From 7f7ba91570169130cb50b093e9ee148f37e21889 Mon Sep 17 00:00:00 2001
From: Umputun <umputun@gmail.com>
Date: Fri, 9 Feb 2024 15:57:31 -0600
Subject: [PATCH] add a pair of encode/decode json functions

---
 rest.go      | 20 +++++++++++++++++++-
 rest_test.go | 48 ++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 63 insertions(+), 5 deletions(-)

diff --git a/rest.go b/rest.go
index 1b321ec..d8181f3 100644
--- a/rest.go
+++ b/rest.go
@@ -10,7 +10,7 @@ import (
 )
 
 // JSON is a map alias, just for convenience
-type JSON map[string]interface{}
+type JSON map[string]any
 
 // RenderJSON sends data as json
 func RenderJSON(w http.ResponseWriter, data interface{}) {
@@ -97,3 +97,21 @@ func ParseFromTo(r *http.Request) (from, to time.Time, err error) {
 	}
 	return from, to, nil
 }
+
+// DecodeJSON decodes json request from http.Request to given type
+func DecodeJSON[T any](r *http.Request, res *T) error {
+	if err := json.NewDecoder(r.Body).Decode(&res); err != nil {
+		return fmt.Errorf("decode json: %w", err)
+	}
+	return nil
+}
+
+// EncodeJSON encodes given type to http.ResponseWriter and sets status code and content type header
+func EncodeJSON[T any](w http.ResponseWriter, status int, v T) error {
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	w.WriteHeader(status)
+	if err := json.NewEncoder(w).Encode(v); err != nil {
+		return fmt.Errorf("encode json: %w", err)
+	}
+	return nil
+}
diff --git a/rest_test.go b/rest_test.go
index a31d264..c78b952 100644
--- a/rest_test.go
+++ b/rest_test.go
@@ -1,6 +1,7 @@
 package rest
 
 import (
+	"bytes"
 	"encoding/json"
 	"errors"
 	"io"
@@ -15,7 +16,6 @@ import (
 )
 
 func TestRest_RenderJSON(t *testing.T) {
-
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		j := JSON{"key1": 1, "key2": "222"}
 		RenderJSON(w, j)
@@ -35,7 +35,6 @@ func TestRest_RenderJSON(t *testing.T) {
 }
 
 func TestRest_RenderJSONFromBytes(t *testing.T) {
-
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		require.NoError(t, RenderJSONFromBytes(w, r, []byte("some data")))
 	}))
@@ -53,7 +52,6 @@ func TestRest_RenderJSONFromBytes(t *testing.T) {
 }
 
 func TestRest_RenderJSONWithHTML(t *testing.T) {
-
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		j := JSON{"key1": "val1", "key2": 2.0, "html": `<div> blah </div>`}
 		require.NoError(t, RenderJSONWithHTML(w, r, j))
@@ -77,7 +75,6 @@ func TestRest_RenderJSONWithHTML(t *testing.T) {
 }
 
 func TestParseFromTo(t *testing.T) {
-
 	tbl := []struct {
 		query    string
 		from, to time.Time
@@ -123,6 +120,49 @@ func TestParseFromTo(t *testing.T) {
 
 }
 
+func TestDecodeJSONRequest(t *testing.T) {
+	type record struct {
+		Field1 string `json:"field1"`
+		Field2 int    `json:"field2"`
+	}
+
+	inp := `{"field1":"value1","field2":2}`
+	req := httptest.NewRequest(http.MethodPost, "/test", bytes.NewBufferString(inp))
+	req.Header.Set("Content-Type", "application/json")
+
+	var obj record
+	err := DecodeJSON(req, &obj)
+	require.NoError(t, err)
+	assert.Equal(t, "value1", obj.Field1)
+	assert.Equal(t, 2, obj.Field2)
+}
+
+func TestEncodeJSONResponse(t *testing.T) {
+	type record struct {
+		Field1 string `json:"field1"`
+		Field2 int    `json:"field2"`
+	}
+
+	obj := record{Field1: "value1", Field2: 2}
+	w := httptest.NewRecorder()
+	if err := EncodeJSON(w, http.StatusOK, obj); err != nil {
+		t.Errorf("Failed to encode JSON response: %v", err)
+	}
+
+	resp := w.Result()
+	defer resp.Body.Close()
+
+	assert.Equal(t, http.StatusOK, resp.StatusCode)
+	assert.Equal(t, "application/json; charset=utf-8", resp.Header.Get("Content-Type"))
+
+	var decodedObj record
+	err := json.NewDecoder(resp.Body).Decode(&decodedObj)
+	require.NoError(t, err)
+
+	assert.Equal(t, obj.Field1, decodedObj.Field1)
+	assert.Equal(t, obj.Field2, decodedObj.Field2)
+}
+
 func getTestHandlerBlah() http.HandlerFunc {
 	fn := func(rw http.ResponseWriter, req *http.Request) {
 		_, _ = rw.Write([]byte("blah"))