import Logging
import Routes

public extension DehumidifierSize.Request {

  private static let minTempEfficiency = 65.0
  private static let minRHEfficiency = 60.0
  private static let dehumidifierSizes = [
    33: "https://www.santa-fe-products.com/product/ultramd33-dehumidifier/",
    70: "https://www.santa-fe-products.com/product/santa-fe-ultra70-dehumidifier/",
    100: "https://www.santa-fe-products.com/product/ultra98-dehumidifier/",
    118: "https://www.santa-fe-products.com/product/ultra120-dehumidifier/",
    155: "https://www.santa-fe-products.com/product/ultra1559dehumidifier/",
    205: "https://www.santa-fe-products.com/product/ultra205-dehumidifier/"
  ]

  func respond(_ logger: Logger) async throws -> DehumidifierSize.Response {
    try validate()

    let pintsPerDay = (latentLoad / 1054) * 24
    var capacityFactor = 1.0
    var warnings: [String] = []

    if temperature < Self.minTempEfficiency {
      if temperature < 60 {
        capacityFactor *= 0.5
        warnings.append(
          "Very low temperature will severely reduce dehumidifier efficiency."
        )
      } else {
        capacityFactor *= 0.7
        warnings.append(
          "Low temperature will severely reduce dehumidifier efficiency."
        )
      }
    }

    if humidity < Self.minRHEfficiency {
      capacityFactor *= 0.8
      warnings.append(
        "Low relative humidity will significantly reduce moisture removal rate."
      )
    }

    let requiredCapacity = pintsPerDay / capacityFactor

    addDefaultWarnings(&warnings)

    // TODO: Return an error if required capacity is larger than biggest residential dehumidifier.
    // TODO: Return early here ??
    if requiredCapacity > 205 {
      logger.debug("Required capacity exceeds residential unit.")
      warnings.append(
        "Required capacity exceeds largest standard residential unit - consider multiple units or a commercial system"
      )
    }

    let (recommendedSize, recommendedUrl) = parseRecommendedSize(requiredCapacity)

    logger.debug("Recommend size: \(recommendedSize)")

    return .init(
      requiredCapacity: requiredCapacity,
      pintsPerDay: pintsPerDay,
      recommendedSize: recommendedSize,
      recommendedUrl: recommendedUrl,
      warnings: warnings
    )
  }

  private func validate() throws {
    guard latentLoad > 0 else {
      throw DehumidiferSizeValidationError.latentLoadShouldBeGreaterThanZero
    }
    guard temperature > 0 else {
      throw DehumidiferSizeValidationError.temperatureShouldBeGreaterThanZero
    }
    guard humidity > 0 else {
      throw DehumidiferSizeValidationError.humidityShouldBeGreaterThanZero
    }
  }

  private func parseRecommendedSize(_ requiredCapacity: Double) -> (Int, String) {
    // TODO: Return an error if required capacity is larger than biggest residential dehumidifier.

    // Ensure the keys are sorted, otherwise it gives unpredictable results.
    let key = Self.dehumidifierSizes.keys.sorted()
      .first { Double($0) >= requiredCapacity }
      // Use the largest dehumidifier because the requirement is larger than the largest key.
      ?? 255

    return (key, Self.dehumidifierSizes[key]!)
  }

  private func addDefaultWarnings(_ warnings: inout [String]) {
    // High humidity warnings
    if humidity > 65 {
      warnings.append(
        "High relative humidity - unit may need to run continuously."
      )
    }

    if humidity > 80 {
      warnings.append(
        "Extreme humidity levels - address moisture sources and improve ventilation before dehumidification."
      )
    }

    // Temperature warnings
    if temperature < 60 {
      warnings.append(
        "Temperature too low for effective dehumidification - consider raising space temperature first."
      )
    }
  }
}

enum DehumidiferSizeValidationError: Error {
  case latentLoadShouldBeGreaterThanZero
  case temperatureShouldBeGreaterThanZero
  case humidityShouldBeGreaterThanZero
}