X-Git-Url: https://git.openstreetmap.org./rails.git/blobdiff_plain/79420631ceb2cb0f33e127b06e7b4f8a461b9281..f412c80d3f3fbb496fcd0baa09c464fa179dd839:/lib/diff_reader.rb diff --git a/lib/diff_reader.rb b/lib/diff_reader.rb index f7c51d797..c2e7f1839 100644 --- a/lib/diff_reader.rb +++ b/lib/diff_reader.rb @@ -7,52 +7,103 @@ class DiffReader include ConsistencyValidations # maps each element type to the model class which handles it - MODELS = { - "node" => Node, - "way" => Way, + MODELS = { + "node" => Node, + "way" => Way, "relation" => Relation - } + }.freeze ## # Construct a diff reader by giving it a bunch of XML +data+ to parse # in OsmChange format. All diffs must be limited to a single changeset # given in +changeset+. def initialize(data, changeset) - @reader = XML::Reader.new data + @reader = XML::Reader.string(data) @changeset = changeset + # document that's (re-)used to handle elements expanded out of the + # diff processing stream. + @doc = XML::Document.new + @doc.root = XML::Node.new("osm") end ## - # An element-block mapping for using the LibXML reader interface. + # Reads the next element from the XML document. Checks the return value + # and throws an exception if an error occurred. + def read_or_die + # NOTE: XML::Reader#read returns false for EOF and raises an + # exception if an error occurs. + @reader.read + rescue LibXML::XML::Error => ex + raise OSM::APIBadXMLError.new("changeset", xml, ex.message) + end + + ## + # An element-block mapping for using the LibXML reader interface. # # Since a lot of LibXML reader usage is boilerplate iteration through # elements, it would be better to DRY and do this in a block. This # could also help with error handling...? def with_element - # skip the first element, which is our opening element of the block - @reader.read - # loop over all elements. - # NOTE: XML::Reader#read returns 0 for EOF and -1 for error. - while @reader.read == 1 - break if @reader.node_type == 15 # end element - next unless @reader.node_type == 1 # element - yield @reader.name + # if the start element is empty then don't do any processing, as + # there won't be any child elements to process! + unless @reader.empty_element? + # read the first element + read_or_die + + while @reader.node_type != 15 # end element + # because we read elements in DOM-style to reuse their DOM + # parsing code, we don't always read an element on each pass + # as the call to @reader.next in the innermost loop will take + # care of that for us. + if @reader.node_type == 1 # element + name = @reader.name + attributes = {} + + if @reader.has_attributes? + while @reader.move_to_next_attribute == 1 + attributes[@reader.name] = @reader.value + end + + @reader.move_to_element + end + + yield name, attributes + else + read_or_die + end + end end + read_or_die end ## - # An element-block mapping for using the LibXML reader interface. + # An element-block mapping for using the LibXML reader interface. # # Since a lot of LibXML reader usage is boilerplate iteration through # elements, it would be better to DRY and do this in a block. This # could also help with error handling...? def with_model - with_element do |model_name| + with_element do |model_name, _model_attributes| model = MODELS[model_name] - raise "Unexpected element type #{model_name}, " + - "expected node, way, relation." if model.nil? - yield model, @reader.expand + if model.nil? + raise OSM::APIBadUserInput.new("Unexpected element type #{model_name}, " + + "expected node, way or relation.") + end + # new in libxml-ruby >= 2, expand returns an element not associated + # with a document. this means that there's no encoding parameter, + # which means basically nothing works. + expanded = @reader.expand + + # create a new, empty document to hold this expanded node + new_node = @doc.import(expanded) + @doc.root << new_node + + yield model, new_node @reader.next + + # remove element from doc - it will be garbage collected and the + # rest of the document is re-used in the next iteration. + @doc.root.child.remove! end end @@ -61,7 +112,7 @@ class DiffReader # such as save_ and delete_with_history. def check(model, xml, new) raise OSM::APIBadXMLError.new(model, xml) if new.nil? - unless new.changeset_id == @changeset.id + unless new.changeset_id == @changeset.id raise OSM::APIChangesetMismatchError.new(new.changeset_id, @changeset.id) end end @@ -71,19 +122,22 @@ class DiffReader # is *not* transactional, so code which calls it should ensure that the # appropriate transaction block is in place. # - # On a failure to meet preconditions (e.g: optimistic locking fails) + # On a failure to meet preconditions (e.g: optimistic locking fails) # an exception subclassing OSM::APIError will be thrown. def commit + # data structure used for mapping placeholder IDs to real IDs + ids = { :node => {}, :way => {}, :relation => {} } - node_ids, way_ids, rel_ids = {}, {}, {} - ids = { :node => node_ids, :way => way_ids, :relation => rel_ids} + # take the