#!/usr/bin/env python3 -u
# Copyright 2022 The OFA-Sys Team. 
# All rights reserved.
# This source code is licensed under the Apache 2.0 license 
# found in the LICENSE file in the root directory.

import logging
import os
import sys

import numpy as np
import torch
from fairseq import distributed_utils, options, tasks, utils
from fairseq.dataclass.utils import convert_namespace_to_omegaconf
from fairseq.logging import progress_bar
from fairseq.utils import reset_logging
from omegaconf import DictConfig

import torch.distributed as dist

from utils import checkpoint_utils
from utils.eval_utils import eval_step, merge_results

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("ofa.evaluate")


def apply_half(t):
    if t.dtype is torch.float32:
        return t.to(dtype=torch.half)
    return t


def main(cfg: DictConfig, **kwargs):
    utils.import_user_module(cfg.common)

    reset_logging()
    logger.info(cfg)

    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"

    # Fix seed for stochastic decoding
    if cfg.common.seed is not None and not cfg.generation.no_seed_provided:
        np.random.seed(cfg.common.seed)
        utils.set_torch_seed(cfg.common.seed)

    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)

    # Load ensemble
    overrides = eval(cfg.common_eval.model_overrides)
    logger.info("loading model(s) from {}".format(cfg.common_eval.path))
    models, saved_cfg, task = checkpoint_utils.load_model_ensemble_and_task(
        utils.split_paths(cfg.common_eval.path),
        arg_overrides=overrides,
        suffix=cfg.checkpoint.checkpoint_suffix,
        strict=(cfg.checkpoint.checkpoint_shard_count == 1),
        num_shards=cfg.checkpoint.checkpoint_shard_count,
    )

    # loading the dataset should happen after the checkpoint has been loaded so we can give it the saved task config
    task.load_dataset(cfg.dataset.gen_subset, task_cfg=saved_cfg.task)

    # Move models to GPU
    for model, ckpt_path in zip(models, utils.split_paths(cfg.common_eval.path)):
        if kwargs['ema_eval']:
            logger.info("loading EMA weights from {}".format(ckpt_path))
            model.load_state_dict(checkpoint_utils.load_ema_from_checkpoint(ckpt_path)['model'])
        model.eval()
        if use_fp16:
            model.half()
        if use_cuda and not cfg.distributed_training.pipeline_model_parallel:
            model.cuda()
        model.prepare_for_inference_(cfg)

    # Load dataset (possibly sharded)
    itr = task.get_batch_iterator(
        dataset=task.dataset(cfg.dataset.gen_subset),
        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=cfg.distributed_training.distributed_world_size,
        shard_id=cfg.distributed_training.distributed_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,
        default_log_format=("tqdm" if not cfg.common.no_progress_bar else "simple"),
    )

    # Initialize generator
    generator = task.build_generator(models, cfg.generation)

    results = []
    score_sum = torch.FloatTensor([0]).cuda()
    score_cnt = torch.FloatTensor([0]).cuda()
    for sample in progress:
        if "net_input" not in sample:
            continue
        sample = utils.move_to_cuda(sample) if use_cuda else sample
        sample = utils.apply_to_sample(apply_half, sample) if cfg.common.fp16 else sample
        with torch.no_grad():
            result, scores = eval_step(task, generator, models, sample, **kwargs)
        results += result
        score_sum += sum(scores) if scores is not None else 0
        score_cnt += len(scores) if scores is not None else 0
        progress.log({"sentences": sample["nsentences"]})

    dist.barrier()
    merge_results(task, cfg, logger, score_cnt, score_sum, results)


def cli_main():
    parser = options.get_generation_parser()
    parser.add_argument("--ema-eval", action='store_true', help="Use EMA weights to make evaluation.")
    parser.add_argument("--beam-search-vqa-eval", action='store_true', help="Use beam search for vqa evaluation (faster inference speed but sub-optimal result), if not specified, we compute scores for each answer in the candidate set, which is slower but can obtain best result.")
    args = options.parse_args_and_arch(parser)
    cfg = convert_namespace_to_omegaconf(args)
    distributed_utils.call_main(cfg, main, ema_eval=args.ema_eval, beam_search_vqa_eval=args.beam_search_vqa_eval)


if __name__ == "__main__":
    cli_main()
