# Copyright (c) 2024, Alibaba Group;
# Licensed 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.


import glob
import os
import time
from collections import OrderedDict
from concurrent.futures import ThreadPoolExecutor
from typing import Any, Dict, Iterator, List, Optional, Tuple

import pyarrow as pa
from pyarrow import parquet
from torch import distributed as dist

from tzrec.constant import Mode
from tzrec.datasets.dataset import BaseDataset, BaseReader, BaseWriter
from tzrec.datasets.utils import calc_slice_position
from tzrec.features.feature import BaseFeature
from tzrec.protos import data_pb2
from tzrec.utils import dist_util
from tzrec.utils.logging_util import logger


def _reader_iter(
    input_files: List[str],
    batch_size: int,
    parquet_metas: List[parquet.FileMetaData],
    columns: Optional[List[str]],
    start: int,
    end: int,
    worker_id: int,
) -> Iterator[pa.RecordBatch]:
    cnt = 0
    for input_file in input_files:
        if cnt >= end:
            break

        metadata = parquet_metas[input_file]
        if cnt + metadata.num_rows <= start:
            cnt += metadata.num_rows
            continue
        else:
            i = 0
            for i in range(metadata.num_row_groups):
                row_group_rows = metadata.row_group(i).num_rows
                if cnt + row_group_rows <= start:
                    cnt += row_group_rows
                    continue
                else:
                    break

            row_groups = list(range(i, metadata.num_row_groups))
            parquet_file = parquet.ParquetFile(input_file)
            for batch in parquet_file.iter_batches(
                batch_size, row_groups=row_groups, columns=columns, use_threads=False
            ):
                if cnt + len(batch) <= start:
                    logger.debug(
                        f"worker {worker_id} skip batch. "
                        f"start: {start}, end: {end}, cnt: {cnt}, len: {len(batch)}."
                    )
                elif cnt <= start:
                    logger.debug(
                        f"worker {worker_id} yield start batch. "
                        f"start: {start}, end: {end}, cnt: {cnt}, len: {len(batch)}."
                    )
                    yield batch[start - cnt :]
                elif cnt + len(batch) > end:
                    yield batch[: end - cnt]
                else:
                    yield batch

                cnt += len(batch)
                if cnt >= end:
                    break
            parquet_file.close()


def _get_metadata(input_file: str) -> Tuple[str, parquet.FileMetaData]:
    parquet_file = parquet.ParquetFile(input_file)
    metadata = parquet_file.metadata
    parquet_file.close()
    return input_file, metadata


class ParquetDataset(BaseDataset):
    """Dataset for reading data with parquet format.

    Args:
        data_config (DataConfig): an instance of DataConfig.
        features (list): list of features.
        input_path (str): data input path.
    """

    def __init__(
        self,
        data_config: data_pb2.DataConfig,
        features: List[BaseFeature],
        input_path: str,
        **kwargs: Any,
    ) -> None:
        super().__init__(data_config, features, input_path, **kwargs)
        # pyre-ignore [29]
        self._reader = ParquetReader(
            input_path,
            self._batch_size,
            list(self._selected_input_names) if self._selected_input_names else None,
            self._data_config.drop_remainder,
            shuffle=self._data_config.shuffle and self._mode == Mode.TRAIN,
            shuffle_buffer_size=self._data_config.shuffle_buffer_size,
            drop_redundant_bs_eq_one=self._mode != Mode.PREDICT,
        )
        self._init_input_fields()


class ParquetReader(BaseReader):
    """Parquet reader class.

