#!/bin/bash

## README
#
# Automatic PostgreSQL backup script
# Version:        v1.0.0
# Author:         Emzi0767
# Usage:
#  ./backup_db.sh <database> <username> <password> <max_count>
#
# Use with cron. This script will automatically backup your
# PostgreSQL database, compress the backup

NAME="Automatic PostgreSQL backup script"
VERSION="v1.0.0"
AUTHOR="Emzi0767"
USAGE="./backup_db.sh <database> <username> <password> <max_count>"

do_backup() {
	echo "Beginning database backup..."

	#############################
	# Backup initialisation logic
	#############################

	targetdir="/home/emzi0767/dat/db_backups/$1"

	# Check if the directory doesn't exist, and if it doesn't, create it
	if [ ! -d "$targetdir" ]
	then
		echo "Target directory ($targetdir) doesn't exist, creating"
		mkdir "$targetdir"
	fi

	# Enter the target directory
	cd "$targetdir"

	#############################
	# Postgres backup logic
	#############################

	filename="$1_$(date +%s).sql"

	echo "Database: $1"
	echo "Username: $2"
	echo "Target:   $filename"

	# Dump the database
	PGPASSWORD="$3" pg_dump -U "$2" -d "$1" > "$filename"

	echo "Postgres dump completed, compressing"

	xz -z9e "$filename"

	echo "Completed"

	#############################
	# Backup trimming logic
	#############################

	files=$(ls -1 | grep '\.sql$' | tail -n +$4)
	filecount=$(echo -n "$files" | wc -l)

	echo "Trimming backups to $4 latest"
	echo "Will remove $filecount files"

	for i in $files
	do
		echo "Removed $i"
		rm $i
	done

	echo "Backups trimmed"
}

print_usage() {
	echo "$NAME $VERSION by $AUTHOR"
	echo "Usage:"
	echo "  $USAGE"
}

if [ "$1" == "--help" ] || [ "$1" == "-h" ]
then
	print_usage
elif [ -z "$1" ] || [ -z "$2" ] || [ -z "$3" ] || [ -z "$4" ]
then
	print_usage
else
	do_backup "$1" "$2" "$3" "$4"
fi