Please note the creation of a new export through the API is synchronous. As a result, the HTTP request may time out if there’s a lot of data.
Make sure your API key can create exports in Lucca Timesheet.
1

Preliminaries

You first need to retrieve the export-configuration identifier.The export-configuration identifier exportConfigurationId is the second integer URL path parameter when browsing the graphical interface for Lucca Timesheet export feature. For example, if the UI URL looks like this when browsing to the export-configuration: https://example.ilucca.net/timmi-timesheet/legacy-settings#/export/1/3/latest, then the identifier is 3.Then, you may want to retrieve the identifier of the latest successful export, it will help you track the progress of any new export you’ll then create. This can be achieved through the API:
GET /api/v3/timmiexports?configurationId={configurationId}&orderBy=createdAt,desc,id,desc&archivedAt=null&paging=0,1&fields=id,createdat HTTP/1.1
Host: example.ilucca.net
Authorization: lucca application={API_TOKEN}
Accept: application/json
{
  "data": {
    "items": [
      {
        "id": 289,
        "createdAt": "2021-01-01T08:45:32Z"
      } 
    ]
  }
}
2

Trigger an export

When creating an export, two parameters are required:
  1. A date-time endsAt, which indicates that all elements prior to it should be exported. Format is YYYY-MM-DDT00:M00:00 (time component must be equal to midnight).
  2. An export-configuration ID configurationId (cf “preliminaries” above).
Chose the endsAt date carefully when creating a payroll variables export, as you may have calculation rules that handle time on a weekly basis (triggered on sundays). If so, consider exporting on a Monday at midnight (i.e. “00:00:00”) rather than on the first day of the next month.
Then, you can forge the following HTTP request:
POST /api/v3/timmiexports/run?fields=id HTTP/1.1
Host: example.ilucca.net
Authorization: lucca application={API_KEY}
Content-Type: application/json
Accept: application/json
{
  "endsAt": {date},
  "configurationId": {exportConfigurationId}
}
The export creation is a synchronous process. As a result, the server will only respond once the export has been fully and successfully generated. This can take some time, and even time out. Your safest bet is to abort the connexion, and track the export creation progress by polling (cf. below).
3

Track export progress

In order to figure out if the export is complete or not, you can poll the server with the following HTTP request (you need the lastExportId and exportConfigurationId retrieved in the “preliminaries” step):
GET /api/v3/timmiexports?configurationId={configurationId}&id=greaterthan,{lastExportId}&archivedAt=null&fields=id,createdat HTTP/1.1
Host: example.ilucca.net
Authorization: lucca application={API_KEY}
Accept: application/json
{
  "data": {
    "items": [
      {
        "id": 290,
        "createdAt": "2021-02-01T12:23:12Z"
      }
    ]
}
If the export was successful, then take note of its id: generatedExportId = data.items[0].id.
Problem is: you will never know if the export has actually failed.Therefore, you may try creating (cf. step #2) a new export again after an arbitrary amount of time (say, one hour) has passed, but your polling requests still return an empty items array, as your previous request has probably failed.
4

Retrieve the export content

If the export was successfully created, you may retrieve its content with the following HTTP request:
GET /api/v3/api/v3/timmiexports/{generatedExportId}?fields=id,name,createdAt,configurationId,startsAt,endsAt,exportFiles,entries[id,name,amount,amountUnit,externalCode,endsAt,owner[id,lastName,firstName],timeType[id,name,payTreatment],axisSections[id,name,code,axisId,active,startOn,endOn]] HTTP/1.1
Host: example.ilucca.net
Authorization: lucca application={API_KEY}
Content-Type: application/json
Accept: application/json