class Standard
  # @!group Central Air Source Heat Pump

  # Prototype CentralAirSourceHeatPump object using PlantComponentUserDefined
  #
  # @param model [OpenStudio::Model::Model] OpenStudio model object
  # @param hot_water_loop [<OpenStudio::Model::PlantLoop>] a hot water loop served by the central air source heat pump
  # @param name [String] the name of the central air source heat pump, or nil in which case it will be defaulted
  # @param cop [Double] air source heat pump rated cop
  # @return [OpenStudio::Model::PlantComponentUserDefined] a plant component representing the air source heat pump
  # @todo update curve to better calculate based on the rated cop
  # @todo refactor to use the new EnergyPlus central air source heat pump object when it becomes available
  #   set hot_water_loop to an optional keyword argument, and add input keyword arguments for other characteristics
  def create_central_air_source_heat_pump(model,
                                          hot_water_loop,
                                          name: nil,
                                          cop: 3.65)

    # create the PlantComponentUserDefined object as a proxy for the Central Air Source Heat Pump
    plant_comp = OpenStudio::Model::PlantComponentUserDefined.new(model)
    if name.nil?
      if !hot_water_loop.nil?
        name = "#{hot_water_loop.name} Central Air Source Heat Pump"
      else
        name = 'Central Air Source Heat Pump'
      end
    end

    # change equipment name for EMS validity
    plant_comp.setName(name.gsub(/[ +-.]/, '_'))

    # set plant component properties
    plant_comp.setPlantLoadingMode('MeetsLoadWithNominalCapacityHiOutLimit')
    plant_comp.setPlantLoopFlowRequestMode('NeedsFlowIfLoopIsOn')

    # plant design volume flow rate internal variable
    vdot_des_int_var = OpenStudio::Model::EnergyManagementSystemInternalVariable.new(model, 'Plant Design Volume Flow Rate')
    vdot_des_int_var.setName("#{plant_comp.name}_Vdot_Des_Int_Var")
    vdot_des_int_var.setInternalDataIndexKeyName(hot_water_loop.handle.to_s)

    # inlet temperature internal variable
    tin_int_var = OpenStudio::Model::EnergyManagementSystemInternalVariable.new(model, 'Inlet Temperature for Plant Connection 1')
    tin_int_var.setName("#{plant_comp.name}_Tin_Int_Var")
    tin_int_var.setInternalDataIndexKeyName(plant_comp.handle.to_s)

    # inlet mass flow rate internal variable
    mdot_int_var = OpenStudio::Model::EnergyManagementSystemInternalVariable.new(model, 'Inlet Mass Flow Rate for Plant Connection 1')
    mdot_int_var.setName("#{plant_comp.name}_Mdot_Int_Var")
    mdot_int_var.setInternalDataIndexKeyName(plant_comp.handle.to_s)

    # inlet specific heat internal variable
    cp_int_var = OpenStudio::Model::EnergyManagementSystemInternalVariable.new(model, 'Inlet Specific Heat for Plant Connection 1')
    cp_int_var.setName("#{plant_comp.name}_Cp_Int_Var")
    cp_int_var.setInternalDataIndexKeyName(plant_comp.handle.to_s)

    # inlet density internal variable
    rho_int_var = OpenStudio::Model::EnergyManagementSystemInternalVariable.new(model, 'Inlet Density for Plant Connection 1')
    rho_int_var.setName("#{plant_comp.name}_rho_Int_Var")
    rho_int_var.setInternalDataIndexKeyName(plant_comp.handle.to_s)

    # load request internal variable
    load_int_var = OpenStudio::Model::EnergyManagementSystemInternalVariable.new(model, 'Load Request for Plant Connection 1')
    load_int_var.setName("#{plant_comp.name}_Load_Int_Var")
    load_int_var.setInternalDataIndexKeyName(plant_comp.handle.to_s)

