using AIXM::Refinements

module AIXM
  class Component

    # Geometries define a 3D airspace horizontally.
    #
    # For a geometry to be valid, it must be comprised of either:
    # * exactly one point
    # * exactly one circle
    # * at least three points, arcs or borders (the last of which a point with
    #   identical coordinates as the first)
    #
    # ===Cheat Sheet in Pseudo Code:
    #   geometry = AIXM.geometry
    #   geometry.add_segment(AIXM.point or AIXM.arc or AIXM.border or AIXM.circle)
    #
    # @example Built by passing elements to the initializer
    #   geometry = AIXM.geometry(
    #     AIXM.point(...),
    #     AIXM.point(...)
    #   )
    #
    # @example Built by adding segments
    #   geometry = AIXM.geometry
    #   geometry.add_segment(AIXM.point(...))
    #
    # @see https://gitlab.com/openflightmaps/ofmx/wikis/Airspace#avx-border-vertex
    class Geometry < Component
      include AIXM::Concerns::Association

      # @!method segments
      #   @return [Array<AIXM::Component::Geometry::Point,
      #     AIXM::Component::Geometry::RhumbLine
      #     AIXM::Component::Geometry::Arc,
      #     AIXM::Component::Geometry::Circle,
      #     AIXM::Component::Geometry::Border>] points, rhumb lines, arcs, borders or circle
      #
      # @!method add_segment(segment)
      #   @param segment [AIXM::Component::Geometry::Point,
      #     AIXM::Component::Geometry::RhumbLine,
      #     AIXM::Component::Geometry::Arc,
      #     AIXM::Component::Geometry::Circle,
      #     AIXM::Component::Geometry::Border]
      #   @return [self]
      has_many :segments, accept: %i(point rhumb_line arc circle border)

      # @!method airspace
      #   @return [AIXM::Feature::Airspace] airspace the geometry defines
      belongs_to :airspace

      # See the {cheat sheet}[AIXM::Component::Geometry] for examples on how to
      # create instances of this class.
      def initialize(*segments)
        segments.each { add_segment(_1) }
      end

      # @return [String]
      def inspect
        %Q(#<#{self.class} segments=#{segments.count.inspect}>)
      end

      # Whether the geometry is closed
      #
      # @return [Boolean]
      def closed?
        point? || circle? || polygon?
      end

      # Whether a single point geometry
      #
      # @return [Boolean]
      def point?
        segments.size == 1 &&
          segments.first.is_a?(AIXM::Component::Geometry::Point)
      end

      # Whether a circle shaped geometry
      #
      # @return [Boolean]
      def circle?
        segments.size == 1 &&
          segments.first.is_a?(AIXM::Component::Geometry::Circle)
      end

      # Whether a polygon shaped geometry
      #
      # @return [Boolean]
      def polygon?
        segments.size >= 3 &&
          !segments.any? { _1.is_a?(AIXM::Component::Geometry::Circle) } &&
          segments.last.is_a?(AIXM::Component::Geometry::Point) &&
          segments.first.xy == segments.last.xy
      end

      # @!visibility private
      def add_to(builder)
        fail(GeometryError.new("geometry is not closed", self)) unless closed?
        segments.each { _1.add_to(builder) }
      end
    end

  end
end