# Reopen the OpenStudio class to add methods to apply standards to this object
class OpenStudio::Model::WaterHeaterMixed
  # Applies the standard efficiency ratings and typical losses and paraisitic loads to this object.
  # Efficiency and skin loss coefficient (UA)
  # Per PNNL http://www.energycodes.gov/sites/default/files/documents/PrototypeModelEnhancements_2014_0.pdf
  # Appendix A: Service Water Heating
  #
  # @param template [String] valid choices: 'DOE Ref Pre-1980', 'DOE Ref 1980-2004', '90.1-2004', '90.1-2007', '90.1-2010', '90.1-2013'
  # @param standards [Hash] the OpenStudio_Standards spreadsheet in hash format
  # @return [Bool] true if successful, false if not
  def apply_efficiency(template)
    # Get the capacity of the water heater
    # TODO add capability to pull autosized water heater capacity
    # if the Sizing:WaterHeater object is ever implemented in OpenStudio.
    capacity_w = heaterMaximumCapacity
    if capacity_w.empty?
      OpenStudio.logFree(OpenStudio::Warn, 'openstudio.standards.WaterHeaterMixed', "For #{name}, cannot find capacity, standard will not be applied.")
      return false
    else
      capacity_w = capacity_w.get
    end
    capacity_btu_per_hr = OpenStudio.convert(capacity_w, 'W', 'Btu/hr').get
    capacity_kbtu_per_hr = OpenStudio.convert(capacity_w, 'W', 'kBtu/hr').get

    # Get the volume of the water heater
    # TODO add capability to pull autosized water heater volume
    # if the Sizing:WaterHeater object is ever implemented in OpenStudio.
    volume_m3 = tankVolume
    if volume_m3.empty?
      OpenStudio.logFree(OpenStudio::Warn, 'openstudio.standards.WaterHeaterMixed', "For #{name}, cannot find volume, standard will not be applied.")
      return false
    else
      volume_m3 = volume_m3.get
    end
    volume_gal = OpenStudio.convert(volume_m3, 'm^3', 'gal').get

    # Get the heater fuel type
    fuel_type = heaterFuelType
    unless fuel_type == 'NaturalGas' || fuel_type == 'Electricity'
      OpenStudio.logFree(OpenStudio::Warn, 'openstudio.standards.WaterHeaterMixed', "For #{name}, fuel type of #{fuel_type} is not yet supported, standard will not be applied.")
    end

    # Calculate the water heater efficiency and
    # skin loss coefficient (UA)
    # Calculate the energy factor (EF)
    # From PNNL http://www.energycodes.gov/sites/default/files/documents/PrototypeModelEnhancements_2014_0.pdf
    # Appendix A: Service Water Heating
    water_heater_eff = nil
    ua_btu_per_hr_per_f = nil
    sl_btu_per_hr = nil
    case fuel_type
    when 'Electricity'
      case template
      when 'DOE Ref Pre-1980', 'DOE Ref 1980-2004', '90.1-2004', '90.1-2007', '90.1-2010', '90.1-2013'

        if capacity_w <= 12_000 # I think this should be 12000W, use variable capacity_w instead of capacity_btu_per_hr (as per PNNL doc)
          # Fixed water heater efficiency per PNNL
          water_heater_eff = 1
          # Calculate the minimum Energy Factor (EF)
          base_ef, vol_drt = case template
                             when 'DOE Ref Pre-1980', 'DOE Ref 1980-2004', '90.1-2004', '90.1-2007'
                               [0.93, 0.00132]
                             when '90.1-2010'
                               [0.97, 0.00132]
                             when '90.1-2013'
                               [0.97, 0.00035]
                             end

          ef = base_ef - (vol_drt * volume_gal)
          # Calculate the skin loss coefficient (UA)
          ua_btu_per_hr_per_f = (41_094 * (1 / ef - 1)) / (24 * 67.5)
        else
          # Fixed water heater efficiency per PNNL
          water_heater_eff = 1
          # Calculate the skin loss coefficient (UA)
          case template
          when 'DOE Ref Pre-1980', 'DOE Ref 1980-2004', '90.1-2004', '90.1-2007', '90.1-2010'
            # Calculate the max allowable standby loss (SL)
            sl_btu_per_hr = 20 + (35 * Math.sqrt(volume_gal)) 
            # Calculate the skin loss coefficient (UA)
            ua_btu_per_hr_per_f = sl_btu_per_hr / 70
          when '90.1-2013'
            # Calculate the percent loss per hr
            hrly_loss_pct = (0.3 + 27 / volume_gal) / 100
            # Convert to Btu/hr, assuming:
            # Water at 120F, density = 8.25 lb/gal
            # 1 Btu to raise 1 lb of water 1 F
            # Therefore 8.25 Btu / gal of water * deg F
            # 70F delta-T between water and zone
            hrly_loss_btu_per_hr = hrly_loss_pct * volume_gal * 8.25 * 70
            # Calculate the skin loss coefficient (UA)
            ua_btu_per_hr_per_f = hrly_loss_btu_per_hr / 70
          end
        end