    # supply outlet node setpoint temperature sensor
    setpt_mgr_sch_sen = OpenStudio::Model::EnergyManagementSystemSensor.new(model, 'Schedule Value')
    setpt_mgr_sch_sen.setName("#{plant_comp.name}_Setpt_Mgr_Temp_Sen")
    hot_water_loop.supplyOutletNode.setpointManagers.each do |m|
      if m.to_SetpointManagerScheduled.is_initialized
        setpt_mgr_sch_sen.setKeyName(m.to_SetpointManagerScheduled.get.schedule.name.to_s)
      end
    end

    # outdoor air drybulb temperature sensor
    oa_dbt_sen = OpenStudio::Model::EnergyManagementSystemSensor.new(model, 'Site Outdoor Air Drybulb Temperature')
    oa_dbt_sen.setName("#{plant_comp.name}_OA_DBT_Sen")
    oa_dbt_sen.setKeyName('Environment')

    # minimum mass flow rate actuator
    mdot_min_act = plant_comp.minimumMassFlowRateActuator.get
    mdot_min_act.setName("#{plant_comp.name}_Mdot_Min_Act")

    # maximum mass flow rate actuator
    mdot_max_act = plant_comp.maximumMassFlowRateActuator.get
    mdot_max_act.setName("#{plant_comp.name}_Mdot_Max_Act")

    # design flow rate actuator
    vdot_des_act = plant_comp.designVolumeFlowRateActuator.get
    vdot_des_act.setName("#{plant_comp.name}_Vdot_Des_Act")

    # minimum loading capacity actuator
    cap_min_act = plant_comp.minimumLoadingCapacityActuator.get
    cap_min_act.setName("#{plant_comp.name}_Cap_Min_Act")

    # maximum loading capacity actuator
    cap_max_act = plant_comp.maximumLoadingCapacityActuator.get
    cap_max_act.setName("#{plant_comp.name}_Cap_Max_Act")

    # optimal loading capacity actuator
    cap_opt_act = plant_comp.optimalLoadingCapacityActuator.get
    cap_opt_act.setName("#{plant_comp.name}_Cap_Opt_Act")

    # outlet temperature actuator
    tout_act = plant_comp.outletTemperatureActuator.get
    tout_act.setName("#{plant_comp.name}_Tout_Act")

    # mass flow rate actuator
    mdot_req_act = plant_comp.massFlowRateActuator.get
    mdot_req_act.setName("#{plant_comp.name}_Mdot_Req_Act")

    # heat pump COP curve
    constant_coeff = 1.932 + (cop - 3.65)
    hp_cop_curve = OpenStudio::Model::CurveQuadratic.new(model)
    hp_cop_curve.setCoefficient1Constant(constant_coeff)
    hp_cop_curve.setCoefficient2x(0.227674286)
    hp_cop_curve.setCoefficient3xPOW2(-0.007313143)
    hp_cop_curve.setMinimumValueofx(1.67)
    hp_cop_curve.setMaximumValueofx(12.78)
    hp_cop_curve.setInputUnitTypeforX('Temperature')
    hp_cop_curve.setOutputUnitType('Dimensionless')

    # heat pump COP curve index variable
    hp_cop_curve_idx_var = OpenStudio::Model::EnergyManagementSystemCurveOrTableIndexVariable.new(model, hp_cop_curve)

    # high outlet temperature limit actuator
    tout_max_act = OpenStudio::Model::EnergyManagementSystemActuator.new(plant_comp, 'Plant Connection 1', 'High Outlet Temperature Limit')
    tout_max_act.setName("#{plant_comp.name}_Tout_Max_Act")

    # init program
    init_pgrm = plant_comp.plantInitializationProgram.get
    init_pgrm.setName("#{plant_comp.name}_Init_Pgrm")
    init_pgrm_body = <<-EMS
    SET Loop_Exit_Temp = #{hot_water_loop.sizingPlant.designLoopExitTemperature}
    SET Loop_Delta_Temp = #{hot_water_loop.sizingPlant.loopDesignTemperatureDifference}
    SET Cp = @CPHW Loop_Exit_Temp
    SET rho = @RhoH2O Loop_Exit_Temp
    SET #{vdot_des_act.handle} = #{vdot_des_int_var.handle}
    SET #{mdot_min_act.handle} = 0
    SET Mdot_Max = #{vdot_des_int_var.handle} * rho
    SET #{mdot_max_act.handle} = Mdot_Max
    SET Cap = Mdot_Max * Cp * Loop_Delta_Temp
    SET #{cap_min_act.handle} = 0
    SET #{cap_max_act.handle} = Cap
    SET #{cap_opt_act.handle} = 1 * Cap
    EMS
    init_pgrm.setBody(init_pgrm_body)

