Merge remote-tracking branch 'openstreetmap/pull/1030' into next

[rails.git] / app / controllers / changeset_controller.rb

diff --git a/app/controllers/changeset_controller.rb b/app/controllers/changeset_controller.rb
index ff956f2acaf51184970dac2f7fe5980c91c40abe..da066a73afa4bc703f293067ad536ea7c63536e7 100644 (file)
--- a/app/controllers/changeset_controller.rb
+++ b/app/controllers/changeset_controller.rb
@@ -1,71 +1,67 @@
 # The ChangesetController is the RESTful interface to Changeset objects
 
 class ChangesetController < ApplicationController
 # The ChangesetController is the RESTful interface to Changeset objects
 
 class ChangesetController < ApplicationController

-  require 'xml/libxml'
-
-  before_filter :authorize, :only => [:create, :update, :delete, :upload, :include, :close]
-  before_filter :check_write_availability, :only => [:create, :update, :delete, :upload, :include]
-  before_filter :check_read_availability, :except => [:create, :update, :delete, :upload, :download, :query]
-  after_filter :compress_output
-
-  # Help methods for checking boundary sanity and area size
-  include MapBoundary
+  layout "site"
+  require "xml/libxml"
+
+  skip_before_action :verify_authenticity_token, :except => [:list]
+  before_action :authorize_web, :only => [:list, :feed, :comments_feed]
+  before_action :set_locale, :only => [:list, :feed, :comments_feed]
+  before_action :authorize, :only => [:create, :update, :delete, :upload, :include, :close, :comment, :subscribe, :unsubscribe, :hide_comment, :unhide_comment]
+  before_action :require_moderator, :only => [:hide_comment, :unhide_comment]
+  before_action :require_allow_write_api, :only => [:create, :update, :delete, :upload, :include, :close, :comment, :subscribe, :unsubscribe, :hide_comment, :unhide_comment]
+  before_action :require_public_data, :only => [:create, :update, :delete, :upload, :include, :close, :comment, :subscribe, :unsubscribe]
+  before_action :check_api_writable, :only => [:create, :update, :delete, :upload, :include, :comment, :subscribe, :unsubscribe, :hide_comment, :unhide_comment]
+  before_action :check_api_readable, :except => [:create, :update, :delete, :upload, :download, :query, :list, :feed, :comment, :subscribe, :unsubscribe, :comments_feed]
+  before_action(:only => [:list, :feed, :comments_feed]) { |c| c.check_database_readable(true) }
+  around_action :api_call_handle_error, :except => [:list, :feed, :comments_feed]
+  around_action :api_call_timeout, :except => [:list, :feed, :comments_feed, :upload]
+  around_action :web_timeout, :only => [:list, :feed, :comments_feed]

 
   # Helper methods for checking consistency
   include ConsistencyValidations
 
   # Create a changeset from XML.
   def create
 
   # Helper methods for checking consistency
   include ConsistencyValidations
 
   # Create a changeset from XML.
   def create

-    if request.put?
-      cs = Changeset.from_xml(request.raw_post, true)
+    assert_method :put

 
 

-      if cs
-        cs.user_id = @user.id
-        cs.save_with_tags!
-        render :text => cs.id.to_s, :content_type => "text/plain"
-      else
-        render :nothing => true, :status => :bad_request
-      end
-    else
-      render :nothing => true, :status => :method_not_allowed
-    end
+    cs = Changeset.from_xml(request.raw_post, true)
+
+    # Assume that Changeset.from_xml has thrown an exception if there is an error parsing the xml
+    cs.user_id = @user.id
+    cs.save_with_tags!
+
+    # Subscribe user to changeset comments
+    cs.subscribers << @user
+
+    render :text => cs.id.to_s, :content_type => "text/plain"

   end
 
   ##
   end
 
   ##

-  # Return XML giving the basic info about the changeset. Does not 
+  # Return XML giving the basic info about the changeset. Does not

   # return anything about the nodes, ways and relations in the changeset.
   def read
   # return anything about the nodes, ways and relations in the changeset.
   def read

