#! /bin/bash

#check permissions
if [[ $EUID -ne 0 ]]; then
    echo ""
    echo "This script must be run as root! Login as root, sudo or su." 
    echo ""
    exit 1;
fi

# #load code functions
# source create_swap_salt.sh

# #setup permissions for functions
# chmod 500 create_swap_salt.sh

# echo ""
# echo "--------------------------------------------------------------------------"
# echo "setupSwap - creates swap space on your server based on AWS guidelines"
# echo "--------------------------------------------------------------------------"
# echo ""
# echo "This will remove an existing swap file and then create a new one. "
# echo "Please read the disclaimer and review the code before proceeding."
# echo ""

# echo -n " Do you want to proceed? (y/n): "; read proceed
# if [ "$proceed" == "y" ]; then
#     echo ""
    
#     swapSetup

# else

#     echo "You chose to exit. Bye!"

# fi

# echo ""
# echo "--------------------------------------------------------------------------"
# echo ""

# exit 0


removeSwap() {
    echo "Will remove swap and backup fstab."
    echo ""

    #get the date time to help the scripts
    backupTime=$(date +%y-%m-%d--%H-%M-%S)

    #get the swapfile name
    swapSpace=$(swapon -s | tail -1 |  awk '{print $1}' | cut -d '/' -f 2)
    #debug: echo $swapSpace

    #turn off swapping
    swapoff /"$swapSpace"

    #make backup of fstab
    cp /etc/fstab /etc/fstab."$backupTime"
    
    #remove swap space entry from fstab
    sed -i "/swap/d" /etc/fstab

    #remove swapfile
    rm -f "/$swapSpace"

    echo ""
    echo "--> Done"
    echo ""
}

###############
### Spinner ###
###############
function spinner() {
    {
        spinner="/|\\-/|\\-"
        while :
        do
            for i in $(seq 0 7)
            do
            echo -n "${spinner:$i:1}"
            echo -en "\010"
            sleep 1
            done
        done
    }
}

########################################
### Add Swappiness setting to sysctl ###
########################################
if ! grep swappiness /etc/sysctl.conf; then
    echo 80 > /proc/sys/vm/swappiness
    echo 'vm.swappiness = 80' >> /etc/sysctl.conf
fi

################################################################################################
### This function identifies available ram, calculates the swap file size and configures it ####
################################################################################################
function createSwap() {
    {
        echo "Will create a swap and setup fstab."
        echo ""

        ### Get available physical ram
        availMemMb=$(grep MemTotal /proc/meminfo | awk '{print $2}')
        ### Debug: echo $availMemMb
        
        ### Convert from kb to mb to gb
        gb=$(awk "BEGIN {print $availMemMb/1024/1024}")
        ### to debug: echo $gb
        
        ### Round the number to nearest gb
        gb=$(echo "$gb" | awk '{print ($0-int($0)<0.499)?int($0):int($0)+1}')
        ### to debug: echo $gb

        echo "-> Available Physical RAM: $gb Gb"
        echo ""
        if [ "$gb" -eq 0 ]; then
            echo "Something went wrong! Memory cannot be 0!"
            exit 1;
        fi

        if [ "$gb" -le 2 ]; then
            echo "   Memory is less than or equal to 2 Gb"
            swapSizeGb=$(( gb * 2 ))
            echo "   -> Set swap size to $swapSizeGb Gb"
        fi
        if [ "$gb" -gt 2 ] && [ "$gb" -lt 32 ]; then
            echo "   Memory is more than 2 Gb and less than to 32 Gb."
            swapSizeGb=$(( gb + 4 - 2 ))
            echo "   -> Set swap size to $swapSizeGb Gb."
        fi
        if [ "$gb" -gt 32 ]; then
            echo "   Memory is more than or equal to 32 Gb."
            swapSizeGb=$gb
            echo "   -> Set swap size to $swapSizeGb Gb."
        fi
        echo ""

        echo "Creating the swap file! This may take a few minutes."
        echo ""

        ############################
        ### Create the swap file ###
        ############################
        
        ### start the spinner:
        spinner &
        
        ### Note its PID:
        SPIN_PID=$!
        
        ### Kill the spinner on any signal, including our own exit.
        trap "kill -9 $SPIN_PID" $(seq 0 15)

        ### Convert gb to mb to avoid error: 
        mb=$(( gb * 1024 ))

        ### Create a swap file on root system and set file size to mb variable
        echo "-> Create swap file."
        echo ""
        dd if=/dev/zero of=/swapfile bs=1M count=$mb

        ### Set the rw permissions
        echo "-> Set swap file permissions."
        echo ""
        chmod 600 /swapfile

        ###  Mkswap file
        echo "-> Creating swap."
        echo ""
        mkswap /swapfile

        ### Enable the swap file for use
        echo "-> Turn on swap."
        echo ""
        swapon /swapfile

        echo ""

        ### Check and update (if needed) the fstab
        if grep -q "swap" /etc/fstab; then
            echo "-> The fstab contains a swap entry."
            #do nothing
        else
            echo "-> The fstab does not contain a swap entry. Adding an entry."
            echo "/swapfile swap swap defaults 0 0" >> /etc/fstab    
        fi

        echo ""
        echo "--> Done"
        echo ""

        exit 1
    }
}

function swapSetup() {
    {
        #check if swap is on
        isSwapOn=$(swapon -s | tail -1)

        if [[ "$isSwapOn" == "" ]]; then
            echo "No swap has been configured! Will create."
            echo ""

            createSwap
        else
            echo "Swap has been configured. Will remove and then re-create the swap."
            echo ""
            
            removeSwap
            createSwap
        fi

        echo 'Setup swap complete! Check output to confirm everything is good.'
    }
}

swapSetup

##### Notes #####
#Root
# lvresize /swap -L +2G (to increase swap by 2G)
# lvreduce /swap -L -1G (to reduce the swap by 1Gb)
#Drive
# lvresize /dev/swap -L +2G (to increase swap by 2G)
# lvreduce /dev/swap -L -1G (to reduce the swap by 1Gb)