#!/bin/sh

# Generic Backup Script
# This script takes no arguments and is designed to be run from anywhere.
# Cron it out, have fun. This is generic enough to be used anywhere by just
# about anything.
#
# MIT License
#
# Copyright (c) 2017 Tom "SamuraiLink3" Webster
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

# The command you will use to backup data (create a tar file, mysqldump, psql,
# etc.). The backup command redirects output to the backup filename. If you're
# using tar, don't write the output to a file, the script will take care of that
# automatically.
backup_command="/usr/bin/wget https://s3.samurailink3.com/public/WhistleCrewWiki.tar.gz -O -"

# Optionally filter the backup data through compression. If you're doing stream
# compression, like with tar, additional compression won't help you. If you're
# using something like mysqldump, additional compression can save you a decent
# amount of space. Leaving this as "" will disable compression piping.
compression_command=""

# Where you want your backup files stored.
# NO TRAILING SLASH!
# USE ABSOLUTE PATHS!!!
# Like this: `/home/backups`
# NOT LIKE THIS: `/home/backups/`
backup_directory="/home/samurailink3/WhistleCrewWikiBackups"

# The prefix and suffix of the backup file you will create. This is helpful if
# you have multiple types of backups (databases and flat files, for instance) in
# the same backup directory.
# The filename will look like PREFIX-TIMESTAMP.SUFFIX
backup_filename_prefix="WhistleCrewWiki"
backup_filename_suffix="tar.gz"

# How many backups do you want to keep before rolling the oldest one off?
number_of_backups_to_keep="28" # Every 6 hours, 4 times per day, keep 1 week

# The filename that will store the timestamp of any/all failed backups. This
# file will be located in the backup_directory.
failure_log_filename="FAILURE.LOG"

##
## From this point on, the script starts.
## You shouldn't need to configure anything below this block.
##

# Exit on pipeline error
set -e
# Exit on undefined variable
set -u

# Create the backups directory
mkdir -p $backup_directory

# Increment the number of backups to keep, this keeps our tail pipe chain sane.
_=$((number_of_backups_to_keep=$number_of_backups_to_keep+1))

# Create a timestamp variable.
# The benefit to this date format (other than it being a widely used standard)
# is that it naturally sorts into chronological order, making our `ls -l` stupid
# easy. We're stripping ':' because some filesystems don't like it.
timestamp=`date -u +%FT%T%zs | tr -d ":"`

# This stores the backup data into a temp file, it will be compressed, and
# archived later. We are checking the return code after the command has run. You
# don't want mysqldump (or whatever you're using) to crash with exit code 1,
# then you carry on your merry way. That would make for a really bad late-night
# recovery, finding out that your 'backups' aren't really backups.

if [ "$compression_command" = "" ]; then
  echo "Starting backup command: $backup_command"
  $backup_command > $backup_directory/$backup_filename_prefix-$timestamp.$backup_filename_suffix
else
  echo "Starting backup command: $backup_command | $compression_command"
  $backup_command | $compression_command > $backup_directory/$backup_filename_prefix-$timestamp.$backup_filename_suffix
fi
# If the exit code of the previous command was not '0', freak out and exit.
# You can do what you want to here, kick off an email, shut down the system,
# format the root partition, whatever. Right now, I'm just echoing a failure
# message and exiting with code 1 (failure).
if [ "$?" = 0 ]
then
  echo "Backup command complete."
else
  if [ $compression_command = "" ]; then
    echo "$timestamp: Backup command failed. [$backup_command]" >> $backup_directory/$failure_log_filename
  else
    echo "$timestamp: Backup command failed. [$backup_command | $compression_command]" >> $backup_directory/$failure_log_filename
  fi
  exit 1
fi

# Let's break down this pipe (Unix):
#   `find -E $backup_directory/ -regex "$backup_directory/$backup_filename_prefix-.*\.$backup_filename_suffix":`
#     We're going to look for all backup files in the backup directory and return
#     a list of them.
#   `sort`
#     Next, sort the list so we can chop out the ones to remove. Otherwise we
#     could remove something we need.
#   `awk '{a[i++]=$0} END {for (j=i-1; j>=0;) print a[j--] }'`
#     Reverse the list so we can chop out the files we want to keep.
#   `tail -n +$number_of_backups_to_keep`
#     Here, we're going to start at the number of backups we want to keep
#     (plus one, so the line count works appropriately).
#   `awk '{a[i++]=$0} END {for (j=i-1; j>=0;) print a[j--] }'`
#     Re-Reverse the list for readability.

to_remove=`find $backup_directory/ -type f -name "$backup_filename_prefix-*.$backup_filename_suffix" | sort | awk '{a[i++]=$0} END {for (j=i-1; j>=0;) print a[j--] }' | tail -n +$number_of_backups_to_keep | awk '{a[i++]=$0} END {for (j=i-1; j>=0;) print a[j--] }'`
# Then grab the count here. If it's '0', we're not going to delete anything
to_remove_count=`find $backup_directory/ -type f -name "$backup_filename_prefix-*.$backup_filename_suffix" | sort | awk '{a[i++]=$0} END {for (j=i-1; j>=0;) print a[j--] }' | tail -n +$number_of_backups_to_keep | awk '{a[i++]=$0} END {for (j=i-1; j>=0;) print a[j--] }' | wc -l`

if [ $to_remove_count -eq 0 ]
then
  echo "No backup files to remove."
else
  echo "Removing these files:
$to_remove"
  # Figure out where we are
  you_are_here=`pwd`
  # Head out to the backup directory
  cd $backup_directory || exit 1
  # Clean up the old backup files
  rm $to_remove
  # Head back to where you were
  cd $you_are_here || exit 1
fi

echo "Cleanup Complete!"
exit 0