import gc
import os
import sys
import threading

import numpy as np
import psutil
import torch
from accelerate import Accelerator
from datasets import load_dataset
from torch.utils.data import DataLoader
from tqdm import tqdm
from transformers import AutoModelForSeq2SeqLM, AutoTokenizer, get_linear_schedule_with_warmup, set_seed

from peft import LoraConfig, TaskType, get_peft_model


def levenshtein_distance(str1, str2):
    # TC: O(N^2)
    # SC: O(N^2)
    if str1 == str2:
        return 0
    num_rows = len(str1) + 1
    num_cols = len(str2) + 1
    dp_matrix = np.empty((num_rows, num_cols))
    dp_matrix[0, :] = range(num_cols)
    dp_matrix[:, 0] = range(num_rows)

    for i in range(1, num_rows):
        for j in range(1, num_cols):
            if str1[i - 1] == str2[j - 1]:
                dp_matrix[i, j] = dp_matrix[i - 1, j - 1]
            else:
                dp_matrix[i, j] = min(dp_matrix[i - 1, j - 1], dp_matrix[i - 1, j], dp_matrix[i, j - 1]) + 1

    return dp_matrix[num_rows - 1, num_cols - 1]


def get_closest_label(eval_pred, classes):
    min_id = sys.maxsize
    min_edit_distance = sys.maxsize
    for i, class_label in enumerate(classes):
        edit_distance = levenshtein_distance(eval_pred.strip(), class_label)
        if edit_distance < min_edit_distance:
            min_id = i
            min_edit_distance = edit_distance
    return classes[min_id]


# Converting Bytes to Megabytes
def b2mb(x):
    return int(x / 2**20)


# This context manager is used to track the peak memory usage of the process
class TorchTracemalloc:
    def __enter__(self):
        gc.collect()
        torch.cuda.empty_cache()
        torch.cuda.reset_max_memory_allocated()  # reset the peak gauge to zero
        self.begin = torch.cuda.memory_allocated()
        self.process = psutil.Process()

        self.cpu_begin = self.cpu_mem_used()
        self.peak_monitoring = True
        peak_monitor_thread = threading.Thread(target=self.peak_monitor_func)
        peak_monitor_thread.daemon = True
        peak_monitor_thread.start()
        return self

    def cpu_mem_used(self):
        """get resident set size memory for the current process"""
        return self.process.memory_info().rss

    def peak_monitor_func(self):
        self.cpu_peak = -1

        while True:
            self.cpu_peak = max(self.cpu_mem_used(), self.cpu_peak)

            # can't sleep or will not catch the peak right (this comment is here on purpose)
            # time.sleep(0.001) # 1msec

            if not self.peak_monitoring:
                break

    def __exit__(self, *exc):
        self.peak_monitoring = False

        gc.collect()
        torch.cuda.empty_cache()
        self.end = torch.cuda.memory_allocated()
        self.peak = torch.cuda.max_memory_allocated()
        self.used = b2mb(self.end - self.begin)
        self.peaked = b2mb(self.peak - self.begin)

        self.cpu_end = self.cpu_mem_used()
        self.cpu_used = b2mb(self.cpu_end - self.cpu_begin)
        self.cpu_peaked = b2mb(self.cpu_peak - self.cpu_begin)
        # print(f"delta used/peak {self.used:4d}/{self.peaked:4d}")


def main():
    accelerator = Accelerator()
    # model_name_or_path = "bigscience/T0_3B"
    model_name_or_path = "facebook/bart-large"
    dataset_name = "twitter_complaints"
    peft_config = LoraConfig(
        task_type=TaskType.SEQ_2_SEQ_LM, inference_mode=False, r=8, lora_alpha=32, lora_dropout=0.1
    )
    text_column = "Tweet text"
    label_column = "text_label"
    lr = 3e-3
    num_epochs = 5
    batch_size = 8
    seed = 42
    do_test = False
    set_seed(seed)

    dataset = load_dataset("ought/raft", dataset_name)
    classes = [k.replace("_", " ") for k in dataset["train"].features["Label"].names]
    dataset = dataset.map(
        lambda x: {"text_label": [classes[label] for label in x["Label"]]},
        batched=True,
        num_proc=1,
    )

