/**
 * Token Metrics Utility
 *
 * Provides token estimation, metrics calculation, and formatted header generation
 * for displaying token reduction statistics in tool responses.
 *
 * Supports the v0.12.0 token metrics feature - shows before/after token counts,
 * reduction percentage, threats blocked, and elapsed time.
 */
/**
 * Token metrics data structure
 */
export interface TokenMetrics {
    tokensBefore: number;
    tokensAfter: number;
    reductionPct: number;
    threatsBlocked: number;
    elapsedMs: number;
}
/**
 * Estimates token count from character count using GPT-family approximation.
 *
 * Formula: tokens ≈ characters / 4 (rounded up)
 *
 * This is a standard approximation for GPT-family models. For production
 * use cases requiring exact token counts, consider using tiktoken or similar.
 *
 * @param text Input text to estimate tokens for
 * @returns Estimated token count
 */
export declare function estimateTokens(text: string): number;
/**
 * Calculates token metrics from raw and sanitized content.
 *
 * Handles edge cases:
 * - Empty raw content → tokensBefore = 0
 * - Sanitized longer than raw (shouldn't happen) → reductionPct = 0
 * - Ensures reduction percentage is never negative
 *
 * @param rawContent Original content before sanitization
 * @param sanitizedContent Content after sanitization
 * @param threatsBlocked Number of threats detected and blocked
 * @param elapsedMs Elapsed time in milliseconds
 * @returns TokenMetrics object
 */
export declare function calculateMetrics(rawContent: string, sanitizedContent: string, threatsBlocked: number, elapsedMs: number): TokenMetrics;
/**
 * Formats token metrics as a visually-structured header box.
 *
 * Output format:
 * ```
 * ╔═ visus-mcp ═══════════════════════════════╗
 * ║ 4,200 → 890 tokens · 79% reduction        ║
 * ║ 3 threats blocked · fetch 1.2s            ║
 * ╚════════════════════════════════════════════╝
 * ```
 *
 * Box width is dynamically sized to fit content. Uses Unicode box-drawing
 * characters for clean visual appearance.
 *
 * @param metrics Token metrics to format
 * @returns Formatted header string (includes trailing newline for separation)
 */
export declare function formatMetricsHeader(metrics: TokenMetrics): string;
/**
 * Checks if token metrics should be displayed based on environment configuration.
 *
 * Defaults to true. Can be disabled by setting VISUS_SHOW_METRICS=false.
 *
 * @returns true if metrics should be displayed, false otherwise
 */
export declare function shouldShowMetrics(): boolean;
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