# - Try to find SLEPC
# Once done this will define
#
#  SLEPC_FOUND        - system has SLEPc
#  SLEPC_INCLUDE_DIRS - include directories for SLEPc
#  SLEPC_LIBRARIES    - libraries for SLEPc
#  SLEPC_DIR          - directory where SLEPc is built
#  SLEPC_VERSION      - version of SLEPc
#  SLEPC_VERSION_MAJOR - First number in SLEPC_VERSION
#  SLEPC_VERSION_MINOR - Second number in SLEPC_VERSION
#  SLEPC_VERSION_SUBMINOR - Third number in SLEPC_VERSION
#
# Assumes that PETSC_DIR and PETSC_ARCH has been set by
# already calling find_package(PETSc)

#=============================================================================
# Copyright (C) 2010-2012 Garth N. Wells, Anders Logg and Johannes Ring
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in
#    the documentation and/or other materials provided with the
#    distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
#=============================================================================
#
# Taken from https://github.com/live-clones/libadjoint/blob/master/cmake/modules/FindSLEPc.cmake

find_package(PETSc REQUIRED)
find_package(MPI REQUIRED)

# Set debian_arches (PETSC_ARCH for Debian-style installations)
foreach (debian_arches linux kfreebsd)
  if ("${CMAKE_BUILD_TYPE}" STREQUAL "Debug")
    set(DEBIAN_FLAVORS ${debian_arches}-gnu-c-debug ${debian_arches}-gnu-c-opt ${DEBIAN_FLAVORS})
  else()
    set(DEBIAN_FLAVORS ${debian_arches}-gnu-c-opt ${debian_arches}-gnu-c-debug ${DEBIAN_FLAVORS})
  endif()
endforeach()

# List of possible locations for SLEPC_DIR
set(slepc_dir_locations "")
list(APPEND slepc_dir_locations "/usr/lib/slepc")
list(APPEND slepc_dir_locations "/opt/local/lib/petsc")    # Macports
list(APPEND slepc_dir_locations "/usr/local/lib/slepc")
list(APPEND slepc_dir_locations "$ENV{HOME}/slepc")

# Try to figure out SLEPC_DIR by finding slepc.h
find_path(SLEPC_DIR include/slepc.h
  HINTS ${SLEPC_DIR} $ENV{SLEPC_DIR}
  PATHS ${slepc_dir_locations}
  DOC "SLEPc directory")

# Report result of search for SLEPC_DIR
if (DEFINED SLEPC_DIR)
  message(STATUS "SLEPC_DIR is ${SLEPC_DIR}")
else()
  message(STATUS "SLEPC_DIR is empty")
endif()

# Get variables from SLEPc configuration
if (SLEPC_DIR)

  find_library(SLEPC_LIBRARY
    NAMES slepc
    HINTS
      ${SLEPC_DIR}/lib
      $ENV{SLEPC_DIR}/lib
      ${SLEPC_DIR}/${PETSC_ARCH}/lib
      $ENV{SLEPC_DIR}/$ENV{PETSC_ARCH}/lib
    NO_DEFAULT_PATH
    DOC "The SLEPc library")
  find_library(SLEPC_LIBRARY
    NAMES slepc
    DOC "The SLEPc library")
  mark_as_advanced(SLEPC_LIBRARY)

  # Find SLEPc config file
  find_file(SLEPC_CONFIG_FILE NAMES slepc_common PATHS
    ${SLEPC_DIR}/lib/slepc/conf
    ${SLEPC_DIR}/lib/slepc-conf ${SLEPC_DIR}/conf)

  # Create a temporary Makefile to probe the SLEPc configuration
  set(slepc_config_makefile ${PROJECT_BINARY_DIR}/Makefile.slepc)
  file(WRITE ${slepc_config_makefile}
"# This file was autogenerated by FindSLEPc.cmake
SLEPC_DIR  = ${SLEPC_DIR}
PETSC_ARCH = ${PETSC_ARCH}
PETSC_DIR = ${PETSC_DIR}
include ${SLEPC_CONFIG_FILE}
show :
	-@echo -n \${\${VARIABLE}}
")

  # Define macro for getting SLEPc variables from Makefile
  macro(SLEPC_GET_VARIABLE var name)
    set(${var} "NOTFOUND" CACHE INTERNAL "Cleared" FORCE)
    execute_process(COMMAND ${MAKE_EXECUTABLE} --no-print-directory -f ${slepc_config_makefile} show VARIABLE=${name}
      OUTPUT_VARIABLE ${var}
      RESULT_VARIABLE slepc_return)
  endmacro()

  # Call macro to get the SLEPc variables
  slepc_get_variable(SLEPC_INCLUDE SLEPC_INCLUDE)
  slepc_get_variable(SLEPC_EXTERNAL_LIB SLEPC_EXTERNAL_LIB)

