X-Git-Url: https://git.openstreetmap.org/rails.git/blobdiff_plain/e48cbc6a5f54a0e18dc581ccbac3b13284313125..fb70a89a36e42a7e439e4e99e449a109d0c3cd86:/app/controllers/changeset_controller.rb

diff --git a/app/controllers/changeset_controller.rb b/app/controllers/changeset_controller.rb
index 3e88eeec3..eaa87df7b 100644
--- a/app/controllers/changeset_controller.rb
+++ b/app/controllers/changeset_controller.rb
@@ -1,173 +1,596 @@
 # The ChangesetController is the RESTful interface to Changeset objects
 
 class ChangesetController < ApplicationController
+  layout 'site'
   require 'xml/libxml'
 
-  before_filter :authorize, :only => [:create, :update, :delete, :upload]
-  before_filter :check_write_availability, :only => [:create, :update, :delete, :upload]
-  before_filter :check_read_availability, :except => [:create, :update, :delete, :upload]
+  skip_before_filter :verify_authenticity_token, :except => [:list]
+  before_filter :authorize_web, :only => [:list, :feed, :comments_feed]
+  before_filter :set_locale, :only => [:list, :feed, :comments_feed]
+  before_filter :authorize, :only => [:create, :update, :delete, :upload, :include, :close, :comment, :subscribe, :unsubscribe, :hide_comment, :unhide_comment]
+  before_filter :require_moderator, :only => [:hide_comment, :unhide_comment]
+  before_filter :require_allow_write_api, :only => [:create, :update, :delete, :upload, :include, :close, :comment, :subscribe, :unsubscribe, :hide_comment, :unhide_comment]
+  before_filter :require_public_data, :only => [:create, :update, :delete, :upload, :include, :close, :comment, :subscribe, :unsubscribe]
+  before_filter :check_api_writable, :only => [:create, :update, :delete, :upload, :include, :comment, :subscribe, :unsubscribe, :hide_comment, :unhide_comment]
+  before_filter :check_api_readable, :except => [:create, :update, :delete, :upload, :download, :query, :list, :feed, :comment, :subscribe, :unsubscribe, :comments_feed]
+  before_filter(:only => [:list, :feed, :comments_feed]) { |c| c.check_database_readable(true) }
   after_filter :compress_output
+  around_filter :api_call_handle_error, :except => [:list, :feed, :comments_feed]
+  around_filter :web_timeout, :only => [:list, :feed, :comments_feed]
+
+  # 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
-  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!
 
-  def create_prim(ids, prim, nd)
-    prim.version = 0
-    prim.user_id = @user.id
-    prim.visible = true
-    prim.save_with_history!
+    # Subscribe user to changeset comments
+    cs.subscribers << @user
 
-    ids[nd['id'].to_i] = prim.id
+    render :text => cs.id.to_s, :content_type => "text/plain"
   end
 
-  def fix_way(w, node_ids)
-    w.nds = w.instance_eval { @nds }.
-      map { |nd| node_ids[nd] || nd }
-    return w
+  ##
+  # Return XML giving the basic info about the changeset. Does not
+  # return anything about the nodes, ways and relations in the changeset.
+  def read
+    changeset = Changeset.find(params[:id])
+
+    render :text => changeset.to_xml(params[:include_discussion].presence).to_s, :content_type => "text/xml"
   end
 
-  def fix_rel(r, ids)
-    r.members = r.instance_eval { @members }.
-      map { |memb| [memb[0], ids[memb[0]][memb[1].to_i] || memb[1], memb[2]] }
-    return r
+  ##
+  # marks a changeset as closed. this may be called multiple times
+  # on the same changeset, so is idempotent.
+  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
+    # 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!
+    render :text => ""
   end
-  
-  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
+
+  ##
+  # insert a (set of) points into a changeset bounding box. this can only
+  # increase the size of the bounding box. this is a hint that clients can
+  # set either before uploading a large number of changes, or changes that
+  # the client (but not the server) knows will affect areas further away.
+  def expand_bbox
+    # only allow POST requests, because although this method is
+    # idempotent, there is no "document" to PUT really...
+    assert_method :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?
+
+    # 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
+
+    # 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
 
+  ##
+  # Upload a diff in a single transaction.
+  #
+  # This means that each change within the diff must succeed, i.e: that
+  # each version number mentioned is still current. Otherwise the entire
+  # transaction *must* be rolled back.
+  #
+  # Furthermore, each element in the diff can only reference the current
+  # changeset.
+  #
+  # Returns: a diffResult document, as described in
+  # http://wiki.openstreetmap.org/wiki/OSM_Protocol_Version_0.6
   def upload
-    if not request.put?
-      render :nothing => true, :status => :method_not_allowed
-      return
-    end
+    # 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
+    assert_method :post
 