    Args:
        input_path (str): data input path.
        batch_size (int): batch size.
        selected_cols (list): selection column names.
        drop_remainder (bool): drop last batch.
        shuffle (bool): shuffle data or not.
        shuffle_buffer_size (int): buffer size for shuffle.
        drop_redundant_bs_eq_one (bool): drop last redundant batch with batch_size
            equal one to prevent train_eval hung.
    """

    def __init__(
        self,
        input_path: str,
        batch_size: int,
        selected_cols: Optional[List[str]] = None,
        drop_remainder: bool = False,
        shuffle: bool = False,
        shuffle_buffer_size: int = 32,
        drop_redundant_bs_eq_one: bool = False,
        **kwargs: Any,
    ) -> None:
        super().__init__(
            input_path,
            batch_size,
            selected_cols,
            drop_remainder,
            shuffle,
            shuffle_buffer_size,
        )
        self._pg = dist_util.get_dist_object_pg()
        self._drop_redundant_bs_eq_one = drop_redundant_bs_eq_one

        self._ordered_cols = None
        self.schema = []
        self._input_files = []
        for input_path in self._input_path.split(","):
            self._input_files.extend(glob.glob(input_path))
        if len(self._input_files) == 0:
            raise RuntimeError(f"No parquet files exist in {self._input_path}.")

        parquet_file = parquet.ParquetFile(self._input_files[0])
        if self._selected_cols:
            self._ordered_cols = []
            for field in parquet_file.schema_arrow:
                # pyre-ignore [58]
                if field.name in selected_cols:
                    self.schema.append(field)
                    self._ordered_cols.append(field.name)
        else:
            self.schema = parquet_file.schema_arrow
        parquet_file.close()

        rank = int(os.environ.get("RANK", 0))
        world_size = int(os.environ.get("WORLD_SIZE", 1))

        # get parquet metadata
        self._parquet_metas = {}
        parquet_metas_per_rank = {}
        with ThreadPoolExecutor(max_workers=os.cpu_count()) as executor:
            for k, v in executor.map(
                _get_metadata, self._input_files[rank::world_size]
            ):
                parquet_metas_per_rank[k] = v
        if self._pg is not None:
            parquet_metas_list = [None] * world_size
            dist.all_gather_object(parquet_metas_list, parquet_metas_per_rank)
            for v in parquet_metas_list:
                self._parquet_metas.update(v)
        else:
            self._parquet_metas = parquet_metas_per_rank

        self._num_rows = []
        for input_file in self._input_files:
            self._num_rows.append(self._parquet_metas[input_file].num_rows)

    def to_batches(
        self, worker_id: int = 0, num_workers: int = 1
    ) -> Iterator[Dict[str, pa.Array]]:
        """Get batch iterator."""
        start, end, _ = calc_slice_position(
            sum(self._num_rows),
            worker_id,
            num_workers,
            self._batch_size,
            self._drop_redundant_bs_eq_one,
        )

        if len(self._input_files) > 0:
            reader = _reader_iter(
                self._input_files,
                self._batch_size,
                self._parquet_metas,
                self._ordered_cols,
                start,
                end,
                worker_id,
            )
            yield from self._arrow_reader_iter(reader)


class ParquetWriter(BaseWriter):
    """Parquet writer class.

    Args:
        output_path (str): data output path.
    """

    def __init__(self, output_path: str, **kwargs: Any) -> None:
        rank = int(os.environ.get("RANK", 0))
        if rank == 0:
            if not os.path.exists(output_path):
                os.makedirs(output_path)
        else:
            while not os.path.exists(output_path):
                time.sleep(1)
        output_path = os.path.join(output_path, f"part-{rank}.parquet")
        super().__init__(output_path)
        self._writer = None

    def write(self, output_dict: OrderedDict[str, pa.Array]) -> None:
        """Write a batch of data."""
        if not self._lazy_inited:
            schema = []
            for k, v in output_dict.items():
                schema.append((k, v.type))
            self._writer = parquet.ParquetWriter(
                self._output_path, schema=pa.schema(schema)
            )
            self._lazy_inited = True
        record_batch = pa.RecordBatch.from_arrays(
            list(output_dict.values()),
            list(output_dict.keys()),
        )
        self._writer.write(record_batch)

    def close(self) -> None:
        """Close and commit data."""
        if self._writer is not None:
            self._writer.close()
        super().close()
