require "rubygems"
require "nokogiri"

module GeoRuby
  module Gpx4r

    #An interface to GPX files
    class GpxFile
      attr_reader :record_count, :file_root #:xmin, :ymin, :xmax, :ymax, :zmin, :zmax, :mmin, :mmax, :file_length

      include Enumerable

      # Opens a GPX file. Both "abc.shp" and "abc" are accepted.
      def initialize(file, *opts) #with_z = true, with_m = true)
        @file_root = file.gsub(/\.gpx$/i,"")
        raise MalformedGpxException.new("Missing GPX File") unless
          File.exists? @file_root + ".gpx"
        @points, @envelope = [], nil
        @gpx = File.open(@file_root + ".gpx", "rb")
        opt = opts.inject({}) { |o, h| h.merge(o) }
        parse_file(opt[:with_z], opt[:with_m])
      end

      #force the reopening of the files compsing the shp. Close before calling this.
      def reload!
        initialize(@file_root)
      end

      #opens a GPX "file". If a block is given, the GpxFile object is yielded to it and is closed upon return. Else a call to <tt>open</tt> is equivalent to <tt>GpxFile.new(...)</tt>.
      def self.open(file, *opts)
        gpxfile = GpxFile.new(file, *opts)
        if block_given?
          yield gpxfile
          # gpxfile.close
        else
          gpxfile
        end
      end

      #Closes a gpxfile
      def close
        @gpx.close
      end

      #Tests if the file has no record
      def empty?
        record_count == 0
      end

      #Goes through each record
      def each
        (0...record_count).each do |i|
          yield get_record(i)
        end
      end
      alias :each_record :each

      #Returns record +i+
      def [](i)
        get_record(i)
      end

      #Returns all the records
      def records
        @points
      end

      # Return the GPX file as LineString
      def as_line_string
        GeoRuby::SimpleFeatures::LineString.from_points(@points)
      end
      alias :as_polyline :as_line_string

      # Return the GPX file as a Polygon
      # If the GPX isn't closed, a line from the first
      # to the last point will be created to close it.
      def as_polygon
        GeoRuby::SimpleFeatures::Polygon.from_points([@points[0] == @points[-1] ?  @points : @points.push(@points[0].clone)])
      end

      # Return GPX Envelope
      def envelope
        @envelope ||= as_polygon.envelope
      end

      private

      def get_record(i)
        @points[i]
      end

      # wpt => waypoint => TODO?
      # rte(pt) => route
      # trk(pt) => track /
      def parse_file(with_z, with_m)
        data = @gpx.read
        @file_mode = data =~ /trkpt/ ? "//trkpt" : (data =~ /wpt/ ? "//wpt" : "//rtept")
        Nokogiri.HTML(data).search(@file_mode).each do |tp|
          z = z.inner_text.to_f if with_z && z = tp.at("ele")
          m = m.inner_text if with_m && m = tp.at("time")
          @points << GeoRuby::SimpleFeatures::Point.from_coordinates([tp["lon"].to_f, tp["lat"].to_f, z, m],4326,with_z, with_m)
        end
        close
        @record_count = @points.length
        self.envelope
      rescue => e
        raise MalformedGpxException.new("Bad GPX. Error: #{e}")
        # trackpoint.at("gpxdata:hr").nil? # heartrate
      end

    end

    class MalformedGpxException < StandardError
    end

  end

end