require 'earth/locality'

class FlightSegment < ActiveRecord::Base
  self.primary_key = "row_hash"
  
  extend CohortScope
  self.minimum_cohort_size = 1
  
  # Cutting this for now because if iata code is missing we have to look up airports using both city and country; don't know how to do this with ActiveRecord
  # - Ian 6/12/2011
  # # If airport iata code is missing, associate with all airports in a city
  # # We need this to calculate distance when importing ICAO segments - see cm1 flight_segment.rb
  # has_many :origin_city_airports,      :foreign_key => 'city', :primary_key => 'origin_airport_city',      :class_name => 'Airport'
  # has_many :destination_city_airports, :foreign_key => 'city', :primary_key => 'destination_airport_city', :class_name => 'Airport'
  
  # Enable flight_segment.aircraft
  cache_fuzzy_match_with :aircraft, :primary_key => :aircraft_description, :foreign_key => :description
  
  class << self
    def update_averages!
      # Derive load factor, which is passengers divided by available seats
      where('seats > 0').update_all 'load_factor = 1.0 * passengers / seats'
      
      # Assume a load factor of 1 where passengers > available seats
      where('passengers > seats AND seats > 0').update_all 'load_factor = 1'
      
      # FIXME TODO: what is 90.718474
      # Derive freight share as a fraction of the total weight carried
      where('(freight + mail + passengers) > 0').update_all 'freight_share = 1.0 * (freight + mail) / (freight + mail + (passengers * 90.718474))'
      
      # Derive average seats per flight
      where('flights > 0').update_all 'seats_per_flight = 1.0 * seats / flights'
    end
  end
  
  falls_back_on :distance         => lambda { weighted_average(:distance,         :weighted_by => :passengers) }, # 2077.1205         data1 10-12-2010
                :seats_per_flight => lambda { weighted_average(:seats_per_flight, :weighted_by => :passengers) }, # 144.15653537046   data1 10-12-2010
                :load_factor      => lambda { weighted_average(:load_factor,      :weighted_by => :passengers) }, # 0.78073233770097  data1 10-12-2010
                :freight_share    => lambda { weighted_average(:freight_share,    :weighted_by => :passengers) }  # 0.022567224170157 data1 10-12-2010
  
  col :row_hash                            # auto-generated primary key
  col :origin_airport_iata_code            # iata code
  col :origin_airport_city                 # city
  col :origin_country_iso_3166_code        # iso code
  col :destination_airport_iata_code       # iata code
  col :destination_airport_city            # city
  col :destination_country_iso_3166_code   # iso code
  col :airline_bts_code                    # bts code
  col :airline_icao_code                   # icao code
  col :airline_name                        # text description derived from bts or icao code
  col :aircraft_bts_code                   # bts code
  col :aircraft_description                # text description derived from BTS T100 or ICAO TFS
  col :flights,          :type => :integer # number of flights over month or year
  col :passengers,       :type => :integer # total passengers on all flights
  col :seats,            :type => :integer # total seats on all flights
  col :seats_per_flight, :type => :float   # average seats per flight; make this a float
  col :load_factor,      :type => :float   # passengers / seats
  col :freight_share,    :type => :float   # (freight + mail) / (freight + mail + (passengers * average passenger weight))
  col :distance,         :type => :float   # flight distance
  col :distance_units                      # 'kilometres'
  col :payload_capacity, :type => :float   # aircraft maximum payload capacity rating; float b/c unit conversion
  col :payload_capacity_units              # 'kilograms'
  col :freight,          :type => :float   # total freight on all flights performed; float b/c unit conversion
  col :freight_units                       # 'kilograms'
  col :mail,             :type => :float   # total mail on all flights performed; float b/c unit conversion
  col :mail_units                          # 'kilograms'
  col :month,            :type => :integer # month of flight
  col :year,             :type => :integer # year of flight
  col :source                              # 'BTS T100' or 'ICAO TFS'
  add_index :origin_airport_iata_code
  add_index :origin_airport_city
  add_index :destination_airport_iata_code
  add_index :destination_airport_city
  add_index :airline_bts_code
  add_index :airline_icao_code
  add_index :airline_name
  add_index :aircraft_bts_code
  add_index :aircraft_description
  add_index :year
end