feat: Completes hvac-system-performance views and api call.

Sources/ApiController/ApiController.swift

@@ -32,7 +32,7 @@ extension ApiController: DependencyKey {
 
       case let .calculateHVACSystemPerformance(request):
         logger.debug("Calculating hvac system performance: \(request)")
-        fatalError()
+        return try await request.respond(logger: logger)
 
       case let .calculateMoldRisk(request):
         logger.debug("Calculating mold risk: \(request)")

Sources/ApiController/Extensions/HVACSystemPerformance.swift

@@ -0,0 +1,92 @@
+import Dependencies
+import Foundation
+import Logging
+import PsychrometricClient
+import Routes
+
+public extension HVACSystemPerformance.Request {
+
+  // TODO: Check if we should use psychrometrics for the request conditions instead
+  private static let airDensity = 0.075 // lb/ft^3 at standard conditions.
+  private static let specificHeat = 0.24 // BTU/lb at standard conditions (imperial).
+
+  func respond(logger: Logger) async throws -> HVACSystemPerformance.Response {
+    @Dependency(\.psychrometricClient) var psychrometricClient
+
+    try validate()
+
+    let altitude = parseAltitude()
+    let temperatureSplit = returnAirTemperature - supplyAirTemperature
+
+    let returnAirProperties = try await psychrometricClient.psychrometricProperties(.dryBulb(
+      .init(.init(returnAirTemperature)),
+      relativeHumidity: returnAirHumidity%,
+      altitude: altitude
+    ))
+
+    let supplyAirProperties = try await psychrometricClient.psychrometricProperties(.dryBulb(
+      .init(.init(supplyAirTemperature)),
+      relativeHumidity: supplyAirHumidity%,
+      altitude: altitude
+    ))
+
+    let airMassFlow = airflow * 60 * Self.airDensity
+    logger.debug("Air mass flow: \(airMassFlow)")
+    let condensationRate = airMassFlow * (
+      returnAirProperties.humidityRatio.value - supplyAirProperties.humidityRatio.value
+    ) // lb/hr
+    let sensibleCapacity = airMassFlow * Self.specificHeat * temperatureSplit
+    logger.debug("Return enthalpy: \(returnAirProperties.enthalpy.value)")
+    logger.debug("Supply enthalpy: \(supplyAirProperties.enthalpy.value)")
+    let deltaEnthalpy = returnAirProperties.enthalpy.value - supplyAirProperties.enthalpy.value
+    logger.debug("Delta enthalpy: \(deltaEnthalpy)")
+    let totalCapacity = airMassFlow * deltaEnthalpy
+
+    let capacity = HVACSystemPerformance.Capacity(
+      total: totalCapacity,
+      sensible: sensibleCapacity,
+      latent: totalCapacity - sensibleCapacity
+    )
+
+    let systemMetrics = HVACSystemPerformance.SystemMetrics(
+      cfmPerTon: airflow / systemSize,
+      targetTemperatureSplit: (systemSize * 12000 * 0.75) / (1.08 * airflow),
+      actualTemperatureSplit: temperatureSplit,
+      condensationRatePoundsPerHour: condensationRate
+    )
+
+    return .init(
+      returnAirProperties: returnAirProperties,
+      supplyAirProperties: supplyAirProperties,
+      capacity: capacity,
+      systemMetrics: systemMetrics
+    )
+  }
+
+  private func parseAltitude() -> Length {
+    guard let altitude, altitude > 0 else { return .seaLevel }
+    return .init(altitude)
+  }
+
+  private func validate() throws {
+    guard returnAirTemperature > 0 else {
+      throw ValidationError(message: "Return air temperature should be greater than 0.")
+    }
+    guard returnAirHumidity > 0 else {
+      throw ValidationError(message: "Return air humidity should be greater than 0.")
+    }
+    guard supplyAirTemperature > 0 else {
+      throw ValidationError(message: "Supply air temperature should be greater than 0.")
+    }
+    guard supplyAirHumidity > 0 else {
+      throw ValidationError(message: "Supply air humidity should be greater than 0.")
+    }
+    guard systemSize > 0 else {
+      throw ValidationError(message: "System size should be greater than 0.")
+    }
+  }
+
+  struct ValidationError: Error {
+    let message: String
+  }
+}