Api GatewayResponse class

ApiGatewayResponse.kt

package com.myblockbuster

import com.fasterxml.jackson.core.JsonProcessingException
import com.fasterxml.jackson.databind.ObjectMapper
import com.myblockbuster.core.Model
import org.apache.logging.log4j.LogManager
import java.nio.charset.StandardCharsets
import java.util.*

/**
 * Instead of having a generic response for everything now the Response class is an interface
 * and we create a specific implementation of it
 */
class ApiGatewayResponse(
        val statusCode: Int = 200,
        var body: String? = null,
        val headers: Map<String, String>? = Collections.emptyMap(),
        val isBase64Encoded: Boolean = false
): Response {

  companion object {
    inline fun build(block: Builder.() -> Unit) = Builder().apply(block).build()
    val LOG = LogManager.getLogger() // Singleton Logger
  }

  /**
   * Uses the Builder pattern to create the response
   */
  class Builder {
    var objectMapper: ObjectMapper = ObjectMapper()
    var statusCode: Int = 200
    var rawBody: String? = null
    var headers: Map<String, String>? = Collections.emptyMap()
    var objectBody: Model? = null
    var listBody: List<Any>? = null
    var binaryBody: ByteArray? = null
    var base64Encoded: Boolean = false

    fun build(): ApiGatewayResponse {
      var body: String? = null

      when {
        rawBody != null -> body = rawBody as String
        objectBody != null || (listBody != null && listBody!!.isNotEmpty()) -> try {
          body = when {
            objectBody != null -> objectMapper.writeValueAsString(objectBody)
            else -> objectMapper.writeValueAsString(listBody)
          }
        } catch (e: JsonProcessingException) {
          LOG.error("Failed to serialize object", e)
          throw RuntimeException(e)
        }
        binaryBody != null -> body = String(Base64.getEncoder().encode(binaryBody), StandardCharsets.UTF_8)
      }
      return ApiGatewayResponse(statusCode, body, headers, base64Encoded)
    }
  }
}