#!/bin/bash
# copyright 2007 Gilbert Ashley <amigo@ibiblio.org>
# BashTrix tr is an implementation of the 'tr' command
# written in pure shell.
VERSION=0.3

# 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 "		which occur repeatedly with a single character"
echo "  Note: -d and -s cannot be used together."
echo "      --help     display this help and exit"
echo "      --version  output version information and exit"
exit
}
# show version information
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
# look-up table for uppercase conversion 
_upper_case()
{
    ## a look-up table is the fastest method
    case $1 in
        a*) _UPR=A ;;        b*) _UPR=B ;;
        c*) _UPR=C ;;        d*) _UPR=D ;;
        e*) _UPR=E ;;        f*) _UPR=F ;;
        g*) _UPR=G ;;        h*) _UPR=H ;;
        i*) _UPR=I ;;        j*) _UPR=J ;;
        k*) _UPR=K ;;        l*) _UPR=L ;;
        m*) _UPR=M ;;        n*) _UPR=N ;;
        o*) _UPR=O ;;        p*) _UPR=P ;;
        q*) _UPR=Q ;;        r*) _UPR=R ;;
        s*) _UPR=S ;;        t*) _UPR=T ;;
        u*) _UPR=U ;;        v*) _UPR=V ;;
        w*) _UPR=W ;;        x*) _UPR=X ;;
        y*) _UPR=Y ;;        z*) _UPR=Z ;;
        *) _UPR=${1%${1#?}} ;;
    esac
    echo $_UPR
}

# look-up table for lowercase conversion 
_lower_case()
{
    _LWR=
    case $1 in
        A*) _LWR=a ;;        B*) _LWR=b ;;
        C*) _LWR=c ;;        D*) _LWR=d ;;
        E*) _LWR=e ;;        F*) _LWR=f ;;
        G*) _LWR=g ;;        H*) _LWR=h ;;
        I*) _LWR=i ;;        J*) _LWR=j ;;
        K*) _LWR=k ;;        L*) _LWR=l ;;
        M*) _LWR=m ;;        N*) _LWR=n ;;
        O*) _LWR=o ;;        P*) _LWR=p ;;
        Q*) _LWR=q ;;        R*) _LWR=r ;;
        S*) _LWR=s ;;        T*) _LWR=t ;;
        U*) _LWR=u ;;        V*) _LWR=v ;;
        W*) _LWR=w ;;        X*) _LWR=x ;;
        Y*) _LWR=y ;;        Z*) _LWR=z ;;
        *) _LWR=${1%${1#?}} ;;
    esac
    echo $_LWR
}


if [[ $# -gt 0 ]] ; then
	while [[ $# -gt 0 ]] ; do
		FILE_NAME="$1"
		if [ ! -r "$1" ] ; then
			echo "Cannot find file $1" 1>&2
			exit 1
		else
			FILE_LINE_COUNT=0
			LINE=
			IFS=
			while read LINE ; do
				OUTPUT_STRING=
				STRING=$LINE
				case $STRING in
					*$PATTERN_1*) 
						if [[ $DELETE_CHARS ]] ; then
						  # replace PATTERN_1 with nothing
						  OUTPUT_STRING=${STRING//$PATTERN_1/}
						elif [[ $SQUEEZE_REPEATS ]] ; then
						 # replace repeated PATTERN_1 characters
						 OUTPUT_STRING=${STRING//$PATTERN_1$PATTERN_1/$PATTERN_1}
						else
							if [[ "${PATTERN_1}" = "[a-z]" ]] && [[ "${PATTERN_2}" = "[A-Z]" ]] ; then
								for CHAR in a b c d e f g h i j k l m n o p q r s t u v w x y z ; do
								REPLACEMENT_CHAR=$(_upper_case $CHAR)
									case $STRING in
										*$CHAR*) 
											STRING=${STRING//$CHAR/$REPLACEMENT_CHAR}
										;;
									esac
								done
								OUTPUT_STRING=$STRING
							#find and print the ascii char number
							# printf "%d\n" "'A"
							elif [[ "${PATTERN_1}" = "[A-Z]" ]] && [[ "${PATTERN_2}" = "[a-z]" ]] ; then
								for CHAR in A B C D E F G H I J K L M N O P Q R S T U V W X Y Z ; do
								REPLACEMENT_CHAR=$(_lower_case $CHAR)
									case $STRING in
										*$CHAR*) 
											STRING=${STRING//$CHAR/$REPLACEMENT_CHAR}
										;;
									esac
								done
								OUTPUT_STRING=$STRING
							
							else
							 # replace PATTERN_1 with PATTERN_2
							 OUTPUT_STRING=${STRING//$PATTERN_1/$PATTERN_2}
							fi
						fi
					;;
					# non-matching lines are output as-is
					*) OUTPUT_STRING=$STRING
					;;
				esac
				echo $OUTPUT_STRING
			done <"$1"
			
		fi
	# go to next FILE in $@
	shift
	done
else
	# piped input is presumed to be separated into lines already
	LINE=
	IFS=
	while read LINE ; do
		OUTPUT_STRING=
		STRING=$LINE
		case $STRING in
			*$PATTERN_1*)
				if [[ $DELETE_CHARS ]] ; then
				 # replace PATTERN_1 with nothing
				 OUTPUT_STRING=${STRING//$PATTERN_1/}
				elif [[ $SQUEEZE_REPEATS ]] ; then
				 # replace repeated PATTERN_1 characters
				 OUTPUT_STRING=${STRING//$PATTERN_1$PATTERN_1/$PATTERN_1}
				else
				 # replace PATTERN_1 with PATTERN_2
				 OUTPUT_STRING=${STRING//$PATTERN_1/$PATTERN_2}
				fi
			;;
			# non-matching lines are output as-is
			*) OUTPUT_STRING=$STRING
			;;
		esac
		echo $OUTPUT_STRING
		# go to next line in stdin
		shift
	done
fi