import type { Bytes } from '../io/types';

/**
 * Trigger browser download
 * @param filename download as filename
 * @param data data or url to download
 * @param type content type
 * @param raw if true, data is treated as raw data, not url
 */
export async function download(filename: string, data: any, { type = 'application/octet-stream', raw = false } = {}) {
	const a = document.createElement('a');
	let closer: () => void = () => null;
	try {
		a.download = filename;

		// url or data url
		if (typeof data === 'string' && /^(https?:|data:)/.test(data) && !raw) {
			a.href = data;
			// 只有 same-origin 才能 download
			if (/^https?:/.test(data)) {
				if (new URL(data).origin !== location.origin) {
					// 非同源
					a.href = '';
					data = await fetch(data).then((res) => res.blob());
				}
			}
		} else if (typeof data === 'string') {
			data = new TextEncoder().encode(data);
		}

		if (data instanceof Uint8Array) {
			data = new Blob([data as Bytes], { type });
		}
		if (data instanceof File || data instanceof Blob || data instanceof MediaSource) {
			a.href = URL.createObjectURL(data);
			closer = () => {
				URL.revokeObjectURL(a.href);
			};
		} else {
			console.error(`invalid download data`, data);
			throw new Error(`can not download ${data && Object.getPrototypeOf(data)}`);
		}
		a.click();
	} finally {
		closer();
	}
}