#!/usr/bin/env python3
#
# Copyright 2021 Xiaomi Corporation (Author: Fangjun Kuang)
#
# See ../../../../LICENSE for clarification regarding multiple authors
#
# 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 argparse
import logging
from collections import defaultdict
from pathlib import Path
from typing import Dict, List, Tuple

import torch
import torch.nn as nn
from asr_datamodule import AishellAsrDataModule
from beam_search import beam_search, greedy_search
from conformer import Conformer
from decoder import Decoder
from joiner import Joiner
from model import Transducer

from icefall.checkpoint import average_checkpoints, load_checkpoint
from icefall.env import get_env_info
from icefall.lexicon import Lexicon
from icefall.utils import (
    AttributeDict,
    setup_logger,
    store_transcripts,
    str2bool,
    write_error_stats,
)


def get_parser():
    parser = argparse.ArgumentParser(
        formatter_class=argparse.ArgumentDefaultsHelpFormatter
    )

    parser.add_argument(
        "--epoch",
        type=int,
        default=30,
        help="It specifies the checkpoint to use for decoding."
        "Note: Epoch counts from 0.",
    )
    parser.add_argument(
        "--avg",
        type=int,
        default=10,
        help="Number of checkpoints to average. Automatically select "
        "consecutive checkpoints before the checkpoint specified by "
        "'--epoch'. ",
    )

    parser.add_argument(
        "--exp-dir",
        type=str,
        default="transducer_stateless/exp",
        help="The experiment dir",
    )

    parser.add_argument(
        "--lang-dir",
        type=str,
        default="data/lang_char",
        help="The lang dir",
    )

    parser.add_argument(
        "--decoding-method",
        type=str,
        default="greedy_search",
        help="""Possible values are:
          - greedy_search
          - beam_search
        """,
    )

    parser.add_argument(
        "--beam-size",
        type=int,
        default=4,
        help="Used only when --decoding-method is beam_search",
    )

    parser.add_argument(
        "--context-size",
        type=int,
        default=2,
        help="The context size in the decoder. 1 means bigram; 2 means tri-gram",
    )
    parser.add_argument(
        "--max-sym-per-frame",
        type=int,
        default=3,
        help="Maximum number of symbols per frame",
    )
    parser.add_argument(
        "--export",
        type=str2bool,
        default=False,
        help="""When enabled, the averaged model is saved to
        transducer_stateless/exp/pretrained.pt. Note: only model.state_dict()
        is saved. pretrained.pt contains a dict {"model": model.state_dict()},
        which can be loaded by `icefall.checkpoint.load_checkpoint()`.
        """,
    )

    return parser


def get_params() -> AttributeDict:
    params = AttributeDict(
        {
            # parameters for conformer
            "feature_dim": 80,
            "encoder_out_dim": 512,
            "subsampling_factor": 4,
            "attention_dim": 512,
            "nhead": 8,
            "dim_feedforward": 2048,
            "num_encoder_layers": 12,
            "vgg_frontend": False,
            "env_info": get_env_info(),
        }
    )
    return params


def get_encoder_model(params: AttributeDict):
    # TODO: We can add an option to switch between Conformer and Transformer
    encoder = Conformer(
        num_features=params.feature_dim,
        output_dim=params.encoder_out_dim,
        subsampling_factor=params.subsampling_factor,
        d_model=params.attention_dim,
        nhead=params.nhead,
        dim_feedforward=params.dim_feedforward,
        num_encoder_layers=params.num_encoder_layers,
        vgg_frontend=params.vgg_frontend,
    )
    return encoder


def get_decoder_model(params: AttributeDict):
    decoder = Decoder(
        vocab_size=params.vocab_size,
        embedding_dim=params.encoder_out_dim,
        blank_id=params.blank_id,
        context_size=params.context_size,
    )
    return decoder


def get_joiner_model(params: AttributeDict):
    joiner = Joiner(
        input_dim=params.encoder_out_dim,
        output_dim=params.vocab_size,
    )
    return joiner


def get_transducer_model(params: AttributeDict):
    encoder = get_encoder_model(params)
    decoder = get_decoder_model(params)
    joiner = get_joiner_model(params)

    model = Transducer(
        encoder=encoder,
        decoder=decoder,
        joiner=joiner,
    )
    return model


def decode_one_batch(
    params: AttributeDict,
    model: nn.Module,
    lexicon: Lexicon,
    batch: dict,
) -> Dict[str, List[List[str]]]:
    """Decode one batch and return the result in a dict. The dict has the
    following format:

