X-Git-Url: https://git.openstreetmap.org./rails.git/blobdiff_plain/721dd9c27d299455b9159457a095716f797389f1..a5f72216395fb490a984dd86575f855c94a6a02f:/lib/diff_reader.rb

diff --git a/lib/diff_reader.rb b/lib/diff_reader.rb
index 6a053e4ad..2784646af 100644
--- a/lib/diff_reader.rb
+++ b/lib/diff_reader.rb
@@ -4,55 +4,102 @@
 # Uses the streaming LibXML "Reader" interface to cut down on memory
 # usage, so hopefully we can process fairly large diffs.
 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
+
+  ##
+  # 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 => e
+    raise OSM::APIBadXMLError.new("changeset", xml, e.message)
   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_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?
+            attributes[@reader.name] = @reader.value while @reader.move_to_next_attribute == 1
+
+            @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, "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
 
@@ -61,9 +108,7 @@ 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 
-      raise OSM::APIChangesetMismatchError.new(new.changeset_id, @changeset.id)
-    end
+    raise OSM::APIChangesetMismatchError.new(new.changeset_id, @changeset.id) unless new.changeset_id == @changeset.id
   end
 
   ##
@@ -71,40 +116,48 @@ 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, "Document element should be 'osmChange'." if @reader.name != "osmChange"
 
-    result = OSM::API.new.get_xml_doc
+    result = OSM::API.new.xml_doc
     result.root.name = "diffResult"
 
-    # loop at the top level, within the <osmChange> element (although we
-    # don't actually check this...)
-    with_element do |action_name|
-      if action_name == 'create'
+    # loop at the top level, within the <osmChange> element
+    with_element do |action_name, action_attributes|
+      case action_name
+      when "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|
-          new = model.from_xml_node(xml, true)
+          new = model.from_xml_node(xml, :create => true)
           check(model, xml, new)
 
           # 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, "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
@@ -113,57 +166,92 @@ class DiffReader
           xml_result["new_version"] = new.version.to_s
           result.root << xml_result
         end
-        
-      elsif action_name == 'modify'
+
+      when "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|
           # get the new element from the XML payload
-          new = model.from_xml_node(xml, false)
+          new = model.from_xml_node(xml, :create => 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'
+      when "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
 
       else
         # no other actions to choose from, so it must be the users fault!
-        raise OSM::APIChangesetActionInvalid.new(action_name)
+        raise OSM::APIChangesetActionInvalid, action_name
       end
     end
 
     # return the XML document to be rendered back to the client
-    return result
+    result
   end
-
 end