Finding next empty row after a particular "Header" row - google-apps-script

Question

I have just started trying out the script editor of the Google Sheets.
Here is what I am trying to do:
I have a few "headers" in Sheet A. I will name them Header A, B, and C.
1 | Header A
2 | text 1
3 | text 2
4 | (empty row)
5 | Header B
6 | text 1
7 | text 2
8 | (empty row)
9 | Header C
10 | text 1
11 | text 2
Sheet B
1 | text 1 | date | Header A
2 | text 2 | date | Header B
3 | text 3 | date | Header B
4 | text 4 | date | Header C
5 | text 5 | date | Header A
When I update my data on Sheet B, it will be automatically be updated on Sheet A based on my custom attributes in Sheet B. I need it to be able to update the data on Sheet B onto Sheet A's empty row after the specific Headers.
Currently I am stuck at getting the next empty row in Sheet A. I am able to get the row that my Headers are in but I couldn't find any help online finding the next empty row after each specific Headers.
I could not find any classes that is provided. All I can see is getLastRow which is not what I want. I wonder can this be done?
Below is my current code:
function getScheduleStatus(){
var ss = SpreadsheetApp.getActiveSpreadsheet();
var name = ss.getSheetByName("Production Schedule");
var rng = name.getDataRange();
var last_row = rng.getLastRow();
var data = rng.getValues();
var str_upcoming = "upcoming"
var rows = [];
for (var i=0; i < data.length; i++) {
if (data[i][0].toLowerCase() == str_upcoming) {
Logger.log("true");
rows.push(i);
}
}
var row = Number(rows)+Number(rng.getRow());
Logger.log(row);
}
Currently I am able to find the Header as well as getting the row number.
Hope you guys can understand.

Answer 1

Take a look at Faster way to find the first empty row; the answers there can be adapted to your situation.
The fastest solution there was Don Kirby's, and since you have a single column of data, it is ideal. We just need to change it to start searching from a particular headerRow!
/**
* Search column A starting at the given row, to find
* the first following empty row. Uses spreadsheet row numbers.
* From: https://stackoverflow.com/a/38194740/1677912
*
* #param {Number} headerRow Row number to start search at.
*
* #returns {Number} Target empty row.
*/
function getFirstEmptyRowAfter(headerRow) {
var spr = SpreadsheetApp.getActiveSpreadsheet();
var column = spr.getRange('A:A');
var values = column.getValues(); // get all data in one call
var ct = headerRow; // Start at row after headerRow (0-adjusted)
while ( values[ct][0] != "" ) {
ct++;
}
return (ct + 1); // (1-adjusted)
}