#!/usr/bin/env bash

# Minecraft server automatic backup management script
# https://github.com/nicolaschan/minecraft-backup
# MIT License
#
# For Minecraft servers running in a GNU screen.
# For most convenience, run automatically with cron.

# Default Configuration 
SCREEN_NAME="" # Name of the GNU Screen or tmux pane your Minecraft server is running in
SERVER_WORLD="" # Server world directory
BACKUP_DIRECTORY="" # Directory to save backups in
MAX_BACKUPS=128 # -1 indicates unlimited
DELETE_METHOD="thin" # Choices: thin, sequential, none; sequential: delete oldest; thin: keep last 24 hourly, last 30 daily, and monthly (use with 1 hr cron interval)
COMPRESSION_ALGORITHM="gzip" # Leave empty for no compression
COMPRESSION_FILE_EXTENSION=".gz" # Leave empty for no compression; Precede with a . (for example: ".gz")
COMPRESSION_LEVEL=3 # Passed to the compression algorithm
ENABLE_CHAT_MESSAGES=false # Tell players in Minecraft chat about backup status
PREFIX="Backup" # Shows in the chat message
DEBUG=false # Enable debug messages
SUPPRESS_WARNINGS=false # Suppress warnings
WINDOW_MANAGER="screen" # Choices: screen, tmux

# Other Variables (do not modify)
DATE_FORMAT="%F_%H-%M-%S"
TIMESTAMP=$(date +$DATE_FORMAT)

log-fatal () {
  echo -e "\033[0;31mFATAL:\033[0m $*"
}
log-warning () {
  echo -e "\033[0;33mWARNING:\033[0m $*"
}

while getopts 'a:cd:e:f:hi:l:m:o:p:qs:vw:' FLAG; do
  case $FLAG in
    a) COMPRESSION_ALGORITHM=$OPTARG ;;
    c) ENABLE_CHAT_MESSAGES=true ;;
    d) DELETE_METHOD=$OPTARG ;;
    e) COMPRESSION_FILE_EXTENSION=".$OPTARG" ;;
    f) TIMESTAMP=$OPTARG ;;
    h) echo "Minecraft Backup"
       echo "Repository: https://github.com/nicolaschan/minecraft-backup"
       echo "-a    Compression algorithm (default: gzip)"
       echo "-c    Enable chat messages"
       echo "-d    Delete method: thin (default), sequential, none"
       echo "-e    Compression file extension, exclude leading \".\" (default: gz)"
       echo "-f    Output file name (default is the timestamp)"
       echo "-h    Shows this help text"
       echo "-i    Input directory (path to world folder)"
       echo "-l    Compression level (default: 3)"
       echo "-m    Maximum backups to keep, use -1 for unlimited (default: 128)"
       echo "-o    Output directory"
       echo "-p    Prefix that shows in Minecraft chat (default: Backup)"
       echo "-q    Suppress warnings"
       echo "-s    Screen name, tmux session name, or hostname:port:password for RCON"
       echo "-v    Verbose mode"
       echo "-w    Window manager: screen (default), tmux, RCON"
       exit 0
       ;;
    i) SERVER_WORLD=$OPTARG ;;
    l) COMPRESSION_LEVEL=$OPTARG ;;
    m) MAX_BACKUPS=$OPTARG ;;
    o) BACKUP_DIRECTORY=$OPTARG ;;
    p) PREFIX=$OPTARG ;;
    q) SUPPRESS_WARNINGS=true ;;
    s) SCREEN_NAME=$OPTARG ;;
    v) DEBUG=true ;;
    w) WINDOW_MANAGER=$OPTARG ;;
    *) log-fatal "Invalid option -$FLAG"; exit 1 ;;
  esac
done

rcon-command () {
  HOST="$(echo "$1" | cut -d: -f1)"
  PORT="$(echo "$1" | cut -d: -f2)"
  PASSWORD="$(echo "$1" | cut -d: -f3-)"
  COMMAND="$2"

  reverse-hex-endian () {
    # Given a 4-byte hex integer, reverse endianness
    while read -r -d '' -N 8 INTEGER; do
      echo "$INTEGER" | sed -E 's/(..)(..)(..)(..)/\4\3\2\1/'
    done
  }

