/**
 * SPDX-License-Identifier: CC0-1.0
 *
 * Copyright (C) 2021, 2026 Woj. Kosior <koszko@koszko.org>
 */

(() => {

blockJsOnUrl("https://drive.google.com/drive/folders/*");

/* Define how to handle various mime types used by Google. */

const defaultLinkProducer = id => ({
    view: `https://drive.google.com/file/d/${id}`,
    download: `https://drive.google.com/uc?export=download&id=${id}`
});

const knownMimes = {
    "application/vnd.google-apps.folder": {
	links: id => ({
	    view: `https://drive.google.com/drive/folders/${id}`
	}),
	type: "folder",
	is_folder: true
    },
    "application/vnd.google-apps.shortcut": {
	links: id => ({
	    view: `https://drive.google.com/drive/folders/${id}`
	}),
	type: "shortcut",
	is_folder: true
    },
    "application/vnd.google-apps.document": {
	links: id => ({
	    view: `https://docs.google.com/document/d/${id}`,
	    download: `https://docs.google.com/document/d/${id}/export?format=odt`,
	}),
	type: "Google text document",
	newMime: "application/vnd.oasis.opendocument.text"
    },
    "application/vnd.google-apps.spreadsheet": {
	links: id => ({
	    view: `https://docs.google.com/spreadsheets/d/${id}`,
	    download: `https://docs.google.com/spreadsheets/d/${id}/export?format=ods`
	}),
	type: "Google spreadsheet",
	newMime: "application/vnd.oasis.opendocument.spreadsheet"
    },
    "application/vnd.google-apps.presentation": {
	links: id => ({
	    view: `https://docs.google.com/presentation/d/${id}`,
	    download: `https://docs.google.com/presentation/d/${id}/export/pptx`
	}),
	type: "Google presentation",
	newMime: "application/vnd.openxmlformats-officedocument.presentationml.presentation"
    },
    "application/vnd.google-apps.drawing": {
	links: id => ({
	    view: `https://docs.google.com/drawings/d/${id}`,
	    download: `https://docs.google.com/drawings/d/${id}/export/jpeg`
	}),
	type: "Google drawing",
	newMime: "image/jpeg"
    },
    "application/vnd.google-apps.script": {
	links: id => ({
	    download: `https://script.google.com/feeds/download/export?format=json&id=${id}`
	}),
	type: "Google script",
	newMime: "application/vnd.google-apps.script+json"
    },
    "application/vnd.google-apps.jam": {
	links: id => ({
	    download: `https://jamboard.google.com/export?id=${id}`
	}),
	type: "Google jam",
	newMime: "application/pdf"
    },
    /*
     * Human-friendly names defined below will be displayed to the user instead
     * of raw mime types.  Please add more here.
     */
    ...[
        [              "image/jpeg", "JPEG image"],
        ["application/octet-stream", "binary data"],
        [         "application/pdf", "PDF document"],
        [         "application/rar", "RAR archive"],
        [         "application/zip", "ZIP archive"]
    ].map(([mime, displayName]) => [
        mime,
        {
	    links: id => defaultLinkProducer,
	    type: displayName,
	    newMime: mime
        }
    ])
};

function getMimeInfo(mime) {
    return knownMimes[mime] || {
	links: defaultLinkProducer,
	type: mime || "",
	newMime: mime || "application/octet-stream"
    };
}

function transformDocument(origDoc) {
    /*
     * Prepare folder contents data as well as data regarding the folder itself.
     */

    const contents = new Map();

    function add_contents_item(item)
    {
        const old_item = contents.get(item.id) || {};
        Object.assign(old_item, item);
        contents.set(item.id, old_item);
    }

    const this_folder = {};

    function replace_string_escape(match, group)
    {
        return String.fromCharCode(`0x${group}`);
    }

    function try_parse(data, replace_x_escapes)
    {
        if (!data)
	    return null;

        if (replace_x_escapes)
	    data = data.replaceAll(/\\x([0-9a-f]{2})/g, replace_string_escape);

        try {
	    return JSON.parse(data);
        } catch (e) {
	    console.log(e);
        }

        return null;
    }

    function process_file_data(file_data, callback)
    {
        if (!Array.isArray(file_data) || !typeof file_data[0] === "string") {
	    console.log("cannot process the following file data object:",
		        file_data);
	    return;
        }