  # Remove temporary Makefile
  file(REMOVE ${slepc_config_makefile})

  # Extract include paths and libraries from compile command line
  include(ResolveCompilerPaths)
  resolve_includes(SLEPC_INCLUDE_DIRS "${SLEPC_INCLUDE}")
  resolve_libraries(SLEPC_EXTERNAL_LIBRARIES "${SLEPC_EXTERNAL_LIB}")

  # Add variables to CMake cache and mark as advanced
  set(SLEPC_INCLUDE_DIRS ${SLEPC_INCLUDE_DIRS} CACHE STRING "SLEPc include paths." FORCE)
  set(SLEPC_LIBRARIES ${SLEPC_LIBRARY} CACHE STRING "SLEPc libraries." FORCE)
  mark_as_advanced(SLEPC_INCLUDE_DIRS SLEPC_LIBRARIES)
endif()

if (SLEPC_SKIP_BUILD_TESTS)
  set(SLEPC_VERSION "UNKNOWN")
  set(SLEPC_VERSION_OK TRUE)
elseif (SLEPC_LIBRARIES AND SLEPC_INCLUDE_DIRS)

  # Set flags for building test program
  set(CMAKE_REQUIRED_INCLUDES ${SLEPC_INCLUDE_DIRS})
  set(CMAKE_REQUIRED_LIBRARIES ${SLEPC_LIBRARIES} PETSc::PETSc MPI::MPI_CXX)

  # Check SLEPc version
  set(SLEPC_CONFIG_TEST_VERSION_CPP
    "${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/slepc_config_test_version.cpp")
  file(WRITE ${SLEPC_CONFIG_TEST_VERSION_CPP} "
#include <iostream>
#include \"slepcversion.h\"

int main() {
  std::cout << SLEPC_VERSION_MAJOR << \".\"
        << SLEPC_VERSION_MINOR << \".\"
        << SLEPC_VERSION_SUBMINOR;
  return 0;
}
")

  try_run(
    SLEPC_CONFIG_TEST_VERSION_EXITCODE
    SLEPC_CONFIG_TEST_VERSION_COMPILED
    ${CMAKE_CURRENT_BINARY_DIR}
    ${SLEPC_CONFIG_TEST_VERSION_CPP}
    CMAKE_FLAGS
      "-DINCLUDE_DIRECTORIES:STRING=${CMAKE_REQUIRED_INCLUDES}"
    COMPILE_OUTPUT_VARIABLE COMPILE_OUTPUT
    RUN_OUTPUT_VARIABLE OUTPUT
    )

  if (SLEPC_CONFIG_TEST_VERSION_EXITCODE EQUAL 0)
    set(SLEPC_VERSION "${OUTPUT}" CACHE STRING "SLEPC version number")
    string(REPLACE "." ";" SLEPC_VERSION_LIST ${SLEPC_VERSION})
    list(GET SLEPC_VERSION_LIST 0 SLEPC_VERSION_MAJOR)
    list(GET SLEPC_VERSION_LIST 1 SLEPC_VERSION_MINOR)
    list(GET SLEPC_VERSION_LIST 2 SLEPC_VERSION_SUBMINOR)
    mark_as_advanced(SLEPC_VERSION)
    mark_as_advanced(SLEPC_VERSION_MAJOR SLEPC_VERSION_MINOR SLEPC_VERSION_SUBMINOR)
  endif()

  if (SLEPc_FIND_VERSION)
    # Check if version found is >= required version
    if (NOT "${SLEPC_VERSION}" VERSION_LESS "${SLEPc_FIND_VERSION}")
      set(SLEPC_VERSION_OK TRUE CACHE BOOL "")
    endif()
  else()
    # No specific version requested
    set(SLEPC_VERSION_OK TRUE CACHE BOOL "")
  endif()
  mark_as_advanced(SLEPC_VERSION_OK)
endif()

# Standard package handling
include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(SLEPc
  FOUND_VAR SLEPC_FOUND
  FAIL_MESSAGE "SLEPc could not be found. Be sure to set SLEPC_DIR, PETSC_DIR, and PETSC_ARCH."
  VERSION_VAR SLEPC_VERSION
  REQUIRED_VARS SLEPC_LIBRARIES SLEPC_DIR SLEPC_INCLUDE_DIRS SLEPC_VERSION_OK)

if (SLEPC_FOUND)
  if (NOT TARGET SLEPc::SLEPc)
    add_library(SLEPc::SLEPc UNKNOWN IMPORTED)
    set_target_properties(SLEPc::SLEPc PROPERTIES
      IMPORTED_LOCATION "${SLEPC_LIBRARIES}"
      INTERFACE_INCLUDE_DIRECTORIES "${SLEPC_INCLUDE_DIRS}"
      INTERFACE_LINK_LIBRARIES PETSc::PETSc
      )
  endif()
endif()