      when 'NECB 2011'
        volume_l_per_s = volume_m3 * 1000
        if capacity_btu_per_hr <= OpenStudio.convert(12, 'kW', 'Btu/hr').get
          # Fixed water heater efficiency per PNNL
          water_heater_eff = 1
          # Calculate the max allowable standby loss (SL)
          sl_w = if volume_l_per_s < 270
                   40 + 0.2 * volume_l_per_s # assume bottom inlet
                 else
                   0.472 * volume_l_per_s - 33.5
                 end # assume bottom inlet
          sl_btu_per_hr = OpenStudio.convert(sl_w, 'W', 'Btu/hr').get
        else
          # Fixed water heater efficiency per PNNL
          water_heater_eff = 1
          # Calculate the max allowable standby loss (SL)   # use this - NECB does not give SL calculation for cap > 12 kW
          sl_btu_per_hr = 20 + (35 * Math.sqrt(volume_gal))
        end
        # Calculate the skin loss coefficient (UA)
        ua_btu_per_hr_per_f = sl_btu_per_hr / 70
      end

    when 'NaturalGas'
      case template # TODO: inconsistency; ref buildings don't calculate water heater UA the same way
      when 'DOE Ref Pre-1980', 'DOE Ref 1980-2004'
        water_heater_eff = 0.78
        ua_btu_per_hr_per_f = 11.37
      when '90.1-2004', '90.1-2007', '90.1-2010', '90.1-2013', 'NECB 2011'
        if capacity_btu_per_hr <= 75_000
          # Fixed water heater thermal efficiency per PNNL
          water_heater_eff = 0.82
          # Calculate the minimum Energy Factor (EF)
          base_ef, vol_drt = case template
                             when '90.1-2004', '90.1-2007'
                               [0.62, 0.0019]
                             when '90.1-2010', 'NECB 2011'
                               [0.67, 0.0019]
                             when '90.1-2013'
                               [0.67, 0.0005]
                             end

          ef = base_ef - (vol_drt * volume_gal)
          # Calculate the Recovery Efficiency (RE)
          # based on a fixed capacity of 75,000 Btu/hr
          # and a fixed volume of 40 gallons by solving
          # this system of equations:
          # ua = (1/.95-1/re)/(67.5*(24/41094-1/(re*cap)))
          # 0.82 = (ua*67.5+cap*re)/cap
          cap = 75_000.0
          re = (Math.sqrt(6724 * ef**2 * cap**2 + 40_409_100 * ef**2 * cap - 28_080_900 * ef * cap + 29_318_000_625 * ef**2 - 58_636_001_250 * ef + 29_318_000_625) + 82 * ef * cap + 171_225 * ef - 171_225) / (200 * ef * cap)
          # Calculate the skin loss coefficient (UA)
          # based on the actual capacity.
          ua_btu_per_hr_per_f = (water_heater_eff - re) * capacity_btu_per_hr / 67.5
        else
          # Thermal efficiency requirement from 90.1
          et = 0.8
          # Calculate the max allowable standby loss (SL)
          cap_adj, vol_drt = case template
                   when '90.1-2004', '90.1-2007', '90.1-2010', 'NECB 2011'
                     [800, 110]
                   when '90.1-2013'
                     [799, 16.6]
                   end
          sl_btu_per_hr = (capacity_btu_per_hr / cap_adj + vol_drt * Math.sqrt(volume_gal))
          # Calculate the skin loss coefficient (UA)
          ua_btu_per_hr_per_f = (sl_btu_per_hr * et) / 70
          # Calculate water heater efficiency
          water_heater_eff = (ua_btu_per_hr_per_f * 70 + capacity_btu_per_hr * et) / capacity_btu_per_hr
        end
      end
    end

