Userscript that adds a button to Omniva's interface to immediately take you to eMTA and fill in the right fields. Use at your own discretion.

omniva_autodeclare.user.js

// ==UserScript==
// @name        Omniva auto-declare
// @namespace   rebane
// @match       https://maasikas.emta.ee/smartdecl/wicket/page
// @match       https://maasikas.emta.ee/smartdecl/parcel
// @match       https://minu.omniva.ee/s/*
// @match       https://minuold.omniva.ee/s/*
// @grant       none
// @version     1.1
// @author      rebane
// @description Userscript that adds a button to Omniva's interface to immediately take you to eMTA and fill in the right fields. Use at your own discretion.
// ==/UserScript==

function addEmtaButton() {
  const tracking = document.querySelector(".info-step__h1")?.innerText;

  if (!tracking) {
    setTimeout(()=>addEmtaButton(), 100);
    return;
  }

  const mrn = Array.from(document.querySelectorAll(".customs-overview-field__text")).find(e=>e.innerText.includes("MRN")).lastChild.textContent;
  const params = `${tracking}:${mrn}`.replace(/[^\w:]/g, '');
  const emtaUrl = `https://maasikas.emta.ee/smartdecl/parcel#${params}`;

  const emtaLink = document.createElement('a');
  emtaLink.innerText = "e-MTA autofill";
  emtaLink.href = emtaUrl;
  emtaLink.rel = "noreferrer";
  emtaLink.classList.add("button2", "button2--primary", "customs__link");

  document.querySelector(".customs__info").insertAdjacentElement("afterend", emtaLink);
}

function autofillRedirect() {
  const pageId = parseInt(document.location.search.slice(1));
  const targetUrl = `https://maasikas.emta.ee/smartdecl/parcel?${pageId}-1.ILinkListener-newDeclarationLink${document.location.hash}`;
  document.location.href = targetUrl;
}

function attemptAutofill() {
  const [tracking, mrn] = document.location.hash.slice(1).split(":");
  document.querySelector("#id-parcel-nr").value = tracking;
  document.querySelector("#id-prev-mrn").value = mrn;
  document.querySelector("#id-check-nes").checked = true;
}

window.addEventListener("load", () => {
  if (document.location.href.startsWith("https://minu.omniva.ee/s/") || document.location.href.startsWith("https://minuold.omniva.ee/s/")) {
    addEmtaButton();
  }
  if (document.location.hash.includes(":")) {
    switch (document.location.href.split("?")[0]) {
      case "https://maasikas.emta.ee/smartdecl/parcel":
        autofillRedirect();
        break;
      case "https://maasikas.emta.ee/smartdecl/wicket/page":
        attemptAutofill();
        break;
    }
  };
});