zulip/static/js/compose.js

import Handlebars from "handlebars/runtime";
import $ from "jquery";
import _ from "lodash";

import render_compose_all_everyone from "../templates/compose_all_everyone.hbs";
import render_compose_announce from "../templates/compose_announce.hbs";
import render_compose_invite_users from "../templates/compose_invite_users.hbs";
import render_compose_not_subscribed from "../templates/compose_not_subscribed.hbs";
import render_compose_private_stream_alert from "../templates/compose_private_stream_alert.hbs";

import * as channel from "./channel";
import * as common from "./common";
import * as compose_actions from "./compose_actions";
import * as compose_fade from "./compose_fade";
import * as compose_pm_pill from "./compose_pm_pill";
import * as compose_state from "./compose_state";
import * as compose_ui from "./compose_ui";
import * as drafts from "./drafts";
import * as echo from "./echo";
import * as loading from "./loading";
import * as markdown from "./markdown";
import * as notifications from "./notifications";
import * as peer_data from "./peer_data";
import * as people from "./people";
import * as reminder from "./reminder";
import * as rendered_markdown from "./rendered_markdown";
import * as resize from "./resize";
import * as rtl from "./rtl";
import * as sent_messages from "./sent_messages";
import * as server_events from "./server_events";
import * as settings_config from "./settings_config";
import * as stream_data from "./stream_data";
import * as stream_edit from "./stream_edit";
import * as subs from "./subs";
import * as transmit from "./transmit";
import * as ui_report from "./ui_report";
import * as upload from "./upload";
import * as util from "./util";
import * as zcommand from "./zcommand";

// Docs: https://zulip.readthedocs.io/en/latest/subsystems/sending-messages.html

/* Track the state of the @all warning. The user must acknowledge that they are spamming the entire
   stream before the warning will go away. If they try to send before explicitly dismissing the
   warning, they will get an error message too.

   undefined: no @all/@everyone in message;
   false: user typed @all/@everyone;
   true: user clicked YES */

let user_acknowledged_all_everyone;
let user_acknowledged_announce;
let wildcard_mention;
let uppy;

export let wildcard_mention_large_stream_threshold = 15;
export const announce_warn_threshold = 60;
export const uploads_domain = document.location.protocol + "//" + document.location.host;
export const uploads_path = "/user_uploads";

export const uploads_re = new RegExp(
    "\\]\\(" + uploads_domain + "(" + uploads_path + "[^\\)]+)\\)",
    "g",
);

function make_uploads_relative(content) {
    // Rewrite uploads in Markdown links back to domain-relative form
    return content.replace(uploads_re, "]($1)");
}

function show_all_everyone_warnings(stream_id) {
    const stream_count = peer_data.get_subscriber_count(stream_id) || 0;

    const all_everyone_template = render_compose_all_everyone({
        count: stream_count,
        mention: wildcard_mention,
    });
    const error_area_all_everyone = $("#compose-all-everyone");

    // only show one error for any number of @all or @everyone mentions
    if (!error_area_all_everyone.is(":visible")) {
        error_area_all_everyone.append(all_everyone_template);
    }

    error_area_all_everyone.show();
    user_acknowledged_all_everyone = false;
}

export function compute_show_video_chat_button() {
    const available_providers = page_params.realm_available_video_chat_providers;
    if (page_params.realm_video_chat_provider === available_providers.disabled.id) {
        return false;
    }

    if (
        page_params.realm_video_chat_provider === available_providers.jitsi_meet.id &&
        !page_params.jitsi_server_url
    ) {
        return false;
    }

    return true;
}

export function update_video_chat_button_display() {
    const show_video_chat_button = compute_show_video_chat_button();
    $("#below-compose-content .video_link").toggle(show_video_chat_button);
    $(".message-edit-feature-group .video_link").toggle(show_video_chat_button);
}

export function clear_all_everyone_warnings() {
    $("#compose-all-everyone").hide();
    $("#compose-all-everyone").empty();
    $("#compose-send-status").hide();
}

function show_sending_indicator(whats_happening) {
    $("#sending-indicator").text(whats_happening);
    $("#sending-indicator").show();
}

function show_announce_warnings(stream_id) {
    const stream_count = peer_data.get_subscriber_count(stream_id) || 0;

    const announce_template = render_compose_announce({count: stream_count});
    const error_area_announce = $("#compose-announce");

    if (!error_area_announce.is(":visible")) {
        error_area_announce.append(announce_template);
    }

    error_area_announce.show();
    user_acknowledged_announce = false;
}

export function clear_announce_warnings() {
    $("#compose-announce").hide();
    $("#compose-announce").empty();
    $("#compose-send-status").hide();
}

export function clear_invites() {
    $("#compose_invite_users").hide();
    $("#compose_invite_users").empty();
}

export function clear_private_stream_alert() {
    $("#compose_private_stream_alert").hide();
    $("#compose_private_stream_alert").empty();
}

