ioquatix/geospatial

# Copyright, 2015, by Samuel G. D. Williams. <http://www.codeotaku.com>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

require 'matrix'

module Geospatial
    # A circle is a geometric primative where the center is a location and the radius is in meters.
    class Circle
        class << self
            alias [] new
        end
        
        # Center must be a vector, radius must be a numeric value.
        def initialize(center, radius)
            @center = center
            @radius = radius
        end
        
        attr :center
        attr :radius
        
        def to_s
            "#{self.class}[#{@center}, #{@radius}]"
        end
        
        def distance_from(point)
            Location.new(point[0], point[1]).distance_from(@center)
        end
        
        def include_point?(point, radius = @radius)
            distance_from(point) <= radius
        end
        
        def include_box?(other)
            # We must contain the for corners of the other box:
            other.corners do |corner|
                return false unless include_point?(corner)
            end
            
            return true
        end
        
        def include_circle?(other)
            # We must be big enough to contain the other point:
            @radius >= other.radius && include_point?(other.center.to_a, @radius - other.radius)
        end
        
        def include?(other)
            case other
            when Box
                include_box?(other)
            when Circle
                include_circle?(other)
            end
        end
        
        def intersect?(other)
            case other
            when Box
                intersect_with_box?(other)
            when Circle
                intersect_with_circle?(other)
            end
        end
        
        def midpoints
            @bounds ||= @center.bounding_box(@radius)
            
            yield([@bounds[:longitude].begin, @center.latitude])
            yield([@bounds[:longitude].end, @center.latitude])
            yield([@center.longitude, @bounds[:latitude].begin])
            yield([@center.longitude, @bounds[:latitude].end])
        end
        
        def intersect_with_box?(other)
            # If we contain any of the four corners:
            other.corners do |corner|
                return true if include_point?(corner)
            end
            
            midpoints do |midpoint|
                return true if other.include_point?(midpoint)
            end
            
            return false
        end
        
        def intersect_with_circle?(other)
            include_point?(other.center.to_a, @radius + other.radius)
        end
    end
end