% Decay Cell Values

/**
 * @constant {Object} CONFIG
 * @property {boolean} useCustomMenu - Set to true to use the custom menu for user input for range and decay amount.
 * @property {number} decayPercentage - The default percentage of decay to apply.
 * @property {number} chunkSize - The maximum number of rows to process in a single batch.
 */
const CONFIG = {
  useCustomMenu: false,
  decayPercentage: 10,
  chunkSize: 1000
};

/**
 * Adds a custom menu to the Google Sheet when opened.
 */
function onOpen() {
  const ui = SpreadsheetApp.getUi();
  ui.createMenu("Decay Operations")
    .addItem("Apply Decay", "startDecay_")
    .addToUi();
}

/**
 * Starts the decay process based on the configuration.
 */
function startDecay_() {
  if (CONFIG.useCustomMenu) {
    showDecayDialog_();
  } else {
    const sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
    const range = sheet.getActiveRange();
    Decay(range, CONFIG.decayPercentage);
  }
}

/**
 * Shows a dialog to the user to input the range and decay amount.
 */
function showDecayDialog_() {
  const ui = SpreadsheetApp.getUi();
  const rangeResponse = ui.prompt(
    "Decay Operation",
    "Enter the range (e.g., A1:A100) to apply decay:",
    ui.ButtonSet.OK_CANCEL
  );
  if (rangeResponse.getSelectedButton() == ui.Button.CANCEL) return;
  const decayResponse = ui.prompt(
    "Decay Operation",
    "Enter the decay percentage (e.g., 10 for 10%):",
    ui.ButtonSet.OK_CANCEL
  );
  if (decayResponse.getSelectedButton() == ui.Button.CANCEL) return;
  const range = rangeResponse.getResponseText();
  const decayPercentage = parseFloat(decayResponse.getResponseText());
  if (
    isNaN(decayPercentage) ||
    decayPercentage <= 0 ||
    decayPercentage >= 100
  ) {
    ui.alert(
      "Invalid decay percentage. Please enter a number between 1 and 99."
    );
    return;
  }
  Decay(range, decayPercentage);
}

/**
 * Applies decay to the values in the specified range of the Google Sheet.
 * Processes the data in chunks if the dataset is larger than the configured chunk size.
 *
 * @param {string|GoogleAppsScript.Spreadsheet.Range} range - The range to decay, can be A1 notation or a Range object.
 * @param {number} decayPercentage - The percentage of decay to apply.
 */
function Decay(range, decayPercentage) {
  const sheet = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  const selectedRange =
    typeof range === "string" ? sheet.getRange(range) : range;
  const values = selectedRange.getValues();
  const decayFactor = 1 - decayPercentage / 100;
  if (values.length > CONFIG.chunkSize) {
    processInChunks_(selectedRange, values, decayFactor, CONFIG.chunkSize);
  } else {
    applyDecay_(values, decayFactor);
    selectedRange.setValues(values);
  }
  SpreadsheetApp.flush();
}
const processInChunks_ = (range, values, decayFactor, chunkSize) => {
  for (let start = 0; start < values.length; start += chunkSize) {
    const chunk = values.slice(start, start + chunkSize);
    applyDecay_(chunk, decayFactor);
    range.offset(start, 0, chunk.length, 1).setValues(chunk);
  }
};
const applyDecay_ = (values, decayFactor) => {
  values.forEach((row) => {
    if (typeof row[0] === "number") row[0] *= decayFactor;
  });
};