// 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 <glog/logging.h>

#include <stddef.h>

#include <stdint.h>

#include <vector>

#include "common/status.h"

#include "core/column/column.h"

#include "storage/segment/options.h"

#include "storage/segment/page_builder.h"

#include "storage/segment/page_decoder.h"

#include "util/coding.h"

#include "util/faststring.h"

#include "util/slice.h"

namespace doris {

namespace segment_v2 {

// prefix encoding for string dictionary

//

// BinaryPrefixPage := Entry^EntryNum, Trailer

// Entry := SharedPrefixLength(vint), UnsharedLength(vint), Byte^UnsharedLength

// Trailer := NumEntry(uint32_t), RESTART_POINT_INTERVAL(uint8_t)

//            RestartPointStartOffset(uint32_t)^NumRestartPoints,NumRestartPoints(uint32_t)

class BinaryPrefixPageBuilder : public PageBuilderHelper<BinaryPrefixPageBuilder> {

public:

    using Self = BinaryPrefixPageBuilder;

    friend class PageBuilderHelper<Self>;

    Status init() override { return reset(); }

    bool is_page_full() override { return size() >= _options.data_page_size; }

    Status add(const uint8_t* vals, size_t* add_count) override;

    Status finish(OwnedSlice* slice) override;

    Status reset() override {

        _restart_points_offset.clear();

        _last_entry.clear();

        _count = 0;

        _buffer.clear();

        _finished = false;

        _raw_data_size = 0;

        return Status::OK();

    }

    uint64_t size() const override {

        if (_finished) {

            return _buffer.size();

        } else {

            return _buffer.size() + (_restart_points_offset.size() + 2) * sizeof(uint32_t);

        }

    }

    size_t count() const override { return _count; }

    uint64_t get_raw_data_size() const override { return _raw_data_size; }

private:

    BinaryPrefixPageBuilder(const PageBuilderOptions& options) : _options(options) {}

    PageBuilderOptions _options;

    std::vector<uint32_t> _restart_points_offset;

    // Holds the most recently added entry; used by add() to compute the

    // shared-prefix length against the next entry.

    faststring _last_entry;

    size_t _count = 0;

    bool _finished = false;

    faststring _buffer;

    uint64_t _raw_data_size = 0;

    // This is a empirical value, Kudu and LevelDB use this default value

    static const uint8_t RESTART_POINT_INTERVAL = 16;

};

class BinaryPrefixPageDecoder : public PageDecoder {

public:

    BinaryPrefixPageDecoder(Slice data, const PageDecoderOptions& options)

            : _data(data), _parsed(false) {}

    Status init() override;

    Status seek_to_position_in_page(size_t pos) override;

    Status seek_at_or_after_value(const void* value, bool* exact_match) override;

    Status next_batch(size_t* n, MutableColumnPtr& dst) override;

    size_t count() const override {

        DCHECK(_parsed);

        return _num_values;

    }

    size_t current_index() const override {

        DCHECK(_parsed);

        return _cur_pos;

    }

private:

    // decode shared and non-shared entry length from `ptr`.

    // return ptr past the parsed value when success.

    // return nullptr on failure

    const uint8_t* _decode_value_lengths(const uint8_t* ptr, uint32_t* shared,

                                         uint32_t* non_shared);

    // return start pointer of the restart point at index `restart_point_index`

    const uint8_t* _get_restart_point(size_t restart_point_index) const {

        return reinterpret_cast<const uint8_t*>(_data.get_data()) +

               decode_fixed32_le(_restarts_ptr + restart_point_index * sizeof(uint32_t));

    }

    // read next value at `_cur_pos` and `_next_ptr` into `_current_value`.

    // return OK and advance `_next_ptr` on success. `_cur_pos` is not modified.

    // return EndOfFile when no more entry can be read.

    // return other error status otherwise.

    Status _read_next_value();

    // seek to the first value at the given restart point

    Status _seek_to_restart_point(size_t restart_point_index);

    Slice _data;

    bool _parsed = false;

    size_t _num_values = 0;

    uint8_t _restart_point_internal = 0;

    uint32_t _num_restarts = 0;

    // pointer to _footer start

    const uint8_t* _footer_start = nullptr;

    // pointer to restart offsets array

    const uint8_t* _restarts_ptr = nullptr;

    // ordinal of the first value to return in next_batch()

    uint32_t _cur_pos = 0;

    // first value to return in next_batch()

    faststring _current_value;

    // pointer to the start of next value to read, advanced by `_read_next_value`

    const uint8_t* _next_ptr = nullptr;

};

} // namespace segment_v2

} // namespace doris