#!/bin/bash
#
# This script dumps the PostgreSQL db in a Docker container
# managed by Docker Compose using the selected command within
# the database container and pipes the results into an
# appropriately named/dated file...
#
# It also manages rolling out older backups to avoid filling
# your storage...
#
# Default retention
BU_TO_KEEP_HOURLY=24
BU_TO_KEEP_DAILY=7
BU_TO_KEEP_WEEKLY=4
BU_TO_KEEP_MONTHLY=12
BU_TO_KEEP_YEARLY=7
#
BU_FROOT=alldbs
BU_FROOT_HOURLY=hourly
BU_FROOT_DAILY=daily
BU_FROOT_WEEKLY=weekly
BU_FROOT_MONTHLY=monthly
BU_FROOT_YEARLY=yearly
#
# this can be overridden at invocation
BU_CONF=default-docker-compose.conf
# # output for debugging...
VERBOSE=0
#
# Stuff that should be universal for this install...
# where we can find this app...
MAIN_DIR=/etc/dbbackup
# determine today's date
DATE=`date   '+%Y-%m-%d-%a'`
# determine today's date
TIME=`date   '+%H-%M-%S'`
# temporary holding point for email
TMP_EMAIL=/tmp/tmp_dbbackup_email.$DATE_$TIME
# log file
LOG=/var/log/dbbackup.log
#
# Commands
# gzip command
GZIP=`which gzip`
# grep command
GREP=`which grep`
# email program
MAIL=`which mail`
# database dump utility
DC=`which docker-compose`
#DEF_ARGS="-C -d -O -x"
#
# pattern for "ls" command to build list of
# pruneable backup files...
# -1t = 1 column, ordered by time of last mod
PRUNEABLES_CMD="ls -1t"
# function to direct a message...
message() {
  #
  # a timestamp for logging purposes
  TIMESTAMP=`date  '+%Y-%m-%d %H:%M.%S'`
  echo "$0: $TIMESTAMP $@" >> $LOG
  if test -f $TMP_EMAIL ; then
    echo "$0: $TIMESTAMP $@" >> $TMP_EMAIL
  fi
  verbose "$TIMESTAMP $@"
}
# create the temporary email file
create_tmp_email() {
  touch $TMP_EMAIL
  if test -f $TMP_EMAIL ; then
    message "created temporary email  $TMP_EMAIL"
  else
    message "failed to create temporary email  $TMP_EMAIL"
  fi
}
# send the contents of the temporary file to the
# designated report recipient
send_email_report() {
  if test -f $TMP_EMAIL ; then
    message "sending email report to $EMAIL"
    $MAIL -s "$EMAIL_SUBJ" $EMAIL < $TMP_EMAIL
    rm $TMP_EMAIL
    if test -f $TMP_EMAIL ; then
      message "failed to remove temporary email  $TMP_EMAIL"
    else
      message "successfully removed temporary email  $TMP_EMAIL"
    fi
    message "email report successfully sent"
  fi
}
# insert a blank line into the log and on the console
insert_blank() {
  echo "" >> $LOG
  verbose ""
}
# function to direct a message...
verbose() {
  if test $VERBOSE = 1 ; then
    echo "$@"
  fi
}
#
# delete old backups
delete_old() {
  #
  verbose "deleting old files based on $1"
  # pattern to search for to build the list...
  PATTERN="$BU_DIR/$1-*.*"
  # build the list, with the suffix...
  PRUNEABLES=`$PRUNEABLES_CMD $PATTERN`
  if  test "$?" -eq "0" ; then
    message "pruning older files based on $PATTERN"
    BU_TO_KEEP=$2
    message "keeping last $BU_TO_KEEP backups"
    #
    # set counter
    NUM=0
    # go through the list of files and remove those we don't want
    for PRUNEABLE in $PRUNEABLES
    do
      NUM=$(($NUM + 1))
      if test $NUM -gt $BU_TO_KEEP ; then
        message "deleting $PRUNEABLE"
        rm $PRUNEABLE 2>&1 > /dev/null
      else
        message "keeping $PRUNEABLE"
      fi
    done
  else
    message "No files with $PATTERN to delete"
  fi
}
#
#
do_backup() {
   FILE=$1
   VER=`$DC exec $DC_CONTAINER pg_config --version`
   verbose "Postgres version $VER - echoing to backup: $FILE"
   echo "--" > $FILE
   echo "-- PostgreSQL Version: $VER" >> $FILE
   echo "--" >> $FILE
   echo "" >> $FILE
   CMD="$DC exec $DC_CONTAINER $DUMP_CMD"
   verbose "doing database dump: $CMD"
   $CMD >> $FILE
}

#
# cycle through the command line options
while test $# -ne 0 ; do
  case $1 in
    --config|-c)
      shift # shift from the flag to the value
      verbose "setting configuration directory to $1"
      BU_CONF=$1
    ;;
    --hourly|-h)
      verbose "running hourly backup"
      TASK=HOURLY
    ;;
    --daily|-d)
      verbose "running daily backup"
      TASK=DAILY
    ;;
    --weekly|-w)
      verbose "running weekly backup"
      TASK=WEEKLY
    ;;
    --monthly|-m)
      verbose "running monthly backup"
      TASK=MONTHLY
    ;;
    --yearly|-y)
      verbose "running yearly backup"
      TASK=YEARLY
    ;;
  esac
  shift
done
#
#
# create the blank email report
create_tmp_email
#
if test -f $MAIN_DIR/$BU_CONF ; then
    verbose "Reading default in $MAIN_DIR/$BU_CONF"
    source $MAIN_DIR/$BU_CONF
else
    message "ERROR: Couldn't find or read $MAIN_DIR/$BU_CONF"
    exit 1
fi
#
# run through the various tasks
verbose "using configuration file $BU_CONF"
# go to the Docker Compose directory where we need to be to run the
# docker-compose commands
verbose "going to $DC_DIR"
OLD_DIR=`pwd`
cd $DC_DIR
#
# a timestamp for logging purposes
STAMP=`date  '+%Y-%m-%d_%H-%M-%S'`
#
# generate the filename
INC="BU_FROOT_$TASK"
FILEPART=$BU_FROOT-${!INC}
FILENAME=$FILEPART-$STAMP.sql
FILEPATH=$BU_DIR/$FILENAME
#
# delete stale backups
TO_KEEP="BU_TO_KEEP_$TASK"
delete_old $FILEPART ${!TO_KEEP}
#
message "backing up all the databases into $FILEPATH"
# dump the data into the file
#
do_backup $FILEPATH $TASK
#
message "completed backup"
# compress the backup
message "compressing $FILEPATH"
$GZIP $FILEPATH
# return to where you started from...
cd $OLD_DIR
#
# sent resulting email report
#
send_email_report
exit 0