    # Convert to SI
    ua_btu_per_hr_per_c = OpenStudio.convert(ua_btu_per_hr_per_f, 'Btu/hr*R', 'W/K').get

    # Set the water heater properties
    # Efficiency
    setHeaterThermalEfficiency(water_heater_eff)
    # Skin loss
    setOffCycleLossCoefficienttoAmbientTemperature(ua_btu_per_hr_per_c)
    setOnCycleLossCoefficienttoAmbientTemperature(ua_btu_per_hr_per_c)
    # TODO: Parasitic loss (pilot light)
    # PNNL document says pilot lights were removed, but IDFs
    # still have the on/off cycle parasitic fuel consumptions filled in
    setOnCycleParasiticFuelType(fuel_type)
    # self.setOffCycleParasiticFuelConsumptionRate(??)
    setOnCycleParasiticHeatFractiontoTank(0)
    setOffCycleParasiticFuelType(fuel_type)
    # self.setOffCycleParasiticFuelConsumptionRate(??)
    setOffCycleParasiticHeatFractiontoTank(0.8)

    # set part-load performance curve
    if template == 'NECB 2011' && fuel_type == 'NaturalGas'
      plf_vs_plr_curve = model.add_curve('SWH-EFFFPLR-NECB2011')
      setPartLoadFactorCurve(plf_vs_plr_curve)
    end

    # Append the name with standards information
    setName("#{name} #{water_heater_eff.round(3)} Therm Eff")
    OpenStudio.logFree(OpenStudio::Info, 'openstudio.model.WaterHeaterMixed', "For #{template}: #{name}; thermal efficiency = #{water_heater_eff.round(3)}, skin-loss UA = #{ua_btu_per_hr_per_f.round}Btu/hr")

    return true
  end

  # Applies the correct fuel type for the water heaters
  # in the baseline model.  For most standards and for most building
  # types, the baseline uses the same fuel type as the proposed.
  # However, certain standards like 90.1-2013 require a change
  # in some scenarios.
  #
  # @param building_type [String] the building type
  # @return [Bool] returns true if successful, false if not.
  def apply_prm_baseline_fuel_type(template, building_type)
    # For all standards except 90.1-2013
    # baseline is same as proposed per
    # Table G3.1 item 11.b
    unless template == '90.1-2013'
      return true
    end

    # Determine the building-type specific
    # fuel requirements from Table G3.1.1-2
    new_fuel = nil
    case building_type
    when 'SecondarySchool', 'PrimarySchool', # School/university
         'SmallHotel', # Motel
         'LargeHotel', # Hotel
         'QuickServiceRestaurant', # Dining: Cafeteria/fast food
         'FullServiceRestaurant', # Dining: Family
         'MidriseApartment', 'HighriseApartment', # Multifamily
         'Hospital', # Hospital
         'Outpatient' # Health-care clinic
      new_fuel = 'NaturalGas'
    when 'SmallOffice', 'MediumOffice', 'LargeOffice', # Office
         'RetailStandalone', 'RetailStripmall', # Retail
         'Warehouse' # Warehouse
      new_fuel = 'Electricity'
    else
      new_fuel = 'NaturalGas'
    end

    # Change the fuel type if necessary
    old_fuel = heaterFuelType
    unless new_fuel == old_fuel
      setHeaterFuelType(new_fuel)
      OpenStudio.logFree(OpenStudio::Info, 'openstudio.standards.WaterHeaterMixed', "For #{name}, changed baseline water heater fuel from #{old_fuel} to #{new_fuel}.")
    end

    return true
  end

  # Finds capacity in Btu/hr
  #
  # @return [Double] capacity in Btu/hr to be used for find object
  def find_capacity()

    # Get the coil capacity
    capacity_w = nil
    if self.heaterMaximumCapacity.is_initialized
      capacity_w = self.heaterMaximumCapacity.get
    elsif self.autosizedHeaterMaximumCapacity.is_initialized
      capacity_w = self.autosizedHeaterMaximumCapacity.get
    else
      OpenStudio::logFree(OpenStudio::Warn, 'openstudio.standards.WaterHeaterMixed', "For #{self.name} capacity is not available.")
      return false
    end

    # Convert capacity to Btu/hr
    capacity_btu_per_hr = OpenStudio.convert(capacity_w, "W", "Btu/hr").get

    return capacity_btu_per_hr

  end
end