%% For cross building using erlang:system_info() does not work as rebar runs
%% using the build hosts Erlang runtime.
%% If CXX envrionment variable is defined we are most likely running in a cross environment.
{CXX,Target,Sysroot} =
    case os:getenv("CXX") of
    false    ->
        {"g++",erlang:system_info(system_architecture),""};
    Compiler ->
        {Compiler,string:strip(os:cmd(Compiler ++ " -dumpmachine"),   right, $\n),
                  string:strip(os:cmd(Compiler ++ " -print-sysroot"), right, $\n)}
    end,

%% Commonly on Linux, compilers report the target triplet as <arch>-<vendor>-linux,
%% however, Erlang runtime reports and expects it as <arch>-<vendor>-linux-gnu.
%% Fix by appending "-gnu".
Mach = case string:str(Target,"linux") of
    0 -> Target;
    _ -> case string:words(Target,$-) of
         4 -> Target;
         _ -> Target ++ "-gnu"
         end
    end,

Vsn = string:strip(os:cmd("git describe --always --tags --abbrev=0 | sed 's/^v//'"), right, $\n),

%% Check for Linux capability API (Install package: libcap-devel).
{LinCXX, LinLD} =
    case file:read_file_info(Sysroot ++ "/usr/include/sys/capability.h") of
    {ok, _} -> {" -DHAVE_CAP", " -lcap"};
    _       -> {"", ""}
    end,

X64=case Mach of
    "x86_64" ++ _E -> " -m64";
    _              -> ""
    end,

OptimLevel =
    case os:getenv("OPTIMIZE") of
    false  -> "0";
    "true" -> "2";
    Level  -> list_to_integer(Level), Level
    end,

% Merge configuration options read from rebar.config with those dynamically set below
maps:to_list(lists:foldl(
    fun({K, V}, M) ->
        case maps:find(K, M) of
        {ok, V0} -> M#{K => V0 ++ V};
        error    -> M#{K => V}
        end
    end,
    maps:from_list(CONFIG),
    [
        {port_env,  [{"solaris", "CXXFLAGS", "$CXXFLAGS -DHAVE_SETREUID" ++ X64},
                     {"solaris", "LDFLAGS",  "$LDFLAGS -lrt" ++ X64},

                     {"darwin",  "CXXFLAGS", "$CXXFLAGS -DHAVE_SETREUID" ++ X64},
                     {"darwin",  "LDFLAGS",  "$LDFLAGS" ++ X64},

                     {"freebsd",   "CXXFLAGS", "$CXXFLAGS -DHAVE_SETRESUID" ++ X64},
                     {"freebsd",   "LDFLAGS",  "$LDFLAGS" ++ X64},

                     {"linux",   "CXXFLAGS", "$CXXFLAGS -DHAVE_SETRESUID" ++ LinCXX},
                     {"linux",   "LDFLAGS",  "$LDFLAGS" ++ LinLD},

                     {"CC",  CXX},
                     {"CXX", CXX},
                     {"CXXFLAGS", "$CXXFLAGS -DHAVE_PTRACE -std=c++98 -O" ++ OptimLevel}
                    ]},

        {port_specs,[{filename:join(["priv", Mach, "exec-port"]), ["c_src/*.cpp"]}]},
        {edoc_opts, [{overview,     "src/overview.edoc"},
                     {title,        "The exec application"},
                     {includes,     ["include"]},
                     {def,          {vsn, Vsn}},
                     {stylesheet_file, "src/edoc.css"},
                     {app_default,  "http://www.erlang.org/doc/man"}]}
    ]
)).