Implementation of the implementation we talked about yesterday.

scheduler.rb

require 'chronic'

class Scheduler
  def self.process(params)
    raise 'start_date must be supplied' if params[:start_date].nil?
    raise 'end_date must be supplied' if params[:end_date].nil?
    raise 'occurs_on must be supplied' if params[:occurs_on].nil?

    start_date = DateTime.parse params[:start_date]
    end_date = DateTime.parse params[:end_date]
    selected_days = params[:occurs_on].map { |day, _| day.to_i }
    
    raise 'End date cannot earlier than start date' if end_date < start_date

    num_days = (end_date - start_date).to_i


    # Collect all the dates between start_date and end_date
    dates = [start_date]
    num_days.times do
      tomorrow = dates.last.advance days: 1
      dates.push tomorrow
    end

    # Select only dates whose day is what the user selected
    dates_to_be_scheduled = []
    selected_days.each do |day|
      dates_to_be_scheduled.push dates.select { |date| date.wday == day }
    end

    dates_to_be_scheduled.flatten.sort
  end

end