-    begin
-      changeset = Changeset.find(params[:id])
-      render :text => changeset.to_xml.to_s, :content_type => "text/xml"
-    rescue ActiveRecord::RecordNotFound
-      render :nothing => true, :status => :not_found
-    end
+    changeset = Changeset.find(params[:id])
+
+    render :text => changeset.to_xml(params[:include_discussion].presence).to_s, :content_type => "text/xml"

   end
   end

-  
+

   ##
   # marks a changeset as closed. this may be called multiple times
   # on the same changeset, so is idempotent.
   ##
   # marks a changeset as closed. this may be called multiple times
   # on the same changeset, so is idempotent.

-  def close 
-    unless request.put?
-      render :nothing => true, :status => :method_not_allowed
-      return
-    end
-    
-    changeset = Changeset.find(params[:id])    
+  def close
+    assert_method :put
+
+    changeset = Changeset.find(params[:id])

     check_changeset_consistency(changeset, @user)
 
     # to close the changeset, we'll just set its closed_at time to
     check_changeset_consistency(changeset, @user)
 
     # to close the changeset, we'll just set its closed_at time to

-    # now. this might not be enough if there are concurrency issues, 
+    # now. this might not be enough if there are concurrency issues,

     # but we'll have to wait and see.
     changeset.set_closed_time_now
 
     changeset.save!
     # but we'll have to wait and see.
     changeset.set_closed_time_now
 
     changeset.save!

-    render :nothing => true
-  rescue ActiveRecord::RecordNotFound
-    render :nothing => true, :status => :not_found
-  rescue OSM::APIError => ex
-    render ex.render_opts
+    render :text => ""

   end
 
   ##
   end
 
   ##


@@ -76,45 +72,39 @@ class ChangesetController < ApplicationController
   def expand_bbox
     # only allow POST requests, because although this method is
     # idempotent, there is no "document" to PUT really...
   def expand_bbox
     # only allow POST requests, because although this method is
     # idempotent, there is no "document" to PUT really...

-    if request.post?
-      cs = Changeset.find(params[:id])
-      check_changeset_consistency(cs, @user)
-
-      # keep an array of lons and lats
-      lon = Array.new
-      lat = Array.new
-
-      # the request is in pseudo-osm format... this is kind-of an
-      # abuse, maybe should change to some other format?
-      doc = XML::Parser.string(request.raw_post).parse
-      doc.find("//osm/node").each do |n|
-        lon << n['lon'].to_f * GeoRecord::SCALE
-        lat << n['lat'].to_f * GeoRecord::SCALE
-      end
-
-      # add the existing bounding box to the lon-lat array
-      lon << cs.min_lon unless cs.min_lon.nil?
-      lat << cs.min_lat unless cs.min_lat.nil?
-      lon << cs.max_lon unless cs.max_lon.nil?
-      lat << cs.max_lat unless cs.max_lat.nil?
+    assert_method :post

 
 

-      # collapse the arrays to minimum and maximum
-      cs.min_lon, cs.min_lat, cs.max_lon, cs.max_lat = 
-        lon.min, lat.min, lon.max, lat.max
+    cs = Changeset.find(params[:id])
+    check_changeset_consistency(cs, @user)

 
 

-      # save the larger bounding box and return the changeset, which
-      # will include the bigger bounding box.
-      cs.save!
-      render :text => cs.to_xml.to_s, :content_type => "text/xml"
+    # keep an array of lons and lats
+    lon = []
+    lat = []

 
 

-    else
-      render :nothing => true, :status => :method_not_allowed
+    # the request is in pseudo-osm format... this is kind-of an
+    # abuse, maybe should change to some other format?
+    doc = XML::Parser.string(request.raw_post, :options => XML::Parser::Options::NOERROR).parse
+    doc.find("//osm/node").each do |n|
+      lon << n["lon"].to_f * GeoRecord::SCALE
+      lat << n["lat"].to_f * GeoRecord::SCALE

