Enable access to HTTP headers

CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required (VERSION 3.7)
 project (mastodon-cpp
-         VERSION 0.3.2
+         VERSION 0.3.3
          LANGUAGES CXX
 )
 

README.md

@@ -108,7 +108,7 @@ If you use a debug build, you get more verbose error messages.
     * [x] Handle HTTP statuses 301, 302, 307 and 308
     * [x] Support registering as an application
 * Version 0.4.0
-    * [ ] Handle X-RateLimit header
+    * [x] Handle X-RateLimit header
     * [ ] Streaming API
 * Later
     * [ ] Asynchronous I/O

src/examples/example8_rate_limiting.cpp

@@ -0,0 +1,53 @@
+/*  This file is part of mastodon-cpp.
+ *  In this example we look at HTTP headers to determine how many calls we are
+ *  allowed to make.
+ */
+
+#include <iostream>
+#include <vector>
+#include <string>
+#include <cstdint>
+#include "../mastodon-cpp.hpp"
+
+using Mastodon::API;
+
+int main(int argc, char *argv[])
+{
+    if (argc < 3)
+    {
+        std::cerr << "usage: " << argv[0] << " <instance> <access token>\n";
+        return 1;
+    }
+
+    Mastodon::API masto(argv[1], argv[2]);
+    masto.set_useragent("mastodon-cpp-example/1.3.3.7");
+    std::string answer;
+    std::uint16_t ret;
+
+    ret = masto.get(API::v1::accounts_verify_credentials, answer);
+    if (ret == 0)
+    {
+        std::string remaining = masto.get_header("X-RateLimit-Remaining");
+        std::string reset = masto.get_header("X-RateLimit-Reset");
+        std::cout << "You are allowed to make " << remaining
+                  << " calls until the counter is reset at " << reset << '\n';
+
+        if (std::stoi(remaining) <= 1)
+        {
+            std::cout << "🔥 Please let the server cool off a bit! 🔥\n";
+        }
+    }
+    else if (ret == 3)
+    {
+        std::cerr << "The URL has permanently changed.\n" <<
+                     "New URL: " << answer << '\n';
+        return ret;
+    }
+    else
+    {
+        std::cerr << "Error code: " << ret << '\n';
+        return ret;
+    }
+
+    return 0;
+}

src/http_sync.cpp

@@ -65,6 +65,8 @@ const std::uint16_t API::http::request_sync(const method &meth,
             "Connection: close",
             "Authorization: Bearer " + _access_token
         });
+        // Get headers from server
+        request.setOpt<curlpp::options::Header>(true);
         request.setOpt<curlopts::FollowLocation>(true);
         request.setOpt<curlopts::WriteStream>(&oss);
         if (!formdata.empty())
@@ -93,9 +95,13 @@ const std::uint16_t API::http::request_sync(const method &meth,
         request.perform();
         std::uint16_t ret = curlpp::infos::ResponseCode::get(request);
         ttdebug << "Response code: " << ret << '\n';
+        size_t pos = oss.str().find("\r\n\r\n");
+        _headers = oss.str().substr(0, pos);
+
         if (ret == 200 || ret == 302 || ret == 307)
         {   // OK or Found or Temporary Redirect
-            answer = oss.str();
+            // Only return body
+            answer = oss.str().substr(pos + 4);
         }
         else if (ret == 301 || ret == 308)
         {   // Moved Permanently or Permanent Redirect
@@ -122,3 +128,8 @@ const std::uint16_t API::http::request_sync(const method &meth,
 
     return 0;
 }
+
+const void API::http::get_headers(string &headers) const
+{
+    headers = _headers;
+}

src/mastodon-cpp.cpp

@@ -216,3 +216,18 @@ const std::uint16_t API::register_app2(const string &instance,
         return ret;
     }
 }
+
+const string API::get_header(const std::string &header) const
+{
+    string headers;
+    _http.get_headers(headers);
+    size_t startpos = headers.find(header);
+    if (startpos != std::string::npos)
+    {
+        startpos = headers.find(':', startpos) + 2;
+        size_t endpos = headers.find("\r\n", startpos);
+        return headers.substr(startpos, endpos - startpos);
+    }
+
+    return "";
+}

src/mastodon-cpp.hpp

@@ -32,6 +32,7 @@
  *  @example example5_follow_unfollow.cpp
  *  @example example6_toot_delete-toot.cpp
  *  @example example7_register_app.cpp
+ *  @example example8_rate_limiting.cpp
  */
 namespace Mastodon
 {
@@ -472,6 +473,15 @@ public:
                             const parametermap &parameters,
                             std::string &answer);
 
+    /*!
+         *  @brief  Gets the header from the last answer.
+         *
+         *  @param  header  The header to search
+         *
+         *  @return The header, or "" on error.
+         */
+        const std::string get_header(const std::string &header) const;
+
 private:
     const std::string _instance;
     std::string _access_token;
@@ -531,10 +541,13 @@ private:
                                          const curlpp::Forms &formdata,
                                          std::string &answer);
 
+        const void get_headers(std::string &headers) const;
+
     private:
         const API &parent;
         const std::string _instance;
         const std::string _access_token;
+        std::string _headers;
     } _http;
 };
 }