Class-as-a-Function Pattern

class GreetingFunction {
  /// The name that should be greeted.
  name: String (1)

  /// The phrase used to greet [name].
  greeting: String = "Hello" (2)

  /// The derived greeting.
  fixed message: String = "\(greeting), \(name)!" (3)
}

greetPigeon: String = new GreetingFunction { name = "Pigeon" }.message (4)

greetHawk: String = new GreetingFunction { name = "Hawk"; greeting = "Good day" }.message (5)

class Temperature {
  fahrenheit: Float = celsius * 9 / 5 + 32
  celsius: Float = kelvin - 273.15
  kelvin: Float = (fahrenheit - 32) / 9 * 5 + 273.15
}

fToK = new Temperature { fahrenheit = 72.0 }.kelvin
fToC = new Temperature { fahrenheit = 72.0 }.celsius
kToF = new Temperature { kelvin = 300.0 }.fahrenheit
kToC = new Temperature { kelvin = 300.0 }.celsius
cToF = new Temperature { celsius = 20.0 }.fahrenheit
cToK = new Temperature { celsius = 20.0 }.kelvin

module SimpleApplication

import "package://pkg.pkl-lang.org/pkl-k8s/k8s@1.1.0#/K8sResource.pkl"
import "package://pkg.pkl-lang.org/pkl-k8s/k8s@1.1.0#/api/apps/v1/Deployment.pkl"
import "package://pkg.pkl-lang.org/pkl-k8s/k8s@1.1.0#/api/core/v1/Service.pkl"
import "package://pkg.pkl-lang.org/pkl-k8s/k8s@1.1.0#/api/networking/v1/Ingress.pkl"

// input properties:
/// Web application name
name: String

/// Container image tag
image: String

/// Application Pod replica count
replicas: Int32? = 1

/// HTTP listen port
port: UInt16 = 8080

/// URL Path to use for liveness checking
livenessPath: String? = "/livez"

/// URL Path to use for readiness checking
readinessPath: String? = "/readyz"

// output properties:
local app = this (1)

/// Kubernetes labels used for all output resources and selectors
labels: Mapping<String, String> = new { (2)
  ["app.kubernetes.io/name"] = name
}

/// Kuberetes [Deployment] that manages the application Pods.
deployment: Deployment = new { (3)
  metadata {
    name = app.name
    labels = app.labels
  }
  spec {
    replicas = app.replicas
    template {
      metadata {
        labels = app.labels
      }
      spec {
        containers {
          new {
            name = app.name
            image = app.image
            when (livenessPath != null) {
              livenessProbe {
                httpGet {
                  port = app.port
                  path = livenessPath
                }
              }
            }
            when (readinessPath != null) {
              readinessProbe {
                httpGet {
                  port = app.port
                  path = readinessPath
                }
              }
            }
          }
        }
      }
    }
  }
}

/// Kubernetes [Service] that provides a cluster-internal VIP for the application.
service: Service = new { (3)
  metadata {
    name = app.name
    labels = app.labels
  }
  spec {
    selector = app.labels
    ports {
      new {
        name = "http"
        port = app.port
      }
    }
  }
}

/// Kubernetes [Ingress] that exposes a VIP for the application outside the cluster.
ingress: Ingress = new { (3)
  metadata {
    name = app.name
    labels = app.labels
  }
  spec {
    defaultBackend {
      service {
        name = app.service?.metadata?.name!!
        port  {
          number = app.service.spec?.ports!![0].port
        }
      }
    }
  }
}

/// All Kubernetes resources needed to deploy the application.
resources: Listing<K8sResource> = new { (4)
  deployment
  service
  ingress
}

import "SimpleApplication.pkl"
import "package://pkg.pkl-lang.org/pkl-k8s/k8s@1.1.0#/K8sResource.pkl"
import "package://pkg.pkl-lang.org/pkl-k8s/k8s@1.1.0#/api/networking/v1/NetworkPolicy.pkl"

/// The most basic [SimpleApplication] usage.
///
/// The application image is expected to listen on port 8080 and provide `/livez` and `/readyz` paths
app1: Listing<K8sResource> = new SimpleApplication {
  name = "app1"
  image = "myregistry/app1:latest"
}.resources

/// Usage of [SimpleApplication] with additional input properties overridden.
app2: Listing<K8sResource> = new SimpleApplication {
  name = "app2"
  image = "myregistry/app2:latest"
  replicas = 3
  port = 9090
  livenessPath = null
  readinessPath = "/healthz"
}.resources

/// Advanced [SimpleApplication] usage where output properties are amended.
///
/// This example amends [deployment] directly to set properties not exposed by [SimpleApplication]'s simple API.
/// It also amends [resources] to add an additional resource required specifically by this application.
app3: Listing<K8sResource> = new SimpleApplication {
  name = "app3"
  image = "myregistry/app3:latest"
  labels {
    ["app.kubernetes.io/instance"] = "\(name)-staging"
  }
  deployment {
    spec {
      template {
        spec {
          securityContext {
            runAsNonRoot = true
          }
          initContainers {
            new {
              name = "my-init-container"
              // ...
            }
          }
        }
      }
    }
  }
  resources {
    new NetworkPolicy {
      // ...
    }
  }
}.resources