# The ChangesetController is the RESTful interface to Changeset objects

class ChangesetController < ApplicationController
  layout 'site'
  require 'xml/libxml'

  skip_before_filter :verify_authenticity_token, :except => [:list]
  before_filter :authorize_web, :only => [:list, :feed]
  before_filter :set_locale, :only => [:list, :feed]
  before_filter :authorize, :only => [:create, :update, :delete, :upload, :include, :close]
  before_filter :require_allow_write_api, :only => [:create, :update, :delete, :upload, :include, :close]
  before_filter :require_public_data, :only => [:create, :update, :delete, :upload, :include, :close]
  before_filter :check_api_writable, :only => [:create, :update, :delete, :upload, :include]
  before_filter :check_api_readable, :except => [:create, :update, :delete, :upload, :download, :query, :list, :feed]
  before_filter(:only => [:list, :feed]) { |c| c.check_database_readable(true) }
  after_filter :compress_output
  around_filter :api_call_handle_error, :except => [:list, :feed]
  around_filter :web_timeout, :only => [:list, :feed]

  # Helper methods for checking consistency
  include ConsistencyValidations

  # Create a changeset from XML.
  def create
    assert_method :put

    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!
    render :text => cs.id.to_s, :content_type => "text/plain"
  end

  ##
  # 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.to_s, :content_type => "text/xml"
  end
  
  ##
  # 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 :nothing => true
  end

  ##
  # 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
    # 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

    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
  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 
  # 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])
    
    # 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.
    elements.sort! do |a, b| 
      if (a.timestamp == b.timestamp)
        a.version <=> b.version
      else
        a.timestamp <=> b.timestamp 
      end
    end
    
    # 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
        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
          else
            # must be a modify
            modified = XML::Node.new "modify"
            modified << elt.to_xml_node
          end
        end
    end

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

  ##
  # 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.scoped
    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'])

    # 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 :nothing => true, :status => :bad_request
    end
  end

  ##
  # list edits (open changesets) in reverse chronological order
  def list
    if request.format == :atom and params[:page]
      redirect_to params.merge({ :page => nil }), :status => :moved_permanently
    else
      changesets = conditions_nonempty(Changeset.scoped)

      if params[:display_name]
        user = User.find_by_display_name(params[:display_name])
        
        if user and user.active?
          if user.data_public? or user == @user
            changesets = changesets.where(:user_id => user.id)
          else
            changesets = changesets.where("false")
          end
        else
          render_unknown_user params[:display_name]
          return
        end
      end
      
      if params[:friends]
        if @user
          changesets = changesets.where(:user_id => @user.friend_users.public)
        elsif request.format == :html
          require_user
          return
        end
      end

      if params[:nearby]
        if @user
          changesets = changesets.where(:user_id => @user.nearby)
        elsif request.format == :html
          require_user
          return
        end
      end

      if params[:bbox]
        bbox = BoundingBox.from_bbox_params(params)
      elsif params[:minlon] and params[:minlat] and params[:maxlon] and params[:maxlat]
        bbox = BoundingBox.from_lon_lat_params(params)
      end

      if bbox
        changesets = conditions_bbox(changesets, bbox)
        bbox_link = render_to_string :partial => "bbox", :object => bbox
      end
      
      if user
        user_link = render_to_string :partial => "user", :object => user
      end
      
      if params[:friends] and @user
        @title =  t 'changeset.list.title_friend'
        @heading =  t 'changeset.list.heading_friend'
        @description = t 'changeset.list.description_friend'
      elsif params[:nearby] and @user
        @title = t 'changeset.list.title_nearby'
        @heading = t 'changeset.list.heading_nearby'
        @description = t 'changeset.list.description_nearby'
      elsif user and bbox
        @title =  t 'changeset.list.title_user_bbox', :user => user.display_name, :bbox => bbox.to_s
        @heading =  t 'changeset.list.heading_user_bbox', :user => user.display_name, :bbox => bbox.to_s
        @description = t 'changeset.list.description_user_bbox', :user => user_link, :bbox => bbox_link
      elsif user
        @title =  t 'changeset.list.title_user', :user => user.display_name
        @heading =  t 'changeset.list.heading_user', :user => user.display_name
        @description = t 'changeset.list.description_user', :user => user_link
      elsif bbox
        @title =  t 'changeset.list.title_bbox', :bbox => bbox.to_s
        @heading =  t 'changeset.list.heading_bbox', :bbox => bbox.to_s
        @description = t 'changeset.list.description_bbox', :bbox => bbox_link
      else
        @title =  t 'changeset.list.title'
        @heading =  t 'changeset.list.heading'
        @description = t 'changeset.list.description'
      end

      @page = (params[:page] || 1).to_i
      @page_size = 20

      @bbox = bbox
      
      @edits = changesets.order("changesets.created_at DESC").offset((@page - 1) * @page_size).limit(@page_size).preload(:user, :changeset_tags)

      render :action => :list
    end
  end

  ##
  # list edits as an atom feed
  def feed
    list
  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
      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

  ##
  # 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
  
end
