Write a Python script to calculate the moving average of a time series.
Implement the function below using a fixed-size sliding window. Return the average for every complete window, preserving input order. The output should be a list of floating-point values. Assume the input contains at least one value and that window_size is between 1 and the length of values, inclusive.
Function signature: def moving_average(values, window_size):
def moving_average(values, window_size):