     end
 
     end
 

-  rescue ActiveRecord::RecordNotFound
-    render :nothing => true, :status => :not_found
-  rescue OSM::APIError => ex
-    render ex.render_opts
+    # add the existing bounding box to the lon-lat array
+    lon << cs.min_lon unless cs.min_lon.nil?
+    lat << cs.min_lat unless cs.min_lat.nil?
+    lon << cs.max_lon unless cs.max_lon.nil?
+    lat << cs.max_lat unless cs.max_lat.nil?
+
+    # collapse the arrays to minimum and maximum
+    cs.min_lon = lon.min
+    cs.min_lat = lat.min
+    cs.max_lon = lon.max
+    cs.max_lat = lat.max
+
+    # save the larger bounding box and return the changeset, which
+    # will include the bigger bounding box.
+    cs.save!
+    render :text => cs.to_xml.to_s, :content_type => "text/xml"

   end
 
   ##
   end
 
   ##


@@ -127,134 +117,116 @@ class ChangesetController < ApplicationController
   # Furthermore, each element in the diff can only reference the current
   # changeset.
   #
   # Furthermore, each element in the diff can only reference the current
   # changeset.
   #

-  # Returns: a diffResult document, as described in 
-  # http://wiki.openstreetmap.org/index.php/OSM_Protocol_Version_0.6
+  # Returns: a diffResult document, as described in
+  # http://wiki.openstreetmap.org/wiki/OSM_Protocol_Version_0.6

   def upload
     # only allow POST requests, as the upload method is most definitely
     # not idempotent, as several uploads with placeholder IDs will have
     # different side-effects.
     # see http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.1.2
   def upload
     # only allow POST requests, as the upload method is most definitely
     # not idempotent, as several uploads with placeholder IDs will have
     # different side-effects.
     # see http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.1.2

-    unless request.post?
-      render :nothing => true, :status => :method_not_allowed
-      return
-    end
+    assert_method :post

 
     changeset = Changeset.find(params[:id])
     check_changeset_consistency(changeset, @user)
 
     changeset = Changeset.find(params[:id])
     check_changeset_consistency(changeset, @user)

-    
+

     diff_reader = DiffReader.new(request.raw_post, changeset)
     Changeset.transaction do
       result = diff_reader.commit
       render :text => result.to_s, :content_type => "text/xml"
     end
     diff_reader = DiffReader.new(request.raw_post, changeset)
     Changeset.transaction do
       result = diff_reader.commit
       render :text => result.to_s, :content_type => "text/xml"
     end

-    
-  rescue ActiveRecord::RecordNotFound
-    render :nothing => true, :status => :not_found
-  rescue OSM::APIError => ex
-    render ex.render_opts

   end
 
   ##
   # download the changeset as an osmChange document.
   #
   # to make it easier to revert diffs it would be better if the osmChange
   end
 
   ##
   # download the changeset as an osmChange document.
   #
   # to make it easier to revert diffs it would be better if the osmChange

-  # format were reversible, i.e: contained both old and new versions of 
+  # format were reversible, i.e: contained both old and new versions of

   # modified elements. but it doesn't at the moment...
   #
   # this method cannot order the database changes fully (i.e: timestamp and
   # version number may be too coarse) so the resulting diff may not apply
   # modified elements. but it doesn't at the moment...
   #
   # this method cannot order the database changes fully (i.e: timestamp and
   # version number may be too coarse) so the resulting diff may not apply

-  # to a different database. however since changesets are not atomic this 
+  # to a different database. however since changesets are not atomic this

   # behaviour cannot be guaranteed anyway and is the result of a design
   # choice.
   def download
     changeset = Changeset.find(params[:id])
   # behaviour cannot be guaranteed anyway and is the result of a design
   # choice.
   def download
     changeset = Changeset.find(params[:id])

-    
-    # get all the elements in the changeset and stick them in a big array.
-    elements = [changeset.old_nodes, 
-                changeset.old_ways, 
-                changeset.old_relations].flatten
-    
-    # sort the elements by timestamp and version number, as this is the 
-    # almost sensible ordering available. this would be much nicer if 
-    # global (SVN-style) versioning were used - then that would be 
+
+    # get all the elements in the changeset which haven't been redacted
+    # and stick them in a big array.
+    elements = [changeset.old_nodes.unredacted,
+                changeset.old_ways.unredacted,
+                changeset.old_relations.unredacted].flatten
+
+    # sort the elements by timestamp and version number, as this is the
+    # almost sensible ordering available. this would be much nicer if
+    # global (SVN-style) versioning were used - then that would be