    tokenizer = AutoTokenizer.from_pretrained(model_name_or_path)
    target_max_length = max([len(tokenizer(class_label)["input_ids"]) for class_label in classes])

    def preprocess_function(examples):
        inputs = examples[text_column]
        targets = examples[label_column]
        model_inputs = tokenizer(inputs, truncation=True)
        labels = tokenizer(
            targets, max_length=target_max_length, padding="max_length", truncation=True, return_tensors="pt"
        )
        labels = labels["input_ids"]
        labels[labels == tokenizer.pad_token_id] = -100
        model_inputs["labels"] = labels
        return model_inputs

    with accelerator.main_process_first():
        processed_datasets = dataset.map(
            preprocess_function,
            batched=True,
            num_proc=1,
            remove_columns=dataset["train"].column_names,
            load_from_cache_file=True,
            desc="Running tokenizer on dataset",
        )
    accelerator.wait_for_everyone()

    train_dataset = processed_datasets["train"]
    eval_dataset = processed_datasets["train"]
    test_dataset = processed_datasets["test"]

    def collate_fn(examples):
        return tokenizer.pad(examples, padding="longest", return_tensors="pt")

    train_dataloader = DataLoader(
        train_dataset, shuffle=True, collate_fn=collate_fn, batch_size=batch_size, pin_memory=True
    )
    eval_dataloader = DataLoader(eval_dataset, collate_fn=collate_fn, batch_size=batch_size, pin_memory=True)
    test_dataloader = DataLoader(test_dataset, collate_fn=collate_fn, batch_size=batch_size, pin_memory=True)

    # creating model
    model = AutoModelForSeq2SeqLM.from_pretrained(model_name_or_path)
    model = get_peft_model(model, peft_config)
    model.print_trainable_parameters()

    # optimizer
    optimizer = torch.optim.AdamW(model.parameters(), lr=lr)

    # lr scheduler
    lr_scheduler = get_linear_schedule_with_warmup(
        optimizer=optimizer,
        num_warmup_steps=0,
        num_training_steps=(len(train_dataloader) * num_epochs),
    )

    model, train_dataloader, eval_dataloader, test_dataloader, optimizer, lr_scheduler = accelerator.prepare(
        model, train_dataloader, eval_dataloader, test_dataloader, optimizer, lr_scheduler
    )
    accelerator.print(model)

    is_ds_zero_3 = False
    if getattr(accelerator.state, "deepspeed_plugin", None):
        is_ds_zero_3 = accelerator.state.deepspeed_plugin.zero_stage == 3

    for epoch in range(num_epochs):
        with TorchTracemalloc() as tracemalloc:
            model.train()
            total_loss = 0
            for step, batch in enumerate(tqdm(train_dataloader)):
                outputs = model(**batch)
                loss = outputs.loss
                total_loss += loss.detach().float()
                accelerator.backward(loss)
                optimizer.step()
                lr_scheduler.step()
                optimizer.zero_grad()
        # Printing the GPU memory usage details such as allocated memory, peak memory, and total memory usage
        accelerator.print("GPU Memory before entering the train : {}".format(b2mb(tracemalloc.begin)))
        accelerator.print("GPU Memory consumed at the end of the train (end-begin): {}".format(tracemalloc.used))
        accelerator.print("GPU Peak Memory consumed during the train (max-begin): {}".format(tracemalloc.peaked))
        accelerator.print(
            "GPU Total Peak Memory consumed during the train (max): {}".format(
                tracemalloc.peaked + b2mb(tracemalloc.begin)
            )
        )

        accelerator.print("CPU Memory before entering the train : {}".format(b2mb(tracemalloc.cpu_begin)))
        accelerator.print("CPU Memory consumed at the end of the train (end-begin): {}".format(tracemalloc.cpu_used))
        accelerator.print("CPU Peak Memory consumed during the train (max-begin): {}".format(tracemalloc.cpu_peaked))
        accelerator.print(
            "CPU Total Peak Memory consumed during the train (max): {}".format(
                tracemalloc.cpu_peaked + b2mb(tracemalloc.cpu_begin)
            )
        )
        train_epoch_loss = total_loss / len(train_dataloader)
        train_ppl = torch.exp(train_epoch_loss)
        accelerator.print(f"{epoch=}: {train_ppl=} {train_epoch_loss=}")

