"""Shared domain primitives.

Pure Python — no framework, no I/O. The domain layer must stay importable
without FastAPI, SQLAlchemy or a database connection.
"""

from __future__ import annotations

import re
import uuid
from datetime import UTC, datetime

_SLUG_RE = re.compile(r"[^a-z0-9]+")


def new_id() -> str:
    """Opaque, URL-safe entity id (portable across SQLite and PostgreSQL)."""
    return uuid.uuid4().hex


def utcnow() -> datetime:
    return datetime.now(UTC)


def slugify(value: str, *, max_length: int = 48) -> str:
    """ASCII slug. Non-ASCII input (e.g. Persian) collapses to a stable fallback.

    Persian organization names do not transliterate, so we keep a short random
    suffix appended by the caller when the slug would be empty.
    """
    slug = _SLUG_RE.sub("-", value.strip().lower()).strip("-")
    slug = slug[:max_length].strip("-")
    if not slug:
        slug = f"x{uuid.uuid4().hex[:8]}"
    return slug


def ensure_unique_slug(base: str, taken: set[str], *, max_length: int = 48) -> str:
    """Append ``-2``, ``-3`` ... until the slug is free."""
    candidate = base[:max_length]
    if candidate not in taken:
        return candidate
    n = 2
    while True:
        suffix = f"-{n}"
        candidate = f"{base[: max_length - len(suffix)]}{suffix}"
        if candidate not in taken:
            return candidate
        n += 1