// 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.

#include "exec/spill/spill_file_reader.h"

#include <glog/logging.h>

#include <algorithm>

#include "common/cast_set.h"

#include "common/exception.h"

#include "core/block/block.h"

#include "exec/spill/spill_file_manager.h"

#include "io/file_factory.h"

#include "io/fs/file_reader.h"

#include "io/fs/local_file_system.h"

#include "runtime/exec_env.h"

#include "runtime/query_context.h"

#include "runtime/runtime_state.h"

#include "util/debug_points.h"

#include "util/slice.h"

namespace doris {

namespace io {

class FileSystem;

} // namespace io

SpillFileReader::SpillFileReader(RuntimeState* state, RuntimeProfile* profile,

                                 std::string spill_dir, size_t part_count)

        : _spill_dir(std::move(spill_dir)),

          _part_count(part_count),

          _resource_ctx(state->get_query_ctx()->resource_ctx()) {

    // Internalize counter setup

    RuntimeProfile* custom_profile = profile->get_child("CustomCounters");

    DCHECK(custom_profile != nullptr);

    _read_file_timer = custom_profile->get_counter("SpillReadFileTime");

    _deserialize_timer = custom_profile->get_counter("SpillReadDerializeBlockTime");

    _read_block_count = custom_profile->get_counter("SpillReadBlockCount");

    _read_block_data_size = custom_profile->get_counter("SpillReadBlockBytes");

    _read_file_size = custom_profile->get_counter("SpillReadFileBytes");

    _read_rows_count = custom_profile->get_counter("SpillReadRows");

    _read_file_count = custom_profile->get_counter("SpillReadFileCount");

}

Status SpillFileReader::open() {

    if (_is_open || _part_count == 0) {

        return Status::OK();

    }

    RETURN_IF_ERROR(_open_part(0));

    _is_open = true;

    return Status::OK();

}

Status SpillFileReader::_open_part(size_t part_index) {

    _close_current_part();

    _current_part_index = part_index;

    _part_opened = true;

    std::string part_path = _spill_dir + "/" + std::to_string(part_index);

    SCOPED_TIMER(_read_file_timer);

    COUNTER_UPDATE(_read_file_count, 1);

    RETURN_IF_ERROR(io::global_local_filesystem()->open_file(part_path, &_file_reader));

    size_t file_size = _file_reader->size();

    DCHECK(file_size >= 16); // max_sub_block_size + block count

    Slice result((char*)&_part_block_count, sizeof(size_t));

    // read block count

    size_t bytes_read = 0;

    RETURN_IF_ERROR(_file_reader->read_at(file_size - sizeof(size_t), result, &bytes_read));

    DCHECK(bytes_read == 8);

    // read max sub block size

    bytes_read = 0;

    result.data = (char*)&_part_max_sub_block_size;

    RETURN_IF_ERROR(_file_reader->read_at(file_size - sizeof(size_t) * 2, result, &bytes_read));

    DCHECK(bytes_read == 8);

    // The buffer is used for two purposes:

    // 1. Reading the block start offsets array (needs _part_block_count * sizeof(size_t) bytes)

    // 2. Reading a single block's serialized data (needs up to _part_max_sub_block_size bytes)

    // We must ensure the buffer is large enough for either case, so take the maximum.

    size_t buff_size = std::max(_part_block_count * sizeof(size_t), _part_max_sub_block_size);

    if (buff_size > _read_buff.size()) {

        _read_buff.reserve(buff_size);

    }

    // Read the block start offsets array from the end of the file.