        - key: It indicates the setting used for decoding. For example,
               if greedy_search is used, it would be "greedy_search"
               If beam search with a beam size of 7 is used, it would be
               "beam_7"
        - value: It contains the decoding result. `len(value)` equals to
                 batch size. `value[i]` is the decoding result for the i-th
                 utterance in the given batch.
    Args:
      params:
        It's the return value of :func:`get_params`.
      model:
        The neural model.
      batch:
        It is the return value from iterating
        `lhotse.dataset.K2SpeechRecognitionDataset`. See its documentation
        for the format of the `batch`.
      lexicon:
        It contains the token symbol table and the word symbol table.
    Returns:
      Return the decoding result. See above description for the format of
      the returned dict.
    """
    device = model.device
    feature = batch["inputs"]
    assert feature.ndim == 3

    feature = feature.to(device)
    # at entry, feature is (N, T, C)

    supervisions = batch["supervisions"]
    feature_lens = supervisions["num_frames"].to(device)

    encoder_out, encoder_out_lens = model.encoder(x=feature, x_lens=feature_lens)
    hyps = []
    batch_size = encoder_out.size(0)

    for i in range(batch_size):
        # fmt: off
        encoder_out_i = encoder_out[i:i+1, :encoder_out_lens[i]]
        # fmt: on
        if params.decoding_method == "greedy_search":
            hyp = greedy_search(
                model=model,
                encoder_out=encoder_out_i,
                max_sym_per_frame=params.max_sym_per_frame,
            )
        elif params.decoding_method == "beam_search":
            hyp = beam_search(
                model=model, encoder_out=encoder_out_i, beam=params.beam_size
            )
        else:
            raise ValueError(f"Unsupported decoding method: {params.decoding_method}")
        hyps.append([lexicon.token_table[i] for i in hyp])

    if params.decoding_method == "greedy_search":
        return {"greedy_search": hyps}
    else:
        return {f"beam_{params.beam_size}": hyps}


def decode_dataset(
    dl: torch.utils.data.DataLoader,
    params: AttributeDict,
    model: nn.Module,
    lexicon: Lexicon,
) -> Dict[str, List[Tuple[str, List[str], List[str]]]]:
    """Decode dataset.

    Args:
      dl:
        PyTorch's dataloader containing the dataset to decode.
      params:
        It is returned by :func:`get_params`.
      model:
        The neural model.
    Returns:
      Return a dict, whose key may be "greedy_search" if greedy search
      is used, or it may be "beam_7" if beam size of 7 is used.
      Its value is a list of tuples. Each tuple contains two elements:
      The first is the reference transcript, and the second is the
      predicted result.
    """
    num_cuts = 0

    try:
        num_batches = len(dl)
    except TypeError:
        num_batches = "?"

    if params.decoding_method == "greedy_search":
        log_interval = 100
    else:
        log_interval = 2

    results = defaultdict(list)
    for batch_idx, batch in enumerate(dl):
        texts = batch["supervisions"]["text"]
        cut_ids = [cut.id for cut in batch["supervisions"]["cut"]]

        hyps_dict = decode_one_batch(
            params=params,
            model=model,
            lexicon=lexicon,
            batch=batch,
        )

        for name, hyps in hyps_dict.items():
            this_batch = []
            assert len(hyps) == len(texts)
            for cut_id, hyp_words, ref_text in zip(cut_ids, hyps, texts):
                ref_words = ref_text.split()
                this_batch.append((cut_id, ref_words, hyp_words))

            results[name].extend(this_batch)

        num_cuts += len(texts)

        if batch_idx % log_interval == 0:
            batch_str = f"{batch_idx}/{num_batches}"

            logging.info(f"batch {batch_str}, cuts processed until now is {num_cuts}")
    return results


def save_results(
    params: AttributeDict,
    test_set_name: str,
    results_dict: Dict[str, List[Tuple[str, List[str], List[str]]]],
):
    test_set_wers = dict()
    for key, results in results_dict.items():
        recog_path = params.res_dir / f"recogs-{test_set_name}-{params.suffix}.txt"
        results = sorted(results)
        store_transcripts(filename=recog_path, texts=results, char_level=True)

