From 73fbf8dfafe4a4c1454bcfb7343837efd9d2240a Mon Sep 17 00:00:00 2001
From: Russell Troxel <russelltroxel@gmail.com>
Date: Tue, 28 Mar 2023 11:33:13 -0700
Subject: [PATCH] Add Panic Recovery & Logging to Client JSON Unmarshalling
 (#139)

---
 internal/client/client.go      | 28 +++++++++++++++++++++++++++-
 internal/client/client_test.go | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/internal/client/client.go b/internal/client/client.go
index b57f89a..09abe3b 100644
--- a/internal/client/client.go
+++ b/internal/client/client.go
@@ -4,8 +4,10 @@ import (
 	"crypto/tls"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"net/url"
+	"strings"
 
 	"github.com/onedr0p/exportarr/internal/config"
 	"go.uber.org/zap"
@@ -62,6 +64,30 @@ func NewClient(config *config.Config) (*Client, error) {
 	}, nil
 }
 
+func (c *Client) unmarshalBody(b io.Reader, target interface{}) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			// return recovered panic as error
+			err = fmt.Errorf("Recovered from panic: %s", r)
+
+			log := zap.S()
+			if zap.S().Level() == zap.DebugLevel {
+				s := new(strings.Builder)
+				_, copyErr := io.Copy(s, b)
+				if copyErr != nil {
+					zap.S().Errorw("Failed to copy body to string in recover",
+						"error", err, "recover", r)
+				}
+				log = log.With("body", s.String())
+			}
+			log.Errorw("Recovered while unmarshalling response", "error", r)
+
+		}
+	}()
+	err = json.NewDecoder(b).Decode(target)
+	return
+}
+
 // DoRequest - Take a HTTP Request and return Unmarshaled data
 func (c *Client) DoRequest(endpoint string, target interface{}, queryParams ...map[string]string) error {
 	values := c.URL.Query()
@@ -84,5 +110,5 @@ func (c *Client) DoRequest(endpoint string, target interface{}, queryParams ...m
 		return fmt.Errorf("Failed to execute HTTP Request(%s): %w", url, err)
 	}
 	defer resp.Body.Close()
-	return json.NewDecoder(resp.Body).Decode(target)
+	return c.unmarshalBody(resp.Body, target)
 }
diff --git a/internal/client/client_test.go b/internal/client/client_test.go
index df6bdbf..5c48724 100644
--- a/internal/client/client_test.go
+++ b/internal/client/client_test.go
@@ -1,6 +1,7 @@
 package client
 
 import (
+	"encoding/json"
 	"fmt"
 	"net/http"
 	"net/http/httptest"
@@ -79,3 +80,36 @@ func TestDoRequest(t *testing.T) {
 		})
 	}
 }
+
+func TestDoRequest_PanicRecovery(t *testing.T) {
+	require := require.New(t)
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		ret := struct {
+			TestField  string
+			TestField2 string
+		}{
+			TestField:  "asdf",
+			TestField2: "asdf2",
+		}
+		s, err := json.Marshal(ret)
+		require.NoError(err)
+		w.Write(s)
+		w.WriteHeader(http.StatusOK)
+		return
+	}))
+	defer ts.Close()
+
+	c := &config.Config{
+		URL:        ts.URL,
+		ApiVersion: "v3",
+	}
+
+	client, err := NewClient(c)
+	require.Nil(err, "NewClient should not return an error")
+	require.NotNil(client, "NewClient should return a client")
+
+	err = client.DoRequest("test", nil)
+	require.NotPanics(func() {
+		require.Error(err, "DoRequest should return an error: %s", err)
+	}, "DoRequest should recover from a panic")
+}