Sapo exercice in ruby

paginator.rb

require "awesome_print"

def pagination(current_page, total_pages, boundaries, around)
  elements = []

  # add boundaries elements
  (1..boundaries).to_a.each { |val|
    elements.push(val)
    elements.push(total_pages-val+1)
  }

  # add around elements top limit
  # exclude current page by adding +1 to starting range
  (current_page+1..current_page+around).to_a.each { |val|
    elements.push(val) unless elements.include?(val)
  }

  # add around elements bottom limit
  # include current page by the inverse reason of before
  (current_page-around..current_page).to_a.each { |val|
    elements.push(val) unless elements.include?(val)
  }

  elements.sort!
  elements.uniq!
  elements.select!{ |val| val if val > 0 and val <= total_pages} # filter out elements that we don't need
  elements_clone = elements.clone # we need to iterate trough a copy and change the original
  shifts_needed = 0 # are to compensate the index of the original array, that is changed by inserting the ...
  old_value = nil  # used to detect the gaps between current and past values

  elements_clone.each_with_index { |val, index|
    if old_value.nil?
      old_value = val
      next
    end

    #puts "val: #{val}, old: #{old_value}, index: #{index}, diff: #{val-old_value}" #debug output

    if (val-old_value) > 1
      #puts "gap found at: #{index}" #debug output
      elements.insert((index+shifts_needed), '...')
      shifts_needed += 1
    end

    old_value = val
  }
  puts elements.to_s
  elements
end

pagination(4, 5, 1, 0) # [1, "...", 4, 5]
pagination(4, 10, 2, 2) # [1, 2, 3, 4, 5, 6, "...", 9, 10]
pagination(6, 30, 2, 2) #[1, 2, "...", 4, 5, 6, 7, 8, "...", 29, 30]
pagination(1, 10, 2, 2) # [1, 2, 3, "...", 9, 10]
pagination(6, 30, 2, 2) # [1, 2, 3, "...", 9, 10]
pagination(10, 10, 10, 10) # [1, "...", 4, 5]