dnl GTEST_LIB_CHECK([minimum version [,
dnl                  action if found [,action if not found]]])
dnl
dnl Check for the presence of the Google Test library, optionally at a minimum
dnl version, and indicate a viable version with the HAVE_GTEST flag. It defines
dnl standard variables for substitution including GTEST_CPPFLAGS,
dnl GTEST_CXXFLAGS, GTEST_LDFLAGS, and GTEST_LIBS. It also defines
dnl GTEST_VERSION as the version of Google Test found. Finally, it provides
dnl optional custom action slots in the event GTEST is found or not.
AC_DEFUN([GTEST_LIB_CHECK],
[
dnl Provide a flag to enable or disable Google Test usage.
AC_ARG_ENABLE([gtest],
  [AS_HELP_STRING([--enable-gtest],
                  [Enable tests using the Google C++ Testing Framework.
                  (Default is enabled.)])],
  [],
  [enable_gtest=])
AC_ARG_VAR([GTEST_CONFIG],
           [The exact path of Google Test's 'gtest-config' script.])
AC_ARG_VAR([GTEST_CPPFLAGS],
           [C-like preprocessor flags for Google Test.])
AC_ARG_VAR([GTEST_CXXFLAGS],
           [C++ compile flags for Google Test.])
AC_ARG_VAR([GTEST_LDFLAGS],
           [Linker path and option flags for Google Test.])
AC_ARG_VAR([GTEST_LIBS],
           [Library linking flags for Google Test.])
AC_ARG_VAR([GTEST_VERSION],
           [The version of Google Test available.])
HAVE_GTEST="no"
AS_IF([test "x${enable_gtest}" != "xno"],
  [AC_MSG_CHECKING([for 'gtest-config'])
   AS_IF([test "x${enable_gtest}" = "xyes"],
     [AS_IF([test -x "${enable_gtest}/scripts/gtest-config"],
        [GTEST_CONFIG="${enable_gtest}/scripts/gtest-config"],
        [GTEST_CONFIG="${enable_gtest}/bin/gtest-config"])
      AS_IF([test -x "${GTEST_CONFIG}"], [],
        [AC_MSG_RESULT([no])
         AC_MSG_ERROR([dnl
Unable to locate either a built or installed Google Test.
The specific location '${enable_gtest}' was provided for a built or installed
Google Test, but no 'gtest-config' script could be found at this location.])
         ])],
     [AC_PATH_PROG([GTEST_CONFIG], [gtest-config])])
   AS_IF([test -x "${GTEST_CONFIG}"],
     [AC_MSG_RESULT([${GTEST_CONFIG}])
      m4_ifval([$1],
        [_gtest_min_version="--min-version=$1"
         AC_MSG_CHECKING([for Google Test at least version >= $1])],
        [_gtest_min_version="--min-version=0"
         AC_MSG_CHECKING([for Google Test])])
      AS_IF([${GTEST_CONFIG} ${_gtest_min_version}],
        [AC_MSG_RESULT([yes])
         HAVE_GTEST='yes'],
        [AC_MSG_RESULT([no])])],
     [AC_MSG_RESULT([no])])
   AS_IF([test "x${HAVE_GTEST}" = "xyes"],
     [GTEST_CPPFLAGS=`${GTEST_CONFIG} --cppflags`
      GTEST_CXXFLAGS=`${GTEST_CONFIG} --cxxflags`
      GTEST_LDFLAGS=`${GTEST_CONFIG} --ldflags`
      GTEST_LIBS=`${GTEST_CONFIG} --libs`
      GTEST_VERSION=`${GTEST_CONFIG} --version`
      AC_DEFINE([HAVE_GTEST],[1],[Defined when Google Test is available.])],
     [AS_IF([test "x${enable_gtest}" = "xyes"],
        [AC_MSG_ERROR([dnl
Google Test was enabled, but no viable version could be found.])
         ])])])
AC_SUBST([HAVE_GTEST])
AM_CONDITIONAL([HAVE_GTEST],[test "x$HAVE_GTEST" = "xyes"])
AS_IF([test "x$HAVE_GTEST" = "xyes"],
  [m4_ifval([$2], [$2])],
  [m4_ifval([$3], [$3])])
])