     # unambiguous.
     # unambiguous.

-    elements.sort! do |a, b| 
-      if (a.timestamp == b.timestamp)
+    elements.sort! do |a, b|
+      if a.timestamp == b.timestamp

         a.version <=> b.version
       else
         a.version <=> b.version
       else

-        a.timestamp <=> b.timestamp 
+        a.timestamp <=> b.timestamp

       end
     end
       end
     end

-    
+
+    # create changeset and user caches
+    changeset_cache = {}
+    user_display_name_cache = {}
+

     # create an osmChange document for the output
     result = OSM::API.new.get_xml_doc
     result.root.name = "osmChange"
 
     # generate an output element for each operation. note: we avoid looking
     # create an osmChange document for the output
     result = OSM::API.new.get_xml_doc
     result.root.name = "osmChange"
 
     # generate an output element for each operation. note: we avoid looking

-    # at the history because it is simpler - but it would be more correct to 
+    # at the history because it is simpler - but it would be more correct to

     # check these assertions.
     elements.each do |elt|
       result.root <<
     # check these assertions.
     elements.each do |elt|
       result.root <<

-        if (elt.version == 1) 
+        if elt.version == 1

           # first version, so it must be newly-created.
           created = XML::Node.new "create"
           # first version, so it must be newly-created.
           created = XML::Node.new "create"

-          created << elt.to_xml_node
+          created << elt.to_xml_node(changeset_cache, user_display_name_cache)
+        elsif elt.visible
+          # must be a modify
+          modified = XML::Node.new "modify"
+          modified << elt.to_xml_node(changeset_cache, user_display_name_cache)

         else
         else

-          # get the previous version from the element history
-          prev_elt = elt.class.find(:first, :conditions => 
-                                    ['id = ? and version = ?',
-                                     elt.id, elt.version])
-          unless elt.visible
-            # if the element isn't visible then it must have been deleted, so
-            # output the *previous* XML
-            deleted = XML::Node.new "delete"
-            deleted << prev_elt.to_xml_node
-          else
-            # must be a modify, for which we don't need the previous version
-            # yet...
-            modified = XML::Node.new "modify"
-            modified << elt.to_xml_node
-          end
+          # if the element isn't visible then it must have been deleted
+          deleted = XML::Node.new "delete"
+          deleted << elt.to_xml_node(changeset_cache, user_display_name_cache)

         end
     end
 
     render :text => result.to_s, :content_type => "text/xml"
         end
     end
 
     render :text => result.to_s, :content_type => "text/xml"

-            
-  rescue ActiveRecord::RecordNotFound
-    render :nothing => true, :status => :not_found
-  rescue OSM::APIError => ex
-    render ex.render_opts

   end
 
   ##
   # query changesets by bounding box, time, user or open/closed status.
   def query
   end
 
   ##
   # query changesets by bounding box, time, user or open/closed status.
   def query

+    # find any bounding box
+    bbox = BoundingBox.from_bbox_params(params) if params["bbox"]
+

     # create the conditions that the user asked for. some or all of
     # these may be nil.
     # create the conditions that the user asked for. some or all of
     # these may be nil.

-    conditions = conditions_bbox(params['bbox'])
-    conditions = cond_merge conditions, conditions_user(params['user'])
-    conditions = cond_merge conditions, conditions_time(params['time'])
-    conditions = cond_merge conditions, conditions_open(params['open'])
+    changesets = Changeset.all
+    changesets = conditions_bbox(changesets, bbox)
+    changesets = conditions_user(changesets, params["user"], params["display_name"])
+    changesets = conditions_time(changesets, params["time"])
+    changesets = conditions_open(changesets, params["open"])
+    changesets = conditions_closed(changesets, params["closed"])
+    changesets = conditions_ids(changesets, params["changesets"])

