/* -*- C++ -*-
 * Serene Programming Language
 *
 * Copyright (c) 2019-2022 Sameer Rahmani <lxsameer@gnu.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 2.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef SERENE_EXPRS_EXPRESSION_H
#define SERENE_EXPRS_EXPRESSION_H

#include "serene/context.h"
#include "serene/errors.h"
#include "serene/exprs/traits.h"
#include "serene/namespace.h"
#include "serene/reader/location.h"
#include "serene/semantics.h"
#include "serene/utils.h"

#include <llvm/Support/Error.h>
#include <mlir/IR/BuiltinOps.h>

#include <memory>

namespace serene {

/// Contains all the builtin AST expressions including those which do not appear
/// in the syntax directly. Like function definitions.
namespace exprs {

class Expression;

using Node      = std::shared_ptr<Expression>;
using MaybeNode = llvm::Expected<Node>;

using Ast      = std::vector<Node>;
using MaybeAst = llvm::Expected<Ast>;

constexpr static auto EmptyNode = nullptr;

/// The base class of the expressions which provides the common interface for
/// the expressions to implement.
class SERENE_EXPORT Expression {
public:
  /// The location range provide information regarding to where in the input
  /// string the current expression is used.
  reader::LocationRange location;

  Expression(const reader::LocationRange &loc) : location(loc){};
  virtual ~Expression() = default;

  /// Returns the type of the expression. We need this funciton to perform
  /// dynamic casting of expression object to implementations such as lisp or
  /// symbol.
  virtual ExprType getType() const = 0;

  /// The AST representation of an expression
  virtual std::string toString() const = 0;

  /// Analyzes the semantics of current node and return a new node in case
  /// that we need to semantically rewrite the current node and replace it with
  /// another node. For example to change from a List containing `(def a b)`
  /// to a `Def` node that represents defining a new binding.
  ///
  /// \param state is the analysis state object of the semantic analyzer.
  virtual MaybeNode analyze(semantics::AnalysisState &state) = 0;

  /// Genenates the correspondig SLIR of the expressoin and attach it to the
  /// given module.
  ///
  /// \param ns The namespace that current expression is in it.
  /// \param m  The target MLIR moduleOp to attach the operations to
  virtual void generateIR(serene::Namespace &ns, mlir::ModuleOp &m) = 0;
};

/// Create a new `node` of type `T` and forwards any given parameter
/// to the constructor of type `T`. This is the **official way** to create
/// a new `Expression`. Here is an example:
/// \code
/// auto list = make<List>();
/// \endcode
///
/// \param[args] Any argument with any type passed to this function will be
///              passed to the constructor of type T.
/// \return A unique pointer to an Expression
template <typename T, typename... Args>
Node make(Args &&...args) {
  return std::make_shared<T>(std::forward<Args>(args)...);
};
/// Create a new `node` of type `T` and forwards any given parameter
/// to the constructor of type `T`. This is the **official way** to create
/// a new `Expression`. Here is an example:
/// \code
/// auto list = makeAndCast<List>();
/// \endcode
///
/// \param[args] Any argument with any type passed to this function will be
///              passed to the constructor of type T.
/// \return A unique pointer to a value of type T.
template <typename T, typename... Args>
std::shared_ptr<T> makeAndCast(Args &&...args) {
  return std::make_shared<T>(std::forward<Args>(args)...);
};

/// The helper function to create a new `Node` and returnsit. It should be useds
/// where every we want to return a `MaybeNode` successfully.
template <typename T, typename... Args>
MaybeNode makeSuccessfulNode(Args &&...args) {
  return make<T>(std::forward<Args>(args)...);
};

/// The hlper function to creates an Error (`llvm::Error`) by passing all
/// the given arguments to the constructor of the template param `E`.
template <typename E, typename T = Node, typename... Args>
llvm::Expected<T> makeErrorful(Args &&...args) {
  return llvm::make_error<E>(std::forward<Args>(args)...);
};

/// The hlper function to creates an Error (`llvm::Error`) by passing all
/// the given arguments to the constructor of the template param `E`.
template <typename E, typename... Args>
MaybeNode makeErrorNode(Args &&...args) {
  return makeErrorful<E, Node>(std::forward<Args>(args)...);
};

/// Convert the given AST to string by calling the `toString` method
/// of each node.
SERENE_EXPORT std::string astToString(const Ast *);
/// Converts the given ExprType to string.
std::string stringifyExprType(ExprType);

/// Converts the given AST to string and prints it out
void dump(Ast &);

} // namespace exprs
} // namespace serene

#endif