# Locate an LP64 OpenBLAS implementation together with the CBLAS and LAPACKE
# C interfaces.  LAPACKE may be provided by libopenblas itself or by a separate
# liblapacke library.
#
# Result:
#   REML_OpenBLAS_FOUND
#   REML::OpenBLASLAPACKE
#
# Optional hints/overrides:
#   OpenBLAS_ROOT
#   LAPACKE_ROOT
#   REML_OPENBLAS_LIBRARY
#   REML_LAPACKE_LIBRARY
#   REML_CBLAS_INCLUDE_DIR
#   REML_LAPACKE_INCLUDE_DIR

include(CheckCXXSourceCompiles)
include(CMakePushCheckState)
include(FindPackageHandleStandardArgs)

set(_reml_openblas_hints)
foreach(_root IN ITEMS "${OpenBLAS_ROOT}" "$ENV{OpenBLAS_ROOT}" "$ENV{OPENBLAS_ROOT}" "$ENV{CONDA_PREFIX}")
  if(_root)
    list(APPEND _reml_openblas_hints "${_root}")
  endif()
endforeach()

set(_reml_lapacke_hints ${_reml_openblas_hints})
foreach(_root IN ITEMS "${LAPACKE_ROOT}" "$ENV{LAPACKE_ROOT}")
  if(_root)
    list(PREPEND _reml_lapacke_hints "${_root}")
  endif()
endforeach()

# Prefer package-provided imported targets because they carry static-library
# dependencies (Fortran runtime, pthreads, and libm) correctly.
find_package(OpenBLAS CONFIG QUIET)
if(TARGET OpenBLAS::OpenBLAS)
  set(_reml_openblas_link OpenBLAS::OpenBLAS)
elseif(TARGET OpenBLAS)
  set(_reml_openblas_link OpenBLAS)
endif()

if(NOT _reml_openblas_link)
  find_library(REML_OPENBLAS_LIBRARY
    NAMES openblas libopenblas
    HINTS ${_reml_openblas_hints}
    PATH_SUFFIXES lib lib64 Library/lib
  )
  if(REML_OPENBLAS_LIBRARY)
    set(_reml_openblas_link "${REML_OPENBLAS_LIBRARY}")
  endif()
endif()

find_path(REML_CBLAS_INCLUDE_DIR
  NAMES cblas.h
  HINTS ${_reml_openblas_hints}
  PATH_SUFFIXES include include/openblas Library/include Library/include/openblas
)
find_path(REML_LAPACKE_INCLUDE_DIR
  NAMES lapacke.h
  HINTS ${_reml_lapacke_hints}
  PATH_SUFFIXES include include/openblas include/lapacke Library/include Library/include/openblas
)

find_package(LAPACKE CONFIG QUIET)
if(TARGET LAPACKE::LAPACKE)
  set(_reml_lapacke_link LAPACKE::LAPACKE)
elseif(TARGET LAPACKE)
  set(_reml_lapacke_link LAPACKE)
else()
  find_library(REML_LAPACKE_LIBRARY
    NAMES lapacke liblapacke
    HINTS ${_reml_lapacke_hints}
    PATH_SUFFIXES lib lib64 Library/lib
  )
  if(REML_LAPACKE_LIBRARY)
    set(_reml_lapacke_link "${REML_LAPACKE_LIBRARY}")
  endif()
endif()

if(_reml_lapacke_link)
  # Keep the static-link order dependency first, provider second:
  # liblapacke calls LAPACK symbols supplied by libopenblas.
  set(_reml_link_items ${_reml_lapacke_link} ${_reml_openblas_link})
else()
  set(_reml_link_items ${_reml_openblas_link})
endif()

unset(REML_OPENBLAS_LINK_OK CACHE)
if(REML_CBLAS_INCLUDE_DIR AND REML_LAPACKE_INCLUDE_DIR AND _reml_openblas_link)
  cmake_push_check_state(RESET)
  set(CMAKE_REQUIRED_INCLUDES "${REML_CBLAS_INCLUDE_DIR};${REML_LAPACKE_INCLUDE_DIR}")
  set(CMAKE_REQUIRED_LIBRARIES ${_reml_link_items})
  check_cxx_source_compiles([[
    #include <cblas.h>
    #include <lapacke.h>
    int main() {
      double a[1] = {1.0};
      double b[1] = {1.0};
      double c[1] = {0.0};
      cblas_dgemm(CblasRowMajor, CblasNoTrans, CblasNoTrans,
                  1, 1, 1, 1.0, a, 1, b, 1, 0.0, c, 1);
      return LAPACKE_dpotrf(LAPACK_ROW_MAJOR, 'L', 1, a, 1);
    }
  ]] REML_OPENBLAS_LINK_OK)
  cmake_pop_check_state()
else()
  set(REML_OPENBLAS_LINK_OK FALSE)
endif()

find_package_handle_standard_args(REML_OpenBLAS
  REQUIRED_VARS
    REML_CBLAS_INCLUDE_DIR
    REML_LAPACKE_INCLUDE_DIR
    _reml_openblas_link
    REML_OPENBLAS_LINK_OK
  FAIL_MESSAGE
    "OpenBLAS with LP64 CBLAS and LAPACKE is required. Set OpenBLAS_ROOT/LAPACKE_ROOT, or the REML_* cache variables listed in cmake/FindREML_OpenBLAS.cmake."
)

if(REML_OpenBLAS_FOUND AND NOT TARGET REML::OpenBLASLAPACKE)
  add_library(REML::OpenBLASLAPACKE INTERFACE IMPORTED)
  set_property(TARGET REML::OpenBLASLAPACKE PROPERTY
    INTERFACE_INCLUDE_DIRECTORIES "${REML_CBLAS_INCLUDE_DIR};${REML_LAPACKE_INCLUDE_DIR}")
  set_property(TARGET REML::OpenBLASLAPACKE PROPERTY
    INTERFACE_LINK_LIBRARIES "${_reml_link_items}")
endif()

mark_as_advanced(
  REML_CBLAS_INCLUDE_DIR
  REML_LAPACKE_INCLUDE_DIR
  REML_OPENBLAS_LIBRARY
  REML_LAPACKE_LIBRARY
)