image-handler.ts•2.96 kB
import { z } from "zod";
/**
* Configuration options for image transport
*/
export interface ImageTransportOptions {
maxSize: number;
allowedMimeTypes: string[];
compressionQuality?: number;
}
/**
* Schema for image content validation
*/
export const ImageContentSchema = z.object({
type: z.literal("image"),
data: z.string(),
mimeType: z.string()
});
export type ImageContent = z.infer<typeof ImageContentSchema>;
/**
* Default configuration for image transport
*/
export const DEFAULT_IMAGE_OPTIONS: ImageTransportOptions = {
maxSize: 5 * 1024 * 1024, // 5MB
allowedMimeTypes: ['image/jpeg', 'image/png', 'image/gif', 'image/webp'],
compressionQuality: 0.8
};
/**
* Validates image content against transport options
*/
export function validateImageTransport(content: ImageContent, options: ImageTransportOptions = DEFAULT_IMAGE_OPTIONS): void {
// Validate schema
ImageContentSchema.parse(content);
// Validate MIME type
if (!options.allowedMimeTypes.includes(content.mimeType)) {
throw new Error(`Unsupported image type: ${content.mimeType}. Allowed types: ${options.allowedMimeTypes.join(', ')}`);
}
// Validate base64 format
if (!isBase64(content.data)) {
throw new Error('Invalid base64 image data');
}
// Validate size
const sizeInBytes = Buffer.from(content.data, 'base64').length;
if (sizeInBytes > options.maxSize) {
throw new Error(`Image size ${sizeInBytes} bytes exceeds maximum allowed size of ${options.maxSize} bytes`);
}
}
/**
* Prepares image content for transport
* This function can be extended to handle compression, format conversion, etc.
*/
export function prepareImageForTransport(content: ImageContent, options: ImageTransportOptions = DEFAULT_IMAGE_OPTIONS): ImageContent {
validateImageTransport(content, options);
// For now, we just return the validated content
// Future: implement compression, format conversion, etc.
return content;
}
/**
* Checks if a string is valid base64
*/
function isBase64(str: string): boolean {
if (str === '' || str.trim() === '') {
return false;
}
try {
return btoa(atob(str)) === str;
} catch (err) {
return false;
}
}
/**
* Gets the size of a base64 image in bytes
*/
export function getBase64ImageSize(base64String: string): number {
return Buffer.from(base64String, 'base64').length;
}
/**
* Utility type for messages containing image content
*/
export type MessageWithImage = {
result?: {
content?: Array<ImageContent | { type: string; [key: string]: unknown }>;
};
[key: string]: unknown;
};
/**
* Checks if a message contains image content
*/
export function hasImageContent(message: unknown): message is MessageWithImage {
if (typeof message !== 'object' || message === null) {
return false;
}
const msg = message as MessageWithImage;
return Array.isArray(msg.result?.content) &&
msg.result.content.some(item => item.type === 'image');
}