update distributed_merge method for cases with single element arrays

.rubocop.yml

@@ -19,4 +19,10 @@ Metrics/MethodLength:
   Max: 20
 
 Metrics/AbcSize:
-  Max: 30
+  Max: 35
+
+Metrics/Metrics/CyclomaticComplexity:
+  Max: 10
+
+Metrics/PerceivedComplexity:
+  Max: 10

distributed_merge.gemspec

@@ -8,12 +8,12 @@ Gem::Specification.new do |spec|
   spec.authors = ["Suleyman Musayev"]
   spec.email = ["slmusayev@gmail.com"]
 
-  spec.summary = "Gem that adds the method to merge arrays of unequal size with equalized
-  distribution of elements."
+  spec.summary = "Gem that adds the method to merge arrays of unequal size with
+   distribution of elements."
   spec.description = "This gem extends Array class with the distributed_merge method that
    accepts a two-dimensional array containing an arbitrary number of arrays of varying
-   length and returns a one-dimensional merged array with the equally distributed
-   elements."
+   length and returns a one-dimensional merged array with the elements equally interleaved
+   and distributed."
   spec.license = "MIT"
   spec.required_ruby_version = ">= 2.6.0"
   spec.homepage = "https://github.com/msuliq/distributed_merge"

lib/distributed_merge.rb

@@ -3,20 +3,23 @@
 require_relative "distributed_merge/version"
 
 module DistributedMerge
-  class Array # :nodoc:
+  module DistributedMergeArray # :nodoc:
     # Accepts a two-dimensional array with subarrays of varying size and returns
-    # merged array with the elements distributed evenly.
+    # merged array with the elements distributed across.
 
     def distributed_merge
-      return self unless two_dimensional?
+      return self unless all_arrays? && two_dimensional?
 
-      data = sort_by { |ary| ary.flatten.count }.reverse
+      data = sort_arrays_by_size
       largest = data.first
 
       data.drop(1).each do |ary|
         offset = largest.length / (ary.length + 1)
+
         ary.each_with_index do |el, i|
-          if i == 1
+          if ary.length == 1
+            largest.insert((largest.length / 2), el)
+          elsif i == 1
             largest.insert(((largest.length / 2) - offset), el)
           elsif i.even?
             largest.insert(((largest.length / 2) + (offset + i)), el)
@@ -29,8 +32,18 @@ def distributed_merge
       largest
     end
 
+    def all_arrays?
+      all? { |arg| arg.instance_of?(Array) }
+    end
+
     def two_dimensional?
-      all? { |arg| arg.is_a?(Array) } && flatten(1).count > 1
+      flatten(1).none? { |arg| arg.instance_of?(Array) } && flatten(1).count > 1
+    end
+
+    def sort_arrays_by_size
+      sort_by { |ary| ary.flatten.count }.reverse
     end
   end
 end
+
+Array.include DistributedMerge::DistributedMergeArray