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coder.rb
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coder.rb
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# frozen_string_literal: true
module RGeo
module GeoJSON
# This object encapsulates encoding and decoding settings (principally
# the RGeo::Feature::Factory and the RGeo::GeoJSON::EntityFactory to
# be used) so that you can encode and decode without specifying those
# settings every time.
class Coder
class Error < RGeo::GeoJSON::Error
end
# Create a new coder settings object. The geo factory is passed as
# a required argument.
#
# Options include:
#
# [<tt>:geo_factory</tt>]
# Specifies the geo factory to use to create geometry objects.
# Defaults to the preferred cartesian factory.
# [<tt>:entity_factory</tt>]
# Specifies an entity factory, which lets you override the types
# of GeoJSON entities that are created. It defaults to the default
# RGeo::GeoJSON::EntityFactory, which generates objects of type
# RGeo::GeoJSON::Feature or RGeo::GeoJSON::FeatureCollection.
# See RGeo::GeoJSON::EntityFactory for more information.
def initialize(opts = {})
@geo_factory = opts.fetch(
:geo_factory,
RGeo::Cartesian.preferred_factory(uses_lenient_assertions: true)
)
@entity_factory = opts.fetch(:entity_factory, EntityFactory.instance)
if @geo_factory.property(:has_m_coordinate)
# If a GeoJSON has more than 2 elements, the first one should be
# longitude and the second one latitude. M is not part of GeoJSON
# specifications and only kept here for backward compatibilities.
#
# Quote from https://tools.ietf.org/html/rfc7946#section-3.1.1:
#
# > A position is an array of numbers. There MUST be two or more
# > elements. The first two elements are longitude and latitude, or
# > easting and northing, precisely in that order and using decimal
# > numbers. Altitude or elevation MAY be included as an optional third
# > element.
# >
# > Implementations SHOULD NOT extend positions beyond three elements
# > because the semantics of extra elements are unspecified and
# > ambiguous. Historically, some implementations have used a fourth
# > element to carry a linear referencing measure (sometimes denoted as
# > "M") or a numerical timestamp, but in most situations a parser will
# > not be able to properly interpret these values. The interpretation
# > and meaning of additional elements is beyond the scope of this
# > specification, and additional elements MAY be ignored by parsers.
raise Error, "GeoJSON format cannot handle m coordinate."
end
@num_coordinates = 2
@num_coordinates += 1 if @geo_factory.property(:has_z_coordinate)
end
# Encode the given object as GeoJSON. The object may be one of the
# geometry objects specified in RGeo::Feature, or an appropriate
# GeoJSON wrapper entity supported by this coder's entity factory.
#
# This method returns a JSON object (i.e. a hash). In order to
# generate a string suitable for transmitting to a service, you
# will need to JSON-encode it. This is usually accomplished by
# calling <tt>to_json</tt> on the hash object, if you have the
# appropriate JSON library installed.
#
# Returns nil if nil is passed in as the object.
def encode(object)
return nil if object.nil?
if @entity_factory.is_feature_collection?(object)
{
"type" => "FeatureCollection",
"features" => @entity_factory.map_feature_collection(object) { |f| encode_feature(f) },
}
elsif @entity_factory.is_feature?(object)
encode_feature(object)
else
encode_geometry(object)
end
end
# Decode an object from GeoJSON. The input may be a JSON hash, a
# String, or an IO object from which to read the JSON string.
# If an error occurs, nil is returned.
def decode(input)
if input.is_a?(IO)
input = input.read rescue nil
end
if input.is_a?(String)
input = MultiJson.load(input)
end
return unless input.is_a?(Hash)
case input["type"]
when "FeatureCollection"
features = input["features"]
features = [] unless features.is_a?(Array)
decoded_features = []
features.each do |f|
if f["type"] == "Feature"
decoded_features << decode_feature(f)
end
end
@entity_factory.feature_collection(decoded_features)
when "Feature"
decode_feature(input)
else
decode_geometry(input)
end
end
# Returns the RGeo::Feature::Factory used to generate geometry objects.
attr_reader :geo_factory
# Returns the RGeo::GeoJSON::EntityFactory used to generate GeoJSON
# wrapper entities.
attr_reader :entity_factory
private
def encode_feature(object)
json = {
"type" => "Feature",
"geometry" => encode_geometry(@entity_factory.get_feature_geometry(object)),
"properties" => @entity_factory.get_feature_properties(object).dup,
}
id = @entity_factory.get_feature_id(object)
json["id"] = id if id
json
end
def encode_geometry(object)
return nil if object.nil?