 
     # create the results document
     results = OSM::API.new.get_xml_doc
 
     # add all matching changesets to the XML results document
 
     # create the results document
     results = OSM::API.new.get_xml_doc
 
     # add all matching changesets to the XML results document

-    Changeset.find(:all, 
-                   :conditions => conditions, 
-                   :limit => 100,
-                   :order => 'created_at desc').each do |cs|
+    changesets.order("created_at DESC").limit(100).each do |cs|

       results.root << cs.to_xml_node
     end
 
     render :text => results.to_s, :content_type => "text/xml"
       results.root << cs.to_xml_node
     end
 
     render :text => results.to_s, :content_type => "text/xml"

-
-  rescue ActiveRecord::RecordNotFound
-    render :nothing => true, :status => :not_found
-  rescue OSM::APIError => ex
-    render ex.render_opts

   end
   end

-  
+

   ##
   # updates a changeset's tags. none of the changeset's attributes are
   # user-modifiable, so they will be ignored.
   ##
   # updates a changeset's tags. none of the changeset's attributes are
   # user-modifiable, so they will be ignored.


@@ -265,107 +237,288 @@ class ChangesetController < ApplicationController
   # after succesful update, returns the XML of the changeset.
   def update
     # request *must* be a PUT.
   # after succesful update, returns the XML of the changeset.
   def update
     # request *must* be a PUT.

-    unless request.put?
-      render :nothing => true, :status => :method_not_allowed
-      return
-    end
-    
+    assert_method :put
+

     changeset = Changeset.find(params[:id])
     new_changeset = Changeset.from_xml(request.raw_post)
 
     changeset = Changeset.find(params[:id])
     new_changeset = Changeset.from_xml(request.raw_post)
 

-    unless new_changeset.nil?
-      check_changeset_consistency(changeset, @user)
-      changeset.update_from(new_changeset, @user)
-      render :text => changeset.to_xml, :mime_type => "text/xml"
+    check_changeset_consistency(changeset, @user)
+    changeset.update_from(new_changeset, @user)
+    render :text => changeset.to_xml, :mime_type => "text/xml"
+  end
+
+  ##
+  # list edits (open changesets) in reverse chronological order
+  def list
+    if request.format == :atom && params[:max_id]
+      redirect_to url_for(params.merge(:max_id => nil)), :status => :moved_permanently
+      return
+    end
+
+    if params[:display_name]
+      user = User.find_by(:display_name => params[:display_name])
+      if !user || !user.active?
+        render_unknown_user params[:display_name]
+        return
+      end
+    end
+
+    if (params[:friends] || params[:nearby]) && !@user
+      require_user
+      return
+    end
+
+    if request.format == :html && !params[:list]
+      require_oauth
+      render :action => :history, :layout => map_layout

     else
     else

-      
-      render :nothing => true, :status => :bad_request
+      changesets = conditions_nonempty(Changeset.all)
+
+      if params[:display_name]
+        changesets = if user.data_public? || user == @user
+                       changesets.where(:user_id => user.id)
+                     else
+                       changesets.where("false")
+                     end
+      elsif params[:bbox]
+        changesets = conditions_bbox(changesets, BoundingBox.from_bbox_params(params))
+      elsif params[:friends] && @user
+        changesets = changesets.where(:user_id => @user.friend_users.identifiable)
+      elsif params[:nearby] && @user
+        changesets = changesets.where(:user_id => @user.nearby)
+      end
+
+      if params[:max_id]
+        changesets = changesets.where("changesets.id <= ?", params[:max_id])
+      end
+
+      @edits = changesets.order("changesets.id DESC").limit(20).preload(:user, :changeset_tags, :comments)
+
+      render :action => :list, :layout => false

     end
     end

-      
-  rescue ActiveRecord::RecordNotFound
-    render :nothing => true, :status => :not_found
-  rescue OSM::APIError => ex
-    render ex.render_opts

   end
 
   end
 

-private
-  #------------------------------------------------------------
-  # utility functions below.
-  #------------------------------------------------------------  
+  ##
+  # list edits as an atom feed
+  def feed
+    list
+  end

