""" Code by Nathan Fradet https://github.com/Natooz, reworked by Adam Łukawski https://github.com/sunsetsobserver """

from copy import deepcopy
from pathlib import Path
from random import shuffle

from torch import Tensor, argmax
from torch.utils.data import DataLoader
from torch.cuda import is_available as cuda_available, is_bf16_supported
from torch.backends.mps import is_available as mps_available
from transformers import AutoModelForCausalLM, MistralConfig, Trainer, TrainingArguments, GenerationConfig, AutoTokenizer, AutoModel
from transformers.trainer_utils import set_seed
from evaluate import load as load_metric
from miditok import REMI, TokenizerConfig
from miditok.pytorch_data import DatasetTok, DataCollator
from tqdm import tqdm

# Seed
set_seed(777)

# Creates the tokenizer
tokenizer = AutoTokenizer.from_pretrained("tokenizer")

# Trains the tokenizer with Byte Pair Encoding (BPE) to build the vocabulary, here 10k tokens
midi_paths = list(Path('Maestro').glob('**/*.mid')) + list(Path('Maestro').glob('**/*.midi'))

# Split MIDI paths in train/valid/test sets
total_num_files = len(midi_paths)
num_files_valid = round(total_num_files * 0.2)
num_files_test = round(total_num_files * 0.1)
shuffle(midi_paths)
midi_paths_test = midi_paths[num_files_valid:num_files_valid + num_files_test]

# Loads tokens and create data collator
kwargs_dataset = {"min_seq_len": 256, "max_seq_len": 1024, "tokenizer": tokenizer}
dataset_test = DatasetTok(midi_paths_test, **kwargs_dataset)
collator = DataCollator(
    tokenizer["PAD_None"], tokenizer["BOS_None"], tokenizer["EOS_None"]
)

# Creates model using the correct configuration
model = AutoModel.from_pretrained("./runs/model.safetensors")

collator = DataCollator(tokenizer["PAD_None"], tokenizer["BOS_None"], tokenizer["EOS_None"], copy_inputs_as_labels=True)

(gen_results_path := Path('gen_res')).mkdir(parents=True, exist_ok=True)
generation_config = GenerationConfig(
    max_new_tokens=512,  # extends samples by 512 tokens
    num_beams=1,        # no beam search
    do_sample=True,     # but sample instead
    temperature=0.9,
    top_k=15,
    top_p=0.95,
    epsilon_cutoff=3e-4,
    eta_cutoff=1e-3,
    pad_token_id=tokenizer.padding_token_id,
)

# Here the sequences are padded to the left, so that the last token along the time dimension
# is always the last token of each seq, allowing to efficiently generate by batch
collator.pad_on_left = True
collator.eos_token = None
dataloader_test = DataLoader(dataset_test, batch_size=16, collate_fn=collator)
model.eval()
count = 0
for batch in tqdm(dataloader_test, desc='Testing model / Generating results'):  # (N,T)
    res = model.generate(
        inputs=batch["input_ids"].to(model.device),
        attention_mask=batch["attention_mask"].to(model.device),
        generation_config=generation_config)  # (N,T)

    # Saves the generated music, as MIDI files and tokens (json)
    for prompt, continuation in zip(batch["input_ids"], res):
        generated = continuation[len(prompt):]
        midi = tokenizer.tokens_to_midi([deepcopy(generated.tolist())])
        tokens = [generated, prompt, continuation]  # list compr. as seqs of dif. lengths
        tokens = [seq.tolist() for seq in tokens]
        for tok_seq in tokens[1:]:
            _midi = tokenizer.tokens_to_midi([deepcopy(tok_seq)])
            midi.instruments.append(_midi.instruments[0])
        midi.instruments[0].name = f'Continuation of original sample ({len(generated)} tokens)'
        midi.instruments[1].name = f'Original sample ({len(prompt)} tokens)'
        midi.instruments[2].name = f'Original sample and continuation'
        midi.dump_midi(gen_results_path / f'{count}.mid')
        tokenizer.save_tokens(tokens, gen_results_path / f'{count}.json') 

        count += 1