import SCons.Util, os.path

def generate(env) :
    root = env.Dir("#").abspath
    def relpath(path, start) :
        i = len(os.path.commonprefix([path, start]))
        return path[i+1:]

    def replacePragmaOnce(env, target, source) :
        guard = relpath(source[0].abspath, root).replace("/", "_").replace(".", "_").upper()
        data = source[0].get_contents()
        f = open(str(target[0]), 'wb')
        if "#pragma once" in data :
            f.write(data.replace("#pragma once", "#ifndef %(guard)s\n#define %(guard)s" % {"guard": guard}))
            f.write("\n#endif\n")
        else :
            f.write(data)
        f.close()

    env["BUILDERS"]["ReplacePragmaOnce"] = SCons.Builder.Builder(
        action = SCons.Action.Action(replacePragmaOnce, cmdstr = "$GENCOMSTR"),
        single_source = True)

def exists(env) :
    return True