import { Buffer } from "node:buffer";
import { z } from "zod";
const fallbackFileName = "upload.bin";
const defaultMimeType = "application/octet-stream";
export const imageInputSchema = z
.string()
.min(1)
.describe("Image payload as a base64 string or data URL");
export type ImageInput = z.infer<typeof imageInputSchema>;
export interface PreparedImagePayload {
blob: Blob;
fileName: string;
mimeType: string;
}
export function prepareImagePayload(
image: ImageInput,
fallbackName: string = fallbackFileName,
fallbackType: string = defaultMimeType,
): PreparedImagePayload {
const value = image.trim();
if (value.startsWith("data:")) {
return decodeDataUrl(value, fallbackName, fallbackType);
}
return decodeBase64(value, fallbackName, fallbackType);
}
function decodeDataUrl(dataUrl: string, fallbackName: string, fallbackType: string): PreparedImagePayload {
const match = /^data:([^;,]+)?(;base64)?,(.*)$/i.exec(dataUrl);
if (!match) {
throw new Error("Invalid data URL supplied for image payload");
}
const mimeType = match[1] ?? fallbackType;
const isBase64 = Boolean(match[2]);
const rawPayload = match[3] ?? "";
const buffer = isBase64
? Buffer.from(rawPayload, "base64")
: Buffer.from(decodeURIComponent(rawPayload), "utf8");
if (!buffer.length) {
throw new Error("Image payload is empty after decoding data URL");
}
const blob = new Blob([buffer], { type: mimeType });
return {
blob,
fileName: fallbackName,
mimeType,
};
}
function decodeBase64(base64Value: string, fileName: string, mimeType: string): PreparedImagePayload {
try {
const cleaned = base64Value.replace(/\s+/g, "");
const buffer = Buffer.from(cleaned, "base64");
if (!buffer.length) {
throw new Error("Decoded image payload is empty");
}
const blob = new Blob([buffer], { type: mimeType });
return {
blob,
fileName,
mimeType,
};
} catch (error) {
const message = error instanceof Error ? error.message : String(error);
throw new Error(`Failed to decode base64 image data: ${message}`);
}
}
