fix: ensure hydration doesn't cause nil pointer when followers_n file…

…s aren't present

pkg/instagram/followdata/followdata.go

@@ -28,7 +28,7 @@ type handler struct {
 func NewHandler() Interface {
 	return &handler{
 		fileSystem: filesystem.NewFs(),
-		followData: &followData{},
+		followData: newFollowData(),
 	}
 }
 
@@ -84,35 +84,33 @@ type followData struct {
 	Unfollowers *userList
 }
 
-type userData struct {
-	UserData []userOriginal `json:"string_list_data"`
-}
-
-func newUserList(users []user, showTimestamp bool) *userList {
-	return &userList{
-		users:         users,
-		showTimestamp: showTimestamp,
+func newFollowData() *followData {
+	return &followData{
+		Following:   newUserList(true),
+		Followers:   newUserList(true),
+		Unfollowers: newUserList(false),
 	}
+}
 
+type userData struct {
+	UserData []userOriginal `json:"string_list_data"`
 }
 
 func (fd *followData) hydrateFollowers(data []byte) error {
 	var jsonData []userData
 	if err := json.Unmarshal(data, &jsonData); err != nil {
 		return err
 	}
-	users := make([]user, 0, len(jsonData))
 	for i := range jsonData {
 		ud := jsonData[i].UserData[0]
-		users = append(users, user{
+		fd.Followers.Append(user{
 			ProfileUrl: ud.Href,
 			Username:   ud.Value,
 			Timestamp: &timestamp{
 				Time: time.Unix(int64(ud.Timestamp), 0),
 			},
 		})
 	}
-	fd.Followers = newUserList(users, true)
 	return nil
 }
 
@@ -121,33 +119,29 @@ func (fd *followData) hydrateFollowing(data []byte) error {
 	if err := json.Unmarshal(data, &jsonData); err != nil {
 		return err
 	}
-	users := make([]user, 0, len(jsonData))
 	for i := range jsonData["relationships_following"] {
 		ud := jsonData["relationships_following"][i].UserData[0]
-		users = append(users, user{
+		fd.Following.Append(user{
 			ProfileUrl: ud.Href,
 			Username:   ud.Value,
 			Timestamp: &timestamp{
 				Time: time.Unix(int64(ud.Timestamp), 0),
 			},
 		})
 	}
-	fd.Following = newUserList(users, true)
 	return nil
 }
 
 func (fd *followData) hydrateUnfollowers() {
-	users := make([]user, 0)
 	for i := range fd.Following.users {
 		current := fd.Following.users[i]
 		index := slices.IndexFunc(fd.Followers.users, func(u user) bool {
 			return u.Username == current.Username
 		})
 		if index == -1 {
-			users = append(users, current)
+			fd.Unfollowers.Append(current)
 		}
 	}
-	fd.Unfollowers = newUserList(users, false)
 }
 
 type timestamp struct {
@@ -192,6 +186,13 @@ type userList struct {
 	showTimestamp bool
 }
 
+func newUserList(showTimestamp bool) *userList {
+	return &userList{
+		users:         make([]user, 0),
+		showTimestamp: showTimestamp,
+	}
+}
+
 func (ul *userList) output(format string) (*string, error) {
 	switch format {
 	case instagram.OutputJson:
@@ -292,3 +293,7 @@ func (ul *userList) Limit(limit int) {
 		ul.users = ul.users[:limit]
 	}
 }
+
+func (ul *userList) Append(u user) {
+	ul.users = append(ul.users, u)
+}

pkg/instagram/followdata/followdata_test.go

@@ -22,7 +22,7 @@ func Test_handler_Followers(t *testing.T) {
 		wantErr      bool
 	}{
 		{
-			name: "succeeds to output followers",
+			name: "succeeds to output followers when single followers_n file is present",
 			expectations: func(f *fields) {
 				f.fileSystem.On("FindFiles", instagram.PathFollowers).Return([]string{"file1"}, nil)
 				f.fileSystem.On("ReadFile", "file1").Return([]byte(`[{"string_list_data":[{"href":"https://www.instagram.com/username","value":"username","timestamp":0}]}]`), nil)
@@ -33,6 +33,22 @@ func Test_handler_Followers(t *testing.T) {
 			},
 			wantErr: false,
 		},
+		{
+			name: "succeeds to output followers when multiple followers_n files are present",
+			expectations: func(f *fields) {
+				f.fileSystem.On("FindFiles", instagram.PathFollowers).Return([]string{
+					"file1",
+					"file2",
+				}, nil)
+				f.fileSystem.On("ReadFile", "file1").Return([]byte(`[{"string_list_data":[{"href":"https://www.instagram.com/username1","value":"username1","timestamp":0}]}]`), nil)
+				f.fileSystem.On("ReadFile", "file2").Return([]byte(`[{"string_list_data":[{"href":"https://www.instagram.com/username2","value":"username2","timestamp":0}]}]`), nil)
+			},
+			assertions: func(t *testing.T, f *fields) {
+				f.fileSystem.AssertNumberOfCalls(t, "FindFiles", 1)
+				f.fileSystem.AssertNumberOfCalls(t, "ReadFile", 2)
+			},
+			wantErr: false,
+		},
 		{
 			name: "fails to find files",
 			expectations: func(f *fields) {
@@ -72,7 +88,7 @@ func Test_handler_Followers(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			f := &fields{
 				fileSystem: &filesystem.MockFs{},
-				followData: &followData{},
+				followData: newFollowData(),
 			}
 			h := &handler{
 				fileSystem: f.fileSystem,
@@ -137,7 +153,7 @@ func Test_handler_Following(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			f := &fields{
 				fileSystem: &filesystem.MockFs{},
-				followData: &followData{},
+				followData: newFollowData(),
 			}
 			h := &handler{
 				fileSystem: f.fileSystem,
@@ -208,7 +224,7 @@ func Test_handler_Unfollowers(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			f := &fields{
 				fileSystem: &filesystem.MockFs{},
-				followData: &followData{},
+				followData: newFollowData(),
 			}
 			h := &handler{
 				fileSystem: f.fileSystem,