From cc770c5894ed0663db2581232a7719c95a0595b1 Mon Sep 17 00:00:00 2001
From: Alexander Vieth <a.vieth@tudelft.nl>
Date: Fri, 4 Oct 2024 17:12:37 +0200
Subject: [PATCH] Backwards compatible dependencies (#48)

* Remain compatible with older lz4 and flann versions

* install flann headers to subfolder

* Update README.md
---
 CMakeLists.txt                              | 31 ++++++++++++++++-----
 README.md                                   |  4 +--
 hdi/dimensionality_reduction/CMakeLists.txt | 16 +++++++----
 3 files changed, 36 insertions(+), 15 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index ad0444c..b01bafa 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -73,17 +73,34 @@ message(STATUS "CMAKE_GENERATOR: ${CMAKE_GENERATOR}")
 # -----------------------------------------------------------------------------
 # Dependencies
 # -----------------------------------------------------------------------------
-find_package(lz4 CONFIG REQUIRED)
-find_package(flann CONFIG REQUIRED)
-find_package(OpenMP)
+find_package(lz4 CONFIG)
+if(NOT ${lz4_FOUND})
+    find_package(PkgConfig REQUIRED)
+
+    pkg_check_modules(lz4 REQUIRED IMPORTED_TARGET liblz4)
+    set(LZ4_TARGET PkgConfig::lz4)
+endif()
+
+if(NOT ${lz4_FOUND})
+    message (FATAL_ERROR "lz4 NOT found")
+endif()
+message (STATUS "Found lz4 version ${lz4_VERSION}")
+
+find_package(flann CONFIG)
+if(NOT ${flann_FOUND})
+    find_package(PkgConfig REQUIRED)
 
-if(${flann_FOUND})
-    message (STATUS "Found flann version ${flann_VERSION}")
+    pkg_check_modules(flann REQUIRED flann)
+    set(FLANN_TARGET flann_cpp)
+    set(flann_INCLUDE_DIR "${flann_INCLUDE_DIRS}/flann")
 endif()
 
-if(${lz4_FOUND})
-    message (STATUS "Found lz4 version ${lz4_VERSION}")
+if(NOT ${flann_FOUND})
+    message (FATAL_ERROR "flann NOT found")
 endif()
+message (STATUS "Found flann version ${flann_VERSION}")
+
+find_package(OpenMP)
 
 if(OpenMP_CXX_FOUND)
     message (STATUS "OpenMP found")
diff --git a/README.md b/README.md
index 83ce263..6f39069 100644
--- a/README.md
+++ b/README.md
@@ -64,11 +64,11 @@ When configuring cmake make sure to setup vcpkg with CMAKE_TOOLCHAIN_FILE (`PATH
 
 You may also use system-specific package managers, e.g. on Linux with
 ```bash
-sudo apt-get -y install libflann-dev liblz4-dev
+sudo apt-get -y install libflann-dev liblz4-dev pkg-config
 ```
 and Mac OS with
 ```
-brew install flann lz4
+brew install flann lz4 pkg-config
 ```
 
 ### Generate the build files
diff --git a/hdi/dimensionality_reduction/CMakeLists.txt b/hdi/dimensionality_reduction/CMakeLists.txt
index c85e3f7..e936f07 100644
--- a/hdi/dimensionality_reduction/CMakeLists.txt
+++ b/hdi/dimensionality_reduction/CMakeLists.txt
@@ -97,13 +97,17 @@ if(${HDILib_INSTALL})
     )
 
     # Install dependency headers
-    if(DEFINED flann_INCLUDE_DIR)
-        install(DIRECTORY "${flann_INCLUDE_DIR}/" DESTINATION "${CMAKE_INSTALL_PREFIX}/include" COMPONENT FLANN_HEADERS)
-    else()
-        get_target_property(FLANN_INCLUDE_DIR ${FLANN_TARGET} INTERFACE_INCLUDE_DIRECTORIES)
-        if(FLANN_INCLUDE_DIR)
-            install(DIRECTORY "${FLANN_INCLUDE_DIR}/" DESTINATION "${CMAKE_INSTALL_PREFIX}/include" COMPONENT FLANN_HEADERS)
+    if(NOT flann_INCLUDE_DIR)
+        get_target_property(flann_INCLUDE_DIR ${FLANN_TARGET} INTERFACE_INCLUDE_DIRECTORIES)
+    endif()
+
+    if(flann_INCLUDE_DIR)
+        if(NOT flann_INCLUDE_DIR MATCHES "flann$")
+            set(flann_INCLUDE_DIR "${flann_INCLUDE_DIR}/flann")
         endif()
+
+        message(STATUS "Using flann includes at: ${flann_INCLUDE_DIR}")
+        install(DIRECTORY "${flann_INCLUDE_DIR}/" DESTINATION "${CMAKE_INSTALL_PREFIX}/include/flann" COMPONENT FLANN_HEADERS)
     endif()
 
     install(DIRECTORY "${HNSWLIB_INCLUDE_DIR}/hnswlib/" DESTINATION "${CMAKE_INSTALL_PREFIX}/include/hnswlib" COMPONENT HNSW_HEADERS)