import argparse
import json
from pathlib import Path

import torch
from tqdm import tqdm

from transformers import AutoModelForSeq2SeqLM, AutoTokenizer


try:
    from .utils import calculate_rouge, use_task_specific_params, calculate_bleu_score, trim_batch
except ImportError:
    from utils import calculate_rouge, use_task_specific_params, calculate_bleu_score, trim_batch

DEFAULT_DEVICE = "cuda" if torch.cuda.is_available() else "cpu"


def chunks(lst, n):
    """Yield successive n-sized chunks from lst."""
    for i in range(0, len(lst), n):
        yield lst[i : i + n]


def generate_summaries_or_translations(
    examples: list,
    out_file: str,
    model_name: str,
    batch_size: int = 8,
    device: str = DEFAULT_DEVICE,
    fp16=False,
    task="summarization",
    decoder_start_token_id=None,
    **gen_kwargs,
) -> None:
    fout = Path(out_file).open("w", encoding="utf-8")
    model_name = str(model_name)
    model = AutoModelForSeq2SeqLM.from_pretrained(model_name).to(device)
    if fp16:
        model = model.half()
    if decoder_start_token_id is None:
        decoder_start_token_id = gen_kwargs.pop("decoder_start_token_id", None)

    tokenizer = AutoTokenizer.from_pretrained(model_name)

    # update config with summarization specific params
    use_task_specific_params(model, task)

    for batch in tqdm(list(chunks(examples, batch_size))):
        if "t5" in model_name:
            batch = [model.config.prefix + text for text in batch]
        batch = tokenizer(batch, return_tensors="pt", truncation=True, padding="max_length").to(device)
        input_ids, attention_mask = trim_batch(**batch, pad_token_id=tokenizer.pad_token_id)
        summaries = model.generate(
            input_ids=input_ids,
            attention_mask=attention_mask,
            decoder_start_token_id=decoder_start_token_id,
            **gen_kwargs,
        )
        dec = tokenizer.batch_decode(summaries, skip_special_tokens=True, clean_up_tokenization_spaces=False)
        for hypothesis in dec:
            fout.write(hypothesis + "\n")
            fout.flush()


def run_generate():
    parser = argparse.ArgumentParser()
    parser.add_argument("model_name", type=str, help="like facebook/bart-large-cnn,t5-base, etc.")
    parser.add_argument("input_path", type=str, help="like cnn_dm/test.source")
    parser.add_argument("save_path", type=str, help="where to save summaries")

    parser.add_argument("--reference_path", type=str, required=False, help="like cnn_dm/test_reference_summaries.txt")
    parser.add_argument("--score_path", type=str, required=False, help="where to save the rouge score in json format")
    parser.add_argument("--device", type=str, required=False, default=DEFAULT_DEVICE, help="cuda, cuda:1, cpu etc.")
    parser.add_argument("--task", type=str, default="summarization", help="typically translation or summarization")
    parser.add_argument("--bs", type=int, default=8, required=False, help="batch size")
    parser.add_argument(
        "--decoder_start_token_id",
        type=int,
        default=None,
        required=False,
        help="decoder_start_token_id (otherwise will look at config)",
    )
    parser.add_argument(
        "--n_obs", type=int, default=-1, required=False, help="How many observations. Defaults to all."
    )
    parser.add_argument("--fp16", action="store_true")
    args = parser.parse_args()
    examples = [" " + x.rstrip() if "t5" in args.model_name else x.rstrip() for x in open(args.input_path).readlines()]
    if args.n_obs > 0:
        examples = examples[: args.n_obs]

    generate_summaries_or_translations(
        examples,
        args.save_path,
        args.model_name,
        batch_size=args.bs,
        device=args.device,
        fp16=args.fp16,
        task=args.task,
        decoder_start_token_id=args.decoder_start_token_id,
    )
    if args.reference_path is None:
        return
    # Compute scores
    score_fn = calculate_bleu_score if "translation" in args.task else calculate_rouge
    output_lns = [x.rstrip() for x in open(args.save_path).readlines()]
    reference_lns = [x.rstrip() for x in open(args.reference_path).readlines()][: len(output_lns)]
    scores: dict = score_fn(output_lns, reference_lns)
    if args.score_path is not None:
        json.dump(scores, open(args.score_path, "w+"))
    return scores


if __name__ == "__main__":
    run_generate()
