MM-64718 Improve validation of thread follower imports (#33287)

* MM-64718 Improve validation of thread follower imports

* Add additional test cases and restucture tests

server/channels/app/imports/import_validators.go

@@ -563,6 +563,14 @@ func ValidatePostImportData(data *PostImportData, maxPostSize int) *model.AppErr
 		}
 	}
 
+	if data.ThreadFollowers != nil {
+		for _, follower := range *data.ThreadFollowers {
+			if err := ValidateThreadFollowerImportData(&follower); err != nil {
+				return model.NewAppError("BulkImport", "app.import.validate_post_import_data.thread_follower.error", nil, "", http.StatusBadRequest).Wrap(err)
+			}
+		}
+	}
+
 	return nil
 }
 
@@ -687,6 +695,14 @@ func ValidateDirectPostImportData(data *DirectPostImportData, maxPostSize int) *
 		}
 	}
 
+	if data.ThreadFollowers != nil {
+		for _, follower := range *data.ThreadFollowers {
+			if err := ValidateThreadFollowerImportData(&follower); err != nil {
+				return model.NewAppError("BulkImport", "app.import.validate_direct_post_import_data.thread_follower.error", nil, "", http.StatusBadRequest).Wrap(err)
+			}
+		}
+	}
+
 	return nil
 }
 
@@ -717,6 +733,18 @@ func ValidateEmojiImportData(data *EmojiImportData) *model.AppError {
 	return nil
 }
 
+func ValidateThreadFollowerImportData(data *ThreadFollowerImportData) *model.AppError {
+	if data == nil {
+		return model.NewAppError("BulkImport", "app.import.validate_thread_follower_data.empty.error", nil, "", http.StatusBadRequest)
+	}
+
+	if data.User == nil || *data.User == "" {
+		return model.NewAppError("BulkImport", "app.import.validate_thread_follower_data.user_missing.error", nil, "", http.StatusBadRequest)
+	}
+
+	return nil
+}
+
 func isValidTrueOrFalseString(value string) bool {
 	return value == "true" || value == "false"
 }

server/channels/app/imports/import_validators_test.go

@@ -1541,6 +1541,58 @@ func TestImportValidateEmojiImportData(t *testing.T) {
 	}
 }
 
+func TestImportValidateThreadFollowerImportData(t *testing.T) {
+	testCases := []struct {
+		testName    string
+		input       *ThreadFollowerImportData
+		expectError bool
+	}{
+		{
+			testName: "success",
+			input: &ThreadFollowerImportData{
+				LastViewed:     model.NewPointer(int64(0)),
+				UnreadMentions: model.NewPointer(int64(0)),
+				User:           model.NewPointer("user1"),
+			},
+			expectError: false,
+		},
+		{
+			testName:    "nil",
+			input:       nil,
+			expectError: true,
+		},
+		{
+			testName: "nil user",
+			input: &ThreadFollowerImportData{
+				LastViewed:     model.NewPointer(int64(0)),
+				UnreadMentions: model.NewPointer(int64(0)),
+				User:           nil,
+			},
+			expectError: true,
+		},
+		{
+			testName: "empty user",
+			input: &ThreadFollowerImportData{
+				LastViewed:     model.NewPointer(int64(0)),
+				UnreadMentions: model.NewPointer(int64(0)),
+				User:           model.NewPointer(""),
+			},
+			expectError: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.testName, func(t *testing.T) {
+			err := ValidateThreadFollowerImportData(tc.input)
+			if tc.expectError {
+				require.NotNil(t, err)
+			} else {
+				assert.Nil(t, err)
+			}
+		})
+	}
+}
+
 func checkError(t *testing.T, err *model.AppError) {
 	require.NotNil(t, err, "Should have returned an error.")
 }