Document composition

type DeploymentConfig = {
  serviceName: string;
  replicas: number;
  environment: "development" | "staging" | "production";
  healthCheckPath?: string;
};

class DeploymentConfigBuilder {
  private serviceName?: string;
  private replicas = 1;
  private environment: DeploymentConfig["environment"] = "development";
  private healthCheckPath?: string;

  withServiceName(serviceName: string) {
    this.serviceName = serviceName;
    return this;
  }

  withReplicas(replicas: number) {
    this.replicas = replicas;
    return this;
  }

  forEnvironment(environment: DeploymentConfig["environment"]) {
    this.environment = environment;
    return this;
  }

  withHealthCheck(path: string) {
    this.healthCheckPath = path;
    return this;
  }

  build(): DeploymentConfig {
    if (!this.serviceName) {
      throw new Error("A service name is required.");
    }

    return {
      serviceName: this.serviceName,
      replicas: this.replicas,
      environment: this.environment,
      healthCheckPath: this.healthCheckPath,
    };
  }
}

const productionConfig = new DeploymentConfigBuilder()
  .withServiceName("billing-api")
  .withReplicas(3)
  .forEnvironment("production")
  .withHealthCheck("/health")
  .build();