From f0118cb260f16a6e415580cc3c7491800afc14b5 Mon Sep 17 00:00:00 2001
From: Jaewook Lee <jaewooklee042@gmail.com>
Date: Wed, 15 Nov 2023 16:57:37 +0100
Subject: [PATCH] look for valid nanoflann in system

---
 CMakeLists.txt | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 15a4a36..99618c8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -22,18 +22,27 @@ set(TARGETS_EXPORT_NAME "${PROJECT_NAME}Targets")
 set(namespace "${PROJECT_NAME}::")
 
 # sources
-set(CXX_HEADERS src/napf.hpp third_party/nanoflann.hpp)
+set(CXX_HEADERS src/napf.hpp)
 
 # Interface Library, since it's header only lib
 add_library(napf INTERFACE)
 add_library(napf::napf ALIAS napf)
-target_include_directories(napf
-    INTERFACE
-        $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/src>
-        $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/third_party>
-        $<INSTALL_INTERFACE:${incl_dest}>)
+
+# try to use installed nanoflann.
+# else, include the one in the third_party
+find_package(nanoflann QUIET)
+if(nanoflann_FOUND AND nanoflann_VERSION VERSION_GREATOR_EQUAL "1.5.0")
+  message("nanoflann found - napf will link to nanoflann found in system.")
+  target_link_libraries(napf INTERFACE nanoflann::nanoflann)
+else()
+  set(CXX_HEADERS ${CXX_HEADERS} third_party/nanoflann.hpp)
+  target_include_directories(napf
+      INTERFACE
+          $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/src>
+          $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/third_party>
+          $<INSTALL_INTERFACE:${incl_dest}>)
+endif()
 target_compile_features(napf INTERFACE cxx_std_11)
-#target_compile_options(napf PRIVATE -O3) # everyone can enjoy optimization
 
 if(BUILD_FORTRAN_MODULE)
   message("*** building additional fortran module ***")