From f8b8efcfc68c7dad952be71df0e5dde62c2eca00 Mon Sep 17 00:00:00 2001
From: Oleg Morozenkov <o-morozenkov@yandex-team.ru>
Date: Mon, 14 Sep 2026 22:18:41 +0300
Subject: [PATCH] Parse Telegram error response parameters

---
 include/tgbot/TgException.h |  9 ++++++++-
 src/Api.cpp                 |  6 +++++-
 src/TgException.cpp         |  8 ++++++--
 tests/tgbot/Api.cpp         | 19 +++++++++++++++++++
 4 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/include/tgbot/TgException.h b/include/tgbot/TgException.h
index ab563c07..97cbc428 100644
--- a/include/tgbot/TgException.h
+++ b/include/tgbot/TgException.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include "tgbot/Types.h"
 #include "tgbot/export.h"
 
 #include <stdexcept>
@@ -30,9 +31,15 @@ class TGBOT_API TgException : public std::runtime_error {
         InvalidJson = 101
     };
 
-    TgException(std::string_view description, ErrorCode errorCode);
+    TgException(std::string_view description, ErrorCode errorCode,
+                std::shared_ptr<ResponseParameters> parameters = nullptr);
 
     const ErrorCode errorCode;
+
+    /**
+     * @brief Additional details about the error returned by Telegram, if any.
+     */
+    const std::shared_ptr<ResponseParameters> parameters;
 };
 
 } // namespace TgBot
diff --git a/src/Api.cpp b/src/Api.cpp
index 2a008a72..baa178e9 100644
--- a/src/Api.cpp
+++ b/src/Api.cpp
@@ -39,8 +39,12 @@ nlohmann::json Api::sendRequest(std::string_view method, const std::vector<HttpF
         throw TgException(exception.what(), TgException::ErrorCode::InvalidJson);
     }
     if (!response.value("ok", false)) {
+        std::shared_ptr<ResponseParameters> parameters;
+        if (const auto iterator = response.find("parameters"); iterator != response.end()) {
+            parameters = std::make_shared<ResponseParameters>(iterator->get<ResponseParameters>());
+        }
         throw TgException(response.value("description", "Telegram Bot API request failed"),
-                          static_cast<TgException::ErrorCode>(response.value("error_code", 0)));
+                          static_cast<TgException::ErrorCode>(response.value("error_code", 0)), std::move(parameters));
     }
 
     return response.at("result");
diff --git a/src/TgException.cpp b/src/TgException.cpp
index 88482e2b..7767e1a5 100644
--- a/src/TgException.cpp
+++ b/src/TgException.cpp
@@ -1,10 +1,14 @@
 #include "tgbot/TgException.h"
 
+#include <utility>
+
 namespace TgBot {
 
-TgException::TgException(std::string_view description, ErrorCode errorCode)
+TgException::TgException(std::string_view description, ErrorCode errorCode,
+                         std::shared_ptr<ResponseParameters> parameters)
     : runtime_error(std::string(description))
-    , errorCode(errorCode) {
+    , errorCode(errorCode)
+    , parameters(std::move(parameters)) {
 }
 
 } // namespace TgBot
diff --git a/tests/tgbot/Api.cpp b/tests/tgbot/Api.cpp
index 27408734..c4227def 100644
--- a/tests/tgbot/Api.cpp
+++ b/tests/tgbot/Api.cpp
@@ -60,6 +60,25 @@ TEST(Api, GeneratedMethodMapsTelegramErrors) {
     EXPECT_TRUE(requestThrows(ErrorCode::InvalidJson, "error_code:101"));
 }
 
+TEST(Api, GeneratedMethodPreservesTelegramErrorParameters) {
+    HttpClientMock httpClient;
+    httpClient.response
+        = R"({"ok":false,"error_code":400,"description":"migrated","parameters":{"migrate_to_chat_id":-1001234567890,"retry_after":42}})";
+    TgBot::Api api("token", httpClient, "url");
+
+    try {
+        api.getMe();
+        FAIL() << "Expected TgException";
+    } catch (const TgBot::TgException& exception) {
+        EXPECT_EQ(exception.errorCode, TgBot::TgException::ErrorCode::BadRequest);
+        ASSERT_TRUE(exception.parameters);
+        ASSERT_TRUE(exception.parameters->migrateToChatId);
+        EXPECT_EQ(*exception.parameters->migrateToChatId, -1001234567890);
+        ASSERT_TRUE(exception.parameters->retryAfter);
+        EXPECT_EQ(*exception.parameters->retryAfter, 42);
+    }
+}
+
 TEST(Api, PassesCompleteUrlToHttpClient) {
     HttpClientMock httpClient;
     httpClient.response = R"({"ok":true,"result":{"id":1,"is_bot":true,"first_name":"bot"}})";