Vital Ruby Lab 4

presentation.rb

class Array
  def sum
    inject(0.0) { |result, el| result + el }
  end

  def mean
    sum / size
  end
end

class InvalidScoreError < RuntimeError
end

class Presentation
  attr_reader :presentation_id, :title, :presenter, :subject, :scores

  def initialize(presentation_id, title, presenter, subject)
    @presentation_id, @title, @presenter, @subject = [presentation_id, title, presenter, subject]
    @scores = []
  end

  def self.parse(line)
    self.new(*line.split(':'))
  end

  def add_score(score)
    raise InvalidScoreError if !score.is_a?(Integer) || score < 1 || score > 5
    @scores << score
  end

  def average_score
    return @scores.mean unless @scores.empty?
    0.0
  end
end

processor.rb

require 'presentation'

class Processor
  def initialize
    @presentations = []
  end

  def parse_presentations(text)
    text.lines.each do |line|
      @presentations << Presentation.parse(line)
    end
  end

  def parse_votes(text)
    text.lines.each do |line|
      presentation_id, score = line.split
      presentation = @presentations.detect {|presentation| presentation.presentation_id == presentation_id}
      presentation.add_score(score.to_i)
    end
  end

  def sorted_presentations
    @presentations.sort_by {|presentation| presentation.average_score }
  end

  def good
    sorted_presentations.select {|presentation| presentation.average_score >= 4.0 }
  end

  def bad
    sorted_presentations.select {|presentation| presentation.average_score <= 2.0 }
  end

  def parse
    parse_presentations(File.read('presentations.txt'))
    parse_votes(File.read('votes.txt'))
    puts "Good presentations:"
    good.each do |presentation|
      puts "#{sprintf("%.1f", presentation.average_score)} - #{presentation.title}"
    end
    puts
    puts "Bad presentations:"
    bad.each do |presentation|
      puts "#{sprintf("%.1f", presentation.average_score)} - #{presentation.title}"
    end
  end
end

Rakefile

require 'processor.rb'

task :parse do
  p = Processor.new
  p.parse
end

task :default => :parse