    // The file layout (from end backwards) is:

    //   [block count (size_t)]

    //   [max sub block size (size_t)]

    //   [block start offsets array (_part_block_count * size_t)]

    // So the offsets array starts at:

    //   file_size - (_part_block_count + 2) * sizeof(size_t)

    size_t read_offset = file_size - (_part_block_count + 2) * sizeof(size_t);

    result.data = _read_buff.data();

    result.size = _part_block_count * sizeof(size_t);

    RETURN_IF_ERROR(_file_reader->read_at(read_offset, result, &bytes_read));

    DCHECK(bytes_read == _part_block_count * sizeof(size_t));

    _block_start_offsets.resize(_part_block_count + 1);

    for (size_t i = 0; i < _part_block_count; ++i) {

        _block_start_offsets[i] = *(size_t*)(result.data + i * sizeof(size_t));

    }

    _block_start_offsets[_part_block_count] = file_size - (_part_block_count + 2) * sizeof(size_t);

    _part_read_block_index = 0;

    return Status::OK();

}

void SpillFileReader::_close_current_part() {

    if (_file_reader) {

        (void)_file_reader->close();

        _file_reader.reset();

    }

    _part_block_count = 0;

    _part_read_block_index = 0;

    _part_max_sub_block_size = 0;

    _block_start_offsets.clear();

    _part_opened = false;

}

Status SpillFileReader::read(Block* block, bool* eos) {

    DBUG_EXECUTE_IF("fault_inject::spill_file::read_next_block", {

        return Status::InternalError("fault_inject spill_file read_next_block failed");

    });

    block->clear_column_data();

    if (_part_count == 0) {

        *eos = true;

        return Status::OK();

    }

    // Advance to next part if current part is exhausted

    while (_part_read_block_index >= _part_block_count) {

        size_t next_part = _part_opened ? _current_part_index + 1 : 0;

        if (next_part >= _part_count) {

            *eos = true;

            return Status::OK();

        }

        RETURN_IF_ERROR(_open_part(next_part));

    }

    size_t bytes_to_read = _block_start_offsets[_part_read_block_index + 1] -

                           _block_start_offsets[_part_read_block_index];

    if (bytes_to_read == 0) {

        ++_part_read_block_index;

        *eos = false;

        return Status::OK();

    }

    Slice result(_read_buff.data(), bytes_to_read);

    size_t bytes_read = 0;

    {

        SCOPED_TIMER(_read_file_timer);

        RETURN_IF_ERROR(_file_reader->read_at(_block_start_offsets[_part_read_block_index], result,

                                              &bytes_read));

    }

    DCHECK(bytes_read == bytes_to_read);

    if (bytes_read > 0) {

        COUNTER_UPDATE(_read_file_size, bytes_read);

        ExecEnv::GetInstance()->spill_file_mgr()->update_spill_read_bytes(bytes_read);

        if (_resource_ctx) {

            _resource_ctx->io_context()->update_spill_read_bytes_from_local_storage(bytes_read);

        }

        COUNTER_UPDATE(_read_block_count, 1);

        {

            SCOPED_TIMER(_deserialize_timer);

            if (!_pb_block.ParseFromArray(result.data, cast_set<int>(result.size))) {

                return Status::InternalError("Failed to read spilled block");

            }

            size_t uncompressed_size = 0;

            int64_t uncompressed_time = 0;

            RETURN_IF_ERROR(block->deserialize(_pb_block, &uncompressed_size, &uncompressed_time));

        }

        COUNTER_UPDATE(_read_block_data_size, block->bytes());

        COUNTER_UPDATE(_read_rows_count, block->rows());

    } else {

        block->clear_column_data();

    }

    ++_part_read_block_index;

    *eos = false;

    return Status::OK();

}

Status SpillFileReader::seek(size_t block_index) {

    return _seek_to_block(block_index);

}

Status SpillFileReader::_seek_to_block(size_t block_index) {

    if (_part_count == 0) {

        return Status::OK();

    }

    size_t remaining = block_index;

    for (size_t part_index = 0; part_index < _part_count; ++part_index) {

        RETURN_IF_ERROR(_open_part(part_index));

        if (remaining < _part_block_count) {

            _part_read_block_index = remaining;

            return Status::OK();

        }

        remaining -= _part_block_count;

    }

    // block_index is out of range: position reader at EOS.

    RETURN_IF_ERROR(_open_part(_part_count - 1));

    _part_read_block_index = _part_block_count;

    return Status::OK();

}

Status SpillFileReader::close() {

    _close_current_part();

    _is_open = false;

    return Status::OK();

}

} // namespace doris