How to calculate rest of the amount after comparing current date in pyspark dataframe?

I need to calculate how much I have in my account after today. That means, for the current day how much I left in my original Total_salary.

Below is my sample data set.

start_date    end_date    duration(months)   Total_salary   left_amount

2021-05-03    2022-05-03   12                   1200                400
2019-01-01    2023-01-01   48                   4800                2300
2018-01-01    2020-01-01   24                   2400                0
2020-01-01    2023-01-01   36                   3600                1200
2024-01-01    2027-01-01   36                   3600                3600

I need get the upto current date how much I left, if end_date < current date. Let take first row as an example, I agree with a client for working for 12 months with total salary 1200, by each month I will receive 100 as my salary. So, I need to know today how much I left from my original total_salary. (100*8 = 800, 1200-800 = 400) I don't know how to get SUM up to current date.

I need to implement this in pyspark. Please anyone can help me to sort out this?

Thank you

import datetime
from pyspark.sql import functions as F

current_date = datetime.date.today()

(
    df
    .withColumn('left_months', F.greatest(F.lit(0), F.months_between('end_date', F.lit(current_date))))
    .withColumn('left_amount', F.col('total_salary')/F.col('duration(months)') * F.col('left_months'))
    .withColumn('left_amount', F.least('total_salary', 'left_amount'))
)