// 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 <memory>

#include <utility>

#include "common/status.h" // for Status

#include "core/column/column.h"

namespace doris {

namespace segment_v2 {

// PageDecoder is used to decode page.

class PageDecoder {

public:

    PageDecoder() {}

    virtual ~PageDecoder() {}

    // Call this to do some preparation for decoder.

    // eg: parse data page header

    virtual Status init() = 0;

    // Seek the decoder to the given positional index of the page.

    // For example, seek_to_position_in_page(0) seeks to the first

    // stored entry.

    //

    // It is an error to call this with a value larger than Count().

    // Doing so has undefined results.

    virtual Status seek_to_position_in_page(size_t pos) = 0;

    // Seek the decoder to the given value in the page, or the

    // lowest value which is greater than the given value.

    //

    // If the decoder was able to locate an exact match, then

    // sets *exact_match to true. Otherwise sets *exact_match to

    // false, to indicate that the seeked value is _after_ the

    // requested value.

    //

    // If the given value is less than the lowest value in the page,

    // seeks to the start of the page. If it is higher than the highest

    // value in the page, then returns Status::Error<ENTRY_NOT_FOUND>

    //

    // This will only return valid results when the data page

    // consists of values in sorted order.

    virtual Status seek_at_or_after_value(const void* value, bool* exact_match) {

        return Status::NotSupported("seek_at_or_after_value"); // FIXME

    }

    virtual Status next_batch(size_t* n, MutableColumnPtr& dst) = 0;

    virtual Status read_by_rowids(const rowid_t* rowids, ordinal_t page_first_ordinal, size_t* n,

                                  MutableColumnPtr& dst) {

        return Status::NotSupported("not implement vec op now");

    }

    // Same as `next_batch` except for not moving forward the cursor.

    // When read array's ordinals in `ArrayFileColumnIterator`, we want to read one extra ordinal

    // but do not want to move forward the cursor.

    virtual Status peek_next_batch(size_t* n, MutableColumnPtr& dst) {

        return Status::NotSupported("not implement vec op now");

    }

    // Return the number of elements in this page.

    virtual size_t count() const = 0;

    // Return the position within the page of the currently seeked

    // entry (ie the entry that will next be returned by next_vector())

    virtual size_t current_index() const = 0;

    bool has_remaining() const { return current_index() < count(); }

    virtual Status get_dict_word_info(StringRef* dict_word_info) {

        return Status::NotSupported("get_dict_word_info not implement");

    }

    // Fixed-width decoders can hand out pointers into their decoded page buffer. The owner keeps

    // that page alive after next_batch() returns if the destination column chooses a zero-copy

    // immutable view; destinations that cannot use it still copy through the default column API.

    void set_page_data_owner(std::shared_ptr<void> page_data_owner) {

        _page_data_owner = std::move(page_data_owner);

    }

private:

    DISALLOW_COPY_AND_ASSIGN(PageDecoder);

protected:

    std::shared_ptr<void> _page_data_owner;

};

} // namespace segment_v2

} // namespace doris