fields.js

'use strict';

const favicon_of = async tab => {
	if (!(await pref_of('reqfav')))
		return undefined;
	return favicon_req(tab);
};

const favicon_req = tab => new Promise((resolve, reject) => {
	const byte_flatmap = (f, ab) =>
		Array.prototype.map.call(new Uint8Array(ab), f).join("");
	const abtobs = ab =>
		/* don't you just adore optional arguments */
		byte_flatmap(b => String.fromCharCode(b), ab);
	const abtoh = ab =>
		byte_flatmap(b => `00${b.toString(16)}`.slice(-2), ab);

	let xhr = new XMLHttpRequest();

	xhr.responseType = 'arraybuffer';
	xhr.open("GET", tab.favIconUrl);
	xhr.onload = function() {
		let mime = this.getResponseHeader('Content-Type');
		let [type, subtype] = mime.split("/");

		/* i don't even want to think about whatever weird edge case would
		   make this premature */
		if (type !== "image")
			return resolve(undefined);

		let bin = abtobs(this.response);
		let data = bin;
		let dc = subtype === "svg+xml"
	           ? `,${encodeURIComponent(bin)}`
		       : `;base64,${data = btoa(bin)}`;

		(async () => resolve({
			data: data,
			hash: abtoh(await crypto.subtle.digest('SHA-1', this.response)),
			mime: mime,
			datauri: `data:${mime}${dc}`,
			ext: {
				gif: "gif",
				png: "png",
				jpeg: "jpg",
				['x-icon']: "ico",
				['vnd.microsoft.icon']: "ico",
				bmp: "bmp",
				['svg+xml']: "svg",
				webp: "webp"
			}[subtype]
		}))();
	};
	xhr.onerror = () => resolve(undefined);
	xhr.send();
});


/* field fields:
   - from_tab: function of tab by which field is obtained
   - pull: function of nothing by which field is pulled from thin air
   - target: property of element in popup to insert into
   - get: specify something to retrieve from the value to insert into target,
     if it differs
   - bypref: whether the corresponding popup field activates according to a pref
   - input: whether to install an event listener in the popup */
const field_reads = (() => {
	const field = k => x => x[k],
	      compose = (f, g) => x => f(g(x));

	return {
		rawtitle: {
			from_tab: field("title"),
			target: 'innerHTML'
		},
		title: {
			from_tab: compose(s => s.replace(/[[\]{}|]/g, ''), field("title")),
			target: "value",
			input: true
		},
		tags: {
			pull: async () => pref_of('default_tags'),
			target: "value",
			bypref: 'show_tags',
			input: true
		},
		text: {
			pull: async () => "",
			target: "value",
			bypref: 'show_text',
			input: true
		},
		icon: {
			from_tab: favicon_of,
			get: field("datauri"),
			target: "src"
		},
		url: {
			from_tab: field("url"),
			target: "value",
			input: true
		}
	};
})();

const field_get = (o, r) =>
	(r !== undefined && o.hasOwnProperty('get')) ? o.get(r) : r;

const tab_read = t => async k => {
	const o = field_reads[k];
	const r = await (o.hasOwnProperty('from_tab') ? o.from_tab(t) : o.pull());
	await browser.storage.local.set({[k]: r});
	return field_get(o, r);
};

const current_tab = async () =>
	 (await browser.tabs.query({
		currentWindow: true,
		active: true
	}))[0];