netengine_golf.rb

require 'rspec'
require 'json'
require 'active_support/all'
require 'pry'

def input
  [
    {lastmodificationdate:"2012-11-16",userproject:'FCBIZ',totalcost:10},
    {lastmodificationdate:"2012-11-16",userproject:'LMS',totalcost:20},
    {lastmodificationdate:"2012-11-16",userproject:'NetEngine',totalcost:52},
    {lastmodificationdate:"2012-11-17",userproject:'FCBIZ',totalcost:11},
    {lastmodificationdate:"2012-11-17",userproject:'LMS',totalcost:22},
    {lastmodificationdate:"2012-11-17",userproject:'NetEngine',totalcost:53},
    {lastmodificationdate:"2012-11-18",userproject:'FCBIZ',totalcost:34},
    {lastmodificationdate:"2012-11-18",userproject:'LMS',totalcost:32},
    {lastmodificationdate:"2012-11-18",userproject:'NetEngine',totalcost:55}
  ]
end

def desired_output
  [
   {lastmodificationdate:"2012-12-16",FCBIZ:10,LMS:20,NetEngine:52},
   {lastmodificationdate:"2012-12-17",FCBIZ:11,LMS:22,NetEngine:53},
   {lastmodificationdate:"2012-12-18",FCBIZ:34,LMS:32,NetEngine:55}
 ]
end

class NetEngineGolf
  def jim_1(input)
    input.group_by { |a| a[:date] }.map do |date, values|
      values.inject({}) do |hash, value|
        hash.merge! value
      end
    end
  end

  def jim_2(input)
    input.group_by { |a| a[:date] }.map do |date, values|
      merged = { date: date }
      values.each { |value| merged.merge! value.except(:date) }
      merged
    end
  end
end

describe NetEngineGolf do
  describe "#jim_1" do
    it "turns the input into the output" do
      output = NetEngineGolf.new.jim_1(input)
      output.should == desired_output
    end
  end
  
  describe "#jim_2" do
    it "turns the input into the output" do
      output = NetEngineGolf.new.jim_2(input)
      output.should == desired_output
    end
  end
end