Conditional substitution of patterns in bash strings depending on the beginning of a string - sed

Question

I am new in bash, so excuse me if do not use the right terms.
I need to substitute certain patterns of six characters in a set of files. The order by patterns are substituted depends on the beginning of each string of text.
This is an example of input:
chr1:123-123 5GGGTTAGGGTTAGGGTTAGGGTTAGGGTTA3
chr1:456-456 5TTAGGGTTAGGGTTAGGGTTAGGGTTAGGG3
chr1:789-789 5GGGCTAGGGTTAGGGTTAGGGTTA3
chr1:123-123 etc is the name of the string, they are separated from the string I need to work with by a tab. The string I need to work with is delimited by characters 5 and 3, but I can change them.
I want that all patterns containing T, A, G in anyone of these orders is substituted with X: TTAGGG, TAGGG, AGGGTT, GGGTTA, GGTTAG, GTTAGG.
Similarly, patterns containing CTAGGG, like row 3, in orders similar to the previous one will be substituted with a different character.
The game is repeated with some specific differences for all the 6 characters composing each pattern.
I started writing something like this:
#!/bin/bash
NORMAL=`echo "\033[m"`
RED=`echo "\033[31m"` #red
#read filename for the input file and create a copy and a folder for the output
read -p "Insert name for INPUT file: " INPUT
echo "Creating OUTPUT file " "${RED}"$INPUT"_sub.txt${NORMAL}"
mkdir -p ./"$INPUT"_OUTPUT
cp $INPUT.txt ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
echo
#start the first set of instructions
perfrep
#starting a second set of instructions to substitute pattern with one difference from TTAGGG
onemism
Instructions are
perfrep() {
sed -i -e 's/TTAGGG/X/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
sed -i -e 's/TAGGGT/X/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
sed -i -e 's/AGGGTT/X/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
sed -i -e 's/GGGTTA/X/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
sed -i -e 's/GGTTAG/X/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
sed -i -e 's/GTTAGG/X/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
}
# starting a second set of instructions to substitute pattern with one difference from TTAGGG
onemism(){
sed -i -e 's/[GCA]TAGGG/L/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
sed -i -e 's/G[GCA]TAGG/L/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
sed -i -e 's/GG[GCA]TAG/L/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
sed -i -e 's/GGG[GCA]TA/L/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
sed -i -e 's/AGGG[GCA]T/L/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
sed -i -e 's/TAGGG[GCA]/L/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
}
I will need to repeat also with T[GCA]AGGG, TT[TCG]GGG, TTA[ACT]GG, TTAG[ACT]G and TTAGG[ACT].
Using this procedure, I get for these results for the inputs shown
5GGGXXXXTTA3
5XXXXX3
5GGGLXXTTA3
In my point of view, for my job, the first and second string are both made by X repeated five times, and the order of characters is just slightly different. On the other hand, the third one could be masked like this:
5LXXX3
How do I tell the script that if the string starts with 5GGGTTA instead of 5TTAGGG must start to substitute with
sed -i -e 's/GGGTTA/X/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
instead of
sed -i -e 's/TTAGGG/X/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
?
I will need to repeat with all cases; for instance, if the string starts with GTTAGG I will need to start with
sed -i -e 's/GTTAGG/X/g' ./"$INPUT"_OUTPUT/"$INPUT"_sub.txt
and so on, and add a couple of variation of my pattern.
I need to repeat the substitution with TTAGGG and the variations for all the rows of my input file.
Sorry for the very long question. Thank you all.
Adding information asked by Varun.
Patterns of 6 characters would be TTAGGG , [GCA]TAGGG , T[GCA]AGGG , TT[TCG]GGG , TTA[ACT]GG , TTAG[ACT]G , TTAGG[ACT].
Each one must be checked for a different frame, for instance for TTAGGG we have 6 frames TTAGGG , GTTAGG , GGTTAG, GGGTTA , AGGGTT , TAGGGT.
The same frames must be applied to the pattern containing a variable position.
I will have a total of 42 patterns to check, divided in 7 groups: one containing TTAGGG and derivative frames, 6 with the patterns with a variable position and their derivatives.
TTAGGG and derivatives are the most important and need to be checked first.

Answer 1

#! /usr/bin/awk -f
# generate a "frame" by moving the first char to the end
function rotate(base){ return substr(base,2) substr(base,1,1) }
# Unfortunately awk arrays do not store regexps
# so I am generating the list of derivative strings to match
function generate_derivative(frame,arr, i,j,k,head,read,tail) {
arr[i]=frame;
for(j=1; j<=length(frame); j++) {
head=substr(frame,1,j-1);
read=substr(frame,j,1);
tail=substr(frame,j+1);
for( k=1; k<=3; k++) {
# use a global index to simplify
arr[++Z]= head substr(snp[read],k,1) tail
}
}
}
BEGIN{
fs="\t";
# alternatives to a base
snp["A"]="TCG"; snp["T"]="ACG"; snp["G"]="ATC"; snp["C"]="ATG";
# the primary target
frame="TTAGGG";
Z=1; # warning GLOBAL
X[Z] = frame;
# primary derivatives
generate_derivative(frame, X);
xn = Z;
# secondary shifted targets and their derivatives
for(i=1; i<length(frame); i++){
frame = rotate(frame);
L[++Z] = frame;
generate_derivative(frame, L);
}
}
/^chr[0-9:-]*\t5[ACTG]*3$/ {
# because we care about the order of the prinary matches
for (i=1; i<=xn; i++) {gsub(X[i],"X",$2)}
# since we don't care about the order of the secondary matches
for (hit in L) {gsub(L[hit],"L",$2)}
print
}
END{
# print the matches in the order they are generated
#for (i=1; i<=xn; i++) {print X[i]};
#print ""
#for (i=1+xn; i<=Z; i++) {print L[i]};
}
IFF you can generate a static matching order you can live with then
something like the above Awk script could work. but you say the primary patterns should take precedence and that a secondary rule would be better applied first in some cases. (no can do).
If you need a more flexible matching pattern I would suggest looking at "recursive decent parsing with backtracking" Or "parsing expression grammars".
But then you are not in a bash shell anymore.