// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you 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 <array>

#include <cstddef>

#include <cstdint>

#include "core/string_ref.h"

namespace doris {

// A validated, stack-only plan for one physical Variant scalar. The plan either owns a small

// inline textual fallback or borrows a StringRef until write() returns; it never allocates.

// Callers can therefore preflight a complete batch, reserve its final buffer once, and write

// directly into that buffer without constructing a VariantBuilder per row.

class VariantScalarEncodingPlan {

public:

    static VariantScalarEncodingPlan null_value() noexcept;

    static VariantScalarEncodingPlan boolean(bool value) noexcept;

    // width == 0 selects the narrowest signed integer encoding. Otherwise width must be one of

    // 1, 2, 4, or 8 and value must fit that signed width.

    static VariantScalarEncodingPlan integer(int64_t value, uint8_t width = 0);

    static VariantScalarEncodingPlan float32(float value) noexcept;

    static VariantScalarEncodingPlan float64(double value) noexcept;

    // width == 0 selects the narrowest decimal width. Otherwise width must be 4, 8, or 16.

    static VariantScalarEncodingPlan decimal(__int128 unscaled, uint8_t scale, uint8_t width = 0);

    static VariantScalarEncodingPlan date(int32_t days_since_epoch) noexcept;

    static VariantScalarEncodingPlan timestamp_micros(int64_t value, bool utc_adjusted) noexcept;

    static VariantScalarEncodingPlan timestamp_nanos(int64_t value, bool utc_adjusted) noexcept;

    static VariantScalarEncodingPlan time_ntz_micros(int64_t value) noexcept;

    static VariantScalarEncodingPlan binary(StringRef value);

    static VariantScalarEncodingPlan string(StringRef value);

    static VariantScalarEncodingPlan uuid(const std::array<uint8_t, 16>& value) noexcept;

    // Values outside decimal38 are encoded as their canonical decimal string representation.

    static VariantScalarEncodingPlan largeint(__int128 value) noexcept;

    size_t size() const noexcept { return _encoded_size; }

    bool used_string_fallback() const noexcept { return _used_string_fallback; }

    // Writes exactly size() bytes. Invalid destination/capacity fails before modifying memory.

    void write(char* destination, size_t capacity) const;

private:

    VariantScalarEncodingPlan() = default;

    enum class PayloadKind : uint8_t {

        HEADER_ONLY,

        UNSIGNED,

        SIGNED,

        BORROWED_BYTES,

        UUID,

        INLINE_STRING,

    };

    uint64_t _unsigned_value = 0;

    __int128 _signed_value = 0;

    StringRef _borrowed;

    std::array<uint8_t, 16> _uuid {};

    std::array<char, 40> _inline_string {};

    size_t _encoded_size = 0;

    uint8_t _header = 0;

    uint8_t _payload_width = 0;

    uint8_t _scale = 0;

    uint8_t _inline_size = 0;

    PayloadKind _kind = PayloadKind::HEADER_ONLY;

    bool _has_scale = false;

    bool _has_length = false;

    bool _used_string_fallback = false;

};

} // namespace doris