export function reset_user_acknowledged_all_everyone_flag() {
    user_acknowledged_all_everyone = undefined;
}

export function reset_user_acknowledged_announce_flag() {
    user_acknowledged_announce = undefined;
}

export function clear_preview_area() {
    $("#compose-textarea").show();
    $("#undo_markdown_preview").hide();
    $("#preview_message_area").hide();
    $("#preview_content").empty();
    $("#markdown_preview").show();
}

function update_stream_button(btn_text, title) {
    $("#left_bar_compose_stream_button_big").text(btn_text);
    $("#left_bar_compose_stream_button_big").prop("title", title);
}

function update_conversation_button(btn_text, title) {
    $("#left_bar_compose_private_button_big").text(btn_text);
    $("#left_bar_compose_private_button_big").prop("title", title);
}

export function update_closed_compose_buttons_for_private() {
    const text_stream = i18n.t("New stream message");
    const title_stream = text_stream + " (c)";
    const text_conversation = i18n.t("New private message");
    const title_conversation = text_conversation + " (x)";
    update_stream_button(text_stream, title_stream);
    update_conversation_button(text_conversation, title_conversation);
}

export function update_closed_compose_buttons_for_stream() {
    const text_stream = i18n.t("New topic");
    const title_stream = text_stream + " (c)";
    const text_conversation = i18n.t("New private message");
    const title_conversation = text_conversation + " (x)";
    update_stream_button(text_stream, title_stream);
    update_conversation_button(text_conversation, title_conversation);
}

function update_fade() {
    if (!compose_state.composing()) {
        return;
    }

    const msg_type = compose_state.get_message_type();
    compose_fade.set_focused_recipient(msg_type);
    compose_fade.update_all();
}

export function abort_xhr() {
    $("#compose-send-button").prop("disabled", false);
    uppy.cancelAll();
}

export const zoom_token_callbacks = new Map();
export const video_call_xhrs = new Map();

export function abort_video_callbacks(edit_message_id = "") {
    zoom_token_callbacks.delete(edit_message_id);
    if (video_call_xhrs.has(edit_message_id)) {
        video_call_xhrs.get(edit_message_id).abort();
        video_call_xhrs.delete(edit_message_id);
    }
}

export function empty_topic_placeholder() {
    return i18n.t("(no topic)");
}

export function create_message_object() {
    // Topics are optional, and we provide a placeholder if one isn't given.
    let topic = compose_state.topic();
    if (topic === "") {
        topic = empty_topic_placeholder();
    }

    const content = make_uploads_relative(compose_state.message_content());

    // Changes here must also be kept in sync with echo.try_deliver_locally
    const message = {
        type: compose_state.get_message_type(),
        content,
        sender_id: page_params.user_id,
        queue_id: page_params.queue_id,
        stream: "",
    };
    message.topic = "";

    if (message.type === "private") {
        // TODO: this should be collapsed with the code in composebox_typeahead.js
        const recipient = compose_state.private_message_recipient();
        const emails = util.extract_pm_recipients(recipient);
        message.to = emails;
        message.reply_to = recipient;
        message.private_message_recipient = recipient;
        message.to_user_ids = people.email_list_to_user_ids_string(emails);

        // Note: The `undefined` case is for situations like the
        // is_zephyr_mirror_realm case where users may be
        // automatically created when you try to send a private
        // message to their email address.
        if (message.to_user_ids !== undefined) {
            message.to = people.user_ids_string_to_ids_array(message.to_user_ids);
        }
    } else {
        const stream_name = compose_state.stream_name();
        message.stream = stream_name;
        const sub = stream_data.get_sub(stream_name);
        if (sub) {
            message.stream_id = sub.stream_id;
            message.to = sub.stream_id;
        } else {
            // We should be validating streams in calling code.  We'll
            // try to fall back to stream_name here just in case the
            // user started composing to the old stream name and
            // manually entered the stream name, and it got past
            // validation. We should try to kill this code off eventually.
            blueslip.error("Trying to send message with bad stream name: " + stream_name);
            message.to = stream_name;
        }
        message.topic = topic;
    }
    return message;
}

export function compose_error(error_text, bad_input) {
    $("#compose-send-status")
        .removeClass(common.status_classes)
        .addClass("alert-error")
        .stop(true)
        .fadeTo(0, 1);
    $("#compose-error-msg").html(error_text);
    $("#compose-send-button").prop("disabled", false);
    $("#sending-indicator").hide();
    if (bad_input !== undefined) {
        bad_input.trigger("focus").trigger("select");
    }
}

export function nonexistent_stream_reply_error() {
    $("#nonexistent_stream_reply_error").show();
    $("#compose-reply-error-msg").html("There are no messages to reply to yet.");
    setTimeout(() => {
        $("#nonexistent_stream_reply_error").hide();
    }, 5000);
}