        # The following prints out WERs, per-word error statistics and aligned
        # ref/hyp pairs.
        errs_filename = params.res_dir / f"errs-{test_set_name}-{params.suffix}.txt"
        # we compute CER for aishell dataset.
        results_char = []
        for res in results:
            results_char.append((res[0], list("".join(res[1])), list("".join(res[2]))))
        with open(errs_filename, "w") as f:
            wer = write_error_stats(
                f,
                f"{test_set_name}-{key}",
                results_char,
                enable_log=True,
                compute_CER=True,
            )
            test_set_wers[key] = wer

        logging.info("Wrote detailed error stats to {}".format(errs_filename))

    test_set_wers = sorted(test_set_wers.items(), key=lambda x: x[1])
    errs_info = params.res_dir / f"wer-summary-{test_set_name}-{params.suffix}.txt"
    with open(errs_info, "w") as f:
        print("settings\tCER", file=f)
        for key, val in test_set_wers:
            print("{}\t{}".format(key, val), file=f)

    s = "\nFor {}, CER of different settings are:\n".format(test_set_name)
    note = "\tbest for {}".format(test_set_name)
    for key, val in test_set_wers:
        s += "{}\t{}{}\n".format(key, val, note)
        note = ""
    logging.info(s)


@torch.no_grad()
def main():
    parser = get_parser()
    AishellAsrDataModule.add_arguments(parser)
    args = parser.parse_args()
    args.exp_dir = Path(args.exp_dir)
    args.lang_dir = Path(args.lang_dir)

    params = get_params()
    params.update(vars(args))

    assert params.decoding_method in ("greedy_search", "beam_search")
    params.res_dir = params.exp_dir / params.decoding_method

    params.suffix = f"epoch-{params.epoch}-avg-{params.avg}"
    if params.decoding_method == "beam_search":
        params.suffix += f"-beam-{params.beam_size}"
    else:
        params.suffix += f"-context-{params.context_size}"
        params.suffix += f"-max-sym-per-frame-{params.max_sym_per_frame}"

    setup_logger(f"{params.res_dir}/log-decode-{params.suffix}")
    logging.info("Decoding started")

    device = torch.device("cpu")
    if torch.cuda.is_available():
        device = torch.device("cuda", 0)

    logging.info(f"Device: {device}")

    lexicon = Lexicon(params.lang_dir)

    # params.blank_id = graph_compiler.texts_to_ids("<blk>")[0][0]
    params.blank_id = 0
    params.vocab_size = max(lexicon.tokens) + 1

    logging.info(params)

    logging.info("About to create model")
    model = get_transducer_model(params)

    if params.avg == 1:
        load_checkpoint(f"{params.exp_dir}/epoch-{params.epoch}.pt", model)
    else:
        start = params.epoch - params.avg + 1
        filenames = []
        for i in range(start, params.epoch + 1):
            if start >= 0:
                filenames.append(f"{params.exp_dir}/epoch-{i}.pt")
        logging.info(f"averaging {filenames}")
        model.to(device)
        model.load_state_dict(average_checkpoints(filenames, device=device))

    if params.export:
        logging.info(f"Export averaged model to {params.exp_dir}/pretrained.pt")
        torch.save({"model": model.state_dict()}, f"{params.exp_dir}/pretrained.pt")
        return

    model.to(device)
    model.eval()
    model.device = device

    num_param = sum([p.numel() for p in model.parameters()])
    logging.info(f"Number of model parameters: {num_param}")

    # we need cut ids to display recognition results.
    args.return_cuts = True
    aishell = AishellAsrDataModule(args)
    test_cuts = aishell.test_cuts()
    test_dl = aishell.test_dataloaders(test_cuts)

    test_sets = ["test"]
    test_dls = [test_dl]

    for test_set, test_dl in zip(test_sets, test_dls):
        results_dict = decode_dataset(
            dl=test_dl,
            params=params,
            model=model,
            lexicon=lexicon,
        )

        save_results(
            params=params,
            test_set_name=test_set,
            results_dict=results_dict,
        )

    logging.info("Done!")


torch.set_num_threads(1)
torch.set_num_interop_threads(1)

if __name__ == "__main__":
    main()