#!/usr/bin/env bash

set -Eeo pipefail
trap 's=$?; echo >&2 "$0: Error on line "$LINENO": $BASH_COMMAND"; exit $s' ERR


declare -r PATH_TO_SNAPSHOT_DIRECTORY='/.snapshots'
declare -r MAX_AGE_DAYS=14
declare -r SECONDS_IN_DAY=$((24 * 60 * 60))

function update {

    local snapshot_name
    snapshot_name=$(date --iso-8601=seconds)

    local path_to_snapshot="${PATH_TO_SNAPSHOT_DIRECTORY}/${snapshot_name}"

    btrfs subvolume snapshot -r / "${path_to_snapshot}"

    su --shell /bin/sh --command 'paru -Syu --noconfirm --noprogressbar' system-updater
}

function cleanup_snapshots {

    function get_file_age_days {

        local file_name=$1

        local current_date_epoch
        current_date_epoch=$(date +%s)

        local file_creation_date_epoch
        file_creation_date_epoch=$(date --date="${file_name}" +%s)


        local file_age_days=$(( (current_date_epoch - file_creation_date_epoch) / SECONDS_IN_DAY ))

        printf '%u' "${file_age_days}"
    }


    for path_to_snapshot in $(find ${PATH_TO_SNAPSHOT_DIRECTORY}/* -prune -print | sort -r); do

        local snapshot_name
        snapshot_name=$(basename "${path_to_snapshot}")

        local age_days
        age_days=$(get_file_age_days "${snapshot_name}")

        if [ "${age_days}" -lt ${MAX_AGE_DAYS} ]; then
            printf "Skipping '%s'. Age in days is %u\n" "${path_to_snapshot}" "${age_days}"
        else
            btrfs subvolume delete "${path_to_snapshot}"
        fi
    done
}

if [ "${EUID}" -ne 0 ]; then
    printf 'You must run the script with root privileges\n'
    exit 1
fi

case "${1}" in
    '--update') 
        update
        cleanup_snapshots
    ;;
    '--cleanup')
        cleanup_snapshots
    ;;
    *)
        printf 'Usage: system-update options\n'
        printf '\n'
        printf 'Options:\n'
        printf '    --update        Create btrfs snapshot of root subvolume, update system using paru, cleanup snapshots\n'
        printf '    --cleanup       Cleanup snapshots\n\n'
        printf '\n'
    ;;
esac