/**
 * Attachment Validation Utilities
 *
 * Pure functions for validating email attachment sizes and formatting file sizes
 * into human-readable strings. Shared between frontend (instant feedback) and
 * backend (authoritative validation).
 *
 * @module attachmentValidation
 */
/**
 * Maximum allowed attachment size in bytes (25 MB).
 * Matches the IEmailGatewayConfig.maxMessageSizeBytes default.
 */
export declare const MAX_ATTACHMENT_SIZE_BYTES: number;
/**
 * Validate that a single attachment's size does not exceed the maximum.
 *
 * @param sizeBytes - The size of the attachment in bytes
 * @param maxBytes - The maximum allowed size in bytes
 * @returns true if sizeBytes ≤ maxBytes
 *
 * @example
 * ```typescript
 * validateAttachmentSize(1024, MAX_ATTACHMENT_SIZE_BYTES); // true
 * validateAttachmentSize(30 * 1024 * 1024, MAX_ATTACHMENT_SIZE_BYTES); // false
 * ```
 */
export declare function validateAttachmentSize(sizeBytes: number, maxBytes: number): boolean;
/**
 * Validate that all attachments individually and cumulatively fit within the limit.
 *
 * Returns true if and only if every individual size ≤ maxBytes AND the sum of
 * all sizes ≤ maxBytes.
 *
 * @param sizes - Array of attachment sizes in bytes
 * @param maxBytes - The maximum allowed size in bytes (applies per-file and total)
 * @returns true if all individual sizes and the total are within the limit
 *
 * @example
 * ```typescript
 * validateTotalAttachmentSize([1024, 2048], MAX_ATTACHMENT_SIZE_BYTES); // true
 * validateTotalAttachmentSize([20 * 1024 * 1024, 10 * 1024 * 1024], MAX_ATTACHMENT_SIZE_BYTES); // false (total > 25MB)
 * ```
 */
export declare function validateTotalAttachmentSize(sizes: number[], maxBytes: number): boolean;
/**
 * Format a byte count into a human-readable string with appropriate units.
 *
 * Uses units B, KB, MB, GB. The numeric value is always < 1024 for B, KB, and MB
 * units. GB has no upper bound. Values are rounded to two decimal places for
 * KB, MB, and GB.
 *
 * @param bytes - Non-negative byte count to format
 * @returns Human-readable string (e.g., "1.50 KB", "25.00 MB")
 *
 * @example
 * ```typescript
 * formatFileSize(0);          // "0 B"
 * formatFileSize(512);        // "512 B"
 * formatFileSize(1536);       // "1.50 KB"
 * formatFileSize(26214400);   // "25.00 MB"
 * ```
 */
export declare function formatFileSize(bytes: number): string;
//# sourceMappingURL=attachmentValidation.d.ts.map