first element and check that it is an osmChange element + @reader.read + raise OSM::APIBadUserInput.new("Document element should be 'osmChange'.") if @reader.name != "osmChange" result = OSM::API.new.get_xml_doc + result.root.name = "diffResult" - # loop at the top level, within the element (although we - # don't actually check this...) - with_element do |action_name| - if action_name == 'create' + # loop at the top level, within the element + with_element do |action_name, action_attributes| + if action_name == "create" # create a new element. this code is agnostic of the element type # because all the elements support the methods that we're using. with_model do |model, xml| @@ -92,18 +146,23 @@ class DiffReader # when this element is saved it will get a new ID, so we save it # to produce the mapping which is sent to other elements. - placeholder_id = xml['id'].to_i + placeholder_id = xml["id"].to_i raise OSM::APIBadXMLError.new(model, xml) if placeholder_id.nil? + # check if the placeholder ID has been given before and throw + # an exception if it has - we can't create the same element twice. + model_sym = model.to_s.downcase.to_sym + raise OSM::APIBadUserInput.new("Placeholder IDs must be unique for created elements.") if ids[model_sym].include? placeholder_id + # some elements may have placeholders for other elements in the # diff, so we must fix these before saving the element. - new.fix_placeholders!(ids) + new.fix_placeholders!(ids, placeholder_id) # create element given user new.create_with_history(@changeset.user) - + # save placeholder => allocated ID map - ids[model.to_s.downcase.to_sym][placeholder_id] = new.id + ids[model_sym][placeholder_id] = new.id # add the result to the document we're building for return. xml_result = XML::Node.new model.to_s.downcase @@ -112,8 +171,8 @@ class DiffReader xml_result["new_version"] = new.version.to_s result.root << xml_result end - - elsif action_name == 'modify' + + elsif action_name == "modify" # modify an existing element. again, this code doesn't directly deal # with types, but uses duck typing to handle them transparently. with_model do |model, xml| @@ -121,37 +180,73 @@ class DiffReader new = model.from_xml_node(xml, false) check(model, xml, new) + # if the ID is a placeholder then map it to the real ID + model_sym = model.to_s.downcase.to_sym + client_id = new.id + is_placeholder = ids[model_sym].include? client_id + id = is_placeholder ? ids[model_sym][client_id] : client_id + # and the old one from the database - old = model.find(new.id) + old = model.find(id) + # translate any placeholder IDs to their true IDs. new.fix_placeholders!(ids) + new.id = id + old.update_from(new, @changeset.user) xml_result = XML::Node.new model.to_s.downcase - xml_result["old_id"] = old.id.to_s - xml_result["new_id"] = new.id.to_s + xml_result["old_id"] = client_id.to_s + xml_result["new_id"] = id.to_s # version is updated in "old" through the update, so we must not # return new.version here but old.version! xml_result["new_version"] = old.version.to_s result.root << xml_result end - elsif action_name == 'delete' + elsif action_name == "delete" # delete action. this takes a payload in API 0.6, so we need to do # most of the same checks that are done for the modify. with_model do |model, xml| - new = model.from_xml_node(xml, false) + # delete doesn't have to contain a full payload, according to + # the wiki docs, so we just extract the things we need. + new_id = xml["id"].to_i + raise OSM::APIBadXMLError.new(model, xml, "ID attribute is required") if new_id.nil? + + # if the ID is a placeholder then map it to the real ID + model_sym = model.to_s.downcase.to_sym + is_placeholder = ids[model_sym].include? new_id + id = is_placeholder ? ids[model_sym][new_id] : new_id + + # build the "new" element by modifying the existing one + new = model.find(id) + new.changeset_id = xml["changeset"].to_i + new.version = xml["version"].to_i check(model, xml, new) - old = model.find(new.id) + # fetch the matching old element from the DB + old = model.find(id) # can a delete have placeholders under any circumstances? # if a way is modified, then deleted is that a valid diff? new.fix_placeholders!(ids) - old.delete_with_history!(new, @changeset.user) xml_result = XML::Node.new model.to_s.downcase - xml_result["old_id"] = old.id.to_s + # oh, the irony... the "new" element actually contains the "old" ID + # a better name would have been client/server, but anyway... + xml_result["old_id"] = new_id.to_s + + if action_attributes["if-unused"] + begin + old.delete_with_history!(new, @changeset.user) + rescue OSM::APIAlreadyDeletedError, OSM::APIPreconditionFailedError + xml_result["new_id"] = old.id.to_s + xml_result["new_version"] = old.version.to_s + end + else + old.delete_with_history!(new, @changeset.user) + end + result.root << xml_result end @@ -162,7 +257,6 @@ class DiffReader end # return the XML document to be rendered back to the client - return result + result end - end