/**
 * Statistical analysis for detecting obfuscated or suspicious text segments.
 * Zero dependencies, pure TypeScript.
 */
import type { Severity } from "./types.js";
export type EntropyFinding = {
    type: string;
    message: string;
    severity: Severity;
    evidence: string;
    offset: number;
};
export type EntropyResult = {
    shannonEntropy: number;
    charFrequency: Map<string, number>;
    suspiciousPatterns: EntropyFinding[];
};
/**
 * Calculate Shannon entropy (bits per character) for the full input string.
 */
export declare function shannonEntropy(input: string): number;
/**
 * Build a character frequency map for the input.
 */
export declare function charFrequency(input: string): Map<string, number>;
/**
 * Detect high-entropy segments using a sliding window.
 * Window size: 64 chars.
 * Threshold: 4.5 bits for Latin/ASCII text, 6.5 bits for wide-charset scripts
 * (Korean Hangul, CJK, Japanese) which naturally have high entropy due to
 * their large alphabets (e.g., 11,172 Hangul syllable blocks).
 */
export declare function detectHighEntropySegments(input: string): EntropyFinding[];
/**
 * Detect low-entropy repetition: same character repeated 20+ times,
 * or same short pattern repeated 20+ times.
 */
export declare function detectLowEntropyRepetition(input: string): EntropyFinding[];
/**
 * Detect unusual Unicode block mixing within the same sentence.
 * Flags when Latin, Cyrillic, and CJK characters appear together.
 */
export declare function detectUnicodeMixing(input: string): EntropyFinding[];
/**
 * Detect high density of invisible/control/zero-width characters.
 * Flags if >5% of characters are invisible.
 */
export declare function detectInvisibleCharDensity(input: string): EntropyFinding[];
/**
 * Detect encoding fingerprints suggesting embedded encoded payloads.
 * High ratio of +/= suggests base64; high ratio of % suggests URL encoding.
 */
export declare function detectEncodingFingerprints(input: string): EntropyFinding[];
/**
 * Run full entropy analysis on input text.
 */
export declare function analyzeEntropy(input: string): EntropyResult;