triangle

triangle.rb

TriangleError = Class.new(ArgumentError)

Triangle = Struct.new(:x, :y, :z) do
  def initialize(*args)
    super
    validate
  end

  def type
    TYPES.fetch(uniq_side_lengths)
  end

private

  TYPES = { 1 => :equilateral, 2  => :isosceles, 3 => :scalene }

  def validate
    raise TriangleError if has_disallowed_side_length? || side_too_long?
  end

  def has_disallowed_side_length?
    [x, y, z].any? { |v| v <= 0 }
  end

  def side_too_long?
     x + y <= z || y + z <= x || z + x <= y
  end

  def uniq_side_lengths
    [x, y, z].uniq
  end
end

def triangle(x, y, z)
 Triangle.new(x, y, z).type
end