#!/usr/bin/ruby
#
# Program to create a snapshot and/or rotate a directory of backup snapshots 
# using btrfs subvolume commands.

$LOAD_PATH.unshift("/usr/lib/byteback")
require 'trollop'
require 'byteback'
include Byteback
include Byteback::Log

opts = Trollop::options do

    opt :root, "Backups directory (must be a btrfs subvolume)",
    	:type => :string

    opt :snapshot, "Take a new snapshot"

    opt :prune, "Prune old backups (by 'age' or 'importance')",
    	:type => :string

    opt :list, "List backups (by 'age' or 'importance')",
    	:type => :string

    opt :verbose, "Print diagnostics"

end

@root = opts[:root]
@verbose = opts[:verbose]
@do_snapshot = opts[:snapshot]
@do_list = opts[:list]
@do_prune = opts[:prune]

fatal("Must specify snapshot, prune or list") unless @do_snapshot || @do_prune || @do_list

fatal("--root not readable") unless File.directory?("#{@root}")

@backups = BackupDirectory.new(@root)

def get_snapshots_by(method)
	if method == 'importance'
		@backups.snapshot_times_by_importance.reverse # least important first
	elsif method == 'age'
		@backups.snapshot_times
	else
		raise ArgumentError.new("Unknown snapshot sort method #{method}")
	end
end

if @do_snapshot
	last_snapshot_time = @backups.snapshot_times.last
	fatal("Last snapshot was less than six hours ago") unless 
		!last_snapshot_time || 
		Time.now - @backups.snapshot_times.last >= 6*60*60 # FIXME: make configurable

	info "Making new snapshot"
	@backups.new_snapshot! 
end

if @do_list
	list = get_snapshots_by(@do_list)
	print "Backups in #{@root} by #{@do_list}:\n"
	list.each_with_index do |time, index|
		print "#{sprintf('% 3d',index)}: #{time}\n"
	end
end

if @do_prune
	info "Counting last 10 backups"
	target_free_space = 1.5 * @backups.average_snapshot_size(10)
	info "Want to ensure we have #{target_free_space}"

	if @backups.free >= target_free_space
		info "(we have #{@backups.free} so no action needed)"
	else
		list = get_snapshots_by(@do_prune)

		while @backups.free < target_free_space && !list.empty?
			to_delete = list.pop
			info "Deleting #{to_delete}"
			@backups.delete_snapshot!(to_delete)
			info "Leaves us with #{@backups.free}"
		end
	end
end

info "Finished"