#!/usr/bin/ruby
#
# Program to prune a byteback installation 

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

opts = Trollop::options do

    banner "Prune old backup directories to ensure there's enough space"

    opt :minpercent, "Start prune when disk has less than this %age free",
        :type => :integer,
        :default => 5

    opt :maxpercent, "Stop prune when disk has more than this %age free",
        :type => :integer,
        :default => 10

    opt :list, "List backups in pruning order, no other action"

    opt :prune, "Prune the next backup if necessary"

    opt :order, "Order backups by 'age' or 'importance'",
    	:type => :string,
    	:default => "importance"

    opt :verbose, "Show debugging messages"

end

@order = opts[:order]
@verbose = opts[:verbose]
@do_list = opts[:list]
@do_prune = opts[:prune]
@minpercent = opts[:minpercent]
@maxpercent = opts[:maxpercent]

fatal("Must specify one of --prune or --list") unless 
  (@do_prune || @do_list) && 
  !(@do_prune && @do_list)

fatal("Must specify --order as 'age' or 'importance'") unless
  @order == 'age' || @order == 'importance'

if BackupDirectory.all.empty?
	fatal("No backup directories found, need to run byteback-snapshot")
end

@df_history = DiskFreeHistory.new(ENV['HOME'])
@df_history.new_reading!

# Don't do anything if we've not got two hours of readings
#
if @df_history.list.last.time - @df_history.list.first.time < 7200
	warn("Not enough disc space history to make a decision")
	exit 0
end

gradient_30m = @df_history.gradient(1800)
debug("Disc space gradient over 30m = #{gradient_30m}")
exit

# Check whether we should still be pruning
#
@free = @df_history.list.last.percent_free
PRUNING_FLAG = "#{ENV['HOME']}/.byteback.pruning"

if @free <= @minpercent && !File.exists?(PRUNING_FLAG)
	warn("Starting prune, #{@free}% free (aiming for #{@maxpercent})")
	File.write(PRUNING_FLAG,"") 
elsif @free >= @maxpercent && File.exists?(PRUNING_FLAG)
	warn("Stopping prune, #{@free}% free")
	File.unlink(PRUNING_FLAG) 
elsif File.exists?(PRUNING_FLAG)
	warn("Continuing prune, #{@free}% free (aiming for #{@maxpercent})")
end

def snapshots_in_order
	list = BackupDirectory.all_snapshots
	if list.empty?
		warn("Couldn't find any snapshots (yet?)")
	end
	if @order == 'importance'
		Snapshot.sort_by_importance(list)
	elsif @order == 'age'
		list.sort.reverse
	else
		raise ArgumentError.new("Unknown snapshot sort method #{method}")
	end
end

snapshots = snapshots_in_order

if @do_list
	print "Backups by #{@order}:\n"
	snapshots.each_with_index do |snapshot, index|
		print "#{sprintf('% 3d',index)}: #{snapshot.path}\n"
	end
end

exit 0 unless File.exists?(PRUNING_FLAG) && @do_prune

exit 0 if gradient_30m != 0

info("Deleting #{snapshots.last.path}")
log_system("sudo btrfs subvolume delete #{snapshots.last.path}")