about how to write a shell script to read the text file and perform transform

i have a text file as belows, it includes 2 columns, 1st is the column name, 2nd is the file_name

data_file.txt

column_name    file_name

col1                      file1

col2                      file2

col3                      file1

col4                      file1

col5                      file2

now, i would like to output below result to a text file, which returns all the column name by file name as belows.

file_name     column_name

file1               col1,col3,col4

file2               col2,col5

how can i write a shell script to read the data_file.txt line by line and output the result as above by file name.

anyone knows~