/**
 * SPDX-License-Identifier: LicenseRef-GPL-3.0-or-later-WITH-js-exceptions
 *
 * Make files on drive.google.com downloadable without nonfree js
 *
 * Copyright (C) 2021 Wojtek Kosior <koszko@koszko.org>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU 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 General Public License for more details.
 *
 * As additional permission under GNU GPL version 3 section 7, you
 * may distribute forms of that code without the copy of the GNU
 * GPL normally required by section 4, provided you include this
 * license notice and, in case of non-source distribution, a URL
 * through which recipients can access the Corresponding Source.
 * If you modify file(s) with this exception, you may extend this
 * exception to your version of the file(s), but you are not
 * obligated to do so. If you do not wish to do so, delete this
 * exception statement from your version.
 *
 * As a special exception to the GPL, any HTML file which merely
 * makes function calls to this code, and for that purpose
 * includes it by reference shall be deemed a separate work for
 * copyright law purposes. If you modify this code, you may extend
 * this exception to your version of the code, but you are not
 * obligated to do so. If you do not wish to do so, delete this
 * exception statement from your version.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 * I, Wojtek Kosior, thereby promise not to sue for violation of this file's
 * license. Although I request that you do not make use of this code in a
 * proprietary program, I am not going to enforce this in court.
 */

/* Use with: https://drive.google.com/file/d/** */

const og = {};

for (const node of document.head.childNodes) {
    if (node.tagName === "STYLE") {
	document.head.removeChild(node);
	continue;
    }

    if (node.tagName !== "META")
	continue;

    const match = /^og:(.+)/.exec(node.getAttribute("property"));
    if (!match)
	continue;

    og[match[1]] = node.getAttribute("content");
}

const match = new RegExp("/file/d/([^/]+)").exec(document.URL);
const file_id = match && match[1];

/* Extract file's mime type from script. */

let mime_type;

for (const script of document.scripts) {
    const match = /itemJson\s*:\s*(\[.*\])\s*}\s*;$/.exec(script.textContent);
    if (!match)
	continue;

    let data;
    try {
	data = JSON.parse(match[1]);
    } catch(e) {
	console.log(e);
	continue;
    }

    if (/^[^\/]+\/[^\/]+$/.test(data[11]))
	mime_type = data[11];
}

/* If file is folder, redirect to its page. */

const redirect = file_id &&
      /^application\/vnd.google-apps.(folder|shortcut)$/.test(mime_type);
if (redirect)
    window.location.href = `https://drive.google.com/drive/folders/${file_id}`;

const download_link =
      file_id && `https://drive.google.com/uc?export=download&id=${file_id}`;

const body = document.createElement("body");
const name_div = document.createElement("div");
const download_div = document.createElement("div");
const download_button = document.createElement("a");
const type_div = document.createElement("div");
const type_span = document.createElement("span");
const show_image_div = document.createElement("div");
const show_image_button = document.createElement("button");
const image = document.createElement("img");


let button_text = "download";

if (!og.title)
    button_text += " file";
else
    name_div.textContent = og.title;

name_div.setAttribute("style", "font-weight: bold; display:inline-block;");


if (download_link)
    download_button.setAttribute("href", download_link);
else
    button_text += " (unavailable)";

download_button.textContent = button_text;
download_button.setAttribute("style", "border-radius: 5px; padding: 10px; color: black; background-color: lightgreen; text-decoration: none; box-shadow: -4px 8px 8px #888;");


download_div.appendChild(download_button);
download_div.setAttribute("style", "padding: 10px; display: inline-block; margin: 0 0 10px;");


type_span.textContent = "type: ";
type_span.setAttribute("style", "font-weight: bold; display:inline-block; white-space: pre;");

type_div.setAttribute("style", "margin: 0 0 10px;");
type_div.appendChild(type_span);
if (mime_type || og.type)
    type_div.append(mime_type || og.type);


function show_image()
{
    const image = document.createElement("img");
    image.setAttribute("src", og.image);
    image.setAttribute("width", og["image:width"]);
    image.setAttribute("height", og["image:height"]);
    image.setAttribute("style", "border: 1px solid #eee;");

    document.body.replaceChild(image, show_image_div);
}

show_image_button.setAttribute("style", "border-radius: 5px; padding: 10px; color: black; background-color: lightgreen; box-shadow: -4px 8px 8px #888; font-family: inherit; font-size: inherit; border: none;");
show_image_button.textContent = "show image";
show_image_button.addEventListener("click", show_image);
show_image_div.appendChild(show_image_button);


body.setAttribute("style", "margin: 20px;");
if (og.title)
    body.appendChild(name_div);
body.appendChild(download_div);
if (og.type)
    body.appendChild(type_div);
if (og.image && og["image:width"] && og["image:height"])
    body.appendChild(show_image_div);

if (!redirect)
    document.documentElement.replaceChild(body, document.body);