small deterministic helpers."""

from __future__ import annotations

from dataclasses import is_dataclass, asdict
from datetime import datetime, timezone
from enum import Enum
import hashlib
import json
from typing import Any


def utc_now_iso() -> str:
    return datetime.now(timezone.utc).replace(microsecond=0).isoformat()


def stable_digest(value: Any, *, length: int = 12) -> str:
    encoded = json.dumps(to_plain(value), sort_keys=True, separators=(",", ":")).encode()
    return hashlib.sha256(encoded).hexdigest()[:length]


def compact_dict(mapping: dict[str, Any]) -> dict[str, Any]:
    return {
        key: to_plain(value)
        for key, value in mapping.items()
        if value not in (None, "", [], {}, ())
    }


def to_plain(value: Any) -> Any:
    if isinstance(value, Enum):
        return value.value
    if is_dataclass(value):
        return to_plain(asdict(value))
    if isinstance(value, dict):
        return {
            str(key): to_plain(item)
            for key, item in value.items()
            if item not in (None, "", [], {}, ())
        }
    if isinstance(value, (list, tuple, set)):
        return [to_plain(item) for item in value]
    return value


def parse_iso_datetime(value: str | None) -> datetime | None:
    if not value:
        return None
    raw = value.strip()
    if raw.endswith("Z"):
        raw = raw[:-1] + "+00:00"
    try:
        parsed = datetime.fromisoformat(raw)
    except ValueError:
        return None
    if parsed.tzinfo is None:
        return parsed.replace(tzinfo=timezone.utc)
    return parsed.astimezone(timezone.utc)