  decode-hex-int () {
    # decode little-endian hex integer
    while read -r -d '' -N 8 INTEGER; do
      BIG_ENDIAN_HEX=$(echo "$INTEGER" | reverse-hex-endian)
      echo "$((16#$BIG_ENDIAN_HEX))"
    done
  }

  stream-to-hex () {
    xxd -ps
  }

  hex-to-stream () {
    xxd -ps -r
  }

  encode-int () {
    # Encode an integer as 4 bytes in little endian and return as hex
    INT="$1"
    # Source: https://stackoverflow.com/a/9955198
    printf "%08x" "$INT" | sed -E 's/(..)(..)(..)(..)/\4\3\2\1/' 
  }

  encode () {
    # Encode a packet type and payload for the rcon protocol
    TYPE="$1"
    PAYLOAD="$2"
    REQUEST_ID="$3"
    PAYLOAD_LENGTH="${#PAYLOAD}" 
    TOTAL_LENGTH="$((4 + 4 + PAYLOAD_LENGTH + 1 + 1))"

    OUTPUT=""
    OUTPUT+=$(encode-int "$TOTAL_LENGTH")
    OUTPUT+=$(encode-int "$REQUEST_ID")
    OUTPUT+=$(encode-int "$TYPE")
    OUTPUT+=$(echo -n "$PAYLOAD" | stream-to-hex)
    OUTPUT+="0000"
    
    echo -n "$OUTPUT" | hex-to-stream 
  }

  read-response () {
    # read next response packet and return the payload text
    HEX_LENGTH=$(head -c4 <&3 | stream-to-hex | reverse-hex-endian)
    LENGTH=$((16#$HEX_LENGTH))

    RESPONSE_PAYLOAD=$(head -c $LENGTH <&3 | stream-to-hex)
    echo -n "$RESPONSE_PAYLOAD"
  }

  response-request-id () {
    echo -n "${1:0:8}" | decode-hex-int
  }

  response-type () {
    echo -n "${1:8:8}" | decode-hex-int
  }

  response-payload () {
    echo -n "${1:16:-4}" | hex-to-stream
  }

  login () {
    PASSWORD="$1"
    encode 3 "$PASSWORD" 12 >&3

    RESPONSE=$(read-response "$IN_PIPE")

    RESPONSE_REQUEST_ID=$(response-request-id "$RESPONSE")
    if [ "$RESPONSE_REQUEST_ID" -eq -1 ] || [ "$RESPONSE_REQUEST_ID" -eq 4294967295 ]; then
      log-warning "RCON connection failed: Wrong RCON password" 1>&2
      return 1
    fi
  }

  run-command () {
    COMMAND="$1"
    
    # encode 2 "$COMMAND" 13 >> "$OUT_PIPE"
    encode 2 "$COMMAND" 13 >&3

    RESPONSE=$(read-response "$IN_PIPE")
    response-payload "$RESPONSE"
  }

  # Open a TCP socket
  # Source: https://www.xmodulo.com/tcp-udp-socket-bash-shell.html
  exec 3<>/dev/tcp/"$HOST"/"$PORT"

  login "$PASSWORD" || return 1
  run-command "$COMMAND"

  # Close the socket
  exec 3<&-
  exec 3>&-
}

if [[ $COMPRESSION_FILE_EXTENSION == "." ]]; then
  COMPRESSION_FILE_EXTENSION=""
fi

# Check for missing encouraged arguments
if ! $SUPPRESS_WARNINGS; then
  if [[ $SCREEN_NAME == "" ]]; then
    log-warning "Minecraft screen/tmux/rcon location not specified (use -s)"
  fi
fi
# Check for required arguments
MISSING_CONFIGURATION=false
if [[ $SERVER_WORLD == "" ]]; then
  log-fatal "Server world not specified (use -i)"
  MISSING_CONFIGURATION=true
fi
if [[ $BACKUP_DIRECTORY == "" ]]; then
  log-fatal "Backup directory not specified (use -o)"
  MISSING_CONFIGURATION=true
fi

