#!/usr/bin/env bash
#
# destination - functions acting on the destination host.
#
# Copyright 2015 - 2019 Einhard Leichtfuß
#
# This file is part of rsync-backup.
#
# rsync-backup is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# rsync-backup 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 Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with rsync-backup.  If not, see <https://www.gnu.org/licenses/>.
#


# Setup working directory on the destination files system.
#
# requires: create_new_dir
#
function dest_prepare_initial
{
	create_new_dir "$dest_path" || return $?
	create_new_dir "${dest_path}/work" || return $?

	return $RET_SUCCESS
}


# Setup working directory on the destination file system, check for too new
# (future) backups and refresh the 'latest' symlink.
#
# requires: assert_is_dir, dest_list_backup_dirs, create_new_dir
#           $dest_path
#
# $1: old date: date in $DATEFMT
# $2: new date: date in $DATEFMT
#
function dest_prepare_incremental
{
	local work_dir="${dest_path}/work"
	local old_date="$1"
	local new_date="$2"
	local latest

	assert_is_dir "$dest_path" || return $?
	
	latest="$(dest_list_backup_dirs | tail -1)"

	if [[ "$old_date" != "$latest" ]]
	then
		error "Dates of last backup do not match on source and destination."
		debug_error "source: ${old_date} | dest: ${latest}"
		return $RET_FILE_ERR
	fi

	if ! [[ "$latest" < "$new_date" ]]
	then
		error "Latest backup on destination not older than source."
		return $RET_FILE_ERR
	fi

	# Refresh 'latest' symlink in case it was obsoleted or corrupted.
	ln -sfT "$latest" "${dest_path}/latest" || return $RET_ERROR

	create_new_dir "$work_dir" || return $?

	return $RET_SUCCESS
}


# Finalize the backup creation on the destination host.
#
# requires: dest_refresh_symlinks
#            `-> assert_is_dir, dest_list_backup_dirs,
#                replace_symlink_target, create_dir
#           $dest_path (self, <- dest_refresh_symlinks),
#
# $1: old date: date in $DATEFMT
# $2: new date: date in $DATEFMT
#
function dest_finalize
{
	local old_date="$1"
	local new_date="$2"

	message "Finish installment of new backup..."
	mv -T "${dest_path}/work/${new_date}" "${dest_path}/${new_date}" \
		|| return $RET_ERROR

	message "Remove auxiliary directory tree..."
	rm -rf "${dest_path}/work/${old_date}" || return $RET_ERROR
	rmdir "${dest_path}/work" || return $RET_ERROR

	dest_refresh_symlinks || return $?

	message 'Successfully finished installment of new backup.'
}


# Print existing backup directories.
# Must be run on destination host.
#
# requires: $dest_path
#
function dest_list_backup_dirs
{
	find "$dest_path" -mindepth 1 -maxdepth 1 -type d \
		-regextype posix-extended -regex \
		'.*/[0-9]{4}-[0-1][0-9]-[0-3][0-9]_[0-2][0-9]([0-5][0-9]){2}' \
		-printf '%f\n' \
		| LC_ALL=C sort

	if [[ ${PIPESTATUS[0]} -eq 0 && ${PIPESTATUS[1]} -eq 0 ]]
	then
		return $RET_SUCCESS
	else
		return $RET_ERROR
	fi
}


# Create symbolic links to backup directories.
#
# requires: assert_is_dir, dest_list_backup_dirs, replace_symlink_target,
#           create_dir
#           $dest_path
#
function dest_refresh_symlinks
{
	local -i i
	local -i n
	local -a backup_dirs
	local link
	local ret

	assert_is_dir "$dest_path" || return $?

	backup_dirs=( $(dest_list_backup_dirs || return $?) )
	n=${#backup_dirs[@]}

	replace_symlink_target "${dest_path}/latest" "${backup_dirs[n-1]}" \
		|| return $?

	## by_number
	numdir="${dest_path}/by_number"
	create_dir "$numdir" || return $?

	# Remove old symlinks.
	find "$numdir" -mindepth 1 -maxdepth 1 -type l -regextype posix-extended \
		-regex '.*/[0-9]*' -delete || return $RET_ERROR

	for (( i = 0; i < n; i++ ))
	do
		ln -s "../${backup_dirs[i]}" "$(printf "%s/%.${#n}u" "$numdir" $i)" \
			|| return $RET_FILE_ERR
	done

	return $RET_SUCCESS
}

# vi: ft=bash ts=2 sw=2 noet