1 files changed, 28 insertions, 11 deletions

diff --git a/whiteboard.cpp b/whiteboard.cpp
index be8bcb0..6782385 100644
--- a/whiteboard.cpp
+++ b/whiteboard.cpp
@@ -8,11 +8,13 @@
 #include <sys/types.h>
 
 #include <chrono>
+#include <initializer_list>
 #include <iostream>
 #include <functional>
 #include <filesystem>
 #include <mutex>
 #include <regex>
+#include <sstream>
 #include <string>
 #include <thread>
 #include <unordered_map>
@@ -30,6 +32,8 @@
 #include <boost/asio/connect.hpp>
 #include <boost/asio/ip/tcp.hpp>
 
+#include <fmt/core.h>
+
 #include "libreichwein/file.h"
 
 #include "config.h"
@@ -76,6 +80,19 @@ void Whiteboard::storage_cleanup()
  }
 }
 
+std::string make_xml(const std::initializer_list<std::pair<std::string, std::string>>& key_values)
+{
+ pt::ptree xml;
+ for (const auto& i: key_values) {
+  xml.put(fmt::format("serverinfo.{}", i.first), i.second);
+ }
+
+ std::ostringstream oss;
+ // write_xml_element instead of write_xml to omit <!xml...> header
+ pt::xml_parser::write_xml_element(oss, {}, xml, -1, boost::property_tree::xml_writer_settings<pt::ptree::key_type>{});
+ return oss.str();
+}
+
 std::string Whiteboard::handle_request(const std::string& request)
 {
  try {
@@ -93,7 +110,7 @@ std::string Whiteboard::handle_request(const std::string& request)
    std::string id {xml.get<std::string>("request.id")};
    std::string data {xml.get<std::string>("request.data")};
    m_storage->setDocument(id, data);
-   return {};
+   return make_xml({{"type", "modify"}, {"revision", std::to_string(m_storage->getRevision(id)) }}); 
   } else if (command == "getfile") {
    std::string id {xml.get<std::string>("request.id")};
 
@@ -102,20 +119,19 @@ std::string Whiteboard::handle_request(const std::string& request)
    if (filedata.size() > 30000000)
     throw std::runtime_error("File too big");
 
-   return filedata; 
+   return make_xml({{"type", "getfile"}, {"data", filedata}, {"revision", std::to_string(m_storage->getRevision(id)) }}); 
   } else if (command == "checkupdate") {
    std::string id {xml.get<std::string>("request.id")};
-   std::string checksum_s {xml.get<std::string>("request.checksum")};
-   uint32_t checksum{static_cast<uint32_t>(stoul(checksum_s))};
+   int request_revision {xml.get<int>("request.revision")};
 
-   std::string filedata {m_storage->getDocument(id)};
-   if (checksum != m_storage->checksum32(filedata)) {
-    return filedata;
+   int revision {m_storage->getRevision(id)};
+   if (revision != request_revision) {
+    return make_xml({{"type", "update"}, {"data", m_storage->getDocument(id)}, {"revision", std::to_string(revision) }}); 
    } else {
-    return {};
+    return {}; // no reply
    }
   } else if (command == "newid") {
-   return m_storage->generate_id();
+   return make_xml({{"type", "newid"}, {"id", m_storage->generate_id()}}); 
   } else if (command == "qrcode") {
    std::string url{xml.get<std::string>("request.url")};
    
@@ -124,7 +140,7 @@ std::string Whiteboard::handle_request(const std::string& request)
 
    std::string pngdata {QRCode::getQRCode(url)};
 
-   return pngdata;
+   return make_xml({{"type", "qrcode"}, {"png", pngdata}}); 
   } else {
    throw std::runtime_error("Bad command: "s + command);
   }
@@ -167,7 +183,8 @@ void Whiteboard::do_session(boost::asio::ip::tcp::socket socket)
    data = handle_request(data);
    buffer.consume(buffer.size());
    boost::beast::ostream(buffer) << data;
-   ws.write(buffer.data());
+   if (buffer.data().size() > 0)
+    ws.write(buffer.data());
   }
  } catch (boost::beast::system_error const& se) {
   // This indicates that the session was closed