#!/bin/bash


#full
full() {
	echo "[full]"
	
	#mark running
	touch ${dst_dir}/running

	#max_backups must >= 2
	[ $max_backups -lt 2 ] && max_backups=2 
	
	#get old_backups
	old_backups=$(ls ${dst_dir}/full | wc -l)
	echo "!$old_backups!"

	#delete old backups to max_backups-1
	while [ ${old_backups} -ge ${max_backups} ]
	do
		oldest_dir=$(ls ${dst_dir}/full | sort -n | head -n 1) #find oldest dir by name
		rm -r ${dst_dir}/full/${oldest_dir}
		rm -r ${dst_dir}/diff/${oldest_dir}
		echo "remove ${oldest_dir}"
		old_backups=$((old_backups-1))
	done
	
	#create new backup dir
	mkdir ${dst_dir}/full/$(date +"%F")
	mkdir ${dst_dir}/diff/$(date +"%F")
	
	rsync -av $src_dir ${dst_dir}/full/$(date +"%F")/

	rm ${dst_dir}/running
}


#diff
diff() {
	echo "[diff]"

	#mark running
	touch ${dst_dir}/running

	#max_backups must >= 2
	[ $max_backups -lt 2 ] && max_backups=2 
	
	#find newest full dir by name
	newest_full=$(ls ${dst_dir}/full | sort -rn | head -n 1) 

	#get old_backups
	old_backups=$(ls ${dst_dir}/diff/${newest_full} | wc -l)
	echo "!$old_backups!"

	#delete old backups to max_backups-1
	while [ ${old_backups} -ge ${max_backups} ]
	do
		oldest_dir=$(ls ${dst_dir}/diff/${newest_full} | sort -n | head -n 1) #find oldest dir by name
		rm -r ${dst_dir}/diff/${newest_full}/${oldest_dir}
		echo "remove ${oldest_dir}"
		old_backups=$((old_backups-1))
	done
	
	#create new backup dir
	mkdir ${dst_dir}/diff/${newest_full}/$(date +"%F_T%H")
	
	rsync -av $src_dir ${dst_dir}/diff/${newest_full}/$(date +"%F_T%H")/ --link-dest=../../../full/${newest_full}/

	rm ${dst_dir}/running

}


#init
init() {
	echo "[init]"

	#check src_dir readable
	[ ! -r $src_dir ] && echo "src_dir cannot read"

	#check dst_dir writeable
	if [ ! -w $dst_dir ]; then
		echo "dst_dir cannot write"
	else
		#create needed dir
		mkdir ${dst_dir}/full
		mkdir ${dst_dir}/diff
		echo "init ok"
	fi
}


#------------main-------------#

#assign arg to var
src_dir=$3
dst_dir=$4
mode=$1
max_backups=$2

#check init only
if [[ $src_dir == "" ]] || [[ $dst_dir == "" ]] ; then
	echo no src_dir or dst_dir input
	exit 1
fi

#set src_dir end without /
if [[ $src_dir == */ ]]; then
	src_dir=${src_dir%?}
fi
#set dst_dir end without /
if [[ $dst_dir == */ ]]; then
	dst_dir=${dst_dir%?}
fi

#input debug
#echo "$mode $src_dir $dst_dir"

#check if other processing running
if [ -f ${dst_dir}/running ]; then
	echo "other processing running"
	exit 2
fi

#mode
if [ $mode == "full" ]; then
	full
elif [ $mode == "diff" ]; then
	diff
elif [ $mode == "init" ]; then
	init
else
	echo "no mode select"
	#exit 4
fi

#debug
#echo $(ls ${dst_dir}/full | sort -n | head -n 1)