function compose_not_subscribed_error(error_text, bad_input) {
    $("#compose-send-status")
        .removeClass(common.status_classes)
        .addClass("home-error-bar")
        .stop(true)
        .fadeTo(0, 1);
    $("#compose-error-msg").html(error_text);
    $("#compose-send-button").prop("disabled", false);
    $("#sending-indicator").hide();
    $(".compose-send-status-close").hide();
    if (bad_input !== undefined) {
        bad_input.trigger("focus").trigger("select");
    }
}

export function clear_compose_box() {
    $("#compose-textarea").val("").trigger("focus");
    drafts.delete_draft_after_send();
    compose_ui.autosize_textarea($("#compose-textarea"));
    $("#compose-send-status").hide(0);
    $("#compose-send-button").prop("disabled", false);
    $("#sending-indicator").hide();
}

export function send_message_success(local_id, message_id, locally_echoed) {
    if (!locally_echoed) {
        clear_compose_box();
    }

    echo.reify_message_id(local_id, message_id);
}

export function send_message(request) {
    if (request === undefined) {
        request = create_message_object();
    }

    if (request.type === "private") {
        request.to = JSON.stringify(request.to);
    } else {
        request.to = JSON.stringify([request.to]);
    }

    let local_id;
    let locally_echoed;

    const message = echo.try_deliver_locally(request);
    if (message) {
        // We are rendering this message locally with an id
        // like 92l99.01 that corresponds to a reasonable
        // approximation of the id we'll get from the server
        // in terms of sorting messages.
        local_id = message.local_id;
        locally_echoed = true;
    } else {
        // We are not rendering this message locally, but we
        // track the message's life cycle with an id like
        // loc-1, loc-2, loc-3,etc.
        locally_echoed = false;
        local_id = sent_messages.get_new_local_id();
    }

    request.local_id = local_id;

    sent_messages.start_tracking_message({
        local_id,
        locally_echoed,
    });

    request.locally_echoed = locally_echoed;

    function success(data) {
        send_message_success(local_id, data.id, locally_echoed);
    }

    function error(response) {
        // If we're not local echo'ing messages, or if this message was not
        // locally echoed, show error in compose box
        if (!locally_echoed) {
            compose_error(response, $("#compose-textarea"));
            return;
        }

        echo.message_send_error(message.id, response);
    }

    transmit.send_message(request, success, error);
    server_events.assert_get_events_running(
        "Restarting get_events because it was not running during send",
    );

    if (locally_echoed) {
        clear_compose_box();
    }
}

export function enter_with_preview_open() {
    if (page_params.enter_sends) {
        // If enter_sends is enabled, we attempt to send the message
        finish();
    } else {
        // Otherwise, we return to the compose box and focus it
        $("#compose-textarea").trigger("focus");
    }
}

export function finish() {
    clear_preview_area();
    clear_invites();
    clear_private_stream_alert();
    notifications.clear_compose_notifications();

    const message_content = compose_state.message_content();

    // Skip normal validation for zcommands, since they aren't
    // actual messages with recipients; users only send them
    // from the compose box for convenience sake.
    if (zcommand.process(message_content)) {
        do_post_send_tasks();
        clear_compose_box();
        return undefined;
    }

    if (!validate()) {
        return false;
    }

    if (reminder.is_deferred_delivery(message_content)) {
        reminder.schedule_message();
    } else {
        send_message();
    }
    do_post_send_tasks();
    return true;
}

export function do_post_send_tasks() {
    clear_preview_area();
    // TODO: Do we want to fire the event even if the send failed due
    // to a server-side error?
    $(document).trigger("compose_finished.zulip");
}

export function update_email(user_id, new_email) {
    let reply_to = compose_state.private_message_recipient();

    if (!reply_to) {
        return;
    }

    reply_to = people.update_email_in_reply_to(reply_to, user_id, new_email);

    compose_state.private_message_recipient(reply_to);
}

export function get_invalid_recipient_emails() {
    const private_recipients = util.extract_pm_recipients(
        compose_state.private_message_recipient(),
    );
    const invalid_recipients = private_recipients.filter(
        (email) => !people.is_valid_email_for_compose(email),
    );

    return invalid_recipients;
}

function check_unsubscribed_stream_for_send(stream_name, autosubscribe) {
    let result;
    if (!autosubscribe) {
        return "not-subscribed";
    }

    // In the rare circumstance of the autosubscribe option, we
    // *Synchronously* try to subscribe to the stream before sending
    // the message.  This is deprecated and we hope to remove it; see
    // #4650.
    channel.post({
        url: "/json/subscriptions/exists",
        data: {stream: stream_name, autosubscribe: true},
        async: false,
        success(data) {
            if (data.subscribed) {
                result = "subscribed";
            } else {
                result = "not-subscribed";
            }
        },
        error(xhr) {
            if (xhr.status === 404) {
                result = "does-not-exist";
            } else {
                result = "error";
            }
        },
    });
    return result;
}

