#
#POSIX runtime environment.
#Allows us to run programs that require a POSIX API.
#Does not by itself allow us to build such programs.
#Building POSIX programs requires posix-dev as well.
#NOTE: The following requires 64 bit Windows.
#Should not be a problem in the year 2018.
#

if (WIN32)
#On Windows, we rely on MSYS2 to provide a toolchain which can build
#applications that rely on the POSIX API. This is done in such a way that
#the resulting applications run on Windows using the MSYS2.DLL POSIX emulation
#layer.
set (UNPACKED_ROOT "${CMAKE_INSTALL_PREFIX}/msys64")
ExternalProject_Add (
  posix-runtime
  PREFIX ${CMAKE_INSTALL_PREFIX}
  BUILD_IN_SOURCE 1
  URL https://sourceforge.net/projects/msys2/files/Base/x86_64/msys2-base-x86_64-20180531.tar.xz
  URL_MD5 29ce9b77a0fb8452d1a34858c977852f
  #Unpack to this directory
  SOURCE_DIR ${UNPACKED_ROOT}
  #To make sense of the alchemy below, see https://github.com/msys2/msys2/wiki/MSYS2-installation
  CONFIGURE_COMMAND ${CMAKE_COMMAND} -E env MSYSTEM=MSYS2 CHERE_INVOKING=1 ${UNPACKED_ROOT}/usr/bin/bash.exe --login -c "exit 0"
  #Update the package database and then install development tools
  #See https://github.com/Alexpux/MSYS2-packages/issues/148 for which packages we install
  BUILD_COMMAND ${CMAKE_COMMAND} -E env MSYSTEM=MSYS2 CHERE_INVOKING=1 ${UNPACKED_ROOT}/usr/bin/bash.exe --login -c "pacman -Suu --noconfirm"
  #Install a small batch file ${CMAKE_INSTALL_PREFIX}/bin/posix.cmd which we
  #will use to start a bash shell that can run configure/make
  INSTALL_COMMAND ${CMAKE_COMMAND} -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR> -P ${CMAKE_CURRENT_LIST_DIR}/install.cmake
)
set (POSIX_ROOT "${UNPACKED_ROOT}" PARENT_SCOPE)
set (POSIX_CMD "${CMAKE_INSTALL_PREFIX}/bin/posix.cmd" PARENT_SCOPE)
endif (WIN32)

if (UNIX)
set (POSIX_ROOT "/" PARENT_SCOPE)
#UNIX systems have a builtin bash shell, so there is no need to install anything.
set (POSIX_CMD "" PARENT_SCOPE)

#Define an empty posix-runtime project so that dependencies on a posix runtime can be
#specified indendently of WIN32 or UNIX.
ExternalProject_Add (
  posix-runtime
  BUILD_IN_SOURCE 1
  DOWNLOAD_COMMAND ""
  CONFIGURE_COMMAND ""
  BUILD_COMMAND ""
  INSTALL_COMMAND ""
)
endif (UNIX)