zulip/web/src/local_message.ts

import {all_messages_data} from "./all_messages_data";
import * as blueslip from "./blueslip";
import type {StateData} from "./state_data";

let max_message_id: number;

function truncate_precision(float: number): number {
    return Number.parseFloat(float.toFixed(3));
}

export const get_next_id_float = (function () {
    const already_used = new Set();

    return function (): number | undefined {
        const local_id_increment = 0.01;
        let latest = all_messages_data.last()?.id ?? max_message_id;
        latest = Math.max(0, latest);
        const local_id_float = truncate_precision(latest + local_id_increment);

        if (already_used.has(local_id_float)) {
            // If our id is already used, it is probably an edge case like we had
            // to abort a very recent message.
            blueslip.warn("We don't reuse ids for local echo.");
            return undefined;
        }

        if (local_id_float % 1 > local_id_increment * 5) {
            blueslip.warn("Turning off local echo for this message to let host catch up");
            return undefined;
        }

        if (local_id_float % 1 === 0) {
            // The logic to stop at 0.05 should prevent us from ever wrapping around
            // to the next integer.
            blueslip.error("Programming error");
            return undefined;
        }

        already_used.add(local_id_float);

        return local_id_float;
    };
})();

export function initialize(params: StateData["local_message"]): void {
    max_message_id = params.max_message_id;
}