export function wildcard_mention_allowed() {
    if (
        page_params.realm_wildcard_mention_policy ===
        settings_config.wildcard_mention_policy_values.by_everyone.code
    ) {
        return true;
    }
    if (
        page_params.realm_wildcard_mention_policy ===
        settings_config.wildcard_mention_policy_values.nobody.code
    ) {
        return false;
    }
    if (
        page_params.realm_wildcard_mention_policy ===
        settings_config.wildcard_mention_policy_values.by_stream_admins_only.code
    ) {
        // TODO: Check the user's stream-level role once stream-level admins exist.
        return page_params.is_admin;
    }
    // TODO: Uncomment when we add support for stream-level administrators.
    // if (
    //     page_params.realm_wildcard_mention_policy ===
    //     settings_config.wildcard_mention_policy_values.by_admins_only.code
    // ) {
    //     return page_params.is_admin;
    // }
    if (
        page_params.realm_wildcard_mention_policy ===
        settings_config.wildcard_mention_policy_values.by_full_members.code
    ) {
        if (page_params.is_admin) {
            return true;
        }
        const person = people.get_by_user_id(page_params.user_id);
        const current_datetime = new Date(Date.now());
        const person_date_joined = new Date(person.date_joined);
        const days = (current_datetime - person_date_joined) / 1000 / 86400;

        return days >= page_params.realm_waiting_period_threshold && !page_params.is_guest;
    }
    return !page_params.is_guest;
}

export function set_wildcard_mention_large_stream_threshold(value) {
    wildcard_mention_large_stream_threshold = value;
}

function validate_stream_message_mentions(stream_id) {
    const stream_count = peer_data.get_subscriber_count(stream_id) || 0;

    // If the user is attempting to do a wildcard mention in a large
    // stream, check if they permission to do so.
    if (wildcard_mention !== null && stream_count > wildcard_mention_large_stream_threshold) {
        if (!wildcard_mention_allowed()) {
            compose_error(
                i18n.t("You do not have permission to use wildcard mentions in this stream."),
            );
            return false;
        }

        if (
            user_acknowledged_all_everyone === undefined ||
            user_acknowledged_all_everyone === false
        ) {
            // user has not seen a warning message yet if undefined
            show_all_everyone_warnings(stream_id);

            $("#compose-send-button").prop("disabled", false);
            $("#sending-indicator").hide();
            return false;
        }
    } else {
        // the message no longer contains @all or @everyone
        clear_all_everyone_warnings();
    }
    // at this point, the user has either acknowledged the warning or removed @all / @everyone
    user_acknowledged_all_everyone = undefined;

    return true;
}

function validate_stream_message_announce(sub) {
    const stream_count = peer_data.get_subscriber_count(sub.stream_id) || 0;

    if (sub.name === "announce" && stream_count > announce_warn_threshold) {
        if (user_acknowledged_announce === undefined || user_acknowledged_announce === false) {
            // user has not seen a warning message yet if undefined
            show_announce_warnings(sub.stream_id);

            $("#compose-send-button").prop("disabled", false);
            $("#sending-indicator").hide();
            return false;
        }
    } else {
        clear_announce_warnings();
    }
    // at this point, the user has acknowledged the warning
    user_acknowledged_announce = undefined;

    return true;
}

function validate_stream_message_post_policy(sub) {
    if (page_params.is_admin) {
        return true;
    }

    const stream_post_permission_type = stream_data.stream_post_policy_values;
    const stream_post_policy = sub.stream_post_policy;

    if (stream_post_policy === stream_post_permission_type.admins.code) {
        compose_error(i18n.t("Only organization admins are allowed to post to this stream."));
        return false;
    }

    if (page_params.is_guest && stream_post_policy !== stream_post_permission_type.everyone.code) {
        compose_error(i18n.t("Guests are not allowed to post to this stream."));
        return false;
    }

    const person = people.get_by_user_id(page_params.user_id);
    const current_datetime = new Date(Date.now());
    const person_date_joined = new Date(person.date_joined);
    const days = (current_datetime - person_date_joined) / 1000 / 86400;
    let error_text;
    if (
        stream_post_policy === stream_post_permission_type.non_new_members.code &&
        days < page_params.realm_waiting_period_threshold
    ) {
        error_text = i18n.t(
            "New members are not allowed to post to this stream.<br>Permission will be granted in __days__ days.",
            {days},
        );
        compose_error(error_text);
        return false;
    }
    return true;
}

export function validation_error(error_type, stream_name) {
    let response;

    const context = {};
    context.stream_name = Handlebars.Utils.escapeExpression(stream_name);

    switch (error_type) {
        case "does-not-exist":
            response = i18n.t(
                "<p>The stream <b>__stream_name__</b> does not exist.</p><p>Manage your subscriptions <a href='#streams/all'>on your Streams page</a>.</p>",
                context,
            );
            compose_error(response, $("#stream_message_recipient_stream"));
            return false;
        case "error":
            compose_error(
                i18n.t("Error checking subscription"),
                $("#stream_message_recipient_stream"),
            );
            return false;
        case "not-subscribed": {
            const sub = stream_data.get_sub(stream_name);
            const new_row = render_compose_not_subscribed({
                should_display_sub_button: sub.should_display_subscription_button,
            });
            compose_not_subscribed_error(new_row, $("#stream_message_recipient_stream"));
            return false;
        }
    }
    return true;
}

