// 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 <vector>

#include "common/status.h"

namespace doris::io {

/// A half-open byte range [offset, offset + size) in one file.

struct FileRange {

    size_t offset {0};

    size_t size {0};

    size_t end() const { return offset + size; }

    bool operator==(const FileRange&) const = default;

};

/// Limits applied while adjacent input ranges are grouped into one physical read.

struct FileRangeCoalesceOptions {

    /// Maximum unread gap that may be included between two input ranges.

    size_t max_gap_bytes {0};

    /// Maximum size of a combined range. One indivisible input may exceed this limit.

    size_t max_range_bytes {1};

    /// Maximum combined-range bytes divided by bytes covered by its input ranges.

    double max_read_amplification_ratio {1.0};

    /// Validate the option values independently of any input ranges.

    Status validate() const;

};

/// Groups sorted file ranges without performing file IO.

class FileRangeCoalescer {

public:

    /// `options` must have passed validation. Each input range must be non-empty. Input ranges

    /// must be sorted by offset and mutually disjoint. Callers establish these invariants before

    /// entering the hot path.

    /// `max_range_bytes` limits combining multiple inputs; one indivisible input may be larger and

    /// is returned unchanged.

    static std::vector<FileRange> coalesce(const std::vector<FileRange>& input_ranges,

                                           const FileRangeCoalesceOptions& options);

};

} // namespace doris::io