Bash or Python efficient substring matching and filtering - substring

Question

I have a set of filenames in a directory, some of which are likely to have identical substrings but not known in advance. This is a sorting exercise. I want to move the files with the maximum substring ordered letter match together in a subdirectory named with that number of letters and progress to the minimum match until no matches of 2 or more letters remain. Ignore extensions. Case insensitive. Ignore special characters.
Example.
AfricanElephant.jpg
elephant.jpg
grant.png
ant.png
el_gordo.tif
snowbell.png
Starting from maximum length matches to minimum length matches will result in:
./8/AfricanElephant.jpg and ./8/elephant.jpg
./3/grant.png and ./3/ant.png
./2/snowbell.png and ./2/el_gordo.tif
Completely lost on an efficient bash or python way to do what seems a complex sort.
I found some awk code which is almost there:
{
count=0
while ( match($0,/elephant/) ) {
count++
$0=substr($0,RSTART+1)
}
print count
}
where temp.txt contains a list of the files and is invoked as eg
awk -f test_match.awk temp.txt
Drawback is that a) this is hardwired to look for "elephant" as a string (I don't know how to make it take an input string (rather than file) and an input test string to count against, and
b) I really just want to call a bash function to do the sort as specified
If I had this I could wrap some bash script around this core awk to make it work.

Answer 1

function longest_common_substrings () {
shopt -s nocasematch
for file1 in * ; do for file in * ; do \
if [[ -f "$file1" ]]; then
if [[ -f "$file" ]]; then
base1=$(basename "$file" | cut -d. -f1)
base2=$(basename "$file1" | cut -d. -f1)
if [[ "$file" == "$file1" ]]; then
echo -n ""
else
echo -n "$file $file1 " ; $HOME/Scripts/longest_common_substring.sh "$base1" "$base2" | tr -d '\n' | wc -c | awk '{$1=$1;print}' ;
fi
fi
fi
done ;
done | sort -r -k3 | awk '{ print $1, $3 }' > /tmp/filesort_substring.txt
while IFS= read -r line; do \
file_to_move=$(echo "$line" | awk '{ print $1 }') ;
directory_to_move_to=$(echo "$line" | awk '{ print $2 }') ;
if [[ -f "$file_to_move" ]]; then
mkdir -p "$directory_to_move_to"
\gmv -b "$file_to_move" "$directory_to_move_to"
fi
done < /tmp/filesort_substring.txt
shopt -u nocasematch
where $HOME/Scripts/longest_common_substring.sh is
#!/bin/bash
shopt -s nocasematch
if ((${#1}>${#2})); then
long=$1 short=$2
else
long=$2 short=$1
fi
lshort=${#short}
score=0
for ((i=0;i<lshort-score;++i)); do
for ((l=score+1;l<=lshort-i;++l)); do
sub=${short:i:l}
[[ $long != *$sub* ]] && break
subfound=$sub score=$l
done
done
if ((score)); then
echo "$subfound"
fi
shopt -u nocasematch
Kudos to the original solution for computing the match in the script which I found elsewhere in this site