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
