

/*!
 * \file eta_expand.cc
 *
 * \brief Add abstraction over a function. For example, abs will become (fun x -> abs x).
 *
 */
#include <tvm/relay/type.h>
#include <tvm/relay/transform.h>

namespace tvm {
namespace relay {

Expr EtaExpand(const Expr& e, const Module& mod) {
  tvm::Array<Var> original_params;
  tvm::Array<Expr> params;
  tvm::Array<Var> args;
  tvm::Array<TypeVar> original_type_params;
  Type ret_type;

  if (e->is_type<GlobalVarNode>()) {
    auto gvar_node = e.as_derived<GlobalVarNode>();
    auto func = mod->Lookup(GetRef<GlobalVar>(gvar_node));
    original_params = func->params;
    original_type_params = func->type_params;
    ret_type = func->ret_type;
  } else {
    CHECK(e->is_type<FunctionNode>());
    auto func = GetRef<Function>(e.as_derived<FunctionNode>());
    original_params = func->params;
    original_type_params = func->type_params;
    ret_type = func->ret_type;
  }

  for (size_t i = 0; i < original_params.size(); ++i) {
    auto var = VarNode::make("a", original_params[i]->type_annotation);
    params.push_back(var);
    args.push_back(var);
  }

  auto new_func =
      FunctionNode::make(args, CallNode::make(e, params), ret_type, original_type_params);

  return std::move(new_func);
}

namespace transform {

Pass EtaExpand() {
  runtime::TypedPackedFunc<Function(Function, Module, PassContext)> pass_func =
    [=](Function f, Module m, PassContext pc) {
      return Downcast<Function>(EtaExpand(f, m));
    };
  Pass expanded = CreateFunctionPass(pass_func, 1, "EtaExpand", {});
  return Sequential({expanded, InferType()});
}

TVM_REGISTER_API("relay._transform.EtaExpand")
.set_body_typed(EtaExpand);

}  // namespace transform

}  // namespace relay
}  // namespace tvm
