Add Instance::get_nodeinfo().

include/instance.hpp

@@ -18,6 +18,7 @@
 #define MASTODONPP_INSTANCE_HPP
 
 #include "curl_wrapper.hpp"
+#include "answer.hpp"
 
 #include <cstdint>
 #include <string>
@@ -106,6 +107,9 @@ public:
      *  Queries `/api/v1/instance` for `max_toot_chars'. If the instance doesn't
      *  support it, the limit is assumed to be 500.
      *
+     *  After the first call, the value is saved internally. Subsequent calls
+     *  return the saved value.
+     *
      *  @since  0.1.0
      */
     [[nodiscard]]
@@ -135,6 +139,18 @@ public:
         return _proxy;
     }
 
+    /*!
+     *  @brief  Returns the NodeInfo of the instance.
+     *
+     *  Attempts to download the [NodeInfo]
+     *  (https://nodeinfo.diaspora.software/protocol.html) of the instance and
+     *  returns it. Not every instance has it.
+     *
+     *  @since  0.3.0
+     */
+    [[nodiscard]]
+    answer_type get_nodeinfo();
+
 private:
     const string _hostname;
     const string _baseuri;

src/instance.cpp

@@ -18,13 +18,17 @@
 #include "instance.hpp"
 #include "log.hpp"
 
+#include <algorithm>
 #include <exception>
+#include <vector>
 
 namespace mastodonpp
 {
 
+using std::sort;
 using std::stoull;
 using std::exception;
+using std::vector;
 
 Instance::Instance(const string_view hostname, const string_view access_token)
     : _hostname{hostname}
@@ -77,4 +81,31 @@ uint64_t Instance::get_max_chars()
     return _max_chars;
 }
 
+answer_type Instance::get_nodeinfo()
+{
+    debuglog << "Finding location of NodeInfo on " << _hostname << "…\n";
+    auto answer{make_request(http_method::GET,
+                             _baseuri + "/.well-known/nodeinfo", {})};
+    if (!answer)
+    {
+        debuglog << "NodeInfo not found.\n";
+        return answer;
+    }
+
+    size_t pos{0};
+    vector<string> hrefs;
+    constexpr string_view searchstring{R"("href":")"};
+    while ((pos = answer.body.find(searchstring, pos)) != string::npos)
+    {
+        pos += searchstring.size();
+        auto endpos{answer.body.find('"', pos)};
+        hrefs.push_back(answer.body.substr(pos, endpos - pos));
+        debuglog << "Found href: " << hrefs.back() << '\n';
+    }
+    sort(hrefs.begin(), hrefs.end()); // We assume they are sortable strings.
+    debuglog << "Selecting href: " << hrefs.back() << '\n';
+
+    return make_request(http_method::GET, hrefs.back(), {});
+}
+
 } // namespace mastodonpp