#!/usr/bin/env bash
#
# zectl-prune is used by zectl-hook to rotate Boot Environments

# Tests

if [ "$EUID" -ne 0 ]
  then echo "Please run as root"
  exit
fi

# Vars

# Set where zectl is installed
PATH="$PATH:/usr/bin"
BIN=/usr/bin/zectl
# Get current script name
FILENAME="$(basename "$(test -L "$0" && readlink "$0" || echo "$0")")"
# String to prepend to boot env name
PREFIX="pacmanhook"

# Functions

print () {
    echo -e "\033[1m• $1\033[0m"
}

usage(){ 
    echo "Usage: $FILENAME [options]" 
    echo "-h : afficher l'aide"  
    exit
}

# Get a value from zectl
get_value () {
    value=$("$BIN" get -H "$1" | awk '{print $2}')
    if [[ $value =~ \t- ]]
    then
        return 1
    else
        echo "$value"
    fi

}

# Create a boot env prepended with prefix
zectl_create () {
    bename="$PREFIX-$(date +'%Y%m%dT%H%M%S')"
    $BIN create "$bename" && print "Created $bename"
}

# List boot env by prefix, and omit booted|activated
zectl_list () {
    # TOFIX: sort https://github.com/johnramsden/zectl/issues/18
    # Here: sorting on the be name which contains date
    $BIN list -H | grep "$PREFIX" | grep -Ev '\s+N\s+|\s+NR\s+|\s+R\s+' | sort -k1
}

# Remove latest prefixed boot env 
zectl_purge () {
    latest=$(zectl_list | head -n1 | awk '{print $1}')
    if [[ ! -z $latest ]]
    then
        $BIN destroy "$latest" && print "Destroyed $latest"
    fi
}

# Args

while getopts "h" option; do
    case "${option}" in
        h)
            usage
            ;;
        *)
            usage
            ;;
    esac
done
shift $((OPTIND-1))

# Main

# Get how many boot env to keep from zectl
prune_count=$(get_value pacmanhook-prunecount)

# Test if value is numeric
if [[ $prune_count =~ ^[0-9]+$ ]]
then

    # If keep number is not reach, create a boot env
    if [[ $(zectl_list | wc -l) -lt "$prune_count" ]]
    then
        zectl_create
    # Else remove the latest and create a boot env
    else
        zectl_purge
        zectl_create
    fi
else
    echo 'error: please run "zectl set pacmanhook-prunecount=X" where "X" is the number of boot environment to keep when rotating.'
fi