Awk command has unexpected results when comparing two files - awk

Question

I am using an awk command to compare the first column in two file.
I want to take col1 of file1 and if there is a match in col1 of file2, update the "date updated" in the last column. If there is no match, I want to append the entire line of file1 to file2 and append a "date updated" value to that line as well. Here is the command I'm currently using:
awk 'FNR == NR { f1[$1] = $0; next }
$1 in f1 { print; delete f1[$1] }
END { for (user in f1) print f1[user] }' file1 file2
File1:
tnash,172.2,plasma-de+,serv01,datetimeNEW
jhwagner,169.4,plasma-de+,serv01,datetimeNEW
steadmah,161.1,plasma-de+,serv01,datetimeNEW
guillwt,158.3,plasma-de+,serv01,datetimeNEW
mwinebra,122.2,plasma-de+,serv01,datetimeNEW
jbomba,100.0,plasma-de+,serv01,datetimeNEW
mschrode,161.1,plasma-de+,serv01,datetimeNEW
File2:
jbomba,114.0,plasma-de+,serv01,datetimeOLD
mschrode,104.0,plasma-de+,serv01,datetimeOLD
deleteme,192.0,random,serv01,datetimeOLD #<---- Needs to be removed: WORKS!
Expected Output:(order does not matter)
tnash,172.2,plasma-de+,serv01,datetimeNEW
jhwagner,169.4,plasma-de+,serv01,datetimeNEW
steadmah,161.1,plasma-de+,serv01,datetimeNEW
guillwt,158.3,plasma-de+,serv01,datetimeNEW
mwinebra,122.2,plasma-de+,serv01,datetimeNEW
jbomba,100.0,plasma-de+,serv01,datetimeOLD #<---- NEED THIS VALUE
mschrode,161.1,plasma-de+,serv01,datetimeOLD #<---- NEED THIS VALUE
Current Output:(order does not matter)
tnash,172.2,plasma-de+,serv01,datetimeNEW
jhwagner,169.4,plasma-de+,serv01,datetimeNEW
steadmah,161.1,plasma-de+,serv01,datetimeNEW
guillwt,158.3,plasma-de+,serv01,datetimeNEW
mwinebra,122.2,plasma-de+,serv01,datetimeNEW
jbomba,100.0,plasma-de+,serv01,datetimeNEW #<----WRONG OUTPUT
mschrode,161.1,plasma-de+,serv01,datetimeNEW #<----WRONG OUTPUT
The Logic Broken Down:
If $usr/col1 in file2 does NOT exist in file1
remove entire line from file2
(ex: line3 in file2, user: deleteme)
If $usr/col1 in file1 does NOT exist in file2
append entire line to file2
(ex: lines 1-5 in file1)
So the issue is, when there IS a match between the two files, I need to keep the information from file2, not the information from file1. In the output examples above you'll see I need to keep the datetimeOLD from file2 along with the new information from file1.

Answer 1

Set field separator to comma, and read file2 first:
$ awk -F',' 'FNR==NR{a[$1]=$0;next} $1 in a{print a[$1];next} 1' file2 file1
tnash,172.2,plasma-de+,serv01,datetimeNEW
jhwagner,169.4,plasma-de+,serv01,datetimeNEW
steadmah,161.1,plasma-de+,serv01,datetimeNEW
guillwt,158.3,plasma-de+,serv01,datetimeNEW
mwinebra,122.2,plasma-de+,serv01,datetimeNEW
jbomba,114.0,plasma-de+,serv01,datetimeOLD
mschrode,104.0,plasma-de+,serv01,datetimeOLD