toot-script-condivisione-su-mastodon/src/main.js

/*!
	toot - Cross-instance share page for Mastodon
	Copyright (C) 2020-2021  Nikita Karamov <nick@karamoff.dev>

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Affero General Public License as published
	by the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Affero General Public License for more details.

	You should have received a copy of the GNU Affero General Public License
	along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

const INSTANCE_LIST_URL = "https://api.joinmastodon.org/servers";

const $instance = document.getElementById("instance");
const $instanceDatalist = document.getElementById("instanceDatalist");

/**
 * Adds missing "https://" and ending slash to the URL
 *
 * @param {string} url URL to normalize
 * @return {string} normalized URL
 */
function normalizeUrl(url) {
	if (url.indexOf("http://") == -1 && url.indexOf("https://") == -1) {
		url = "https://" + url;
	}
	if (url.charAt(url.length - 1) !== "/") {
		url = url + "/";
	}
	return url;
}

function onLoadInstancesError() {
	console.error("Couldn't load instance list");
}

function onLoadInstancesSuccess() {
	if (this.status >= 400) {
		return onLoadInstancesError();
	}

	const currentInstance = $instance.value;
	const instanceDomains = JSON.parse(this.responseText).map((i) => i.domain);
	if (currentInstance && instanceDomains.indexOf(currentInstance) < 0) {
		instanceDomains.push(currentInstance);
	}
	instanceDomains.sort();

	for (let i = 0; i < instanceDomains.length; i++) {
		const $option = document.createElement("option");
		$option.value = normalizeUrl(instanceDomains[i]);
		$instanceDatalist.appendChild($option);
	}
}

function loadInstances() {
	if ($instanceDatalist.children.length === 0) {
		const request = new XMLHttpRequest();

		request.addEventListener("load", onLoadInstancesSuccess);
		request.addEventListener("error", onLoadInstancesError);

		request.open("GET", INSTANCE_LIST_URL);
		request.send();
	}
}

const prefillInstance = window.localStorage.getItem("mastodon_instance");

const URLParams = window.location.search.substr(1).split("&");
for (let i = 0; i < URLParams.length; i++) {
	const URLParamPair = URLParams[i].split("=");
	if (URLParamPair[0] === "text") {
		document.getElementById("text").value = decodeURIComponent(URLParamPair[1]);
	} else if (URLParamPair[0] === "instance") {
		prefillInstance = decodeURIComponent(URLParamPair[1]);
	}
}

if (prefillInstance != null) {
	$instance.value = normalizeUrl(prefillInstance);
}

$instance.addEventListener("focus", loadInstances);