EXTENSION_MAP = {
    ".py":   "python",
    ".js":   "javascript",
    ".html": "html",
    ".css":  "css",
    ".yaml": "yaml",
    ".md":   "markdown",
    ".json": "json",
    ".sh":   "bash",
    ".xml":  "xml",
    ".txt":  "plaintext",
}

def get_highlight_language(filename: str) -> str:
    if "." not in filename:
        return "plaintext"
    ext = "." + filename.rsplit(".", 1)[-1].lower()
    return EXTENSION_MAP.get(ext, "plaintext")