 
   ##
 
   ##

-  # merge two conditions
-  def cond_merge(a, b)
-    if a and b
-      a_str = a.shift
-      b_str = b.shift
-      return [ a_str + " and " + b_str ] + a + b
-    elsif a 
-      return a
-    else b
-      return b
+  # Add a comment to a changeset
+  def comment
+    # Check the arguments are sane
+    raise OSM::APIBadUserInput.new("No id was given") unless params[:id]
+    raise OSM::APIBadUserInput.new("No text was given") if params[:text].blank?
+
+    # Extract the arguments
+    id = params[:id].to_i
+    body = params[:text]
+
+    # Find the changeset and check it is valid
+    changeset = Changeset.find(id)
+    raise OSM::APIChangesetNotYetClosedError.new(changeset) if changeset.is_open?
+
+    # Add a comment to the changeset
+    comment = changeset.comments.create(:changeset => changeset,
+                                        :body => body,
+                                        :author => @user)
+
+    # Notify current subscribers of the new comment
+    changeset.subscribers.visible.each do |user|
+      if @user != user
+        Notifier.changeset_comment_notification(comment, user).deliver_now
+      end

     end
     end

+
+    # Add the commenter to the subscribers if necessary
+    changeset.subscribers << @user unless changeset.subscribers.exists?(@user.id)
+
+    # Return a copy of the updated changeset
+    render :text => changeset.to_xml.to_s, :content_type => "text/xml"
+  end
+
+  ##
+  # Adds a subscriber to the changeset
+  def subscribe
+    # Check the arguments are sane
+    raise OSM::APIBadUserInput.new("No id was given") unless params[:id]
+
+    # Extract the arguments
+    id = params[:id].to_i
+
+    # Find the changeset and check it is valid
+    changeset = Changeset.find(id)
+    raise OSM::APIChangesetNotYetClosedError.new(changeset) if changeset.is_open?
+    raise OSM::APIChangesetAlreadySubscribedError.new(changeset) if changeset.subscribers.exists?(@user.id)
+
+    # Add the subscriber
+    changeset.subscribers << @user
+
+    # Return a copy of the updated changeset
+    render :text => changeset.to_xml.to_s, :content_type => "text/xml"

