#!/usr/bin/env python3 -u
# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.

import logging
import os
import sys
from argparse import Namespace
from itertools import chain

import torch
from fairseq import checkpoint_utils, distributed_utils, options, utils
from fairseq.dataclass.utils import convert_namespace_to_omegaconf
from fairseq.logging import metrics, progress_bar
from fairseq.utils import reset_logging
from omegaconf import DictConfig


logging.basicConfig(
    format="%(asctime)s | %(levelname)s | %(name)s | %(message)s",
    datefmt="%Y-%m-%d %H:%M:%S",
    level=os.environ.get("LOGLEVEL", "INFO").upper(),
    stream=sys.stdout,
)
logger = logging.getLogger("fairseq_cli.validate")


def main(cfg: DictConfig, override_args=None):
    if isinstance(cfg, Namespace):
        cfg = convert_namespace_to_omegaconf(cfg)

    utils.import_user_module(cfg.common)

    reset_logging()

    assert (
        cfg.dataset.max_tokens is not None or cfg.dataset.batch_size is not None
    ), "Must specify batch size either with --max-tokens or --batch-size"

    use_fp16 = cfg.common.fp16
    use_cuda = torch.cuda.is_available() and not cfg.common.cpu

    if use_cuda:
        torch.cuda.set_device(cfg.distributed_training.device_id)

    if cfg.distributed_training.distributed_world_size > 1:
        data_parallel_world_size = distributed_utils.get_data_parallel_world_size()
        data_parallel_rank = distributed_utils.get_data_parallel_rank()
    else:
        data_parallel_world_size = 1
        data_parallel_rank = 0

    if override_args is not None:
        overrides = vars(override_args)
        overrides.update(eval(getattr(override_args, "model_overrides", "{}")))
    else:
        overrides = None

    # Load ensemble
    logger.info("loading model(s) from {}".format(cfg.common_eval.path))
    models, saved_cfg, task = checkpoint_utils.load_model_ensemble_and_task(
        [cfg.common_eval.path],
        arg_overrides=overrides,
        suffix=cfg.checkpoint.checkpoint_suffix,
    )
    model = models[0]

    # Move models to GPU
    for model in models:
        model.eval()
        if use_fp16:
            model.half()
        if use_cuda:
            model.cuda()

    # Print args
    logger.info(saved_cfg)

    # Build criterion
    criterion = task.build_criterion(saved_cfg.criterion)
    criterion.eval()

    for subset in cfg.dataset.valid_subset.split(","):
        try:
            task.load_dataset(subset, combine=False, epoch=1, task_cfg=saved_cfg.task)
            dataset = task.dataset(subset)
        except KeyError:
            raise Exception("Cannot find dataset: " + subset)

        # Initialize data iterator
        itr = task.get_batch_iterator(
            dataset=dataset,
            max_tokens=cfg.dataset.max_tokens,
            max_sentences=cfg.dataset.batch_size,
            max_positions=utils.resolve_max_positions(
                task.max_positions(),
                *[m.max_positions() for m in models],
            ),
            ignore_invalid_inputs=cfg.dataset.skip_invalid_size_inputs_valid_test,
            required_batch_size_multiple=cfg.dataset.required_batch_size_multiple,
            seed=cfg.common.seed,
            num_shards=data_parallel_world_size,
            shard_id=data_parallel_rank,
            num_workers=cfg.dataset.num_workers,
            data_buffer_size=cfg.dataset.data_buffer_size,
        ).next_epoch_itr(shuffle=False)
        progress = progress_bar.progress_bar(
            itr,
            log_format=cfg.common.log_format,
            log_interval=cfg.common.log_interval,
            prefix=f"valid on '{subset}' subset",
            default_log_format=("tqdm" if not cfg.common.no_progress_bar else "simple"),
        )

        log_outputs = []
        for i, sample in enumerate(progress):
            sample = utils.move_to_cuda(sample) if use_cuda else sample
            _loss, _sample_size, log_output = task.valid_step(sample, model, criterion)
            progress.log(log_output, step=i)
            log_outputs.append(log_output)

        if data_parallel_world_size > 1:
            log_outputs = distributed_utils.all_gather_list(
                log_outputs,
                max_size=cfg.common.all_gather_list_size,
                group=distributed_utils.get_data_parallel_group(),
            )
            log_outputs = list(chain.from_iterable(log_outputs))

        with metrics.aggregate() as agg:
            task.reduce_metrics(log_outputs, criterion)
            log_output = agg.get_smoothed_values()

        progress.print(log_output, tag=subset, step=i)


def cli_main():
    parser = options.get_validation_parser()
    args = options.parse_args_and_arch(parser)

    # only override args that are explicitly given on the command line
    override_parser = options.get_validation_parser()
    override_args = options.parse_args_and_arch(override_parser, suppress_defaults=True)

    distributed_utils.call_main(
        convert_namespace_to_omegaconf(args), main, override_args=override_args
    )


if __name__ == "__main__":
    cli_main()
