From 8dd38fd182e7976ff6e206d80f9d5f3784d5af6d Mon Sep 17 00:00:00 2001
From: Quentin McGaw <quentin.mcgaw@gmail.com>
Date: Tue, 29 Dec 2020 00:56:51 +0000
Subject: [PATCH] Code maintenance: better JSON decoding for HTTP

---
 internal/provider/piav4.go   | 22 ++++++++--------------
 internal/server/handlerv1.go |  8 ++------
 internal/version/github.go   | 15 ++++-----------
 3 files changed, 14 insertions(+), 31 deletions(-)

diff --git a/internal/provider/piav4.go b/internal/provider/piav4.go
index b207e97e..cb004a7b 100644
--- a/internal/provider/piav4.go
+++ b/internal/provider/piav4.go
@@ -469,19 +469,18 @@ func fetchPIAToken(ctx context.Context, openFile os.OpenFileFunc,
 		return "", err
 	}
 	defer response.Body.Close()
-	b, err := ioutil.ReadAll(response.Body)
 	if response.StatusCode != http.StatusOK {
+		b, _ := ioutil.ReadAll(response.Body)
 		shortenMessage := string(b)
 		shortenMessage = strings.ReplaceAll(shortenMessage, "\n", "")
 		shortenMessage = strings.ReplaceAll(shortenMessage, "  ", " ")
 		return "", fmt.Errorf("%s: response received: %q", response.Status, shortenMessage)
-	} else if err != nil {
-		return "", err
 	}
+	decoder := json.NewDecoder(response.Body)
 	var result struct {
 		Token string `json:"token"`
 	}
-	if err := json.Unmarshal(b, &result); err != nil {
+	if err := decoder.Decode(&result); err != nil {
 		return "", err
 	} else if len(result.Token) == 0 {
 		return "", fmt.Errorf("token is empty")
@@ -534,16 +533,13 @@ func fetchPIAPortForwardData(ctx context.Context, client *http.Client, gateway n
 	if response.StatusCode != http.StatusOK {
 		return 0, "", expiration, fmt.Errorf("cannot obtain signature: %s", response.Status)
 	}
-	b, err := ioutil.ReadAll(response.Body)
-	if err != nil {
-		return 0, "", expiration, fmt.Errorf("cannot obtain signature: %w", err)
-	}
+	decoder := json.NewDecoder(response.Body)
 	var data struct {
 		Status    string `json:"status"`
 		Payload   string `json:"payload"`
 		Signature string `json:"signature"`
 	}
-	if err := json.Unmarshal(b, &data); err != nil {
+	if err := decoder.Decode(&data); err != nil {
 		return 0, "", expiration, fmt.Errorf("cannot decode received data: %w", err)
 	} else if data.Status != "OK" {
 		return 0, "", expiration, fmt.Errorf("response received from PIA has status %s", data.Status)
@@ -580,15 +576,13 @@ func bindPIAPort(ctx context.Context, client *http.Client, gateway net.IP, data
 	if response.StatusCode != http.StatusOK {
 		return fmt.Errorf("cannot bind port: %s", response.Status)
 	}
-	b, err := ioutil.ReadAll(response.Body)
-	if err != nil {
-		return fmt.Errorf("cannot bind port: %w", err)
-	}
+
+	decoder := json.NewDecoder(response.Body)
 	var responseData struct {
 		Status  string `json:"status"`
 		Message string `json:"message"`
 	}
-	if err := json.Unmarshal(b, &responseData); err != nil {
+	if err := decoder.Decode(&responseData); err != nil {
 		return fmt.Errorf("cannot bind port: %w", err)
 	} else if responseData.Status != "OK" {
 		return fmt.Errorf("response received from PIA: %s (%s)", responseData.Status, responseData.Message)
diff --git a/internal/server/handlerv1.go b/internal/server/handlerv1.go
index 8ec53c2a..8663f37a 100644
--- a/internal/server/handlerv1.go
+++ b/internal/server/handlerv1.go
@@ -50,13 +50,9 @@ func (h *handlerV1) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 }
 
 func (h *handlerV1) getVersion(w http.ResponseWriter) {
-	data, err := json.Marshal(h.buildInfo)
-	if err != nil {
+	encoder := json.NewEncoder(w)
+	if err := encoder.Encode(h.buildInfo); err != nil {
 		h.logger.Warn(err)
 		w.WriteHeader(http.StatusInternalServerError)
-		return
-	}
-	if _, err := w.Write(data); err != nil {
-		h.logger.Warn(err)
 	}
 }
diff --git a/internal/version/github.go b/internal/version/github.go
index 0e0255a5..3930ea78 100644
--- a/internal/version/github.go
+++ b/internal/version/github.go
@@ -3,7 +3,6 @@ package version
 import (
 	"context"
 	"encoding/json"
-	"io/ioutil"
 	"net/http"
 	"time"
 )
@@ -35,11 +34,8 @@ func getGithubReleases(ctx context.Context, client *http.Client) (releases []git
 		return nil, err
 	}
 	defer response.Body.Close()
-	b, err := ioutil.ReadAll(response.Body)
-	if err != nil {
-		return nil, err
-	}
-	if err := json.Unmarshal(b, &releases); err != nil {
+	decoder := json.NewDecoder(response.Body)
+	if err := decoder.Decode(&releases); err != nil {
 		return nil, err
 	}
 	return releases, nil
@@ -56,11 +52,8 @@ func getGithubCommits(ctx context.Context, client *http.Client) (commits []githu
 		return nil, err
 	}
 	defer response.Body.Close()
-	b, err := ioutil.ReadAll(response.Body)
-	if err != nil {
-		return nil, err
-	}
-	if err := json.Unmarshal(b, &commits); err != nil {
+	decoder := json.NewDecoder(response.Body)
+	if err := decoder.Decode(&commits); err != nil {
 		return nil, err
 	}
 	return commits, nil