    # sim program
    sim_pgrm = plant_comp.plantSimulationProgram.get
    sim_pgrm.setName("#{plant_comp.name}_Sim_Pgrm")
    sim_pgrm_body = <<-EMS
    SET tmp = #{load_int_var.handle}
    SET tmp = #{tin_int_var.handle}
    SET tmp = #{mdot_int_var.handle}
    SET #{tout_max_act.handle} = 75.0
    IF #{load_int_var.handle} == 0
    SET #{tout_act.handle} = #{tin_int_var.handle}
    SET #{mdot_req_act.handle} = 0
    SET Elec = 0
    RETURN
    ENDIF
    IF #{load_int_var.handle} >= #{cap_max_act.handle}
    SET Qdot = #{cap_max_act.handle}
    SET Mdot = #{mdot_max_act.handle}
    SET #{mdot_req_act.handle} = Mdot
    SET #{tout_act.handle} = (Qdot / (Mdot * #{cp_int_var.handle})) + #{tin_int_var.handle}
    IF #{tout_act.handle} > #{tout_max_act.handle}
    SET #{tout_act.handle} = #{tout_max_act.handle}
    SET Qdot = Mdot * #{cp_int_var.handle} * (#{tout_act.handle} - #{tin_int_var.handle})
    ENDIF
    ELSE
    SET Qdot = #{load_int_var.handle}
    SET #{tout_act.handle} = #{setpt_mgr_sch_sen.handle}
    SET Mdot = Qdot / (#{cp_int_var.handle} * (#{tout_act.handle} - #{tin_int_var.handle}))
    SET #{mdot_req_act.handle} = Mdot
    ENDIF
    SET Tdb = #{oa_dbt_sen.handle}
    SET COP = @CurveValue #{hp_cop_curve_idx_var.handle} Tdb
    SET EIR = 1 / COP
    SET Pwr = Qdot * EIR
    SET Elec = Pwr * SystemTimestep * 3600
    EMS
    sim_pgrm.setBody(sim_pgrm_body)

    # init program calling manager
    init_mgr = plant_comp.plantInitializationProgramCallingManager.get
    init_mgr.setName("#{plant_comp.name}_Init_Pgrm_Mgr")

    # sim program calling manager
    sim_mgr = plant_comp.plantSimulationProgramCallingManager.get
    sim_mgr.setName("#{plant_comp.name}_Sim_Pgrm_Mgr")

    # metered output variable
    elec_mtr_out_var = OpenStudio::Model::EnergyManagementSystemMeteredOutputVariable.new(model, "#{plant_comp.name} Electricity Consumption")
    elec_mtr_out_var.setName("#{plant_comp.name} Electricity Consumption")
    elec_mtr_out_var.setEMSVariableName('Elec')
    elec_mtr_out_var.setUpdateFrequency('SystemTimestep')
    elec_mtr_out_var.setString(4, sim_pgrm.handle.to_s)
    elec_mtr_out_var.setResourceType('Electricity')
    elec_mtr_out_var.setGroupType('HVAC')
    elec_mtr_out_var.setEndUseCategory('Heating')
    elec_mtr_out_var.setEndUseSubcategory('')
    elec_mtr_out_var.setUnits('J')

    # add to supply side of hot water loop if specified
    hot_water_loop.addSupplyBranchForComponent(plant_comp) unless hot_water_loop.nil?

    # add operation scheme
    htg_op_scheme = OpenStudio::Model::PlantEquipmentOperationHeatingLoad.new(model)
    htg_op_scheme.addEquipment(1000000000, plant_comp)
    hot_water_loop.setPlantEquipmentOperationHeatingLoad(htg_op_scheme)

    return plant_comp
  end
end