# This file is used to create SWIG based JNI interfaces to C++ code.  You use
# it by defining some CMake variables and then include(cmake_swig_jni).  You
# would make a CMakeLists.txt file that looks like the following:
#
#   cmake_minimum_required (VERSION 2.8.12)
#   project (example)
#   set(java_package_name "org.mycompany")
#   set(source_files
#       your_cpp_source.cpp
#       more_cpp_source.cpp
#   )
#
#   ### We might need to link our code to some other C++ library like dlib.  You
#   ### can do that by setting additional_link_libraries.  Here is an example of
#   ### linking to dlib:
#   include(../../dlib/dlib/cmake)
#   set(additional_link_libraries dlib::dlib)
#
#   ### Tell swig to put the output files into the parent folder of your CMakeLists.txt 
#   ### file when you run make install.
#   set(install_target_output_folder ..)
#   include(cmake_swig_jni)
#
#   ### Alternatively, instead of using install_target_output_folder, you can tell
#   ### cmake to output the shared library, java source files, and the jar to
#   ### separate output folders.  These commands would put them into folders
#   ### thelib, thesrc, and thejar, respectively.
#   # set(install_shared_library_output_folder thelib)
#   # set(install_java_source_output_folder    thesrc)
#   # set(install_jar_output_folder            thejar)






################################################################################
################################################################################
#                             IMPLEMENTATION DETAILS
################################################################################
################################################################################

cmake_minimum_required (VERSION 2.8.12)

# This block of code tries to figure out what the JAVA_HOME environment
# variable should be by looking at the folder that contains the java
# executable.
if (NOT DEFINED ENV{JAVA_HOME})
   message(STATUS "JAVA_HOME environment variable not set, trying to guess it...")
   find_program(JAVA_EXECUTABLE java)
   # Resolve symbolic links, hopefully this will give us a path in the proper
   # java home directory.
   get_filename_component(JAVA_EXECUTABLE ${JAVA_EXECUTABLE} REALPATH)
   # Pick out the parent directories
   get_filename_component(JAVA_PATH1 ${JAVA_EXECUTABLE} PATH)
   get_filename_component(JAVA_PATH2 ${JAVA_PATH1} PATH)
   get_filename_component(JAVA_PATH3 ${JAVA_PATH2} PATH)
   # and search them for include/jni.h.  If we find that then we probably have
   # a good java home candidate.
   find_path(AUTO_JAVA_HOME include/jni.h
      PATHS
      ${JAVA_PATH1}
      ${JAVA_PATH2}
      ${JAVA_PATH3}
      "C:/Program Files/Java/jdk*"
      "C:/Program Files (x86)/Java/jdk*"
      )

   if (AUTO_JAVA_HOME)
      set(ENV{JAVA_HOME} ${AUTO_JAVA_HOME})
      message(STATUS "Using JAVA_HOME OF " ${AUTO_JAVA_HOME})
   else()
      message(FATAL_ERROR "Couldn't find a folder for JAVA_HOME.  You must set the JAVA_HOME environment variable before running CMake.")
   endif()
endif()

set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/lib")
set(CMAKE_LIBRARY_OUTPUT_DIRECTORY_RELEASE "${CMAKE_CURRENT_BINARY_DIR}/lib")

find_package(SWIG REQUIRED)
find_package(Java REQUIRED)
find_package(JNI REQUIRED)
include(UseSWIG)

macro (add_global_switch def_name )
   if (NOT CMAKE_CXX_FLAGS MATCHES "${def_name}")
      set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${def_name}" 
         CACHE STRING "Flags used by the compiler during all C++ builds." 
         FORCE)
   endif ()
   if (NOT CMAKE_C_FLAGS MATCHES "${def_name}")
      set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${def_name}" 
         CACHE STRING "Flags used by the compiler during all C builds." 
         FORCE)
   endif ()
endmacro()

# SWIG doesn't work if optimizations are enabled and strict aliasing is not
# turned off.  This is a little wonky but it's how SWIG is.
if (CMAKE_COMPILER_IS_GNUCXX)
    add_definitions(-fno-strict-aliasing)
endif()
if (UNIX)
    # we need to make sure all the code is compiled with -fPIC. In particular,
    # it's important that all the code for the whole project is, not just the
    # stuff immediately compiled by us in this cmake file.  So we add -fPIC to
    # the top level cmake flags variables.
    add_global_switch(-fPIC)
endif()

set(dlib_root_path ${CMAKE_CURRENT_LIST_DIR}/../../)

string(REGEX REPLACE "\\." "/" package_path ${java_package_name})
string(REGEX REPLACE "\\..*" "" package_root_name ${java_package_name})

include_directories(${dlib_root_path})

set(CMAKE_SWIG_FLAGS -package ${java_package_name} -I${dlib_root_path})
set(CMAKE_SWIG_OUTDIR ${CMAKE_CURRENT_BINARY_DIR}/lib/java_src/${package_path})

set(output_library_name ${PROJECT_NAME})

# Create the swig.i interface file that swig will run on.  We do it here in
# the cmake script because this lets us automatically include the correct
# output library name into the call to System.loadLibrary().
FILE(WRITE ${CMAKE_CURRENT_BINARY_DIR}/swig.i 
        "
    // Put the global functions in our api into a java class called global.
    %module global 

    %{
    #include <exception>
    #include <stdexcept>
    static JavaVM *cached_jvm = 0;

    JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *jvm, void *reserved) {
        cached_jvm = jvm;
        return JNI_VERSION_1_6;
    }

    static JNIEnv * JNI_GetEnv() {
        JNIEnv *env;
        jint rc = cached_jvm->GetEnv((void **)&env, JNI_VERSION_1_6);
        if (rc == JNI_EDETACHED)
            throw std::runtime_error(\"current thread not attached\");
        if (rc == JNI_EVERSION)
            throw std::runtime_error(\"jni version not supported\");
        return env;
    }

    #include \"swig_api.h\"
    %}

    // Convert all C++ exceptions into java.lang.Exception
    %exception {
        try {
            $action
        } catch(std::exception& e) {
            jclass clazz = jenv->FindClass(\"java/lang/Exception\");
            jenv->ThrowNew(clazz, e.what());
            return $null;
        }
    }

    %pragma(java) jniclasscode=%{
    static { System.loadLibrary(\"${output_library_name}\"); }
    %}

    %include \"swig_api.h\"
    "
)

# There is a bug in CMake's Swig scripts that causes the build to fail if the
# binary folder doesn't contain a folder with the same name as the binary dir.
# So we make a subfolder of the same name to avoid that bug.
get_filename_component(binary_dir_name "${CMAKE_CURRENT_BINARY_DIR}" NAME)
FILE(MAKE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/${binary_dir_name}")

set_source_files_properties(${CMAKE_CURRENT_BINARY_DIR}/swig.i PROPERTIES CPLUSPLUS ON)
swig_add_module(${output_library_name} java ${CMAKE_CURRENT_BINARY_DIR}/swig.i ${source_files})

include_directories(${JNI_INCLUDE_DIRS})
swig_link_libraries(${output_library_name}  ${additional_link_libraries})

# Things to delete when "make clean" is run.
set(clean_files
    ${CMAKE_CURRENT_BINARY_DIR}/intermediate_files_compiled
    ${CMAKE_CURRENT_BINARY_DIR}/lib/java_src 
    )
set_directory_properties(PROPERTIES ADDITIONAL_MAKE_CLEAN_FILES "${clean_files}")

# Compile the java files into a jar file and stick it in the lib folder.  Also, one problem
# with this cmake setup is that it doesn't know that modifications to swig_api.h mean that
# swig.i is invalidated and thus swig needs to be rerun.  So here we also touch swig.i
# every time we build to make it always out of date and force swig to run on each build,
# thus avoiding the stale swig outputs problem that would otherwise irritate people who
# modify something and attempt to rebuild.
add_custom_command(TARGET ${output_library_name} 
   POST_BUILD
   COMMAND cmake -E echo "compiling Java files..."
   COMMAND cmake -E make_directory "${CMAKE_CURRENT_BINARY_DIR}/intermediate_files_compiled"
   COMMAND ${Java_JAVAC_EXECUTABLE} ${CMAKE_SWIG_OUTDIR}/*.java -d "${CMAKE_CURRENT_BINARY_DIR}/intermediate_files_compiled"
   COMMAND cmake -E echo "Making jar file..."
   COMMAND ${Java_JAR_EXECUTABLE} cvf "${CMAKE_CURRENT_BINARY_DIR}/lib/${PROJECT_NAME}.jar" -C "${CMAKE_CURRENT_BINARY_DIR}/intermediate_files_compiled" ${package_root_name}
   COMMAND cmake -E touch swig.i
   )


# Determine the path to our CMakeLists.txt file.
# There is either a bug (or break in compatability maybe) between versions
# of cmake that cause the or expression in this regular expression to be
# necessary.
string(REGEX REPLACE "(cmake_swig_jni|CMakeLists.txt)$" "" base_path ${CMAKE_PARENT_LIST_FILE})

#if the including cmake script set the install_target_output_folder variable
#then make it so we install the compiled library and jar into that folder
if (install_target_output_folder)
    # The directory we will write the output files to.
    set(install_dir "${base_path}${install_target_output_folder}")
    set(CMAKE_INSTALL_PREFIX "${install_dir}")
    set(CMAKE_INSTALL_SYSTEM_RUNTIME_DESTINATION "${install_dir}")
    install(TARGETS ${output_library_name} 
        DESTINATION "${install_dir}"
        )
    install(FILES ${CMAKE_CURRENT_BINARY_DIR}/lib/${PROJECT_NAME}.jar 
        DESTINATION "${install_dir}"
        )
endif()

if (install_shared_library_output_folder)
    set(install_dir "${base_path}${install_shared_library_output_folder}")
    install(TARGETS ${output_library_name} 
        DESTINATION "${install_dir}"
        )
endif()

if (install_java_source_output_folder)
    set(install_dir "${base_path}${install_java_source_output_folder}")
    install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/lib/java_src/${package_root_name}
        DESTINATION "${install_dir}"
        )
endif()

if (install_jar_output_folder)
    set(install_dir "${base_path}${install_jar_output_folder}")
    install(FILES ${CMAKE_CURRENT_BINARY_DIR}/lib/${PROJECT_NAME}.jar 
        DESTINATION "${install_dir}"
        )
endif()


# Copy any system libraries to the output folder.  This really only matters on
# windows where it's good to have the visual studio runtime show up in the lib
# folder so that you don't forget to include it in your binary distribution.
INCLUDE(InstallRequiredSystemLibraries)
foreach (file_i ${CMAKE_INSTALL_SYSTEM_RUNTIME_LIBS})
   add_custom_command(TARGET ${output_library_name}
      POST_BUILD
      COMMAND cmake -E copy ${file_i} "${CMAKE_CURRENT_BINARY_DIR}/lib/"
      )
endforeach()

