remoteProbe.ts — astro Source File

Source Code

import { AstroError, AstroErrorData } from '../../core/errors/index.js';
import type { ImageMetadata } from '../types.js';
import { imageMetadata } from './metadata.js';

/**
 * Infers the dimensions of a remote image by streaming its data and analyzing it progressively until sufficient metadata is available.
 *
 * @param {string} url - The URL of the remote image from which to infer size metadata.
 * @return {Promise<Omit<ImageMetadata, 'src' | 'fsPath'>>} Returns a promise that resolves to an object containing the image dimensions metadata excluding `src` and `fsPath`.
 * @throws {AstroError} Thrown when the fetching fails or metadata cannot be extracted.
 */
export async function inferRemoteSize(url: string): Promise<Omit<ImageMetadata, 'src' | 'fsPath'>> {
	// Start fetching the image
	const response = await fetch(url);
	if (!response.body || !response.ok) {
		throw new AstroError({
			...AstroErrorData.FailedToFetchRemoteImageDimensions,
			message: AstroErrorData.FailedToFetchRemoteImageDimensions.message(url),
		});
	}

	const reader = response.body.getReader();

	let done: boolean | undefined, value: Uint8Array;
	let accumulatedChunks = new Uint8Array();

	// Process the stream chunk by chunk
	while (!done) {
		const readResult = await reader.read();
		done = readResult.done;

		if (done) break;

		if (readResult.value) {
			value = readResult.value;

			// Accumulate chunks
			let tmp = new Uint8Array(accumulatedChunks.length + value.length);
			tmp.set(accumulatedChunks, 0);
			tmp.set(value, accumulatedChunks.length);
			accumulatedChunks = tmp;

			try {
				// Attempt to determine the size with each new chunk
				const dimensions = await imageMetadata(accumulatedChunks, url);

				if (dimensions) {
					await reader.cancel(); // stop stream as we have size now

					return dimensions;
				}
			} catch {
				// This catch block is specifically for `imageMetadata` errors
				// which might occur if the accumulated data isn't yet sufficient.
			}
		}
	}

	throw new AstroError({
		...AstroErrorData.NoImageMetadata,
		message: AstroErrorData.NoImageMetadata.message(url),
	});
}