Add the implementation for the GameOfLife Cell class

1 files changed, 93 insertions, 3 deletions

diff --git a/CLI/ruby/lib/game_of_life/cell.rb b/CLI/ruby/lib/game_of_life/cell.rb
index 62cd3a1..8f4a267 100644
--- a/CLI/ruby/lib/game_of_life/cell.rb
+++ b/CLI/ruby/lib/game_of_life/cell.rb
@@ -1,10 +1,16 @@
 # frozen_string_literal: true
 
+require "pry-byebug"
 module GameOfLife
+  # Class representing a cell in the GemeOfLife universe
+  # @!attribute [r] alive
+  #   @return [True | False] the living state of the cell
+  # @!attribute [r] pos_x
+  #   @return [Integer] the X-axis position of the cell in the universe
+  # @!attribute [r] pos_y
+  #   @return [Integer] the Y-axis position of the cell in the universe
   class Cell
-    attr_accessor :alive, :pos_x, :pos_y
-
-    alias_method :alive?, :alive
+    attr_reader :alive, :pos_x, :pos_y
 
     # Initialize a cell in the game of life universe
     # @param alive [True|False] boolean indicating if the cell is considered alive
@@ -22,5 +28,89 @@ module GameOfLife
     def to_s
       alive? ? LIVE_CELL : DEAD_CELL
     end
+
+    # Evolve a cell in the game of life to the new state in the next generation
+    # @param universe [Array<GameOfLife::Cell>] the {GameOfLife::Universe#current} state of universe
+    # @param living_neighbors [Integer] number of living neighbors, defaults to the private implementation of
+    # {GameOfLife::Cell#living_neighbors} implementation by default
+    # @return [GameOfLife::Cell] representing the new state in the next generation
+    #
+    # @note There are some optimizations of returning a new object only when the state changes, otherwise returning self
+    #   This optimization is done to limit the spacial complexity to O(2*witdht*height) in the worst case scenario
+    # and to O(width * hight) in the best case scenario (when the universe is stale and don't evolve anymore).
+    def evolve!(universe, living_neighbors: living_neighbors(universe))
+      return repopulate! if dead? && living_neighbors == 3
+      return survive! if alive? && [2, 3].include?(living_neighbors)
+      die!
+    end
+
+    # Helper method to define the language used in GameOfLife
+    # @return [True | False] cell living state
+    def alive?
+      @alive
+    end
+
+    # Helper method to define the language used in GameOfLife
+    # @return [True | False] cell dead state
+    # @see #alive?
+    def dead?
+      !alive?
+    end
+
+    # Return the array of all the neighboring cells using the circular universe array
+    # @param universe [Array<GameOfLife::Cell>] the {GameOfLife::Universe#current} state of universe
+    # @return [Array<GameOfLife::Cell>] of all the immediate neighboring cells
+    # @example given a cell "C" in a universe of cells "." the immediate neighbors would be "x" as in
+    # the following different examples
+    #
+    #     .....  |  .xxx.  |  .xCx.  |  xCx..  |  Cx..x  |  xx..x  |
+    #     .xxx.  |  .xCx.  |  .xxx.  |  xxx..  |  xx..x  |  Cx..x  |
+    #     .xCx.  |  .xxx.  |  .....  |  .....  |  .....  |  xx..x  |
+    #     .xxx.  |  .....  |  .....  |  .....  |  .....  |  .....  |
+    #     .....  |  .....  |  .xxx.  |  xxx..  |  xx..x  |  .....  |
+    #
+    # @smell AbcSize higher than configuration, but needed to return the neighboring cells array
+    # rubocop:disable Metrics/AbcSize
+    private def neighbors(universe)
+      [
+        universe[@pos_y - 1][@pos_x - 1], universe[@pos_y - 1][@pos_x], universe[@pos_y - 1][@pos_x + 1],
+        universe[@pos_y][@pos_x - 1], universe[@pos_y][@pos_x + 1],
+        universe[@pos_y + 1][@pos_x - 1], universe[@pos_y + 1][@pos_x], universe[@pos_y + 1][@pos_x + 1]
+      ]
+    end
+    # rubocop:enable Metrics/AbcSize
+
+    # Count the living neighbor cells relatively to the current cell in the {GameOfLife::Universe}
+    # @param universe [Array<GameOfLife::Cell>] the {GameOfLife::Universe#current} state of universe
+    # @return [Integer] the number of living neighbors
+    # @see #neighbors
+    private def living_neighbors(universe)
+      neighbors(universe).select(&:alive?).size
+    end
+
+    # Helper method to define the language used in GameOfLife
+    # @return [GameOfLife::Cell] new living cell
+    # @see #survive!
+    # @see #die!
+    private def repopulate!
+      self.class.new(pos_x: @pos_x, pos_y: @pos_y, alive: true)
+    end
+
+    # Helper method to define the language used in GameOfLife
+    # @return [GameOfLife::Cell] self (since no change in state needed)
+    # @see #repopulate!
+    # @see #die!
+    private def survive!
+      self
+    end
+
+    # Helper method to define the language used in GameOfLife
+    # When a cell is dead returns self otherwise return a new dead cell
+    # @return [GameOfLife::Cell] self (if already dead) or new dead cell
+    # @see #repopulate!
+    # @see #survive!
+    private def die!
+      dead? ? self : self.class.new(pos_x: @pos_x, pos_y: @pos_y, alive: false)
+    end
   end
 end