Opal CoderPad Challenge

challenge.rb

require 'minitest/autorun'

  #The commands available are:   
  # SET <key> <value>  // store the value for key
  # GET <key>          // return the current value for key
  # DELETE <key>       // remove the entry for key
  # COUNT <value>      // return the number of keys that have the given value
  # BEGIN              // start a transaction
  # COMMIT             // commit all transactions
  # ROLLBACK           // rollback current transaction
  # ROLLBACK_ALL       // rollback all transactions
  # HELP               // this list
  #

class SimpleDb
  attr_accessor :data_store
  attr_accessor :transactions
  attr_accessor :in_transaction
  
   def initialize
     self.data_store = {}
     self.transaction = []
     self.in_transaction = false
   end
 
  def database
    return data_store if in_transaction == false
    transaction
  end
  
  def BEGIN
    self.in_transaction = true
    "Transaction (Level/Nest 1) Begin"
  end
  
  def SET(key, value)
    if in_transaction
      self.transactions << {key => value}
    else
      database[key] = value
    end
  end
  
  def COMMIT
    transactions.each do |transaction|
      keys = transaction.keys
      keys.each do |key|
        data_store[key] = data[key]
      end
    end
    self.in_transaction = false
  end
  
  def GET(key)
    value = database[key]
    return "Key not set." if value.nil?
    value
  end
  
  def COUNT(value)
    database.values.count(value)
  end
  
  def DELETE(key)
    database.delete(key)
  end
  
  def ROLLBACK
    self.transactions.pop
    self.in_transaction = false
    "Transaction rolled back."
  end
  
  def ROLLBACK_ALL
    self.transactions = []
    self.in_transaction = false
    "Transactions rolled back."
  end
end


class SimpleDbTest < Minitest::Spec
  before do
    @simple_db = SimpleDb.new
  end

  describe "SimpleDb" do
    describe "Simple commands" do
      before do
        @simple_db.SET("1","1")
      end

      it "should SET and GET data" do
        assert_equal "1", @simple_db.GET("1")
      end
      
      it "should overwrite when SET is called for a key that already exists" do
        @simple_db.SET("1","B")
        assert_equal "B", @simple_db.GET("1")
      end
      
      it "should DELETE data" do
        @simple_db.DELETE("1")
        assert_equal "Key not set.", @simple_db.GET("1")
      end

      it "should return COUNT for num keys with value" do
        assert_equal 1, @simple_db.COUNT("1")
        @simple_db.SET("2", "1")
        assert_equal 2, @simple_db.COUNT("1")
        @simple_db.SET("3", "2")
        assert_equal 2, @simple_db.COUNT("1")
      end

    end
    
    describe "Transactions" do
      before do
        @simple_db.SET("1","1")
      end

      it "should allow transaction BEGIN" do
        message = @simple_db.BEGIN
        assert_equal "Transaction (Level/Nest 1) Begin", message
      end

      it "should allow transaction ROLLBACK" do
        @simple_db.BEGIN
        @simple_db.SET("3", "3")
        message = @simple_db.ROLLBACK
        assert_equal "Transaction rolled back.", message
        assert_equal @simple_db.GET("3"), "Key not set."
      end

      it "should back out all transactions" do
        @simple_db.BEGIN
        @simple_db.SET("3", "3")
        @simple_db.BEGIN
        @simple_db.SET("4", "4")
        message = @simple_db.ROLLBACK_ALL
        assert_equal "Transactions rolled back.", message
        assert_equal "1", @simple_db.GET("1")
        assert_equal "Key not set.", @simple_db.GET("3")
      end

      it "should commit changes" do
        @simple_db.BEGIN
        @simple_db.SET("3", "3")
        @simple_db.COMMIT 
        assert_equal "3", @simple_db.GET("3")
      end
      
      it "should commit all non rolled-back changes" do
        @simple_db.BEGIN
        @simple_db.SET("3", "3")
        @simple_db.BEGIN
        @simple_db.SET("4", "4")
        @simple_db.ROLLBACK
        @simple_db.COMMIT
        assert_equal "3", @simple_db.GET("3")
        assert_equal "Key not set.", @simple_db.GET("4")
      end
    end
  end
end