latest.rb

require 'xml/libxml'
require 'set'
require 'open-uri'

node_ids = Set.new
way_ids = Set.new
rel_ids = Set.new

ARGV.each do |file|
  data = XML::Parser.file(file).parse

  data.find('//node').each do |n|
    node_ids.add(n.attributes['id'].to_i)
  end
  data.find('//way').each do |n|
    way_ids.add(n.attributes['id'].to_i)
  end
  data.find('//relation').each do |n|
    rel_ids.add(n.attributes['id'].to_i)
  end
end

doc = XML::Document.new
osm_change = XML::Node.new("osmChange")
osm_change.attributes['version'] = "0.6"
doc.root = osm_change

def add_element(doc, type, id)
  begin
    http = open("http://api.openstreetmap.org/api/0.6/#{type}/#{id}")
    data = XML::Parser.io(http).parse
    elt = data.find("//#{type}")[0]
    modify = doc.import(XML::Node.new("modify"))
    modify << doc.import(elt)
    doc.root << modify

  rescue OpenURI::HTTPError
    elt = XML::Node.new(type)
    elt.attributes['id'] = id.to_s
    delete = XML::Node.new("delete")
    delete << elt
    doc.root << delete
  end
end

node_ids.each do |node_id|
  add_element(doc, "node", node_id)
end

way_ids.each do |way_id|
  add_element(doc, "way", way_id)
end

rel_ids.each do |rel_id|
  add_element(doc, "relation", rel_id)
end


puts doc.to_s