// 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 <cstddef>

#include <cstdint>

#include <memory>

#include <span>

#include "core/string_ref.h"

#include "util/variant/variant_metadata.h"

#include "util/variant/variant_value.h"

namespace doris {

class VariantBlockBuilder;

struct VariantEncodedBlockStorage;

// Borrows one immutable shared-metadata encoding unit. Offsets are directly compatible with

// ColumnString and always contain num_rows() + 1 entries.

class VariantEncodedBlockView {

public:

    size_t num_rows() const noexcept;

    VariantMetadataRef metadata_ref() const noexcept { return _metadata; }

    VariantValueRef value_at(size_t row) const;

    StringRef value_bytes() const noexcept { return _values; }

    std::span<const uint32_t> value_offsets() const noexcept { return _offsets; }

private:

    friend class VariantEncodedBlock;

    VariantEncodedBlockView(VariantMetadataRef metadata, StringRef values,

                            std::span<const uint32_t> offsets) noexcept

            : _metadata(metadata), _values(values), _offsets(offsets) {}

    VariantMetadataRef _metadata;

    StringRef _values;

    std::span<const uint32_t> _offsets;

};

// Owns one immutable two-pass encoding unit. Views and value refs remain valid until this block is

// destroyed or moved.

class VariantEncodedBlock {

public:

    VariantEncodedBlock(VariantEncodedBlock&&) noexcept;

    VariantEncodedBlock& operator=(VariantEncodedBlock&&) noexcept;

    ~VariantEncodedBlock();

    VariantEncodedBlock(const VariantEncodedBlock&) = delete;

    VariantEncodedBlock& operator=(const VariantEncodedBlock&) = delete;

    VariantEncodedBlockView view() const noexcept;

    size_t num_rows() const noexcept { return view().num_rows(); }

    VariantMetadataRef metadata_ref() const noexcept { return view().metadata_ref(); }

    VariantValueRef value_at(size_t row) const { return view().value_at(row); }

    StringRef value_bytes() const noexcept { return view().value_bytes(); }

    std::span<const uint32_t> value_offsets() const noexcept { return view().value_offsets(); }

private:

    friend class VariantBlockBuilder;

    explicit VariantEncodedBlock(std::unique_ptr<VariantEncodedBlockStorage> storage) noexcept;

    std::unique_ptr<VariantEncodedBlockStorage> _storage;

};

} // namespace doris