decode

#!/usr/bin/env bash

#########################region CONSTANTS#########################
readonly NAME="decode"
readonly ERROR_BAD_METHOD=4
readonly ERROR_NO_INPUT=2
readonly DECODE_METHOD_ESCAPE="escape"
readonly DECODE_METHOD_URL="url"
readonly DECODE_METHOD_UNDERSCORE="underscore"
readonly TRUE="[ a = a ]"
readonly FALSE="[ a = b ]"
readonly DEFAULT_DECODE_METHOD=$DECODE_METHOD_ESCAPE
#########################endregion CONSTANTS#########################

#########################region HELP#########################
show_help() {
    # -d | --decode | --decode_method METHOD: The decoding method to use for values and labels.
    cat << __EOF__
$NAME VALUE [--escape|url|underscore] | $NAME VALUE [-e|u|_] | $NAME -h | $NAME --help

Decodes the given value with the selected method. Defaults to $DEFAULT_DECODE_METHOD

Parameters:
	-u | --url: use url decoding
	-e | --escape: use escape decoding (i.e. use "\\\\" to encode escape sequences)
	-_ | --underscore: use underscore decoding (i.e. replaces all underscores with spaces)
		Defaults to "$DEFAULT_DECODE_METHOD"
    -h | --help: Display this help text.
EXIT STATUS:
	Error Level of $ERROR_BAD_METHOD if selection is invalid.
__EOF__
# Anything else will result in no decoding being used. If this is used, ensure there are no spaces in your values nor labels.
#    -e | --error_on_fail: Set the error level on failure.
}
show_version() {
	cat << __EOF__
$0 1.0.0

Copyright (C) 2024 Justin Morris
__EOF__
}
#########################endregion HELP#########################

#########################region DECODE METHODS#########################
# https://www.gnu.org/software/sed/manual/html_node/Regular-Expressions.html
url_decode() {
    echo -e $(echo "$1" | sed -z -E "s/\\+/ /g" | sed -z -E "s/%([0-9a-fA-F][0-9a-fA-F])/\\\x\1/g")
}

escape_decode() {
    echo -e $(echo "$1" | sed -z -E "s/\\\\/\\\/g")
}

# TODO: TEST
underscore_decode() {
    echo -e $(echo "$1" | sed -z -E "s/_/ /g")
}
#########################endregion DECODE METHODS#########################

#########################region GET OPTIONS#########################
decode_method=$DEFAULT_DECODE_METHOD
encoded=""
not_assigned=$TRUE
while [ "$1" != "" ]; do
    case "$1" in
        -h | --help )
            show_help
            exit
            ;;
        -v | --version )
            show_version
            exit
            ;;
        # #region Flags
		-u | --url )
		    decode_method=$DECODE_METHOD_URL
		    ;;
		-e | --escape )
		    decode_method=$DECODE_METHOD_ESCAPE
		    ;;
		-_ | --underscore )
		    decode_method=$DECODE_METHOD_UNDERSCORE
		    ;;
		# #endregion Flags
        * )
			# if [[ "$decode_method" == "" && $1 =~ ^--(.*)$ ]]; then
			# 	decode_method=${BASH_REMATCH[1]}
			# elif [ "$encoded" = "" ]; then
			if $($not_assigned); then
				encoded=$1
				not_assigned="$FALSE"
            else
                encoded="$encoded $1"
            # else
            #     show_help
            #     exit 1
            fi
            ;;
    esac
    shift
done
if $($not_assigned); then
    show_help
    exit 1
fi
#########################endregion GET OPTIONS#########################

if [[ "$decode_method" = $DECODE_METHOD_URL ]]; then
    echo $(url_decode "$encoded")
elif [[ "$decode_method" = $DECODE_METHOD_UNDERSCORE ]]; then
    echo $(underscore_decode "$encoded")
elif [[ "$decode_method" = $DECODE_METHOD_ESCAPE ]]; then
    echo $(escape_decode "$encoded")
else
    echo "$encoded"
	exit $ERROR_BAD_METHOD
fi
exit # $?