server-go/json.go

// Copyright 2024 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package main

import (
	"encoding/json"
	"fmt"
	"mime"
	"net/http"
)

// parseRequestJSON populates the target with the fields of the JSON-encoded value in the request
// body. It expects the request to have the Content-Type header set to JSON and a body with a
// JSON-encoded value complying with the underlying type of target.
func parseRequestJSON(r *http.Request, target any) error {
	contentType := r.Header.Get("Content-Type")
	mediaType, _, err := mime.ParseMediaType(contentType)
	if err != nil {
		return err
	}
	if mediaType != "application/json" {
		return fmt.Errorf("expecting application/json Content-Type. Got %s", mediaType)
	}

	dec := json.NewDecoder(r.Body)
	dec.DisallowUnknownFields()

	return dec.Decode(target)
}

// renderResponseJSON encodes res as JSON and writes it to w.
func renderResponseJSON(w http.ResponseWriter, res any) {
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(res)
}