rapidjson as external cmake project

CMakeLists.txt

@@ -8,7 +8,10 @@ set(THIRD_PARTY_DIR ${CMAKE_BINARY_DIR}/third_party)
 
 find_package (Threads REQUIRED)
 
+include(cmake/rapidjson.cmake)
 include(cmake/Pistache.cmake)
 
+include_directories(${RAPIDJSON_INCLUDE_DIR})
+
 add_subdirectory(daggy)
 add_subdirectory(tests)

cmake/rapidjson.cmake

@@ -0,0 +1,21 @@
+include(ExternalProject)
+# Download RapidJSON
+ExternalProject_Add(
+    rapidjson
+    PREFIX "vendor/rapidjson"
+    GIT_REPOSITORY "https://github.com/Tencent/rapidjson.git"
+    GIT_TAG f54b0e47a08782a6131cc3d60f94d038fa6e0a51
+    TIMEOUT 10
+    CMAKE_ARGS
+        -DRAPIDJSON_BUILD_TESTS=OFF
+        -DRAPIDJSON_BUILD_DOC=OFF
+        -DRAPIDJSON_BUILD_EXAMPLES=OFF
+    CONFIGURE_COMMAND ""
+    BUILD_COMMAND ""
+    INSTALL_COMMAND ""
+    UPDATE_COMMAND ""
+)
+
+# Prepare RapidJSON (RapidJSON is a header-only library)
+ExternalProject_Get_Property(rapidjson source_dir)
+set(RAPIDJSON_INCLUDE_DIR ${source_dir}/include)