Class: TransformableList

Inherits:
Object
  • Object
show all
Defined in:
lib/transformable_list.rb,
lib/transformable_list/version.rb

Constant Summary collapse

VERSION = 
"0.1.0"

Instance Method Summary collapse

Constructor Details

#initialize(items, matcher: -> a, b { a == b }) ⇒ TransformableList

Returns a new instance of TransformableList.



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# File 'lib/transformable_list.rb', line 5

def initialize(items, matcher: -> a, b { a == b })
  @items = items
  @matcher = matcher
end

Instance Method Details

#transform(new_items) ⇒ Object 



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# File 'lib/transformable_list.rb', line 10

def transform(new_items)
  build_remaining_items_index!

  moves = []
  creates = []
  deletes = []

  indexes_to_keep = Set.new

  new_items.map.with_index do |new_item, new_index|
    if existing_index = find_index_and_eliminate_match(new_item)
      if new_index != existing_index
        moves << [:move, @items[existing_index], new_index]
      end

      indexes_to_keep << existing_index
    else
      creates << [:create, new_item, new_index]
    end
  end

  (0...@items.size).each do |index|
    unless indexes_to_keep.include?(index)
      deletes << [:delete, @items[index], index]
    end
  end

  deletes.sort_by(&:last) + creates.sort_by(&:last) + moves.sort_by(&:last)
end