/**
 * Copyright (c) 2021 OceanBase
 * OceanBase CE is licensed under Mulan PubL v2.
 * You can use this software according to the terms and conditions of the Mulan PubL v2.
 * You may obtain a copy of Mulan PubL v2 at:
 *          http://license.coscl.org.cn/MulanPubL-2.0
 * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
 * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
 * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
 * See the Mulan PubL v2 for more details.
 */

#ifndef OCEANBASE_SQL_OB_EXPR_FUNC_RANDOM_H_
#define OCEANBASE_SQL_OB_EXPR_FUNC_RANDOM_H_

#include "sql/engine/expr/ob_expr_operator.h"

namespace oceanbase {
namespace sql {
class ObExprRandom : public ObFuncExprOperator {
  OB_UNIS_VERSION(1);
  class ObExprRandomCtx : public ObExprOperatorCtx {
  public:
    ObExprRandomCtx();
    virtual ~ObExprRandomCtx();
    void set_seed(uint32_t seed);
    void get_next_random(double& res);

  private:
    static const uint64_t max_value_;
    uint64_t seed1_;
    uint64_t seed2_;
  };

public:
  explicit ObExprRandom(common::ObIAllocator& alloc);
  virtual ~ObExprRandom();
  virtual int calc_result_typeN(
      ObExprResType& type, ObExprResType* types, int64_t param_num, common::ObExprTypeCtx& type_ctx) const override;
  virtual int calc_resultN(
      common::ObObj& result, const common::ObObj* objs, int64_t param_num, common::ObExprCtx& expr_ctx) const override;
  inline void set_seed_const(bool is_seed_const);

  // engine 3.0
  virtual bool need_rt_ctx() const override
  {
    return true;
  }
  virtual int cg_expr(ObExprCGCtx& expr_cg_ctx, const ObRawExpr& raw_expr, ObExpr& rt_expr) const override;
  static int calc_random_expr_const_seed(const ObExpr& expr, ObEvalCtx& ctx, ObDatum& res_datum);
  static int calc_random_expr_nonconst_seed(const ObExpr& expr, ObEvalCtx& ctx, ObDatum& res_datum);

public:
  virtual int assign(const ObExprOperator& other) override;

private:
  bool is_seed_const_;
  // disallow copy
  DISALLOW_COPY_AND_ASSIGN(ObExprRandom);
};

inline void ObExprRandom::set_seed_const(bool is_seed_const)
{
  is_seed_const_ = is_seed_const;
}
} /* namespace sql */
} /* namespace oceanbase */

#endif /* OCEANBASE_SQL_OB_EXPR_FUNC_RANDOM_H_ */