Untitled

#!/bin/bash

encode() {
     text=$1
     shift=$2
     result=""

    for (( i=0; i<${#text}; i++ )); do
        char="${text:$i:1}"

        if [[ "$char" =~ [A-Za-z] ]]; then
            ascii_val=$(printf '%d' "'$char")
            ((ascii_val += shift))

            if [[ "$char" =~ [a-z] && $ascii_val -gt 122 ]]; then
                ((ascii_val -= 26))
            elif [[ "$char" =~ [A-Z] && $ascii_val -gt 90 ]]; then
                ((ascii_val -= 26))
            fi

            result+="$(printf "\\$(printf '%03o' "$ascii_val")")"
        else
            result+="$char"
        fi
    done

    echo "$result"
}


decode() {
     text=$1
     shift=$2

    encode "$text" "$((0 - shift))"
}


validate_text() {
     text=$1

    if [[ ! "$text" =~ ^[A-Za-z[:space:][:punct:][:digit:]]+$ ]]; then
        echo "Error: Input text contains invalid characters."
        exit 1
    fi
}


validate_shift() {
     shift=$1

    if [[ ! "$shift" =~ ^[1-9]$|^1[0-9]$|^2[0-5]$ ]]; then
        echo "Error: Shift value must be a positive integer within the range 1-25."
        exit 1
    fi
}


get_user_input() {
    read -p "Enter text to $1: " user_text
    validate_text "$user_text"

    read -p "Enter shift value (1-25): " shift_value
    validate_shift "$shift_value"

    if [ "$1" == "encode" ]; then
        result=$(encode "$user_text" "$shift_value")
        echo "Encoded text: $result"
    elif [ "$1" == "decode" ]; then
        result=$(decode "$user_text" "$shift_value")
        echo "Decoded text: $result"
    fi
}


if [ "$#" -ne 1 ]; then
    echo "Usage: $0 [-e | -d]"
    exit 1
fi

if [ "$#" -ne 1 ]; then
    echo "Usage: $0 [-e | -d]"
    exit 1
fi


case $1 in
    "-e")
        get_user_input "encode"
        ;;
    "-d")
        get_user_input "decode"
        ;;
    *)
        echo "Invalid option. Use '-e' to encode or '-d' to decode."
        exit 1
        ;;
esac