        const result = {id: file_data[0], folders: []};

        if (Array.isArray(file_data[1])) {
	    for (const item of file_data[1]) {
	        if (typeof item === "string" && item !== this_folder.id)
		    result.folders.push(item);
	    }
        }
        if (typeof file_data[2] === "string")
	    result.filename = file_data[2];
        if (typeof file_data[3] === "string" && file_data[3].search("/") >= 0)
	    result.mime = file_data[3];
        if (typeof file_data[9] === "number")
	    result.date1 = new Date(file_data[9]);
        if (typeof file_data[10] === "number")
	    result.date2 = new Date(file_data[10]);

        callback(result);
    }

    /*
     * By searching for scripts with calls to AF_initDataCallback we get about 7
     * matches. All arguments to this function seem to be arrays parseable as
     * JSON, but their contents are very different and only two of those ~7
     * arrays actually hold some data useful to us. Here we try to filter out
     * the other cases and then extract the useful data.
     */
    function process_af_init_data(data)
    {
        if (!Array.isArray(data) || !/^driveweb/.test(data[0]) ||
	    !Array.isArray(data[1]))
	    return;

        /*
         * First useful "kind" of object we can encounter is this folder's data.
         */
        if (typeof data[1][0] === "string") {
	    process_file_data(data[1], item => Object.assign(this_folder, item));
	    return;
        }

        /*
         * Second "kind" of object holds data about all items in the folder.
         * Folders and Files are stored in separate lists (doesn't matter to us,
         * since we distinguish them based on mime type anyway).
         */
        for (const data_sub of data[1]) {
	    if (!Array.isArray(data_sub) || !/^driveweb/.test(data_sub[0]) ||
	        !Array.isArray(data_sub[1]))
	        continue;
	    for (const item of data_sub[1])
	        process_file_data(item, add_contents_item);
        }
    }

    /*
     * Folder items data actually exists in both of the 2 kinds of scripts we
     * search for. In case of both of the regexes below we call
     * `process_file_data' in the end. As a result, we process the same file
     * multiple time as it appears in 2 scripts. This is, however, a good thing,
     * because it makes a change less likely to break our fix.
     */

    const ivd_data_regex =
          /\s*window\s*\['_DRIVE_ivd'\]\s*=\s*'(\\x5b[^']+)'(.*)$/;
    const af_init_data_regex =
          /AF_initDataCallback\s*\(.+data\s*:\s*(\[.*\])[^\]]+$/;

    for (const script of origDoc.scripts) {
        const ivd_data_match = ivd_data_regex.exec(script.textContent);
        if (ivd_data_match) {
	    const ivd_data = try_parse(ivd_data_match[1], true);
	    if (ivd_data && Array.isArray(ivd_data) &&
                Array.isArray(ivd_data[0])) {
	        for (const item of ivd_data[0])
		    process_file_data(item, add_contents_item);
	    }
        }

        const af_init_data_match = af_init_data_regex.exec(script.textContent);
        if (af_init_data_match) {
	    const af_init_data = try_parse(af_init_data_match[1], false);
	    if (af_init_data)
	        process_af_init_data(af_init_data);
        }
    }

    /* Construct our own user interface. */

    const newDoc = new DOMParser().parseFromString('<html>', 'text/html');

    const body = newDoc.createElement("body");
    const folders = newDoc.createElement("div");
    const files = newDoc.createElement("div");
    const folders_heading = newDoc.createElement("h2");
    const files_heading = newDoc.createElement("h2");

    folders_heading.textContent = "Folders";
    files_heading.textContent = "Files";

    let has_folders = false;
    let has_files = false;

    folders.appendChild(folders_heading);
    files.appendChild(files_heading);

    body.setAttribute("style", "width: 100vw; height: 100vh; overflow: scroll; color: #555; margin: 15px; -webkit-user-select: initial;");

    const drive_folder_regex = /application\/vnd.google-apps.(folder|shortcut)/;

    function add_item_to_view(item_data)
    {
        const item_div = newDoc.createElement("div");
        const item_heading = newDoc.createElement("h4");

