michaelmior / NoSE

module NoSE

  module Random

    # A simple representation of a random ER diagram

    class Network

      attr_reader :entities

      def initialize(params = {})

        @nodes_nb = params.fetch :nodes_nb, 10

        @field_count = RandomGaussian.new params.fetch(:num_fields, 3), 1

        @neighbours = Array.new(@nodes_nb) { Set.new }

      end

      # :nocov:

      def inspect

        @nodes.map do |node|

          @entities[node].inspect

        end.join "\n"

      end

      # :nocov:

      protected

      # Create a random entity to use in the model

      # @return [Entity]

      def create_entity(node)

        num_entities = RandomGaussian.new 10_000, 100

        entity = Entity.new('E' + random_name(node)) * num_entities.rand

        pick_fields entity

        entity

      end

      # Probabilities of selecting various field types

      FIELD_TYPES = [

        [Fields::IntegerField, 0.45].freeze,

        [Fields::StringField,  0.35].freeze,

        [Fields::DateField,    0.1].freeze,

        [Fields::FloatField,   0.1].freeze

      ].freeze

      # Select random fields for an entity

      # @return [void]

      def pick_fields(entity)

        entity << Fields::IDField.new(entity.name + 'ID')

        0.upto(@field_count.rand).each do |field_index|

          entity << random_field(field_index)

        end

      end

      # Generate a random field to add to an entity

      # @return [Fields::Field]

      def random_field(field_index)

        type_rand = rand

        FIELD_TYPES.find do |_, threshold|

          type_rand -= threshold

          type_rand <= threshold

        end[0].send(:new, 'F' + random_name(field_index))

      end

      # Add foreign key relationships for neighbouring nodes

      # @return [void]

        @neighbours.each_with_index do |other_nodes, node|

          other_nodes.each do |other_node|

            @neighbours[other_node].delete node

            if rand > 0.5

              from_node = node

              to_node = other_node

            else

              from_node = other_node

              to_node = node

            end

            from_field = Fields::ForeignKeyField.new(

              'FK' + @entities[to_node].name + 'ID',

              @entities[to_node]

            )

            to_field = Fields::ForeignKeyField.new(

              'FK' + @entities[from_node].name + 'ID',

              @entities[from_node]

            )

            from_field.reverse = to_field

            to_field.reverse = from_field

            @entities[from_node] << from_field

            @entities[to_node] << to_field

          end

        end

      end

      # Add a new link between two nodes

      # @return [void]

      def add_link(node, other_node)

        @neighbours[node] << other_node

        @neighbours[other_node] << node

      end

      # Remove a link between two nodes

      # @return [void]

      def remove_link(node, other_node)

        @neighbours[node].delete other_node

        @neighbours[other_node].delete node

      end

      # Find a new neighbour for a node

      def new_neighbour(node, neighbour)

        unlinkable_nodes = [node, neighbour] + @neighbours[node].to_a

        (@nodes.to_a - unlinkable_nodes).sample

      end

      # Random names of variables combined to create random names

      VARIABLE_NAMES = %w(Foo Bar Baz Quux Corge Grault

                          Garply Waldo Fred Plugh).freeze

      # Generate a random name for an attribute

      # @return [String]

      def random_name(index)

        index.to_s.chars.map(&:to_i).map { |digit| VARIABLE_NAMES[digit] }.join

      end

    end

    # Generates random queries over entities in a given model

    class StatementGenerator

      def initialize(model)

        @model = model

      end

      # Generate a new random insertion to entities in the model

      # @return [Insert]

      def random_insert(connect = true)

        entity = @model.entities.values.sample

        settings = entity.fields.each_value.map do |field|

          "#{field.name}=?"

        end.join ', '

        insert = "INSERT INTO #{entity.name} SET #{settings} "

        # Optionally add connections to other entities

        insert += random_connection(entity) if connect

        Statement.parse insert, @model

      end

      # Generate a random connection for an Insert

      def random_connection(entity)

        connections = entity.foreign_keys.values.sample(2)

        'AND CONNECT TO ' + connections.map do |connection|

          "#{connection.name}(?)"

        end.join(', ')

      end

      # Generate a new random update of entities in the model

      # @return [Update]

      def random_update(path_length = 1, updated_fields = 2,

                        condition_count = 1)

        path = random_path(path_length)

        settings = random_settings path, updated_fields

        from = [path.first.parent.name] + path.entries[1..-1].map(&:name)

        update = "UPDATE #{from.first} FROM #{from.join '.'} " \

                 "SET #{settings} " +

                 random_where_clause(path, condition_count)

        Statement.parse update, @model

      end

      # Get random settings for an update

      # @return [String]

      def random_settings(path, updated_fields)

        # Don't update key fields

        update_fields = path.entities.first.fields.values

        update_fields.reject! { |field| field.is_a? Fields::IDField }

        update_fields.sample(updated_fields).map do |field|

          "#{field.name}=?"

