From 9e77a662a3d859a8f2bba47609a73e90d55e3e08 Mon Sep 17 00:00:00 2001
From: Andre Medeiros <me@andremedeiros.info>
Date: Thu, 15 Jul 2021 13:27:48 -0400
Subject: [PATCH] avoid parsing JSON if it is known empty response

---
 internal/reddit/client.go  | 17 ++++++++++++-----
 internal/reddit/request.go | 23 +++++++++++++++--------
 internal/reddit/types.go   |  2 ++
 3 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/internal/reddit/client.go b/internal/reddit/client.go
index a7091b7..62211b4 100644
--- a/internal/reddit/client.go
+++ b/internal/reddit/client.go
@@ -97,7 +97,7 @@ func (rc *Client) NewAuthenticatedClient(refreshToken, accessToken string) *Auth
 	return &AuthenticatedClient{rc, refreshToken, accessToken, nil}
 }
 
-func (rac *AuthenticatedClient) request(r *Request, rh ResponseHandler) (interface{}, error) {
+func (rac *AuthenticatedClient) request(r *Request, rh ResponseHandler, empty interface{}) (interface{}, error) {
 	req, err := r.HTTPRequest()
 	if err != nil {
 		return nil, err
@@ -135,6 +135,11 @@ func (rac *AuthenticatedClient) request(r *Request, rh ResponseHandler) (interfa
 		}
 		return nil, NewError(val)
 	}
+
+	if r.emptyResponseBytes > 0 && len(bb) == r.emptyResponseBytes {
+		return empty, nil
+	}
+
 	val, err := parser.ParseBytes(bb)
 	if err != nil {
 		return nil, err
@@ -153,7 +158,7 @@ func (rac *AuthenticatedClient) RefreshTokens() (*RefreshTokenResponse, error) {
 		WithBasicAuth(rac.id, rac.secret),
 	)
 
-	rtr, err := rac.request(req, NewRefreshTokenResponse)
+	rtr, err := rac.request(req, NewRefreshTokenResponse, nil)
 	if err != nil {
 		return nil, err
 	}
@@ -166,10 +171,11 @@ func (rac *AuthenticatedClient) MessageInbox(opts ...RequestOption) (*ListingRes
 		WithMethod("GET"),
 		WithToken(rac.accessToken),
 		WithURL("https://oauth.reddit.com/message/inbox.json"),
+		WithEmptyResponseBytes(122),
 	}, opts...)
 	req := NewRequest(opts...)
 
-	lr, err := rac.request(req, NewListingResponse)
+	lr, err := rac.request(req, NewListingResponse, EmptyListingResponse)
 	if err != nil {
 		return nil, err
 	}
@@ -182,11 +188,12 @@ func (rac *AuthenticatedClient) MessageUnread(opts ...RequestOption) (*ListingRe
 		WithMethod("GET"),
 		WithToken(rac.accessToken),
 		WithURL("https://oauth.reddit.com/message/unread.json"),
+		WithEmptyResponseBytes(122),
 	}, opts...)
 
 	req := NewRequest(opts...)
 
-	lr, err := rac.request(req, NewListingResponse)
+	lr, err := rac.request(req, NewListingResponse, EmptyListingResponse)
 	if err != nil {
 		return nil, err
 	}
@@ -201,7 +208,7 @@ func (rac *AuthenticatedClient) Me() (*MeResponse, error) {
 		WithURL("https://oauth.reddit.com/api/v1/me"),
 	)
 
-	mr, err := rac.request(req, NewMeResponse)
+	mr, err := rac.request(req, NewMeResponse, nil)
 	if err != nil {
 		return nil, err
 	}
diff --git a/internal/reddit/request.go b/internal/reddit/request.go
index 089a792..47aff4a 100644
--- a/internal/reddit/request.go
+++ b/internal/reddit/request.go
@@ -11,19 +11,20 @@ import (
 const userAgent = "server:apollo-backend:v1.0 (by /u/iamthatis)"
 
 type Request struct {
-	body   url.Values
-	query  url.Values
-	method string
-	token  string
-	url    string
-	auth   string
-	tags   []string
+	body               url.Values
+	query              url.Values
+	method             string
+	token              string
+	url                string
+	auth               string
+	tags               []string
+	emptyResponseBytes int
 }
 
 type RequestOption func(*Request)
 
 func NewRequest(opts ...RequestOption) *Request {
-	req := &Request{url.Values{}, url.Values{}, "GET", "", "", "", nil}
+	req := &Request{url.Values{}, url.Values{}, "GET", "", "", "", nil, 0}
 	for _, opt := range opts {
 		opt(req)
 	}
@@ -90,3 +91,9 @@ func WithQuery(key, val string) RequestOption {
 		req.query.Set(key, val)
 	}
 }
+
+func WithEmptyResponseBytes(bytes int) RequestOption {
+	return func(req *Request) {
+		req.emptyResponseBytes = bytes
+	}
+}
diff --git a/internal/reddit/types.go b/internal/reddit/types.go
index 0cd818b..123ca21 100644
--- a/internal/reddit/types.go
+++ b/internal/reddit/types.go
@@ -129,3 +129,5 @@ func NewListingResponse(val *fastjson.Value) interface{} {
 
 	return lr
 }
+
+var EmptyListingResponse = &ListingResponse{}