tbusainvoicegen/api/v3/Invoicegen/Generate.php

<?php
use CRM_Tbusainvoicegen_ExtensionUtil as E;

/**
 * Invoicegen.Generate API specification (optional)
 * This is used for documentation and validation.
 *
 * @param array $spec description of fields supported by this API call
 * @return void
 * @see http://wiki.civicrm.org/confluence/display/CRMDOC/API+Architecture+Standards
 */
function _civicrm_api3_invoicegen_Generate_spec(&$spec) {
  $spec['contact_id']['description'] = 'Specify a timebank\'s contact ID to generate the invoice for, or leave blank to select all active timebanks.';
  $spec['billing_period']['description'] = 'The year, a dash, and a 1 or 2 for the first or second half of the year.  E.g. 2019-2 for 7/1/19-12/31/19.';
  $spec['billing_period']['api.required'] = 1;
  $spec['invoice_date']['description'] = 'Date of the invoice(s) to generate, or leave blank for today\'s date. Format as: 2019-7-25';
  $spec['due_date']['description'] = 'Due date of the invoice(s), or leave blank for March 31st/September 30th (based on billing period. Format as: 2019-7-25';
  $spec['period_begin_date']['description'] = 'Period begin date, or leave blank for January 1st/July 1st (based on billing period). Format as: 2019-7-25';
  $spec['period_end_date']['description'] = 'Period end date, or leave blank for June 30th/December 31st (based on billing period). Format as: 2019-7-25';
}

/**
 * Invoicegen.Generate API
 *
 * @param array $params
 * @return array API result descriptor
 * @see civicrm_api3_create_success
 * @see civicrm_api3_create_error
 * @throws API_Exception
 */
function civicrm_api3_invoicegen_Generate($params) {
  $returnValues = CRM_Tbusainvoicegen_Timebank::generate($params);
  return civicrm_api3_create_success($returnValues, $params, 'Invoicegen', 'generate');
}