if $MISSING_CONFIGURATION; then
  exit 1
fi

ARCHIVE_FILE_NAME=$TIMESTAMP.tar$COMPRESSION_FILE_EXTENSION
ARCHIVE_PATH=$BACKUP_DIRECTORY/$ARCHIVE_FILE_NAME

# Minecraft server screen interface functions
message-players () {
  local MESSAGE=$1
  local HOVER_MESSAGE=$2
  message-players-color "$MESSAGE" "$HOVER_MESSAGE" "gray"
}
execute-command () {
  local COMMAND=$1
  if [[ $SCREEN_NAME != "" ]]; then
    case $WINDOW_MANAGER in
      "screen") screen -S "$SCREEN_NAME" -p 0 -X stuff "$COMMAND$(printf \\r)"
        ;;
      "tmux") tmux send-keys -t "$SCREEN_NAME" "$COMMAND" ENTER
        ;;
      "RCON"|"rcon") rcon-command "$SCREEN_NAME" "$COMMAND"
        ;;
    esac
  fi
}
message-players-error () {
  local MESSAGE=$1
  local HOVER_MESSAGE=$2
  message-players-color "$MESSAGE" "$HOVER_MESSAGE" "red"
}
message-players-success () {
  local MESSAGE=$1
  local HOVER_MESSAGE=$2
  message-players-color "$MESSAGE" "$HOVER_MESSAGE" "green"
}
message-players-color () {
  local MESSAGE=$1
  local HOVER_MESSAGE=$2
  local COLOR=$3
  if $DEBUG; then
    echo "$MESSAGE ($HOVER_MESSAGE)"
  fi
  if $ENABLE_CHAT_MESSAGES; then
    execute-command "tellraw @a [\"\",{\"text\":\"[$PREFIX] \",\"color\":\"gray\",\"italic\":true},{\"text\":\"$MESSAGE\",\"color\":\"$COLOR\",\"italic\":true,\"hoverEvent\":{\"action\":\"show_text\",\"value\":{\"text\":\"\",\"extra\":[{\"text\":\"$HOVER_MESSAGE\"}]}}}]"
  fi
}

# Notify players of start
message-players "Starting backup..." "$ARCHIVE_FILE_NAME"

# Parse file timestamp to one readable by "date" 
parse-file-timestamp () {
  local DATE_STRING
  DATE_STRING="$(echo "$1" | awk -F_ '{gsub(/-/,":",$2); print $1" "$2}')"
  echo "$DATE_STRING"
}

# Delete a backup
delete-backup () {
  local BACKUP=$1
  rm "$BACKUP_DIRECTORY"/"$BACKUP"
  message-players "Deleted old backup" "$BACKUP"
}

# Sequential delete method
delete-sequentially () {
  local BACKUPS=("$BACKUP_DIRECTORY"/*)
  while [[ $MAX_BACKUPS -ge 0 && ${#BACKUPS[@]} -gt $MAX_BACKUPS ]]; do
    delete-backup "$(basename "${BACKUPS[0]}")"
    BACKUPS=("$BACKUP_DIRECTORY"/*)
  done
}

# Functions to sort backups into correct categories based on timestamps
is-hourly-backup () {
  local TIMESTAMP=$*
  local MINUTE
  MINUTE=$(date -d "$TIMESTAMP" +%M)
  return "$MINUTE"
}
is-daily-backup () {
  local TIMESTAMP=$*
  local HOUR
  HOUR=$(date -d "$TIMESTAMP" +%H)
  return "$HOUR"
}
is-weekly-backup () {
  local TIMESTAMP=$*
  local DAY
  DAY=$(date -d "$TIMESTAMP" +%u)
  return "$((DAY - 1))"
}

# Helper function to sum an array
array-sum () {
  SUM=0
  for NUMBER in "$@"; do
    (( SUM += NUMBER ))
  done
  echo "$SUM"
}

# Thinning delete method
delete-thinning () {
  # sub-hourly, hourly, daily, weekly is everything else
  local BLOCK_SIZES=(16 24 30)
  # First block is unconditional
  # The next blocks will only accept files whose names cause these functions to return true (0)
  local BLOCK_FUNCTIONS=("is-hourly-backup" "is-daily-backup" "is-weekly-backup")