-    # FIXME: this should really be done without loading the whole XML file
-    # into memory.
-    p = XML::Parser.new
-    p.string  = request.raw_post
-    doc = p.parse
+    changeset = Changeset.find(params[:id])
+    check_changeset_consistency(changeset, @user)
 
-    node_ids, way_ids, rel_ids = {}, {}, {}
-    ids = {"node"=>node_ids, "way"=>way_ids, "relation"=>rel_ids}
+    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
+  end
 
-    res = XML::Document.new
-    res.encoding = 'UTF-8'
-    root = XML::Node.new 'osm'
-    root['version'] = '0.6'
-    root['creator'] = 'OpenStreetMap.org'
-    res.root = root
+  ##
+  # 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
+  # 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
+  # behaviour cannot be guaranteed anyway and is the result of a design
+  # choice.
+  def download
+    changeset = Changeset.find(params[:id])
 
-    root << XML::Node.new_comment(" Warning: this is a 0.6 result document, " +
-      "not a normal OSM file. ")
+    # 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
 
-    Changeset.transaction do
-      doc.find('//osm/create/node').each do |nd|
-	elem = XML::Node.new 'node'
-	node = Node.from_xml_node(nd, true)
-	elem['old_id'] = nd['id']
-	create_prim node_ids, node, nd
-	elem['new_id'] = node.id.to_s
-	elem['new_version'] = node.version.to_s
-	root << elem
-      end
-      doc.find('//osm/create/way').each do |nd|
-	elem = XML::Node.new 'way'
-	way = Way.from_xml_node(nd, true)
-	elem['old_id'] = nd['id']
-	fix_way(way, node_ids)
-	raise OSM::APIPreconditionFailedError.new if !way.preconditions_ok?
-	create_prim way_ids, way, nd
-	elem['new_id'] = way.id.to_s
-	elem['new_version'] = way.version.to_s
-	root << elem
-      end
-      doc.find('//osm/create/relation').each do |nd|
-	elem = XML::Node.new 'relation'
-	relation = Relation.from_xml_node(nd, true)
-	elem['old_id'] = nd['id']
-	fix_rel(relation, ids)
-	raise OSM::APIPreconditionFailedError.new if !relation.preconditions_ok?
-	create_prim rel_ids, relation, nd
-	elem['new_id'] = relation.id.to_s
-	elem['new_version'] = relation.version.to_s
-	root << elem
+    # 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.
+    elements.sort! do |a, b|
+      if (a.timestamp == b.timestamp)
+        a.version <=> b.version
+      else
+        a.timestamp <=> b.timestamp
       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
+    # at the history because it is simpler - but it would be more correct to
+    # check these assertions.
+    elements.each do |elt|
+      result.root <<
+        if (elt.version == 1)
+          # first version, so it must be newly-created.
+          created = XML::Node.new "create"
+          created << elt.to_xml_node(changeset_cache, user_display_name_cache)
+        else
+          unless elt.visible
+            # 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)
+          else
+            # must be a modify
+            modified = XML::Node.new "modify"
+            modified << elt.to_xml_node(changeset_cache, user_display_name_cache)
+          end
+        end
+    end
+
+    render :text => result.to_s, :content_type => "text/xml"
+  end
 
-      doc.find('//osm/modify/relation').each do |nd|
-	elem = XML::Node.new 'relation'
-	new_relation = Relation.from_xml_node(nd)
-	relation = Relation.find(new_relation.id)
-	relation.update_from new_relation, @user
-	elem['old_id'] = elem['new_id'] = relation.id.to_s
-	elem['new_version'] = relation.version.to_s
-	root << elem
+  ##
+  # query changesets by bounding box, time, user or open/closed status.
+  def query
+    # find any bounding box
+    if params['bbox']
+      bbox = BoundingBox.from_bbox_params(params)
+    end
+
+    # create the conditions that the user asked for. some or all of
+    # these may be nil.
+    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
+    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"
+  end
+
+  ##
+  # updates a changeset's tags. none of the changeset's attributes are
+  # user-modifiable, so they will be ignored.
+  #
+  # changesets are not (yet?) versioned, so we don't have to deal with
+  # history tables here. changesets are locked to a single user, however.
+  #
+  # after succesful update, returns the XML of the changeset.
+  def update
+    # request *must* be a PUT.
+    assert_method :put
+
+    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"
+    else
+
+      render :text => "", :status => :bad_request
+    end
+  end
+
+  ##
+  # list edits (open changesets) in reverse chronological order
+  def list
+    if request.format == :atom and params[:max_id]
+      redirect_to 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
-      doc.find('//osm/modify/way').each do |nd|
-	elem = XML::Node.new 'way'
-	new_way = Way.from_xml_node(nd)
-	way = Way.find(new_way.id)
-	way.update_from new_way, @user
-	elem['old_id'] = elem['new_id'] = way.id.to_s
-	elem['new_version'] = way.version.to_s
-	root << elem
+    end
+
+    if (params[:friends] || params[:nearby]) && !@user && request.format == :html
+      require_user
+      return
+    end
+
+    if request.format == :html and !params[:list]
+      require_oauth
+      render :action => :history, :layout => map_layout
+    else
+      changesets = conditions_nonempty(Changeset.all)
+
+      if params[:display_name]
+        if user.data_public? or user == @user
+          changesets = changesets.where(:user_id => user.id)
+        else
+          changesets = 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
-      doc.find('//osm/modify/node').each do |nd|
-	elem = XML::Node.new 'node'
-	new_node = Node.from_xml_node(nd)
-	node = Node.find(new_node.id)
-	node.update_from new_node, @user
-	elem['old_id'] = elem['new_id'] = node.id.to_s
-	elem['new_version'] = node.version.to_s
-	root << elem
+
+      if params[:max_id]
+        changesets = changesets.where("changesets.id <= ?", params[:max_id])
       end
 