if object.factory.property(:has_m_coordinate)
raise Error, "GeoJSON format cannot handle m coordinate."
end
case object
when RGeo::Feature::Point,
RGeo::Feature::LineString,
RGeo::Feature::MultiPoint,
RGeo::Feature::MultiLineString
{
"type" => object.geometry_type.type_name,
"coordinates" => object.coordinates
}
when RGeo::Feature::Polygon
{
"type" => "Polygon",
"coordinates" => right_hand_ruled_coordinates(object)
}
when RGeo::Feature::MultiPolygon
coordinates = Array.new(object.num_geometries) do |i|
right_hand_ruled_coordinates(object.geometry_n(i))
end
{
"type" => "MultiPolygon",
"coordinates" => coordinates
}
when RGeo::Feature::GeometryCollection
{
"type" => "GeometryCollection",
"geometries" => object.map { |geom| encode_geometry(geom) }
}
else
nil
end
end
def right_hand_ruled_coordinates(polygon)
# Exterior should be ccw.
exterior = if clockwise?(polygon.exterior_ring)
polygon.exterior_ring.coordinates.reverse
else
polygon.exterior_ring.coordinates
end
interiors = polygon.interior_rings.map do |ring|
# Interiors should be cw.
next ring.coordinates if clockwise?(ring)
ring.coordinates.reverse
end
[exterior, *interiors]
end
def clockwise?(ring)
RGeo::Cartesian::Analysis.ring_direction(ring) == -1
end
def decode_feature(input)
geometry = input["geometry"]
if geometry
geometry = decode_geometry(geometry)
return unless geometry
end
@entity_factory.feature(geometry, input["id"], input["properties"])
end
def decode_geometry(input)
case input["type"]
when "GeometryCollection"
decode_geometry_collection(input)
when "Point"
decode_point_coords(input["coordinates"])
when "LineString"
decode_line_string_coords(input["coordinates"])
when "Polygon"
decode_polygon_coords(input["coordinates"])
when "MultiPoint"
decode_multi_point_coords(input["coordinates"])
when "MultiLineString"
decode_multi_line_string_coords(input["coordinates"])
when "MultiPolygon"
decode_multi_polygon_coords(input["coordinates"])
else
raise Error, "'#{input['type']}' type is not part of GeoJSON spec."
end
end
def decode_geometry_collection(input)
geometries = input["geometries"]
geometries = [] unless geometries.is_a?(Array)
decoded_geometries = []
geometries.each do |geometry|
geometry = decode_geometry(geometry)
decoded_geometries << geometry if geometry
end
@geo_factory.collection(decoded_geometries)
end
def decode_point_coords(point_coords)
return unless point_coords.is_a?(Array)
@geo_factory.point(*point_coords[0...@num_coordinates].map(&:to_f)) rescue nil
end
def decode_line_string_coords(line_coords)
return unless line_coords.is_a?(Array)
points = []
line_coords.each do |point_coords|
point = decode_point_coords(point_coords)
points << point if point
end
@geo_factory.line_string(points)
end
def decode_polygon_coords(poly_coords)
return unless poly_coords.is_a?(Array)
rings = []
poly_coords.each do |ring_coords|
return unless ring_coords.is_a?(Array)
points = []
ring_coords.each do |point_coords|
point = decode_point_coords(point_coords)
points << point if point
end
ring = @geo_factory.linear_ring(points)
rings << ring if ring
end
if rings.size == 0
nil
else
@geo_factory.polygon(rings[0], rings[1..-1])
end
end
def decode_multi_point_coords(multi_point_coords)
return unless multi_point_coords.is_a?(Array)
points = []
multi_point_coords.each do |point_coords|
point = decode_point_coords(point_coords)
points << point if point
end
@geo_factory.multi_point(points)
end
def decode_multi_line_string_coords(multi_line_coords)
return unless multi_line_coords.is_a?(Array)
lines = []
multi_line_coords.each do |line_coords|
line = decode_line_string_coords(line_coords)
lines << line if line
end
@geo_factory.multi_line_string(lines)
end
def decode_multi_polygon_coords(multi_polygon_coords)
return unless multi_polygon_coords.is_a?(Array)
polygons = []
multi_polygon_coords.each do |poly_coords|
poly = decode_polygon_coords(poly_coords)
polygons << poly if poly
end
@geo_factory.multi_polygon(polygons)
end
end
end
end