export function validate_stream_message_address_info(stream_name) {
    if (stream_data.is_subscribed(stream_name)) {
        return true;
    }
    const autosubscribe = page_params.narrow_stream !== undefined;
    const error_type = check_unsubscribed_stream_for_send(stream_name, autosubscribe);
    return validation_error(error_type, stream_name);
}

function validate_stream_message() {
    const stream_name = compose_state.stream_name();
    if (stream_name === "") {
        compose_error(i18n.t("Please specify a stream"), $("#stream_message_recipient_stream"));
        return false;
    }

    if (page_params.realm_mandatory_topics) {
        const topic = compose_state.topic();
        if (topic === "") {
            compose_error(i18n.t("Please specify a topic"), $("#stream_message_recipient_topic"));
            return false;
        }
    }

    const sub = stream_data.get_sub(stream_name);
    if (!sub) {
        return validation_error("does-not-exist", stream_name);
    }

    if (!validate_stream_message_post_policy(sub)) {
        return false;
    }

    /* Note: This is a global and thus accessible in the functions
       below; it's important that we update this state here before
       proceeding with further validation. */
    wildcard_mention = util.find_wildcard_mentions(compose_state.message_content());

    // If both `@all` is mentioned and it's in `#announce`, just validate
    // for `@all`. Users shouldn't have to hit "yes" more than once.
    if (wildcard_mention !== null && stream_name === "announce") {
        if (
            !validate_stream_message_address_info(stream_name) ||
            !validate_stream_message_mentions(sub.stream_id)
        ) {
            return false;
        }
        // If either criteria isn't met, just do the normal validation.
    } else {
        if (
            !validate_stream_message_address_info(stream_name) ||
            !validate_stream_message_mentions(sub.stream_id) ||
            !validate_stream_message_announce(sub)
        ) {
            return false;
        }
    }

    return true;
}

// The function checks whether the recipients are users of the realm or cross realm users (bots
// for now)
function validate_private_message() {
    if (page_params.realm_private_message_policy === 2) {
        // Frontend check for for PRIVATE_MESSAGE_POLICY_DISABLED
        const user_ids = compose_pm_pill.get_user_ids();
        if (user_ids.length !== 1 || !people.get_by_user_id(user_ids[0]).is_bot) {
            // Unless we're composing to a bot
            compose_error(
                i18n.t("Private messages are disabled in this organization."),
                $("#private_message_recipient"),
            );
            return false;
        }
    }

    if (compose_state.private_message_recipient().length === 0) {
        compose_error(
            i18n.t("Please specify at least one valid recipient"),
            $("#private_message_recipient"),
        );
        return false;
    } else if (page_params.realm_is_zephyr_mirror_realm) {
        // For Zephyr mirroring realms, the frontend doesn't know which users exist
        return true;
    }

    const invalid_recipients = get_invalid_recipient_emails();

    let context = {};
    if (invalid_recipients.length === 1) {
        context = {recipient: invalid_recipients.join()};
        compose_error(
            i18n.t("The recipient __recipient__ is not valid", context),
            $("#private_message_recipient"),
        );
        return false;
    } else if (invalid_recipients.length > 1) {
        context = {recipients: invalid_recipients.join()};
        compose_error(
            i18n.t("The recipients __recipients__ are not valid", context),
            $("#private_message_recipient"),
        );
        return false;
    }
    return true;
}

export function validate() {
    $("#compose-send-button").prop("disabled", true).trigger("blur");
    const message_content = compose_state.message_content();
    if (reminder.is_deferred_delivery(message_content)) {
        show_sending_indicator(i18n.t("Scheduling..."));
    } else {
        show_sending_indicator(i18n.t("Sending..."));
    }

    if (/^\s*$/.test(message_content)) {
        compose_error(i18n.t("You have nothing to send!"), $("#compose-textarea"));
        return false;
    }

    if ($("#zephyr-mirror-error").is(":visible")) {
        compose_error(i18n.t("You need to be running Zephyr mirroring in order to send messages!"));
        return false;
    }

    if (compose_state.get_message_type() === "private") {
        return validate_private_message();
    }
    return validate_stream_message();
}

export function handle_keydown(event, textarea) {
    const code = event.keyCode || event.which;
    const isBold = code === 66;
    const isItalic = code === 73 && !event.shiftKey;
    const isLink = code === 76 && event.shiftKey;

