#!/bin/bash
# copyright 2007 Gilbert Ashley <amigo@ibiblio.org>
# BashTrix tr is an implementation of the 'tr' command
# written in pure shell.
VERSION=0.2

# show program usage
show_usage() {
echo
echo "Usage: ${0##/*} SET1 SET2 [FILE]..."
echo "  or: (cat|echo) FILE | ${0##/*} SET1 SET2"
echo "Translate or delete characters."
echo "Translate, squeeze, and/or delete characters in a line."
echo "With no FILE specified, standard input is read."
echo "  -d	delete characters in SET1, do not translate"
echo "  -s  --squeeze-repeats	replace characters in SET1"
echo "  Note: -d and -s cannot be used together."
echo "		which occur repeatedly with a single character"
echo "      --help     display this help and exit"
echo "      --version  output version information and exit"
exit
}
show_version() {
echo ${0##/*}" (BashTrix) $VERSION"
echo "Copyright 2007 Gilbert Ashley <amigo@ibiblio.org>"
echo "This is free software written in pure shell."
exit
}

for WORD in "$@" ; do
	case $WORD in
		-d) DELETE_CHARS=1 ; shift ;;
		-s) SQUEEZE_REPEATS=1 ; shift ;;
		"-h"|"--help") show_usage ;;
		"--version") show_version ;;
	esac
done

if [[ $DELETE_CHARS ]] && [[ $SQUEEZE_REPEATS ]] ; then
 show_usage
fi

if [[ ! $1 ]] ; then
show_usage
else
	if [[ $DELETE_CHARS ]] ; then
	 PATTERN_1=$1
	 PATTERN_2=""
	 shift 1
	elif [[ $SQUEEZE_REPEATS ]] ; then
	 PATTERN_1=$1
	 PATTERN_2=$PATTERN_1
	 shift 1
	else
	 PATTERN_1=$1
	 PATTERN_2=$2
	 shift 2
	fi
fi

# echo $PATTERN_1:$SIZEOF_PATTERN_1 $PATTERN_2:$SIZEOF_PATTERN_2

if [[ $# -gt 0 ]] ; then
	while [[ $# -gt 0 ]] ; do
		FILE_NAME="$1"
		if [ ! -r "$1" ] ; then
			echo "Cannot find file $1" 1>&2
			exit 1
		else
			FILE_LINE_COUNT=0
			LINE=
			IFS=
			while read LINE ; do
				# add the curent line to the line counter
				(( FILE_LINE_COUNT++ ))
				OUTPUT_STRING=
				STRING=$LINE
				while [[ "$STRING" != "" ]] ; do
					CHUNK_CONTENTS=$(echo ${STRING:0:1})
					
					#NEXT_CHUNK_CONTENTS=$(echo ${STRING:$OFFSET:$OFFSET})
					
					#echo $SIZEOF_STRING:$OFFSET $CHUNK_CONTENTS $NEXT_CHUNK_CONTENTS
					#exit
					
					if [[ ${CHUNK_CONTENTS} = $PATTERN_1 ]] ; then
					  
					  if [[ $DELETE_CHARS ]] ; then
					   OUTPUT_STRING=$OUTPUT_STRING
					   STRING=${STRING:1}
					  elif [[ $SQUEEZE_REPEATS ]] ; then
						NEXT_CHUNK_CONTENTS=$(echo ${STRING:1:1})
						if [[ $NEXT_CHUNK_CONTENTS = $PATTERN_1 ]] ; then
						 # add the PATTERN to OUTPUT
						 OUTPUT_STRING=$OUTPUT_STRING$PATTERN_1
						 # increment by two OFFSETS to remove repeating PATTERN
						 STRING=${STRING:2}
						else
						 OUTPUT_STRING=$OUTPUT_STRING$PATTERN_1
						 STRING=${STRING:1}
						fi
					  else
					   OUTPUT_STRING=$OUTPUT_STRING$PATTERN_2
					   STRING=${STRING:1}
					  fi
					  #echo $OUTPUT_STRING $STRING
					  #exit
					else
					  OUTPUT_STRING=$OUTPUT_STRING$CHUNK_CONTENTS
					  STRING=${STRING:1}
					  #echo $OUTPUT_STRING $STRING
					  #exit
					fi
					#break
					#echo $OUTPUT_STRING $STRING
					#exit
				done
				#shift
				echo $OUTPUT_STRING
			done <"$1"
			
		fi
	# go to next FILE in $@
	shift
	done
else
	# piped input is presumed to be separated into lines already
	FILE_NAME="STDIN"
	# output the requested lines in the file
	FILE_LINE_COUNT=0
	LINE=
	IFS=
	while read LINE ; do
		# add the curent line to the line counter
		(( FILE_LINE_COUNT++ ))
		OUTPUT_STRING=
		STRING=$LINE
		
		while [[ "$STRING" != "" ]] ; do
			SIZEOF_STRING=${#STRING}
			OFFSET=${SIZEOF_PATTERN_1}
			CHUNK_CONTENTS=$(echo ${STRING:0:$OFFSET})
			
			#echo $SIZEOF_STRING:$OFFSET $CHUNK_CONTENTS
			#exit
			
			if [[ ${CHUNK_CONTENTS} = $PATTERN_1 ]] ; then
				
				if [[ $DELETE_CHARS ]] ; then
				 OUTPUT_STRING=$OUTPUT_STRING
				 STRING=${STRING:$OFFSET}
				else
				 OUTPUT_STRING=$OUTPUT_STRING$PATTERN_2
				 STRING=${STRING:$OFFSET}
				fi
				#echo $OUTPUT_STRING $STRING
				#exit
			else
			 OUTPUT_STRING=$OUTPUT_STRING$CHUNK_CONTENTS
			 STRING=${STRING:$OFFSET}
			 #echo $OUTPUT_STRING $STRING
			 #exit
			fi
					
			#echo $OUTPUT_STRING $STRING
			#exit
		done
		
		echo $OUTPUT_STRING
		# go to next line in stdin
		shift
	done
fi