zulip/static/js/compose_fade_helper.js

import * as stream_data from "./stream_data";
import * as sub_store from "./sub_store";
import * as util from "./util";

let focused_recipient;

export function should_fade_message(message) {
    return !util.same_recipient(focused_recipient, message);
}

export function clear_focused_recipient() {
    focused_recipient = undefined;
}

export function set_focused_recipient(recipient) {
    focused_recipient = recipient;
}

function is_pm_recipient(user_id) {
    const recipients = focused_recipient.to_user_ids.split(",");
    return recipients.includes(user_id.toString());
}

export function would_receive_message(user_id) {
    if (focused_recipient.type === "stream") {
        const sub = sub_store.get(focused_recipient.stream_id);
        if (!sub) {
            // If the stream isn't valid, there is no risk of a mix
            // yet, so we sort of "lie" and say they would receive a
            // message.
            return true;
        }

        return stream_data.is_user_subscribed(focused_recipient.stream_id, user_id);
    }

    // PM, so check if the given email is in the recipients list.
    return is_pm_recipient(user_id);
}

export function want_normal_display() {
    // If we're not composing show a normal display.
    if (focused_recipient === undefined) {
        return true;
    }

    // If the user really hasn't specified anything let, then we want a normal display
    if (focused_recipient.type === "stream") {
        // If a stream doesn't exist, there is no real chance of a mix, so fading
        // is just noise to the user.
        if (!sub_store.get(focused_recipient.stream_id)) {
            return true;
        }

        // This is kind of debatable.  If the topic is empty, it could be that
        // the user simply hasn't started typing it yet, but disabling fading here
        // means the feature doesn't help realms where topics aren't mandatory
        // (which is most realms as of this writing).
        if (focused_recipient.topic === "") {
            return true;
        }
    }

    return focused_recipient.type === "private" && focused_recipient.reply_to === "";
}