function containsNewline(key) {
    if (!key)
        return null;
    switch (key.type) {
        case 'alias':
        case 'scalar':
        case 'double-quoted-scalar':
        case 'single-quoted-scalar':
            if (key.source.includes('\n'))
                return true;
            if (key.end)
                for (const st of key.end)
                    if (st.type === 'newline')
                        return true;
            return false;
        case 'flow-collection':
            for (const it of key.items) {
                for (const st of it.start)
                    if (st.type === 'newline')
                        return true;
                if (it.sep)
                    for (const st of it.sep)
                        if (st.type === 'newline')
                            return true;
                if (containsNewline(it.key) || containsNewline(it.value))
                    return true;
            }
            return false;
        default:
            return true;
    }
}

export { containsNewline };