require 'compensate/version'
require 'csv'

module Compensate
  class ProjectSet
    RATE_HIGH = '85'.freeze
    RATE_LOW  = '75'.freeze
    TRAVEL_RATE_HIGH = '55'.freeze
    TRAVEL_RATE_LOW  = '45'.freeze

    def initialize(csv)
      @projects = projects_from_csv(csv)
    end

    def total
      parse_projects_and_handle_duplicates
      apply_billing_rates_to_hash
      calculate_total
    end

    private

    def parse_projects_and_handle_duplicates
      # Split projects up and determine what rate to bill at
      @projects.each do |project|
        rate = project[:rate]
        days_in(project).each do |day|
          date = date_to_string(day)
          billing_hash[date] = rate unless has_been_logged?(day)
        end
      end
    end

    def apply_billing_rates_to_hash
      # splice in the correct billing rate
      billing_hash.each do |k, v|
        billing_hash[k] = if v == 'low'
                            RATE_LOW
                          else
                            RATE_HIGH
                          end
      end
    end

    def calculate_total
      total = all_project_sums.map(&:sum)
      "Total is $#{total.sum}.00"
    end

    def all_project_sums
      ranges = split_projects_into_ranges

      # Apply travel rate to first and last days in each range
      ranges.each do |range|
        range.each_with_index do |r, i|
          r[1] = travel_rate_for(r) if (i == 0) || (i == range.size - 1)
        end
      end

      # Sum each range's billing amount
      ranges.map do |range|
        range.map { |r| total = + r[1].to_i }
      end
    end

    def split_projects_into_ranges
      date_array = billing_hash.to_a
      previous = date_array[0]

      # Calculate where project ranges have gaps
      ranges = date_array.slice_before do |e|
        subsequent = previous
        previous = e
        to_date(subsequent[0]).next_day != to_date(e[0])
      end
    end

    def days_in(project)
      start_date = to_date(project[:start])
      end_date = to_date(project[:end])

      (start_date..end_date)
    end

    def has_been_logged?(day)
      billing_hash.key?(date_to_string(day))
    end

    def travel_rate_for(day)
      case day[1]
      when RATE_HIGH
        TRAVEL_RATE_HIGH
      when RATE_LOW
        TRAVEL_RATE_LOW
      end
    end

    def to_date(string)
      DateTime.strptime(string.to_s, date_format)
    end

    def date_to_string(date)
      date.strftime(date_format)
    end

    def date_format
      '%m/%d/%y'
    end

    def projects_from_csv(csv)
      project_array = []
      CSV.foreach(csv, headers: true) do |row|
        project_array << { rate: row[0], start: row[1], end: row[2] }
      end
      project_array
    end

    def billing_hash
      @billing_hash ||= {}
    end
  end
end