/**
 * Copyright 2022 Jacob K
 * Copyright 2022 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.
 */

// meta: match should be https://***.app.box.com/s/* (*** instead of * for the first section because otherwise plain app.box.com URLs won't work)
// meta: some test cases (mostly found at https://old.reddit.com/search?q="box.com"&include_over_18=on&sort=new)
	// https://uwmadison.app.box.com/s/ydht2incbdmw1lhpjg5t40adguc0fm14
		// umadison's enrollment report
		// pdf
	// https://app.box.com/s/gc4ygloi4qtimeh98dq9mmydyuydawcn
		// password-protected 7z file (nsfw)
	// https://app.box.com/shared/static/su6xx6zx50cd68zdtbm3wfxhh9kwke8x.zip
		// a soundtrack in a zip file
		// This is a static download, so it works without this script.
	// https://app.box.com/s/vysdh2u78yih3c8leetgq82il954a3g3
		// some gambling add
		// pptx
	// https://app.box.com/s/nnlplkmjhimau404qohh9my10pwmo8es
		// a list of books(?)
		// txt
	// https://ucla.app.box.com/s/mv32q624ojihohzh8d0mhhj0b3xluzbz
		// "COVID-19 Pivot Plan Decision Matrix"
		// cannot be downloaded (403 Forbidden): "This user is not allowed to use direct links. Please email "[support address, changes depending on where you are logged in]" for support"
		// If you load the proprietary scripts on this page, you'll see that there is no download button
	// TODO: find a public folder link (the private links I have seem to work)
	// TODO: find a (preferably public) link with a folder inside a folder, as these may need to be handled differently

/* Extract data from a script that sets multiple variables. */ // from here: https://api-demo.hachette-hydrilla.org/content/sgoogle_sheets_download/google_sheets_download.js

let prefetchedData = null; // This variable isn't actually used.
for (const script of document.scripts) {
    const match = /Box.prefetchedData = ({([^;]|[^}];)+})/.exec(script.textContent); // looks for "Box.prefetchedData = " in the script files and then grabs the json text after that.
    if (!match)
	continue;
    prefetchedData = JSON.parse(match[1]);
}

let config = null;
for (const script of document.scripts) {
    const match = /Box.config = ({([^;]|[^}];)+})/.exec(script.textContent); // looks for "Box.config = " in the script files and then grabs the json text after that.
    if (!match)
	continue;
    config = JSON.parse(match[1]);
}

let postStreamData = null;
for (const script of document.scripts) {
    const match = /Box.postStreamData = ({([^;]|[^}];)+})/.exec(script.textContent); // looks for "Box.postStreamData = " in the script files and then grabs the json text after that.
    if (!match)
	continue;
    postStreamData = JSON.parse(match[1]);
}

// empty the initial document body
[...document.body.childNodes].forEach(n => n.remove());

// create div container
const divContainer = document.createElement("div");
document.body.append(divContainer);

const loadingIcon = document.createElement("h1");
loadingIcon.innerText = "loading...";
loadingIcon.style.display = "none";

const error_msg = document.createElement("h1");
error_msg.innerText = "error occured :(";
error_msg.style.display = "none";

divContainer.append(loadingIcon, error_msg);

// get domain from URL
const domain = document.location.href.split("/")[2];

async function hack_file() {
    loadingIcon.style.display = "initial";

    const tokens_url = "/app-api/enduserapp/elements/tokens";
    const file_nr = postStreamData["/app-api/enduserapp/shared-item"].itemID;
    const file_id = `file_${file_nr}`;
    const shared_name = postStreamData["/app-api/enduserapp/shared-item"].sharedName;

    /*
     * We need to perform a POST to obtain a token that will be used later to
     * authenticate against Box's API endpoint.
     */
    const tokens_response = await fetch(tokens_url, {
	method: "POST",
	headers: {
	    "Accept":               "application/json",
	    "Content-Type":         "application/json",
	    "Request-Token":        config.requestToken,
	    "X-Box-Client-Name":    "enduserapp",
	    "X-Box-Client-Version": "20.712.2",
	    "X-Box-EndUser-API":    `sharedName=${shared_name}`,
	    "X-Request-Token":      config.requestToken
	},
	body: JSON.stringify({"fileIDs": [file_id]})
    });
    console.log("tokens_response", tokens_response);

    const access_token = (await tokens_response.json())[file_id].read;
    console.log("access_token", access_token);

    const fields = [
	"permissions", "shared_link", "sha1", "file_version", "name", "size",
	"extension", "representations", "watermark_info",
	"authenticated_download_url", "is_download_available"
    ];

    const file_info_url =
	  `https://api.box.com/2.0/files/${file_nr}?fields=${fields.join()}`;

