json.go

package main

import (
	"encoding/json"
	"log"
	"net/http"
)

// responseWithJSON take the input as a Go data structure type and output a json
func responseWithJSON(w http.ResponseWriter, statusCode int, payload interface{}) {
	data, err := json.Marshal(payload)

	// Handle error if Marshal process gone wrong
	if err != nil {
		log.Printf("Failed to Marshal json response: %v", payload)
		w.WriteHeader(500)
		return
	}

	w.Header().Add("Content-Type", "application/json")
	w.WriteHeader(statusCode)

	// 204 mean no content, so in case this function is being use with 204 but still get passed the payload, it will stop here rather than try to write the payload
	// Go default Write will also check for this status and if we try to pass data, it will have an error
	if statusCode == 204 {
		return
	}

	_, writeErr := w.Write(data)
	if writeErr != nil {
		log.Printf("Failed while writing data after Marshal: %v", err)
		w.WriteHeader(500)
		return
	}
}

func responseWithError(w http.ResponseWriter, statusCode int, msg string) {
	// Handle when back end error
	if statusCode > 499 {
		log.Println("Responding with 5XX error", msg)
	}

	type errResponse struct {
		Error string `json:"error"`
	}

	responseWithJSON(w, statusCode, errResponse{
		Error: msg,
	})
}