ssm.sh

#!/usr/bin/env bash


# Found at https://unix.stackexchange.com/a/415155
function select_option {
    # little helpers for terminal print control and key input
    ESC=$( printf "\033")
    cursor_blink_on()  { printf "$ESC[?25h"; }
    cursor_blink_off() { printf "$ESC[?25l"; }
    cursor_to()        { printf "$ESC[$1;${2:-1}H"; }
    print_option()     { printf "   $1 "; }
    print_selected()   { printf "  $ESC[7m $1 $ESC[27m"; }
    get_cursor_row()   { IFS=';' read -sdR -p $'\E[6n' ROW COL; echo ${ROW#*[}; }
    key_input()        { read -s -n3 key 2>/dev/null >&2
                         if [[ $key = $ESC[A ]]; then echo up;    fi
                         if [[ $key = $ESC[B ]]; then echo down;  fi
                         if [[ $key = ""     ]]; then echo enter; fi; }

    # initially print empty new lines (scroll down if at bottom of screen)
    for opt; do printf "\n"; done

    # determine current screen position for overwriting the options
    local lastrow=`get_cursor_row`
    local startrow=$(($lastrow - $#))

    # ensure cursor and input echoing back on upon a ctrl+c during read -s
    trap "cursor_blink_on; stty echo; printf '\n'; exit" 2
    cursor_blink_off

    local selected=0
    while true; do
        # print options by overwriting the last lines
        local idx=0
        for opt; do
            cursor_to $(($startrow + $idx))
            if [ $idx -eq $selected ]; then
                print_selected "$opt"
            else
                print_option "$opt"
            fi
            ((idx++))
        done

        # user key control
        case `key_input` in
            enter) break;;
            up)    ((selected--));
                   if [ $selected -lt 0 ]; then selected=$(($# - 1)); fi;;
            down)  ((selected++));
                   if [ $selected -ge $# ]; then selected=0; fi;;
        esac
    done

    # cursor position back to normal
    cursor_to $lastrow
    printf "\n"
    cursor_blink_on

    return $selected
}


function preflight {

    if [ -z "$AWS_PROFILE" ]; then
        if [ $? -ne 0 ]; then
            echo "AWS_PROFILE must be set"
            return 1
        fi
    fi

    if [ -z "$AWS_REGION" ]; then
        region=`aws configure get region --profile $AWS_PROFILE`
        if [ $? -ne 0 ]; then
            return 1
        fi
    fi
}

function get_instance_id {
    AWS_PAGER="" AWS_CLI_AUTO_PROMPT=off aws ec2 describe-instances --no-paginate --filters 'Name=instance-state-name,Values=running' "Name=tag:Name,Values=$1" --query 'Reservations[].Instances[].[InstanceId]' --output text
}

preflight

if [ -z "$1" ]; then
    echo "Must supply an instance id or instance name"
    return 1
fi

if [[ $1 =~ ^i-[A-z0-9]{8,17} ]]; then
    instanceId=$1
else
    IFS=$'\n' arr=($(get_instance_id $1))
    if [ ${#arr[@]} -eq 0 ]; then
        echo "Error. Could not find instance with name $1. Exiting..."
        exit 1
    elif [ ${#arr[@]} -eq 1 ]; then
        instanceId=${arr[0]}
    else
        echo "Found multiple instances. Connect to which one?"
        select_option "${arr[@]}"
        choice=$?
        instanceId=${arr[$choice]}
    fi
fi

AWS_CLI_AUTO_PROMPT=off aws ssm start-session --target $instanceId