    /*
     * We need to perform a GET to obtain file metadata. The fields we curently
     * make use of are "authenticated_download_url" and "file_version", but in
     * the request we also include names of other fields that the original Box
     * client would include. The metadata is then dumped as JSON on the page, so
     * the user, if curious, can look at it.
     */
    const file_info_response = await fetch(file_info_url, {
	headers: {
	    "Accept":            "application/json",
	    "Authorization":     `Bearer ${access_token}`,
	    "BoxApi":            `shared_link=${document.URL}`,
	    "X-Box-Client-Name": "ContentPreview",
	    "X-Rep-Hints":       "[3d][pdf][text][mp3][json][jpg?dimensions=1024x1024&paged=false][jpg?dimensions=2048x2048,png?dimensions=2048x2048][dash,mp4][filmstrip]"
	},
    });
    console.log("file_info_response", file_info_response);

    const file_info = await file_info_response.json();
    console.log("file_info", file_info);

    const params = new URLSearchParams();
    params.set("preview",            true);
    params.set("version",            file_info.file_version.id);
    params.set("access_token",       access_token);
    params.set("shared_link",        document.URL);
    params.set("box_client_name",    "box-content-preview");
    params.set("box_client_version", "2.82.0");
    params.set("encoding",           "gzip");

    /* We use file metadata from earlier requests to construct the link. */
    const download_url =
	  `${file_info.authenticated_download_url}?${params.toString()}`;
    console.log("download_url", download_url);

    const downloadButton = document.createElement("a");
    downloadButton.innerText = "download";
    downloadButton.href = download_url;
    downloadButton.setAttribute("style", "border-radius: 10px; padding: 20px; color: #333; background-color: lightgreen; text-decoration: none; box-shadow: -4px 8px 8px #888; display: inline-block;");

    const file_info_header = document.createElement("h2");
    file_info_header.innerText = "File info";

    divContainer.append(downloadButton, file_info_header,
			JSON.stringify(file_info));

    loadingIcon.style.display = "none";
}

function show_error() {
    loadingIcon.style.display = "none";
    error_msg.style.display = "initial";
}

if (postStreamData["/app-api/enduserapp/shared-item"].itemType == "file") {
    /*
     * We call hack_file and in case it asynchronously throws an exception, we
     * make an error message appear.
     */
    hack_file().then(() => {}, show_error);
} else if (postStreamData["/app-api/enduserapp/shared-item"].itemType == "folder") {
	const folderHeader = document.createElement("h1");
	folderHeader.innerText = postStreamData["/app-api/enduserapp/shared-folder"].currentFolderName;
	divContainer.appendChild(folderHeader);
	//console.log(postStreamData["/app-api/enduserapp/shared-folder"]);
	postStreamData["/app-api/enduserapp/shared-folder"].items.forEach(function(element) {
		console.log(element);
		const folderButton = document.createElement("a");
		folderButton.setAttribute("style", "border-radius: 10px; padding: 20px; color: #333; background-color: lightgreen; text-decoration: none; box-shadow: -4px 8px 8px #888; display: inline-block;"); // from https://api-demo.hachette-hydrilla.org/content/sgoogle_sheets_download/google_sheets_download.js
		if (element.type == "file") {
			folderButton.innerText = "loading...";
			// craft request
			var downloadLinkGet = new XMLHttpRequest();
			downloadLinkGet.open("POST", "https://"+domain+"/index.php?rm=box_download_shared_file&shared_name="+postStreamData["/app-api/enduserapp/shared-item"].sharedName+"&file_id="+element.typedID);
			downloadLinkGet.setRequestHeader("User-Agent", "Mozilla/5.0 (X11; Linux x86_64; rv:96.0) Gecko/20100101 Firefox/96.0"); // Would this be set automatically otherwise?
			downloadLinkGet.setRequestHeader("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8");
			downloadLinkGet.setRequestHeader("Accept-Language",  "en-US,en;q=0.5"); // TODO: find a test case in another language
			downloadLinkGet.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
			downloadLinkGet.setRequestHeader("Upgrade-Insecure-Requests", "1");
			downloadLinkGet.onreadystatechange = function() {
				if (downloadLinkGet.readyState === 4) {
					//console.log(downloadLinkGet.status);
					// configure download button and add it
					folderButton.setAttribute("href", downloadLinkGet.responseURL);
					folderButton.innerText = element.name; // show the name of the file
				}
			};
			downloadLinkGet.send("request_token="+config.requestToken);
		} else {
			folderButton.innerText = "[folders inside folders not yet supported]";
		}
		divContainer.appendChild(folderButton);
	})
} else {
	console.log("Error: not implemented");
	// TODO: also display an error on the page
}