// Copyright 2023 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#pragma once

#include <Parsers/IAST.h>

namespace DB
{

/** Sampling factor in the form 0.1 or 1/10.
  * It's important to save it as a rational number without converting it to IEEE-754.
  */
class ASTSampleRatio : public IAST
{
public:
#ifdef __SIZEOF_INT128__
    using BigNum = __uint128_t; /// Must contain the result of multiplying two UInt64.
#else
#warning "No uint128_t type. Sampling ratios cannot work correctly."
    using BigNum = uint64_t;
#endif

    struct Rational
    {
        BigNum numerator = 0;
        BigNum denominator = 1;
    };

    Rational ratio;

    ASTSampleRatio(Rational & ratio_)
        : ratio(ratio_)
    {}

    String getID() const override { return "SampleRatio_" + toString(ratio); }

    ASTPtr clone() const override { return std::make_shared<ASTSampleRatio>(*this); }

    static String toString(BigNum num);
    static String toString(Rational ratio);

    void formatImpl(const FormatSettings & settings, FormatState &, FormatStateStacked) const override
    {
        settings.ostr << toString(ratio);
    }
};

} // namespace DB