georss.rb

# require 'geo_ruby/simple_features/point'
# require 'geo_ruby/simple_features/line_string'
# require 'geo_ruby/simple_features/linear_ring'
# require 'geo_ruby/simple_features/polygon'
# require 'geo_ruby/simple_features/multi_point'
# require 'geo_ruby/simple_features/multi_line_string'
# require 'geo_ruby/simple_features/multi_polygon'
# require 'geo_ruby/simple_features/geometry_collection'
# require 'geo_ruby/simple_features/envelope'

module GeoRuby

  #Raised when an error in the GeoRSS string is detected
  class GeorssFormatError < StandardError
  end

  #Contains tags possibly found on GeoRss Simple geometries
  class GeorssTags < Struct.new(:featuretypetag,:relationshiptag,:elev,:floor,:radius)
  end

  #Parses GeoRSS strings
  #You can also use directly the static method Geometry.from_georss
  class GeorssParser
    attr_reader :georss_tags, :geometry

    #Parses the georss geometry  passed as argument and notifies the factory of events
    #The parser assumes
    def parse(georss,with_tags = false)
      @geometry = nil
      @georss_tags = GeorssTags.new
      parse_geometry(georss,with_tags)
    end

    private
    def parse_geometry(georss,with_tags)
      georss.strip!
      #check for W3CGeo first
      if georss =~ /<[^:>]*:lat\s*>([^<]*)</
        #if valid, it is W3CGeo
        lat = $1.to_f
        if georss =~ /<[^:>]*:long\s*>([^<]*)</
          lon = $1.to_f
          @geometry = Point.from_x_y(lon,lat)
        else
          raise GeorssFormatError.new("Bad W3CGeo GeoRSS format")
        end
      elsif georss =~ /^<\s*[^:>]*:where\s*>/
        #GML format found
        gml = $'.strip
        if gml =~ /^<\s*[^:>]*:Point\s*>/
          #gml point
          if gml =~ /<\s*[^:>]*:pos\s*>([^<]*)/
            point = $1.split(" ")
            #lat comes first
            @geometry = Point.from_x_y(point[1].to_f,point[0].to_f)
          else
            raise GeorssFormatError.new("Bad GML GeoRSS format: Malformed Point")
          end
        elsif gml =~ /^<\s*[^:>]*:LineString\s*>/
          if gml =~ /<\s*[^:>]*:posList\s*>([^<]*)/
            xy = $1.split(" ")
            @geometry = LineString.new
            0.upto(xy.size/2 - 1) { |index| @geometry << Point.from_x_y(xy[index*2 + 1].to_f,xy[index*2].to_f)}
          else
            raise GeorssFormatError.new("Bad GML GeoRSS format: Malformed LineString")
          end
        elsif gml =~ /^<\s*[^:>]*:Polygon\s*>/
          if gml =~ /<\s*[^:>]*:posList\s*>([^<]*)/
            xy = $1.split(" ")
            @geometry = Polygon.new
            linear_ring = LinearRing.new
            @geometry << linear_ring
            xy = $1.split(" ")
            0.upto(xy.size/2 - 1) { |index| linear_ring << Point.from_x_y(xy[index*2 + 1].to_f,xy[index*2].to_f)}
          else
            raise GeorssFormatError.new("Bad GML GeoRSS format: Malformed Polygon")
          end
        elsif gml =~ /^<\s*[^:>]*:Envelope\s*>/
          if gml =~ /<\s*[^:>]*:lowerCorner\s*>([^<]*)</
            lc = $1.split(" ").collect { |x| x.to_f}.reverse
            if gml =~ /<\s*[^:>]*:upperCorner\s*>([^<]*)</
              uc = $1.split(" ").collect { |x| x.to_f}.reverse
              @geometry = Envelope.from_coordinates([lc,uc])
            else
              raise GeorssFormatError.new("Bad GML GeoRSS format: Malformed Envelope")
            end
          else
            raise GeorssFormatError.new("Bad GML GeoRSS format: Malformed Envelope")
          end
        else
          raise GeorssFormatError.new("Bad GML GeoRSS format: Unknown geometry type")
        end
      else
        #must be simple format
        if georss =~ /^<\s*[^>:]*:point([^>]*)>(.*)</m
          tags = $1
          point = $2.gsub(","," ").split(" ")
          @geometry = Point.from_x_y(point[1].to_f,point[0].to_f)
        elsif georss =~ /^<\s*[^>:]*:line([^>]*)>(.*)</m
          tags = $1
          @geometry = LineString.new
          xy = $2.gsub(","," ").split(" ")
          0.upto(xy.size/2 - 1) { |index| @geometry << Point.from_x_y(xy[index*2 + 1].to_f,xy[index*2].to_f)}
        elsif georss =~ /^<\s*[^>:]*:polygon([^>]*)>(.*)</m
          tags = $1
          @geometry = Polygon.new
          linear_ring = LinearRing.new
          @geometry << linear_ring
          xy = $2.gsub(","," ").split(" ")
          0.upto(xy.size/2 - 1) { |index| linear_ring << Point.from_x_y(xy[index*2 + 1].to_f,xy[index*2].to_f)}
        elsif georss =~ /^<\s*[^>:]*:box([^>]*)>(.*)</m
          tags = $1
          corners = []
          xy = $2.gsub(","," ").split(" ")
          0.upto(xy.size/2 - 1) {|index| corners << Point.from_x_y(xy[index*2 + 1].to_f,xy[index*2].to_f)}
          @geometry = Envelope.from_points(corners)
        else
          raise GeorssFormatError.new("Bad Simple GeoRSS format: Unknown geometry type")
        end

        #geometry found: parse tags
        return unless with_tags

        @georss_tags.featuretypetag = $1 if tags =~ /featuretypetag=['"]([^"']*)['"]/
        @georss_tags.relationshiptag = $1 if tags =~ /relationshiptag=['"]([^'"]*)['"]/
        @georss_tags.elev = $1.to_f if tags =~ /elev=['"]([^'"]*)['"]/
        @georss_tags.floor = $1.to_i if tags =~ /floor=['"]([^'"]*)['"]/
        @georss_tags.radius = $1.to_f if tags =~ /radius=['"]([^'"]*)['"]/

      end
    end
  end
end