    // detect Cmd and Ctrl key
    const isCmdOrCtrl = common.has_mac_keyboard() ? event.metaKey : event.ctrlKey;

    if ((isBold || isItalic || isLink) && isCmdOrCtrl) {
        const range = textarea.range();
        function wrap_text_with_markdown(prefix, suffix) {
            if (!document.execCommand("insertText", false, prefix + range.text + suffix)) {
                textarea.range(range.start, range.end).range(prefix + range.text + suffix);
            }
            event.preventDefault();
        }

        if (isBold) {
            // Ctrl + B: Convert selected text to bold text
            wrap_text_with_markdown("**", "**");
            if (!range.length) {
                textarea.caret(textarea.caret() - 2);
            }
        }
        if (isItalic) {
            // Ctrl + I: Convert selected text to italic text
            wrap_text_with_markdown("*", "*");
            if (!range.length) {
                textarea.caret(textarea.caret() - 1);
            }
        }
        if (isLink) {
            // Ctrl + L: Insert a link to selected text
            wrap_text_with_markdown("[", "](url)");
            const position = textarea.caret();
            const txt = textarea[0];

            // Include selected text in between [] parentheses and insert '(url)'
            // where "url" should be automatically selected.
            // Position of cursor depends on whether browser supports exec
            // command or not. So set cursor position accordingly.
            if (range.length > 0) {
                if (document.queryCommandEnabled("insertText")) {
                    txt.selectionStart = position - 4;
                    txt.selectionEnd = position - 1;
                } else {
                    txt.selectionStart = position + range.length + 3;
                    txt.selectionEnd = position + range.length + 6;
                }
            } else {
                textarea.caret(textarea.caret() - 6);
            }
        }

        compose_ui.autosize_textarea(textarea);
        return;
    }
}

export function handle_keyup(event, textarea) {
    // Set the rtl class if the text has an rtl direction, remove it otherwise
    rtl.set_rtl_class_for_textarea(textarea);
}

export function needs_subscribe_warning(user_id, stream_id) {
    // This returns true if all of these conditions are met:
    //  * the user is valid
    //  * the user is not already subscribed to the stream
    //  * the user has no back-door way to see stream messages
    //    (i.e. bots on public/private streams)
    //
    //  You can think of this as roughly answering "is there an
    //  actionable way to subscribe the user and do they actually
    //  need it?".
    //
    //  We expect the caller to already have verified that we're
    //  sending to a valid stream and trying to mention the user.

    const user = people.get_by_user_id(user_id);

    if (!user) {
        return false;
    }

    if (user.is_bot) {
        // Bots may receive messages on public/private streams even if they are
        // not subscribed.
        return false;
    }

    if (stream_data.is_user_subscribed(stream_id, user_id)) {
        // If our user is already subscribed
        return false;
    }

    return true;
}

function insert_video_call_url(url, target_textarea) {
    const link_text = i18n.t("Click to join video call");
    compose_ui.insert_syntax_and_focus(`[${link_text}](${url})`, target_textarea);
}

export function render_and_show_preview(preview_spinner, preview_content_box, content) {
    function show_preview(rendered_content, raw_content) {
        // content is passed to check for status messages ("/me ...")
        // and will be undefined in case of errors
        let rendered_preview_html;
        if (raw_content !== undefined && markdown.is_status_message(raw_content)) {
            // Handle previews of /me messages
            rendered_preview_html =
                "<p><strong>" +
                _.escape(page_params.full_name) +
                "</strong>" +
                rendered_content.slice("<p>/me".length);
        } else {
            rendered_preview_html = rendered_content;
        }

        preview_content_box.html(util.clean_user_content_links(rendered_preview_html));
        rendered_markdown.update_elements(preview_content_box);
    }

    if (content.length === 0) {
        show_preview(i18n.t("Nothing to preview"));
    } else {
        if (markdown.contains_backend_only_syntax(content)) {
            const spinner = preview_spinner.expectOne();
            loading.make_indicator(spinner);
        } else {
            // For messages that don't appear to contain syntax that
            // is only supported by our backend Markdown processor, we
            // render using the frontend Markdown processor (but still
            // render server-side to ensure the preview is accurate;
            // if the `markdown.contains_backend_only_syntax` logic is
            // wrong, users will see a brief flicker of the locally
            // echoed frontend rendering before receiving the
            // authoritative backend rendering from the server).
            const message_obj = {
                raw_content: content,
            };
            markdown.apply_markdown(message_obj);
        }
        channel.post({
            url: "/json/messages/render",
            idempotent: true,
            data: {content},
            success(response_data) {
                if (markdown.contains_backend_only_syntax(content)) {
                    loading.destroy_indicator(preview_spinner);
                }
                show_preview(response_data.rendered, content);
            },
            error() {
                if (markdown.contains_backend_only_syntax(content)) {
                    loading.destroy_indicator(preview_spinner);
                }
                show_preview(i18n.t("Failed to generate preview"));
            },
        });
    }
}

export function warn_if_private_stream_is_linked(linked_stream) {
    // For PMs, we currently don't warn about links to private
    // streams, since you are specifically sharing the existence of
    // the private stream with someone.  One could imagine changing
    // this policy if user feedback suggested it was useful.
    if (compose_state.get_message_type() !== "stream") {
        return;
    }

    const compose_stream = stream_data.get_sub(compose_state.stream_name());
    if (compose_stream === undefined) {
        // We have an invalid stream name, don't warn about this here as
        // we show an error to the user when they try to send the message.
        return;
    }

