#!/usr/bin/env bash
#
# Ramdir creates a reverse-syncing ram drive of any directory
#
# Copyright (C) 2017  Aaron Ball <nullspoon@oper.io>
# 
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#


syncback() {
  local src=${1}
  local dst=${2}
  rsync -a "${src}/" "${dst}/"
}

shutdown() {
  local src=${1}
  local dst=${2}

  printf "\nShutting down\n" >&2

  printf "Final sync back to disk\n"
  syncback "${src}" "${dst}"
  printf "Unmounting %s\n" "${src}"
  sudo umount "${src}"
  printf "Removing %s\n" "${src}"
  sudo rm -rf "${src}"
  exit 0
}

setup() {
  local src=${1}

  local owner # Placeholder for current user name
  local group # Placeholder for current user group name

  # Get directory size
  #                     This is a tab -v-
  origsize=$(du -sm "${src}" | cut -d '	' -f 1)
  newsize=$(( origsize + 500 ))
  
  owner=$(id -u)
  group=$(id -g)
  
  # Create a temp mount destination
  mount="$(sudo mktemp -d /mnt/superspeed.XXXXX)"
  if [ $? -gt 0 ]; then
    printf "Error creating temp mount point.\n" >&2
    return 1
  fi
  
  # Mount
  sudo mount -t tmpfs tmpfs -o size=${newsize}M "${mount}" >&2
  sudo chown ${owner}:${group} ${mount}
  sudo chmod 750 ${mount}

  printf "${mount}"
}

run() {
  local base=${1}
  local bin=${2}

  chmod +x ${base}/${bin}
  ${base}/${bin}
}

main() {
  local path=${1} # Path of software to speed up to 11
  local mount     # Path for ram drive
  local syncstart # Start time of sync disk to ramdrive process
  local syncend   # End time of sync disk to ramdrive process
  
  if [ -z ${path} ]; then
    printf "Path to turbo speed required\n"
    return 1
  fi
  
  # Set up the mount
  mount=$(setup "${path}")
  [ $? -gt 0 ] && return 1

  # Set up our shutdown trigger
  trap "shutdown ${mount} ${path}" SIGINT
  
  # Sync to temp mountpoint
  syncstart=$(date '+%s')
  syncback "${path}" "${mount}"
  syncend=$(date '+%s')

  # Print the transfer time
  printf "Finished sync to ramdrive in %d seconds\n" $(( syncend - syncstart ))
  # Notify when ready
  printf "Your files are available at super speed at ${mount}\n"
  
  # Sync to temp mountpoint
  while true; do
    printf "%s   Syncing %s back to disk\n" "$(date '+%F %T')" "${mount}"
    syncback "${mount}" "${path}"
    sleep 30
  done
}

main ${@}