   end
 
   ##
   end
 
   ##

-  # if a bounding box was specified then parse it and do some sanity 
-  # checks. this is mostly the same as the map call, but without the 
-  # area restriction.
-  def conditions_bbox(bbox)
-    unless bbox.nil?
-      raise OSM::APIBadUserInput.new("Bounding box should be min_lon,min_lat,max_lon,max_lat") unless bbox.count(',') == 3
-      bbox = sanitise_boundaries(bbox.split(/,/))
-      raise OSM::APIBadUserInput.new("Minimum longitude should be less than maximum.") unless bbox[0] <= bbox[2]
-      raise OSM::APIBadUserInput.new("Minimum latitude should be less than maximum.") unless bbox[1] <= bbox[3]
-      return ['min_lon < ? and max_lon > ? and min_lat < ? and max_lat > ?',
-              bbox[2] * GeoRecord::SCALE, bbox[0] * GeoRecord::SCALE, bbox[3]* GeoRecord::SCALE, bbox[1] * GeoRecord::SCALE]
+  # Removes a subscriber from the changeset
+  def unsubscribe
+    # Check the arguments are sane
+    raise OSM::APIBadUserInput.new("No id was given") unless params[:id]
+
+    # Extract the arguments
+    id = params[:id].to_i
+
+    # Find the changeset and check it is valid
+    changeset = Changeset.find(id)
+    raise OSM::APIChangesetNotYetClosedError.new(changeset) if changeset.is_open?
+    raise OSM::APIChangesetNotSubscribedError.new(changeset) unless changeset.subscribers.exists?(@user.id)
+
+    # Remove the subscriber
+    changeset.subscribers.delete(@user)
+
+    # Return a copy of the updated changeset
+    render :text => changeset.to_xml.to_s, :content_type => "text/xml"
+  end
+
+  ##
+  # Sets visible flag on comment to false
+  def hide_comment
+    # Check the arguments are sane
+    raise OSM::APIBadUserInput.new("No id was given") unless params[:id]
+
+    # Extract the arguments
+    id = params[:id].to_i
+
+    # Find the changeset
+    comment = ChangesetComment.find(id)
+
+    # Hide the comment
+    comment.update(:visible => false)
+
+    # Return a copy of the updated changeset
+    render :text => comment.changeset.to_xml.to_s, :content_type => "text/xml"
+  end
+
+  ##
+  # Sets visible flag on comment to true
+  def unhide_comment
+    # Check the arguments are sane
+    raise OSM::APIBadUserInput.new("No id was given") unless params[:id]
+
+    # Extract the arguments
+    id = params[:id].to_i
+
+    # Find the changeset
+    comment = ChangesetComment.find(id)
+
+    # Unhide the comment
+    comment.update(:visible => true)
+
+    # Return a copy of the updated changeset
+    render :text => comment.changeset.to_xml.to_s, :content_type => "text/xml"
+  end
+
+  ##
+  # Get a feed of recent changeset comments
+  def comments_feed
+    if params[:id]
+      # Extract the arguments
+      id = params[:id].to_i
+
+      # Find the changeset
+      changeset = Changeset.find(id)
+
+      # Return comments for this changeset only
+      @comments = changeset.comments.includes(:author, :changeset).limit(comments_limit)
+    else
+      # Return comments
+      @comments = ChangesetComment.includes(:author, :changeset).where(:visible => :true).order("created_at DESC").limit(comments_limit).preload(:changeset)
+    end
+
+    # Render the result
+    respond_to do |format|
+      format.rss
+    end
+  rescue OSM::APIBadUserInput
+    render :text => "", :status => :bad_request
+  end
+
+  private
+
+  #------------------------------------------------------------
+  # utility functions below.
+  #------------------------------------------------------------
+
+  ##
+  # if a bounding box was specified do some sanity checks.
+  # restrict changesets to those enclosed by a bounding box
+  # we need to return both the changesets and the bounding box
+  def conditions_bbox(changesets, bbox)
+    if bbox
+      bbox.check_boundaries
+      bbox = bbox.to_scaled
+
+      changesets.where("min_lon < ? and max_lon > ? and min_lat < ? and max_lat > ?",
+                       bbox.max_lon.to_i, bbox.min_lon.to_i,
+                       bbox.max_lat.to_i, bbox.min_lat.to_i)

     else
     else

-      return nil
+      changesets

     end
   end
 
   ##
   # restrict changesets to those by a particular user
     end
   end
 
   ##
   # restrict changesets to those by a particular user

-  def conditions_user(user)
-    unless user.nil?
-      # user input checking, we don't have any UIDs < 1
-      raise OSM::APIBadUserInput.new("invalid user ID") if user.to_i < 1
+  def conditions_user(changesets, user, name)
+    if user.nil? && name.nil?
+      changesets
+    else
+      # shouldn't provide both name and UID
+      raise OSM::APIBadUserInput.new("provide either the user ID or display name, but not both") if user && name
+
+      # use either the name or the UID to find the user which we're selecting on.
+      u = if name.nil?
+            # user input checking, we don't have any UIDs < 1
+            raise OSM::APIBadUserInput.new("invalid user ID") if user.to_i < 1
+            u = User.find(user.to_i)
+          else
+            u = User.find_by(:display_name => name)
+          end

 
 

-      u = User.find(user.to_i)
-      # should be able to get changesets of public users only, or 
+      # make sure we found a user
+      raise OSM::APINotFoundError.new if u.nil?
+
+      # should be able to get changesets of public users only, or

       # our own changesets regardless of public-ness.
       unless u.data_public?
         # get optional user auth stuff so that users can see their own
         # changesets if they're non-public
         setup_user_auth
       # our own changesets regardless of public-ness.
       unless u.data_public?
         # get optional user auth stuff so that users can see their own
         # changesets if they're non-public
         setup_user_auth

