UNKNOWN_READING = { :total_kwh_consumed_high => nil, :total_kwh_consumed_low => nil, :total_kwh_produced_high => nil, :total_kwh_produced_low => nil, :total_m3_gas_consumed => nil}
  

class Reading < ActiveRecord::Base
     
  def eql_reading?(reading)
    self.total_kwh_consumed_high == reading.total_kwh_consumed_high &&
    self.total_kwh_consumed_low == reading.total_kwh_consumed_low &&
    self.total_kwh_produced_high == reading.total_kwh_produced_high &&
    self.total_kwh_produced_low == reading.total_kwh_produced_low &&
    self.current_kw_consumed == reading.current_kw_consumed &&
    self.current_kw_produced == reading.current_kw_produced &&
    self.total_m3_gas_consumed == reading.total_m3_gas_consumed &&
    self.high_tarif == reading.high_tarif
  end
  
  # reduce precision to 1 digit behind comma
  def total_kwh_consumed_high=(kwh)
    write_attribute(:total_kwh_consumed_high,kwh.round(1))
  end

  # reduce precision to 1 digit behind comma
  def total_kwh_consumed_low=(kwh)
    write_attribute(:total_kwh_consumed_low,kwh.round(1))
  end

  # reduce precision to 1 digit behind comma
  def total_kwh_produced_high=(kwh)
    write_attribute(:total_kwh_produced_high,kwh.round(1))
  end

  # reduce precision to 1 digit behind comma
  def total_kwh_produced_low=(kwh)
    write_attribute(:total_kwh_produced_low,kwh.round(1))
  end
 
  # calculate difference with another reading
  # return a hash with differences (self - reading)
  def diff(reading)
    if reading
      { :total_kwh_consumed_high => (self.total_kwh_consumed_high - reading.total_kwh_consumed_high).round(1),
        :total_kwh_consumed_low => (self.total_kwh_consumed_low - reading.total_kwh_consumed_low).round(1),
        :total_kwh_produced_high => (self.total_kwh_produced_high - reading.total_kwh_produced_high).round(1),
        :total_kwh_produced_low => (self.total_kwh_produced_low - reading.total_kwh_produced_low).round(1),
        :total_m3_gas_consumed => (self.total_m3_gas_consumed - reading.total_m3_gas_consumed).round(3) }
    else
      { :total_kwh_consumed_high => self.total_kwh_consumed_high,
        :total_kwh_consumed_low => self.total_kwh_consumed_low,
        :total_kwh_produced_high => self.total_kwh_produced_high,
        :total_kwh_produced_low => self.total_kwh_produced_low,
        :total_m3_gas_consumed => self.total_m3_gas_consumed }
    end
  end
  
  
  
  #
  # Class methods
  #
  class << self
    # return readings from beginning of 'from' until end of 'to'
    def days(from, to)
      Reading.where("created_at > :begin AND created_at < :end", { :begin => from.to_date.beginning_of_day, :end => to.to_date.end_of_day})  
    end
    
    def day(date)
      Reading.where("created_at > :begin AND created_at < :end", { :begin => date.to_date.beginning_of_day, :end => date.to_date.end_of_day})        
    end
    
    def max_charge_kwh=(kwh)
      @@max_charge_kwh = kwh
    end
    
    def max_charge_kwh
      @@max_charge_kwh
    end
    
    # do not make distinction between high and low consumption/production
    def consumed_and_produced_for_diff(d)

      usage_kwh = (d[:total_kwh_consumed_high].nil? || d[:total_kwh_consumed_low].nil?) ? nil :  d[:total_kwh_consumed_high] + d[:total_kwh_consumed_low] 
      return_kwh = (d[:total_kwh_produced_high].nil? || d[:total_kwh_produced_low].nil?) ? nil : d[:total_kwh_produced_high] + d[:total_kwh_produced_low]

      return usage_kwh, return_kwh
    end
    
    def diff_on(date)
      readings_on = day(date)
      first = readings_on.first
      last = readings_on.last
      if last
        last.diff(first)
      else
        { :total_kwh_consumed_high => 0, :total_kwh_consumed_low => 0, :total_kwh_produced_high => 0, :total_kwh_produced_low => 0, :total_m3_gas_consumed => 0 }
      end
    end

    def diff_between(from_date, to_date)
      readings_on_days = days(from_date, to_date)
      first = readings_on_days.first
      last = readings_on_days.last
      if last
        last.diff(first)
      else
        { :total_kwh_consumed_high => 0, :total_kwh_consumed_low => 0, :total_kwh_produced_high => 0, :total_kwh_produced_low => 0, :total_m3_gas_consumed => 0 }
      end
    end
  end
end