        end.join ', '

      end

      # Generate a new random deletion of entities in the model

      # @return [Delete]

      def random_delete

        path = random_path(1)

        from = [path.first.parent.name] + path.entries[1..-1].map(&:name)

        delete = "DELETE #{from.first} FROM #{from.join '.'} " +

                 random_where_clause(path, 1)

        Statement.parse delete, @model

      end

      # Generate a new random query from entities in the model

      # @return [Query]

                       condition_count = 2, order = false)

        path = random_path path_length

        graph = QueryGraph::Graph.from_path path

        conditions = [

          Condition.new(path.entities.first.fields.values.sample, :'=', nil)

        ]

        condition_count -= 1

        new_fields = random_where_conditions(path, condition_count,

                                             conditions.map(&:field).to_set)

        conditions += new_fields.map do |field|

          Condition.new(field, :'>', nil)

        end

        conditions = Hash[conditions.map do |condition|

          [condition.field.id, condition]

        end]

        params = {

          select: random_select(path, selected_fields),

          model: @model,

          graph: graph,

          key_path: graph.longest_path,

          entity: graph.longest_path.first.parent,

          conditions: conditions,

          order: order ? [graph.entities.to_a.sample.fields.values.sample] : []

        }

        query = Query.new params, nil

        query.hash

        query

      end

      # Get random fields to select for a Query

      # @return [Set<Fields::Field>]

      def random_select(path, selected_fields)

        fields = Set.new

        while fields.length < selected_fields

          fields.add path.entities.sample.fields.values.sample

        end

        fields

      end

      # Produce a random statement according to a given set of weights

      # @return [Statement]

      def random_statement(weights = { query: 80, insert: 10, update: 5,

                                       delete: 5 })

        pick = Pickup.new(weights)

        type = pick.pick(1)

        send(('random_' + type.to_s).to_sym)

      end

      # Return a random path through the entity graph

      # @return [KeyPath]

      def random_path(max_length)

        path = [@model.entities.values.sample.id_field]

        while path.length < max_length

          # Find a list of keys to entities we have not seen before

          last_entity = path.last.entity

          keys = last_entity.foreign_keys.values

          keys.reject! { |key| path.map(&:entity).include? key.entity }

          break if keys.empty?

          # Add a random new key to the path

          path << keys.sample

        end

        KeyPath.new path

      end

      # Produce a random query graph over the entity graph

        graph = QueryGraph::Graph.new

        last_node = graph.add_node @model.entities.values.sample

        while graph.size < max_nodes

          # Get the possible foreign keys to use

          keys = last_node.entity.foreign_keys.values

          keys.reject! { |key| graph.nodes.map(&:entity).include? key.entity }

          break if keys.empty?

          # Pick a random foreign key to traverse

          next_key = keys.sample

          graph.add_edge last_node, next_key.entity, next_key

          # Select a new node to start from, making sure we pick one

          # that still has valid outgoing edges

          last_node = graph.nodes.reject do |node|

            (node.entity.foreign_keys.each_value.map(&:entity) -

             graph.nodes.map(&:entity)).empty?

          end.sample

          break if last_node.nil?

        end

        graph

      end

      private

      # Produce a random where clause using fields along a given path

      # @return [String]

      def random_where_clause(path, count = 2)

        # Ensure we have at least one condition at the beginning of the path

        conditions = [path.entities.first.fields.values.sample]

        conditions += random_where_conditions path, count - 1

        return '' if conditions.empty?

        "WHERE #{conditions.map do |field|

          "#{path.find_field_parent(field).name}.#{field.name} = ?"

        end.join ' AND '}"

      end

      # Produce a random set of fields for a where clause

      # @return [Array<Fields::Field>]

      def random_where_conditions(path, count, exclude = Set.new)

        1.upto(count).map do

          field = path.entities.sample.fields.values.sample

          next nil if field.name == '**' || exclude.include?(field)

          field

        end.compact

      end

      # Get the name to be used in the query for a condition field

      # @return [String]

  end

  # Generate random numbers according to a Guassian distribution

  class RandomGaussian

    def initialize(mean, stddev, integer = true, min = 1)

      @mean = mean

      @stddev = stddev

      @valid = false

      @next = 0

      @integer = integer

      @min = min

    end

    # Return the next valid random number

    # @return [Fixnum]

    def rand

      if @valid

        @valid = false

        clamp @next

      else

        @valid = true

        x, y = self.class.gaussian(@mean, @stddev)

        @next = y

        clamp x

      end

    end

    private

    # Clamp the value to the given minimum

    def clamp(value)

      value = value.to_i if @integer

      [@min, value].max unless @min.nil?

    end

    # Return a random number for the given distribution

    # @return [Array<Fixnum>]

      theta = 2 * Math::PI * rand

      rho = Math.sqrt(-2 * Math.log(1 - rand))

      scale = stddev * rho

      x = mean + scale * Math.cos(theta)

      y = mean + scale * Math.sin(theta)

      [x, y]

    end

  end

end

require_relative 'random/barbasi_albert'

require_relative 'random/watts_strogatz'