-        
-        raise OSM::APINotFoundError if @user.nil? or @user.id != u.id
+
+        raise OSM::APINotFoundError if @user.nil? || @user.id != u.id

       end
       end

-      return ['user_id = ?', u.id]
-    else
-      return nil
+
+      changesets.where(:user_id => u.id)

     end
   end
 
   ##
     end
   end
 
   ##

-  # restrict changes to those during a particular time period
-  def conditions_time(time) 
-    unless time.nil?
-      # if there is a range, i.e: comma separated, then the first is 
+  # restrict changes to those closed during a particular time period
+  def conditions_time(changesets, time)
+    if time.nil?
+      return changesets
+    elsif time.count(",") == 1
+      # if there is a range, i.e: comma separated, then the first is

       # low, second is high - same as with bounding boxes.
       # low, second is high - same as with bounding boxes.

-      if time.count(',') == 1
-        # check that we actually have 2 elements in the array
-        times = time.split(/,/)
-        raise OSM::APIBadUserInput.new("bad time range") if times.size != 2 

 
 

-        from, to = times.collect { |t| DateTime.parse(t) }
-        return ['closed_at >= ? and created_at <= ?', from, to]
-      else
-        # if there is no comma, assume its a lower limit on time
-        return ['closed_at >= ?', DateTime.parse(time)]
-      end
+      # check that we actually have 2 elements in the array
+      times = time.split(/,/)
+      raise OSM::APIBadUserInput.new("bad time range") if times.size != 2
+
+      from, to = times.collect { |t| DateTime.parse(t) }
+      return changesets.where("closed_at >= ? and created_at <= ?", from, to)

     else
     else

-      return nil
+      # if there is no comma, assume its a lower limit on time
+      return changesets.where("closed_at >= ?", DateTime.parse(time))

     end
     # stupid DateTime seems to throw both of these for bad parsing, so
     # we have to catch both and ensure the correct code path is taken.
     end
     # stupid DateTime seems to throw both of these for bad parsing, so
     # we have to catch both and ensure the correct code path is taken.


@@ -376,9 +529,63 @@ private
   end
 
   ##
   end
 
   ##

-  # restrict changes to those which are open
-  def conditions_open(open)
-    return open.nil? ? nil : ['closed_at >= ?', DateTime.now]
+  # return changesets which are open (haven't been closed yet)
+  # we do this by seeing if the 'closed at' time is in the future. Also if we've
+  # hit the maximum number of changes then it counts as no longer open.
+  # if parameter 'open' is nill then open and closed changesets are returned
+  def conditions_open(changesets, open)
+    if open.nil?
+      changesets
+    else
+      changesets.where("closed_at >= ? and num_changes <= ?",
+                       Time.now.getutc, Changeset::MAX_ELEMENTS)
+    end

   end
 
   end
 

+  ##
+  # query changesets which are closed
+  # ('closed at' time has passed or changes limit is hit)
+  def conditions_closed(changesets, closed)
+    if closed.nil?
+      changesets
+    else
+      changesets.where("closed_at < ? or num_changes > ?",
+                       Time.now.getutc, Changeset::MAX_ELEMENTS)
+    end
+  end
+
+  ##
+  # query changesets by a list of ids
+  # (either specified as array or comma-separated string)
+  def conditions_ids(changesets, ids)
+    if ids.nil?
+      changesets
+    elsif ids.empty?
+      raise OSM::APIBadUserInput.new("No changesets were given to search for")
+    else
+      ids = ids.split(",").collect(&:to_i)
+      changesets.where(:id => ids)
+    end
+  end
+
+  ##
+  # eliminate empty changesets (where the bbox has not been set)
+  # this should be applied to all changeset list displays
+  def conditions_nonempty(changesets)
+    changesets.where("num_changes > 0")
+  end
+
+  ##
+  # Get the maximum number of comments to return
+  def comments_limit
+    if params[:limit]
+      if params[:limit].to_i > 0 && params[:limit].to_i <= 10000
+        params[:limit].to_i
+      else
+        raise OSM::APIBadUserInput.new("Comments limit must be between 1 and 10000")
+      end
+    else
+      100
+    end
+  end

 end
 end