    // If the stream we're linking to is not invite-only, then it's
    // public, and there is no need to warn about it, since all
    // members can already see all the public streams.
    //
    // Theoretically, we could still do a warning if there are any
    // guest users subscribed to the stream we're posting to; we may
    // change this policy if user feedback suggests it'd be an
    // improvement.
    if (!linked_stream.invite_only) {
        return;
    }

    // Don't warn if subscribers list of current compose_stream is
    // a subset of linked_stream's subscribers list, because
    // everyone will be subscribed to the linked stream and so
    // knows it exists.  (But always warn Zephyr users, since
    // we may not know their stream's subscribers.)
    if (
        peer_data.is_subscriber_subset(compose_stream.stream_id, linked_stream.stream_id) &&
        !page_params.realm_is_zephyr_mirror_realm
    ) {
        return;
    }

    const stream_name = linked_stream.name;

    const warning_area = $("#compose_private_stream_alert");
    const context = {stream_name};
    const new_row = render_compose_private_stream_alert(context);

    warning_area.append(new_row);
    warning_area.show();
}

export function warn_if_mentioning_unsubscribed_user(mentioned) {
    if (compose_state.get_message_type() !== "stream") {
        return;
    }

    // Disable for Zephyr mirroring realms, since we never have subscriber lists there
    if (page_params.realm_is_zephyr_mirror_realm) {
        return;
    }

    const user_id = mentioned.user_id;

    if (mentioned.is_broadcast) {
        return; // don't check if @all/@everyone/@stream
    }

    const stream_name = compose_state.stream_name();

    if (!stream_name) {
        return;
    }

    const sub = stream_data.get_sub(stream_name);

    if (!sub) {
        return;
    }

    if (needs_subscribe_warning(user_id, sub.stream_id)) {
        const error_area = $("#compose_invite_users");
        const existing_invites_area = $("#compose_invite_users .compose_invite_user");

        const existing_invites = Array.from($(existing_invites_area), (user_row) =>
            Number.parseInt($(user_row).data("user-id"), 10),
        );

        if (!existing_invites.includes(user_id)) {
            const context = {
                user_id,
                stream_id: sub.stream_id,
                name: mentioned.full_name,
                can_subscribe_other_users: page_params.can_subscribe_other_users,
            };

            const new_row = render_compose_invite_users(context);
            error_area.append(new_row);
        }

        error_area.show();
    }
}

export function initialize() {
    $("#below-compose-content .video_link").toggle(compute_show_video_chat_button());
    $(
        "#stream_message_recipient_stream,#stream_message_recipient_topic,#private_message_recipient",
    ).on("keyup", update_fade);
    $(
        "#stream_message_recipient_stream,#stream_message_recipient_topic,#private_message_recipient",
    ).on("change", update_fade);
    $("#compose-textarea").on("keydown", (event) => {
        handle_keydown(event, $("#compose-textarea").expectOne());
    });
    $("#compose-textarea").on("keyup", (event) => {
        handle_keyup(event, $("#compose-textarea").expectOne());
    });

    $("#compose form").on("submit", (e) => {
        e.preventDefault();
        finish();
    });

    resize.watch_manual_resize("#compose-textarea");

    upload.feature_check($("#compose #attach_files"));

    $("#compose-all-everyone").on("click", ".compose-all-everyone-confirm", (event) => {
        event.preventDefault();

        $(event.target).parents(".compose-all-everyone").remove();
        user_acknowledged_all_everyone = true;
        clear_all_everyone_warnings();
        finish();
    });

    $("#compose-announce").on("click", ".compose-announce-confirm", (event) => {
        event.preventDefault();

        $(event.target).parents(".compose-announce").remove();
        user_acknowledged_announce = true;
        clear_announce_warnings();
        finish();
    });

    $("#compose-send-status").on("click", ".sub_unsub_button", (event) => {
        event.preventDefault();

        const stream_name = $("#stream_message_recipient_stream").val();
        if (stream_name === undefined) {
            return;
        }
        const sub = stream_data.get_sub(stream_name);
        subs.sub_or_unsub(sub);
        $("#compose-send-status").hide();
    });

    $("#compose-send-status").on("click", "#compose_not_subscribed_close", (event) => {
        event.preventDefault();

        $("#compose-send-status").hide();
    });

