class CreateDiffRecordService < ApplicationService
  attr_reader :user, :obj, :column_name, :after, :before

  def initialize(user, obj, column_name, before, after)
    @user   = user
    @obj    = obj
    @before = before
    @after  = after
    @column_name = column_name
  end

  def call
    ActiveRecord::Base.transaction do
      diff_record = DiffRecord.create!(user: user, container: obj, column_name: column_name)
      diff_record.create_diff_record_content!(content: diff_content)
    end
  end

  private

  def diff_content
    content = ''
    Diffy::Diff.new(before, after).each do |line|
      next unless line =~ /^[\+-]/

      content += line
    end
    content
  end
end