  # Warn if $MAX_BACKUPS does not have enough room for all the blocks
  TOTAL_BLOCK_SIZE=$(array-sum "${BLOCK_SIZES[@]}")
  if [[  $MAX_BACKUPS != -1 ]] && [[ $TOTAL_BLOCK_SIZE -gt $MAX_BACKUPS ]]; then
    if ! $SUPPRESS_WARNINGS; then
      log-warning "MAX_BACKUPS ($MAX_BACKUPS) is smaller than TOTAL_BLOCK_SIZE ($TOTAL_BLOCK_SIZE)"
    fi
  fi

  local CURRENT_INDEX=0
  local BACKUPS=("$BACKUP_DIRECTORY"/*) # List newest first

  for BLOCK_INDEX in "${!BLOCK_SIZES[@]}"; do
    local BLOCK_SIZE=${BLOCK_SIZES[BLOCK_INDEX]}
    local BLOCK_FUNCTION=${BLOCK_FUNCTIONS[BLOCK_INDEX]}
    local OLDEST_BACKUP_IN_BLOCK_INDEX=$((BLOCK_SIZE + CURRENT_INDEX)) # Not an off-by-one error because a new backup was already saved 
    local OLDEST_BACKUP_IN_BLOCK
    OLDEST_BACKUP_IN_BLOCK="$(basename "${BACKUPS[OLDEST_BACKUP_IN_BLOCK_INDEX]}")"

    if [[ "$OLDEST_BACKUP_IN_BLOCK" == "" ]]; then
      break
    fi

    local OLDEST_BACKUP_TIMESTAMP
    OLDEST_BACKUP_TIMESTAMP=$(parse-file-timestamp "${OLDEST_BACKUP_IN_BLOCK:0:19}")
    local BLOCK_COMMAND="$BLOCK_FUNCTION $OLDEST_BACKUP_TIMESTAMP"

    if $BLOCK_COMMAND; then
      # Oldest backup in this block satisfies the condition for placement in the next block
      if $DEBUG; then
        echo "$OLDEST_BACKUP_IN_BLOCK promoted to next block" 
      fi
    else
      # Oldest backup in this block does not satisfy the condition for placement in next block
      delete-backup "$OLDEST_BACKUP_IN_BLOCK"
      break
    fi

    ((CURRENT_INDEX += BLOCK_SIZE))
  done

  delete-sequentially
}

# Ensure directory exists
mkdir -p "$(dirname "$ARCHIVE_PATH")"

# Disable world autosaving
execute-command "save-off"

# Backup world
START_TIME=$(date +"%s")
case $COMPRESSION_ALGORITHM in
  # No compression
  "") tar -cf "$ARCHIVE_PATH" -C "$SERVER_WORLD" .
    ;;
  # With compression
  *) tar -cf - -C "$SERVER_WORLD" . | $COMPRESSION_ALGORITHM -cv -"$COMPRESSION_LEVEL" - > "$ARCHIVE_PATH" 2>> /dev/null
    ;;
esac
sync
END_TIME=$(date +"%s")

# Enable world autosaving
execute-command "save-on"

# Save the world
execute-command "save-all"

# Delete old backups
delete-old-backups () {
  case $DELETE_METHOD in
    "sequential") delete-sequentially
      ;;
    "thin") delete-thinning
      ;;
  esac
}

# Notify players of completion
WORLD_SIZE_BYTES=$(du -b --max-depth=0 "$SERVER_WORLD" | awk '{print $1}')
ARCHIVE_SIZE_BYTES=$(du -b "$ARCHIVE_PATH" | awk '{print $1}')
ARCHIVE_SIZE=$(du -h "$ARCHIVE_PATH" | awk '{print $1}')
BACKUP_DIRECTORY_SIZE=$(du -h --max-depth=0 "$BACKUP_DIRECTORY" | awk '{print $1}')
TIME_DELTA=$((END_TIME - START_TIME))

# Check that archive size is not null and at least 200 Bytes
if [[ "$WORLD_SIZE_BYTES" -gt 0 && "$ARCHIVE_SIZE" != "" && "$ARCHIVE_SIZE_BYTES" -gt 200 ]]; then
  COMPRESSION_PERCENT=$((ARCHIVE_SIZE_BYTES * 100 / WORLD_SIZE_BYTES))
  message-players-success "Backup complete!" "$TIME_DELTA s, $ARCHIVE_SIZE/$BACKUP_DIRECTORY_SIZE, $COMPRESSION_PERCENT%"
  delete-old-backups
else
  message-players-error "Backup was not saved!" "Please notify an administrator"
fi