    $("#compose_invite_users").on("click", ".compose_invite_link", (event) => {
        event.preventDefault();

        const invite_row = $(event.target).parents(".compose_invite_user");

        const user_id = Number.parseInt($(invite_row).data("user-id"), 10);
        const stream_id = Number.parseInt($(invite_row).data("stream-id"), 10);

        function success() {
            const all_invites = $("#compose_invite_users");
            invite_row.remove();

            if (all_invites.children().length === 0) {
                all_invites.hide();
            }
        }

        function failure(error_msg) {
            clear_invites();
            compose_error(error_msg, $("#compose-textarea"));
            $(event.target).prop("disabled", true);
        }

        function xhr_failure(xhr) {
            const error = JSON.parse(xhr.responseText);
            failure(error.msg);
        }

        const sub = stream_data.get_sub_by_id(stream_id);

        stream_edit.invite_user_to_stream([user_id], sub, success, xhr_failure);
    });

    $("#compose_invite_users").on("click", ".compose_invite_close", (event) => {
        const invite_row = $(event.target).parents(".compose_invite_user");
        const all_invites = $("#compose_invite_users");

        invite_row.remove();

        if (all_invites.children().length === 0) {
            all_invites.hide();
        }
    });

    $("#compose_private_stream_alert").on(
        "click",
        ".compose_private_stream_alert_close",
        (event) => {
            const stream_alert_row = $(event.target).parents(".compose_private_stream_alert");
            const stream_alert = $("#compose_private_stream_alert");

            stream_alert_row.remove();

            if (stream_alert.children().length === 0) {
                stream_alert.hide();
            }
        },
    );

    // Click event binding for "Attach files" button
    // Triggers a click on a hidden file input field

    $("#compose").on("click", "#attach_files", (e) => {
        e.preventDefault();
        $("#compose #file_input").trigger("click");
    });

    $("body").on("click", ".video_link", (e) => {
        e.preventDefault();

        let target_textarea;
        // The data-message-id attribute is only present in the video
        // call icon present in the message edit form.  If present,
        // the request is for the edit UI; otherwise, it's for the
        // compose box.
        const edit_message_id = $(e.target).attr("data-message-id");
        if (edit_message_id !== undefined) {
            target_textarea = $(`#message_edit_content_${CSS.escape(edit_message_id)}`);
        }

        let video_call_link;
        const available_providers = page_params.realm_available_video_chat_providers;
        const show_video_chat_button = compute_show_video_chat_button();

        if (!show_video_chat_button) {
            return;
        }

        if (
            available_providers.zoom &&
            page_params.realm_video_chat_provider === available_providers.zoom.id
        ) {
            abort_video_callbacks(edit_message_id);
            const key = edit_message_id || "";

            const make_zoom_call = () => {
                video_call_xhrs.set(
                    key,
                    channel.post({
                        url: "/json/calls/zoom/create",
                        success(res) {
                            video_call_xhrs.delete(key);
                            insert_video_call_url(res.url, target_textarea);
                        },
                        error(xhr, status) {
                            video_call_xhrs.delete(key);
                            if (
                                status === "error" &&
                                xhr.responseJSON &&
                                xhr.responseJSON.code === "INVALID_ZOOM_TOKEN"
                            ) {
                                page_params.has_zoom_token = false;
                            }
                            if (status !== "abort") {
                                ui_report.generic_embed_error(
                                    i18n.t("Failed to create video call."),
                                );
                            }
                        },
                    }),
                );
            };

            if (page_params.has_zoom_token) {
                make_zoom_call();
            } else {
                zoom_token_callbacks.set(key, make_zoom_call);
                window.open(
                    window.location.protocol + "//" + window.location.host + "/calls/zoom/register",
                    "_blank",
                    "width=800,height=500,noopener,noreferrer",
                );
            }
        } else if (
            available_providers.big_blue_button &&
            page_params.realm_video_chat_provider === available_providers.big_blue_button.id
        ) {
            channel.get({
                url: "/json/calls/bigbluebutton/create",
                success(response) {
                    insert_video_call_url(response.url, target_textarea);
                },
            });
        } else {
            const video_call_id = util.random_int(100000000000000, 999999999999999);
            video_call_link = page_params.jitsi_server_url + "/" + video_call_id;
            insert_video_call_url(video_call_link, target_textarea);
        }
    });

    $("#compose").on("click", "#markdown_preview", (e) => {
        e.preventDefault();
        const content = $("#compose-textarea").val();
        $("#compose-textarea").hide();
        $("#markdown_preview").hide();
        $("#undo_markdown_preview").show();
        $("#preview_message_area").show();

        render_and_show_preview($("#markdown_preview_spinner"), $("#preview_content"), content);
    });

    $("#compose").on("click", "#undo_markdown_preview", (e) => {
        e.preventDefault();
        clear_preview_area();
    });

    uppy = upload.setup_upload({
        mode: "compose",
    });

    $("#compose-textarea").on("focus", () => {
        compose_actions.update_placeholder_text();
    });

    $("#stream_message_recipient_topic").on("focus", () => {
        compose_actions.update_placeholder_text();
    });

    if (page_params.narrow !== undefined) {
        if (page_params.narrow_topic !== undefined) {
            compose_actions.start("stream", {topic: page_params.narrow_topic});
        } else {
            compose_actions.start("stream", {});
        }
    }
}