• It already demonstrates address -> latitude/longitude using Maps.newGeocoder().
• It already demonstrates latitude/longitude -> formatted address.
• It supports country/region bias through GEOCODING_REGION document properties.
• It is sheet-friendly for manual operational cleanup.
• It can be remodelled later as a small, user-triggered Next.js endpoint.

Potential files:

lib/maps/geocoding-client.ts
app/api/maps/geocode/route.ts
app/api/maps/reverse-geocode/route.ts

Potential behavior:

• One address per explicit user action by default.
• Small batch mode only with confirmation.
• Cache by normalized address + region.
• Store results in existing data Json? first, or add a dedicated cache table later.
• Surface quota/cost warnings before broad operations.
• Keep region bias available for Spain, Morocco, Portugal, and future featured cities.

// Geocode Addresses
// Copyright (c) 2016 - 2017 Max Vilimpoc
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

// Bias the geocoding results in favor of these geographic regions.
// The regions are specified as ccTLD codes.
// The original source included a commented REGIONS map for country -> ccTLD.

function getGeocodingRegion() {
  return PropertiesService.getDocumentProperties().getProperty('GEOCODING_REGION') || 'us';
}

/*
function setGeocodingRegion(region) {
  PropertiesService.getDocumentProperties().setProperty('GEOCODING_REGION', region);
  updateMenu();
}

function promptForGeocodingRegion() {
  var ui = SpreadsheetApp.getUi();
  var result = ui.prompt(
    'Set the Geocoding Country Code (currently: ' + getGeocodingRegion() + ')',
    'Enter the 2-letter country code (ccTLD) that you would like ' +
    'the Google geocoder to search first for results. ' +
    'For example: Use \'uk\' for the United Kingdom, \'us\' for the United States, etc. ' +
    'For more country codes, see: https://en.wikipedia.org/wiki/Country_code_top-level_domain',
    ui.ButtonSet.OK_CANCEL
  );

  if (result.getSelectedButton() == ui.Button.OK) {
    setGeocodingRegion(result.getResponseText());
  }
}
*/

// Forward Geocoding -- convert address to GPS position.
function addressToPosition() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var cells = sheet.getActiveRange();
  var popup = SpreadsheetApp.getUi();

  var columnCount = cells.getNumColumns();
  var rowCount = cells.getNumRows();

  if (columnCount < 3) {
    popup.alert("Select at least 3 columns: Address in the leftmost column(s); the geocoded Latitude, Longitude will go into the last 2 columns.");
    return;
  }

  var latColumn = columnCount - 1;
  var lngColumn = columnCount;
  var geocoder = Maps.newGeocoder().setRegion(getGeocodingRegion());
  var addresses = sheet.getRange(cells.getRow(), cells.getColumn(), rowCount, columnCount - 2).getValues();

  for (var addressRow = 1; addressRow <= rowCount; ++addressRow) {
    var address = addresses[addressRow - 1].join(' ');
    address = address.replace(/'/g, "%27");

    Logger.log(address);

    var location = geocoder.geocode(address);

    if (location.status == 'OK') {
      var lat = location["results"][0]["geometry"]["location"]["lat"];
      var lng = location["results"][0]["geometry"]["location"]["lng"];

      cells.getCell(addressRow, latColumn).setValue(lat);
      cells.getCell(addressRow, lngColumn).setValue(lng);
    } else {
      Logger.log(location.status);
    }
  }
}

// Reverse Geocode -- GPS position to nearest address.
function positionToAddress() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var cells = sheet.getActiveRange();
  var popup = SpreadsheetApp.getUi();

  var columnCount = cells.getNumColumns();

  if (columnCount < 3) {
    popup.alert("Select at least 3 columns: Latitude, Longitude in the first 2 columns; the reverse-geocoded Address will go into the last column.");
    return;
  }

  var latColumn = 1;
  var lngColumn = 2;
  var addressColumn = columnCount;
  var geocoder = Maps.newGeocoder().setRegion(getGeocodingRegion());

  for (var addressRow = 1; addressRow <= cells.getNumRows(); ++addressRow) {
    var lat = cells.getCell(addressRow, latColumn).getValue();
    var lng = cells.getCell(addressRow, lngColumn).getValue();
    var location = geocoder.reverseGeocode(lat, lng);

    Logger.log(location.status);

    if (location.status == 'OK') {
      var address = location["results"][0]["formatted_address"];
      cells.getCell(addressRow, addressColumn).setValue(address);
    }
  }
}

• Do not add broad auto-geocoding without a user action.
• Do not geocode entire provider lists by default.
• Normalize and cache address + region before making any external call.
• Prefer small operations attached to a city, provider, hotel, experience, or trip block.
• Keep the AppScript route available as an external runtime option if direct Maps API integration is not yet active.