-      doc.find('//osm/delete/relation').each do |nd|
-	elem = XML::Node.new 'relation'
-	relation = Relation.find(nd['id'])
-	relation.delete_with_history(@user)
-	elem['old_id'] = elem['new_id'] = relation.id.to_s
-	elem['new_version'] = relation.version.to_s
-	root << elem
+      @edits = changesets.order("changesets.id DESC").limit(20).preload(:user, :changeset_tags)
+
+      render :action => :list, :layout => false
+    end
+  end
+
+  ##
+  # list edits as an atom feed
+  def feed
+    list
+  end
+
+  ##
+  # 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.each do |user|
+      if @user != user
+        Notifier.changeset_comment_notification(comment, user).deliver_now
       end
-      doc.find('//osm/delete/way').each do |nd|
-	elem = XML::Node.new 'way'
-	way = Way.find(nd['id'])
-	way.delete_with_relations_and_history(@user)
-	elem['old_id'] = elem['new_id'] = way.id.to_s
-	elem['new_version'] = way.version.to_s
-	root << elem
+    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
+
+  ##
+  # 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
+  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
+      return 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
+      return changesets
+    end
+  end
+
+  ##
+  # restrict changesets to those by a particular user
+  def conditions_user(changesets, user, name)
+    unless user.nil? and name.nil?
+      # shouldn't provide both name and UID
+      raise OSM::APIBadUserInput.new("provide either the user ID or display name, but not both") if user and 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
+
+      # 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
+
+        raise OSM::APINotFoundError if @user.nil? or @user.id != u.id
       end
-      doc.find('//osm/delete/node').each do |nd|
-	elem = XML::Node.new 'node'
-	new_node = Node.from_xml_node(nd)
-	node = Node.find(nd['id'])
-	node.delete_with_history(@user)
-	elem['old_id'] = elem['new_id'] = node.id.to_s
-	elem['new_version'] = node.version.to_s
-	root << elem
+      return changesets.where(:user_id => u.id)
+    else
+      return changesets
+    end
+  end
+
+  ##
+  # restrict changes to those closed during a particular time period
+  def conditions_time(changesets, time)
+    unless time.nil?
+      # if there is a range, i.e: comma separated, then the first is
+      # 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 changesets.where("closed_at >= ? and created_at <= ?", from, to)
+      else
+        # if there is no comma, assume its a lower limit on time
+        return changesets.where("closed_at >= ?", DateTime.parse(time))
       end
+    else
+      return changesets
+    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.
+  rescue ArgumentError => ex
+    raise OSM::APIBadUserInput.new(ex.message.to_s)
+  rescue RuntimeError => ex
+    raise OSM::APIBadUserInput.new(ex.message.to_s)
+  end
+
+  ##
+  # 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?
+      return changesets
+    else
+      return changesets.where("closed_at >= ? and num_changes <= ?",
+                              Time.now.getutc, Changeset::MAX_ELEMENTS)
+    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?
+      return changesets
+    else
+      return 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?
+      return changesets
+    elsif ids.empty?
+      raise OSM::APIBadUserInput.new("No changesets were given to search for")
+    else
+      ids = ids.split(',').collect { |n| n.to_i }
+      return 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)
+    return changesets.where("num_changes > 0")
+  end
 
-    render :text => res.to_s, :content_type => "text/xml"
+  ##
+  # Get the maximum number of comments to return
+  def comments_limit
+    if params[:limit]
+      if params[:limit].to_i > 0 and 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