read_var.sh

#!/bin/bash

read_var() {

    VAR_NAME=$1; shift
    MESSAGE=$1; shift
    REQUIRED=$1; shift
    DEFAULT=$1; shift
    
    # If a set of choices has been provided
    if [[ -n $1 ]]; then
        read -r -a CHOICES < <(echo "$*")
    else
        CHOICES=()
    fi

    # Preparing default message
    DEFAULT_MSG=" [${DEFAULT}]"

    # Save cursor and clear rest of screen
    tput sc
    tput ed
    while true; do
        # Write valid choices
        if [[ ${#CHOICES[@]} -gt 0 ]]; then
            tput el
            tput cud 1
            tput el
            printf "Valid options: [%s]\n" "${CHOICES[@]}"
            tput cuu 2
        fi
        
        tput el
        echo -n "${MESSAGE}${DEFAULT_MSG}: "
        read -r value
        [[ -z ${value} && -n ${DEFAULT} ]] && value=${DEFAULT}

        # Value is empty but marked as required
        if [[ -z "${value}" && "${REQUIRED}" = "true" ]]; then
            tput el
            echo "You must provide a value (press ENTER to try again)"
            read -r
            tput rc
            tput ed
            continue
        fi
        
        # If choices provided, validate
        if [[ ${#CHOICES[@]} -gt 0 ]]; then
            found=false
            for choice in "${CHOICES[@]}"; do
                if [[ "${choice}" == "${value}" ]]; then
                    found=true
                    break
                fi
            done
            tput el
            if [[ ${found} == false ]]; then
                echo "Invalid choice (press ENTER to try again)"
                read -r
                tput rc
                tput ed
                continue
            fi
        fi
        
        # All good
        eval "$VAR_NAME=\"${value}\""
        break

    done

}