import type { TextStatistics } from './statistics.js';
/** The six supported readability formulas, all computed from a `TextStatistics`. */
export type ReadabilityFormula = 'flesch-reading-ease' | 'flesch-kincaid-grade' | 'gunning-fog' | 'smog' | 'coleman-liau' | 'automated-readability';
/**
 * Computes a readability score from pre-computed `TextStatistics` using the
 * standard published definition for `formula` (cited per-case below),
 * rounded to 2 decimals.
 *
 * Contract: every one of these formulas divides by `words` and/or
 * `sentences`, so a stats object with 0 words or 0 sentences (e.g. an empty
 * or non-prose input) would otherwise produce NaN/Infinity. Rather than
 * propagate that, `computeReadability` returns `0` for every formula in
 * that case -- callers (e.g. the `metric` assertion) should treat that 0 as
 * "not enough text to score", not as a genuine "perfectly readable" result.
 */
export declare function computeReadability(formula: ReadabilityFormula, stats: TextStatistics): number;
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