#!/bin/bash

# Usage: editdist reference_text hypothesized_text 
# 
# Set environment variable cleanup=0 if you don't want temporary files removed.
# Set environment variable FSTSYMBOLS to a symbol table file if you want to 
#    parse the files as a sequence of symbols rather than a sequence of bytes.

ref=$(readlink -f "$1")
hyp=$(readlink -f "$2")

refedit=/tmp/${ref##*/}.$$.edit.fst
hypedit=/tmp/${hyp##*/}.$$.edit.fst
umask 077   # files in ugrad /tmp dir shouldn't be readable by other students

# Edit machines were compiled  from grammars/editdist.grm .
# Their sym table was extracted with
#     fstsymbols --save_osymbols=../symbol_tables/edit.sym edit1.fst > /dev/null

edit1="${0%/*}/../fsts/edit1.fst"
edit2="${0%/*}/../fsts/edit2.fst"
editsym="${0%/*}/../symbol_tables/edit.sym"

# Cumulative edit distance stats
total=0   
count=0

while read -r -u3 ref_line; read -r -u4 hyp_line; do 
    ##echo "$line1:$line2"; 

# Convert each file to a single string (replace non-final newlines with spaces),
# and compose its automaton with an edit automaton.
    echo $ref_line | perl -0777 -pe 's/\n(?=.)/ /gs' | FSTSYMBOLS=$editsym fstcompilestring | fstcompose - $edit1 | fstarcsort > $refedit
    echo $hyp_line | perl -0777 -pe 's/\n(?=.)/ /gs' | FSTSYMBOLS=$editsym fstcompilestring | fstcompose $edit2 - | fstarcsort > $hypedit


    # Finally, mash the two edited strings together to find the best alignment.
    editdist=$(fstcompose $refedit $hypedit | fstshortestdistance --reverse | head -1 | cut -f2)
    total=$(($total + $editdist))
    count=$(($count + 1))
    echo "Line $count: edit distance is $editdist"
    echo -e "\t$ref_line\n\t$hyp_line"
done 3< "$ref" 4< "$hyp"

echo "Total edit distance $total over $count lines (about $(($total/$count)) per line)"

if [ "${cleanup:=1}" -eq "1" ]; then
   rm -f $refedit $hypedit
fi