class NSWTopo::GeoJSON::MultiLineString

def buffer(*margins, **options)
  MultiLineString.new(@coordinates + @coordinates.map(&:reverse), @properties).offset(*margins, **options)
end

def dissolve_points
  MultiPoint.new @coordinates.flatten(1), @properties
end

def freeze!
  each { }
  freeze
end

def nodes
  Nodes.new self
end

def offset(*margins, **options)
  linestrings = margins.inject nodes do |nodes, margin|
    nodes.progress limit: margin, **options.slice(:rounding_angle, :cutoff_angle)
  end.readout
  MultiLineString.new linestrings, @properties
end

def path_length
  sum(&:path_length)
end

def samples(interval)
  sampled = flat_map do |linestring|
    distance = linestring.path_length
    linestring.sample_at(interval) do |point, along, angle|
      [point, (2 * along - distance).abs - distance]
    end
  end.sort_by(&:last).map(&:first)
  MultiPoint.new sampled, @properties
end

def smooth(margin, **options)
  linestrings = nodes.tap do |nodes|
    nodes.progress **options.slice(:rounding_angle).merge(limit: margin)
    nodes.progress **options.slice(:rounding_angle, :cutoff_angle).merge(limit: -2 * margin)
    nodes.progress **options.slice(:rounding_angle, :cutoff_angle).merge(limit: margin)
  end.readout
  MultiLineString.new linestrings, @properties
end

def subdivide(count)
  subdivided = flat_map do |linestring|
    linestring.each_cons(2).each_slice(count).map do |pairs|
      pairs.inject { |part, (p0, p1)| part << p1 }
    end
  end
  MultiLineString.new subdivided, @properties
end

def to_multipolygon
  unclaimed, exterior_rings = partition(&:interior?)
  exterior_rings.sort_by(&:signed_area).map(&:to_polygon).map do |polygon|
    interior_rings, unclaimed = unclaimed.partition do |ring|
      polygon.contains? ring.first
    end
    interior_rings.inject(polygon, &:add_ring)
  end.inject(empty_polygons, &:+)
end

def to_polygon
  Polygon.new @coordinates, @properties
end

def trim(amount)
  map do |feature|
    feature.trim amount
  end.reject(&:empty?).inject(empty_linestrings, &:+)
end