Join two files

I have 2 files:

fileA

AAA1:AAA2:AAA3:AAA_4:AAA5:AAA_6:AAA7:AAA_8
BBB1:BBB2:BBB3:BBB_4:BBB5:BBB-6
CCC1:CCC2:CCC3:CCC_4

fileB

AAA_4:XXX1:YYY1
BBB_4:XXX2:YYY2
CCC_4:XXX3:YYY3:ZZZ3
AAA_6:XXX4:YYY4
AAA_8:XXX5:YYY5

Result:

AAA1:AAA2:AAA3:AAA_4:XXX1:YYY1:AAA5:AAA_6:XXX4:YYY4:AAA7:AAA_8:XXX5:YYY5
BBB1:BBB2:BBB3:BBB_4:XXX2:YYY2:BBB5:BBB-6
CCC1:CCC2:CCC3:CCC_4:XXX3:YYY3:ZZZ3

If value from first column (fileA) exist in second file (fileB), copy everything from that line after the appearance of value from first column fileA.
Can some help with some solution, preferred awk programming.

awk -F: 'FNR==NR{o=$1;sub("^[^"FS"]*"FS,"");f2[o]=$0;next}{for(i=1;i<=NF;i++) if($i in f2) $i=$i FS f2[$i]}1' OFS=: fileB fileA

Well, no awk involved, but this seems to work
(I'm not that good with awk myself ... *shrug* )

for i in `cat fileB`
do
  s=`echo $i | cut -d: -f1`
  sed "s/$s/$i/g" fileA > fileA.2
  mv fileA.2 fileA
done

try also:

awk -F: '
NR==FNR {a[c++]=$0; next}
{for (i=0; i<c; i++) if (match(a, $1)) gsub($1, $0, a);}
END {for (i=0; i<c; i++) print a}
' fileA fileB

Thank you all
Now some more condition if value from fileB have no any more columns, add to fileA string "NA:NA"

I have 2 files:

fileA

AAA1:AAA2:AAA3:AAA_4:AAA5:AAA_6:AAA7:AAA_8
BBB1:BBB2:BBB3:BBB_4:BBB5:BBB-6
CCC1:CCC2:CCC3:CCC_4

fileB

AAA_4:XXX1:YYY1
BBB_4:XXX2:YYY2
CCC_4:XXX3:YYY3:ZZZ3
AAA_6:XXX4:YYY4
AAA_8:

Result:

AAA1:AAA2:AAA3:AAA_4:XXX1:YYY1:AAA5:AAA_6:XXX4:YYY4:AAA7:AAA_8:NA:NA
BBB1:BBB2:BBB3:BBB_4:XXX2:YYY2:BBB5:BBB-6
CCC1:CCC2:CCC3:CCC_4:XXX3:YYY3:ZZZ3

If there are any other conditions, now's the time to share them.

Regards,
Alister

that would be all, no more conditions

Try:

awk 'NR==FNR{i=$1; $1=x; A=($2=="")?":NA:NA":$0; next} {for(i=1; i<=NF; i++) $i=$i A[$i]}1' FS=: OFS=: fileB fileA

Working exactly as should be, Thank you.