        item_div.setAttribute("style", "border: 2px solid #999; border-radius: 8px; padding: 10px; display: inline-block; margin: 2px;");

        let item_heading_style = "margin: 8px 4px;";

        if (item_data.filename) {
	    item_heading.textContent = item_data.filename;
        } else {
	    item_heading.textContent = "(no name)";
	    item_heading_style += " font-style:italic;";
        }
        item_heading.setAttribute("style", item_heading_style);
        item_div.appendChild(item_heading);

        const mime_info = getMimeInfo(item_data.mime);

        if (mime_info.type) {
	    const type_div = newDoc.createElement("div");
	    type_div.setAttribute("style", "margin-bottom: 5px;");
	    type_div.textContent = mime_info.type;

	    item_div.appendChild(type_div);
        }

        if (mime_info.is_folder)
	    has_folders = true;
        else
	    has_files = true;

        const links = {};
        if (item_data.id)
	    Object.assign(links, mime_info.links(item_data.id));

        if (links.view) {
	    const view_button = newDoc.createElement("a");
	    view_button.setAttribute("style", "border-radius: 5px; padding: 10px; color: #333; background-color: lightgreen; text-decoration: none; box-shadow: -4px 8px 8px #888; display: inline-block; margin: 5px;");
	    view_button.textContent = "view";
	    view_button.href = links.view;

	    item_div.appendChild(view_button);
        }

        if (links.download) {
	    const download_button = newDoc.createElement("a");
	    download_button.setAttribute("style", "border-radius: 5px; padding: 10px; color: #333; background-color: lightgreen; text-decoration: none; box-shadow: -4px 8px 8px #888; display: inline-block; margin: 5px;");
	    download_button.textContent = "download";
	    download_button.href = links.download;
	    download_button.type = mime_info.newMime;

	    item_div.appendChild(download_button);
        }

        (mime_info.is_folder ? folders : files).appendChild(item_div);
    }

    for (const item of contents.values())
        add_item_to_view(item);

    if (this_folder.filename) {
        const heading = newDoc.createElement("h1");
        heading.textContent = this_folder.filename;
        body.appendChild(heading);
    }
    if (this_folder.folders && this_folder.folders.length > 0) {
        for (const parent_id of this_folder.folders) {
	    const up_button = newDoc.createElement("a");
	    let text = "go up";

	    up_button.setAttribute("style", "border-radius: 5px; padding: 10px; color: #333; background-color: lightgreen; text-decoration: none; box-shadow: -4px 8px 8px #888; display: inline-block; margin: 5px;");
	    up_button.href = `https://drive.google.com/drive/folders/${parent_id}`;
	    if (this_folder.folders.length > 1)
	        text = `${text} (${parent_id})`;
	    up_button.textContent = text;

	    body.appendChild(up_button);
        }
    }
    if (has_folders)
        body.appendChild(folders);
    if (has_files)
        body.appendChild(files);
    if (!(has_files || has_folders)) {
        const no_files_message = newDoc.createElement("h3");
        no_files_message.textContent = "No files found.";
        body.appendChild(no_files_message);
    }

    newDoc.documentElement.replaceChild(body, newDoc.body);

    return '<!DOCTYPE html>\n' + newDoc.documentElement.outerHTML;
}

function alterGoogleDriveFolderResponse(details) {
    if (String(details.statusCode)[0] !== '2')
        return;

    for (const header of details.responseHeaders) {
        if (/^content-type$/i.test(header.name) &&
            !/^text[/]html; *charset *= *utf-8/i.test(header.value))
            return;
    }

    const filter = browser.webRequest.filterResponseData(details.requestId);

    const decoder = new TextDecoder("utf-8");

    const pieces = [];

    filter.ondata = event => pieces.push(
        decoder.decode(event.data, { stream: true })
    );

    filter.onstop = event => {
        const origDoc = new DOMParser()
              .parseFromString(pieces.join(''), 'text/html');
        filter.write(new TextEncoder().encode(transformDocument(origDoc)));
        filter.close();
    };
}

browser.webRequest.onHeadersReceived.addListener(
    alterGoogleDriveFolderResponse,
    {
        urls: ["https://drive.google.com/drive/folders/*"],
        types: ["main_frame", "sub_frame"]
    },
    ["blocking", "responseHeaders"]
);

})();