#!/usr/bin/env bash


    ## ## ## ## ## ## ## ## ## ## ## ## ## ##
   ##                                       ##
  ##           btrfs-snapshots.sh            ##
 ##                                           ##
 ##    Take read-only snapshots of BTRFS      ##
  ##              subvolumes                 ##
   ##                                       ##
    ## ## ## ## ## ## ## ## ## ## ## ## ## ##


##
## Information
## (don't touch unless you are me)
##

NAME="btrfs-snapshots.sh"
VERSION="0.2.0"
AUTHOR="david@socialnerds.org"
LICENSE="MIT"
DESCRIPTION="Take read-only snapshots of BTRFS subvolumes."
WEBSITE="https://git.socialnerds.org/david/scripts"
CHANGELOG=("[2023-10-26][v0.2.0] Complete rewrite"
           "[2021-01-01][v0.1.0] Initial version")


##
## Configuration
##

EXECUTABLE="$(basename $0)"
LIBRARIES="lib.sh"
DEPENDENCIES="basename dirname readlink ln mkdir rm ls date btrfs"
REQUIRE_ROOT=1

SUBVOLUMES="/"
DESTINATION_ROOT=/srv/snapshots

PREFIX="snapshot-"
TIMESTAMP=$(date +%Y%m%d%H%M) #add %S if you want sub-minute snapshots
NAME="$PREFIX$TIMESTAMP"

# How many snapshots should be kept?
MAX_SNAPSHOTS=32


##
## Functions
##

# Print help information
function print_help() {
  printf "%s\n\n%s\n%b\n\n%s\n  %-15s %s\n  %-15s %s\n  %-15s %s\n  %-15s %s\n" \
         "$DESCRIPTION" "Usage:" "$LIB_BOLD$EXECUTABLE <options> <subvolume>$LIB_CLEAR" "Options:" \
         "-h, --help" "Print help screen and exit" \
         "-i, --info" "Print script information and exit" \
         "-v, --verbose" "More verbose output" \
         "-q, --quiet" "No output except errors (overrides -v)"
}


##
## Preflight
##

# Load BASH libraries
SCRIPT_PATH=$(readlink -f "$0")
SCRIPT_DIR=$(dirname "$SCRIPT_PATH")
for LIBRARY in $LIBRARIES; do
  if [[ -r "$SCRIPT_DIR/$LIBRARY" ]]; then
    #echo "Loading library file [$SCRIPT_DIR/$LIBRARY]"
    source "$SCRIPT_DIR/$LIBRARY"
  else
    echo "Error: Cannot load library file [$SCRIPT_DIR/$LIBRARY]"
    exit 1
  fi
done

# Check for root privileges
if ! lib_amiroot && [[ $REQUIRE_ROOT -eq 1 ]]; then
  lib_print "!You need to have root privileges"
  exit 1
fi

# Check for dependencies
MISSING_COMMANDS=$(lib_missing_commands $DEPENDENCIES)
if [[ -n "$MISSING_COMMANDS" ]]; then
  lib_print "!One or more commands missing [$MISSING_COMMANDS]"
  lib_print "Try installing them with your package manager"
  exit 1
fi


##
## Liftoff
##
exit 0
# take the snapshots
for SUBVOLUME in $SUBVOLUMES; do
    if [ -z ${SUBVOLUME#/} ]; then
        SNAPSHOT_PATH="$DESTINATION_ROOT"
    else
	PATH="$DESTINATION_ROOT/${SUBVOLUME#/}"
    fi
    if [ ! -d $SNAPSHOT_PATH ]; then
        echo "warning: snapshot path ($SNAPSHOT_PATH) does not yet exist. creating."
        mkdir -p $SNAPSHOT_PATH
    fi
    if [ -d $SNAPSHOT_PATH/$NAME ]; then
        echo "warning: snapshots with same name already exists. skipping."
    else
	#TODO: handle failed snapshots and failed link creations
        btrfs -q subvolume snapshot -r $SUBVOLUME $SNAPSHOT_PATH/$NAME
	if [ -h $SNAPSHOT_PATH/latest ]; then
	    rm $SNAPSHOT_PATH/latest
	fi
        ln -sf $SNAPSHOT_PATH/$NAME $SNAPSHOT_PATH/latest
    fi
done

# Delete old snapshots
SNAPSHOTS=$(ls -r $SNAPSHOT_PATH | grep $PREFIX)
i=0
for SNAPSHOT in $SNAPSHOTS; do
    if [ $i -ge $MAX_SNAPSHOTS ]; then
	#TODO: handle failed snapshot deletions
	btrfs -q subvolume delete $SNAPSHOT_PATH/$SNAPSHOT
    fi
    i=$((i+1))
done


##
## Here be dragons
##

exit 0