"""Rust identifier hygiene."""

from __future__ import annotations

# Strict and reserved-for-future-use keywords from the Rust reference's
# keyword table, 2021 edition.
_RUST_KEYWORDS = frozenset({
    "as", "break", "const", "continue", "crate", "else", "enum", "extern",
    "false", "fn", "for", "if", "impl", "in", "let", "loop", "match", "mod",
    "move", "mut", "pub", "ref", "return", "self", "Self", "static", "struct",
    "super", "trait", "true", "type", "unsafe", "use", "where", "while",
    "async", "await", "dyn",
    "abstract", "become", "box", "do", "final", "macro", "override", "priv",
    "typeof", "unsized", "virtual", "yield",
    "try",
    "union",  # contextual, but escaping it costs nothing
})


def to_rust_ident(name: str) -> str:
    """`name`, or `r#name` when it collides with a keyword.

    Field casing is left alone — the caller owns that convention.
    """
    if name in _RUST_KEYWORDS:
        return f"r#{name}"
    return name


def to_rust_variant_ident(python_member_name: str) -> str:
    """`SONNET` -> `Sonnet`, `MY_OPTION` -> `MyOption`.

    Enum declarations and enum-valued defaults are emitted from different
    places and both call this; two implementations would disagree.
    """
    return "".join(part.capitalize() for part in python_member_name.split("_") if part)