        model.eval()
        eval_preds = []
        with TorchTracemalloc() as tracemalloc:
            for _, batch in enumerate(tqdm(eval_dataloader)):
                batch = {k: v for k, v in batch.items() if k != "labels"}
                with torch.no_grad():
                    outputs = accelerator.unwrap_model(model).generate(
                        **batch, synced_gpus=is_ds_zero_3
                    )  # synced_gpus=True for DS-stage 3
                outputs = accelerator.pad_across_processes(outputs, dim=1, pad_index=tokenizer.pad_token_id)
                preds = accelerator.gather_for_metrics(outputs).detach().cpu().numpy()
                eval_preds.extend(tokenizer.batch_decode(preds, skip_special_tokens=True))

        # Printing the GPU memory usage details such as allocated memory, peak memory, and total memory usage
        accelerator.print("GPU Memory before entering the eval : {}".format(b2mb(tracemalloc.begin)))
        accelerator.print("GPU Memory consumed at the end of the eval (end-begin): {}".format(tracemalloc.used))
        accelerator.print("GPU Peak Memory consumed during the eval (max-begin): {}".format(tracemalloc.peaked))
        accelerator.print(
            "GPU Total Peak Memory consumed during the eval (max): {}".format(
                tracemalloc.peaked + b2mb(tracemalloc.begin)
            )
        )

        accelerator.print("CPU Memory before entering the eval : {}".format(b2mb(tracemalloc.cpu_begin)))
        accelerator.print("CPU Memory consumed at the end of the eval (end-begin): {}".format(tracemalloc.cpu_used))
        accelerator.print("CPU Peak Memory consumed during the eval (max-begin): {}".format(tracemalloc.cpu_peaked))
        accelerator.print(
            "CPU Total Peak Memory consumed during the eval (max): {}".format(
                tracemalloc.cpu_peaked + b2mb(tracemalloc.cpu_begin)
            )
        )

        correct = 0
        total = 0
        assert len(eval_preds) == len(
            dataset["train"][label_column]
        ), f"{len(eval_preds)} != {len(dataset['train'][label_column])}"
        for pred, true in zip(eval_preds, dataset["train"][label_column]):
            if pred.strip() == true.strip():
                correct += 1
            total += 1
        accuracy = correct / total * 100
        accelerator.print(f"{accuracy=}")
        accelerator.print(f"{eval_preds[:10]=}")
        accelerator.print(f"{dataset['train'][label_column][:10]=}")

    if do_test:
        model.eval()
        test_preds = []
        for _, batch in enumerate(tqdm(test_dataloader)):
            batch = {k: v for k, v in batch.items() if k != "labels"}
            with torch.no_grad():
                outputs = accelerator.unwrap_model(model).generate(
                    **batch, synced_gpus=is_ds_zero_3
                )  # synced_gpus=True for DS-stage 3
            outputs = accelerator.pad_across_processes(outputs, dim=1, pad_index=tokenizer.pad_token_id)
            preds = accelerator.gather(outputs).detach().cpu().numpy()
            test_preds.extend(tokenizer.batch_decode(preds, skip_special_tokens=True))

        test_preds_cleaned = []
        for _, pred in enumerate(test_preds):
            test_preds_cleaned.append(get_closest_label(pred, classes))

        test_df = dataset["test"].to_pandas()
        assert len(test_preds_cleaned) == len(test_df), f"{len(test_preds_cleaned)} != {len(test_df)}"
        test_df[label_column] = test_preds_cleaned
        test_df["text_labels_orig"] = test_preds
        accelerator.print(test_df[[text_column, label_column]].sample(20))

        pred_df = test_df[["ID", label_column]]
        pred_df.columns = ["ID", "Label"]

        os.makedirs(f"data/{dataset_name}", exist_ok=True)
        pred_df.to_csv(f"data/{dataset_name}/predictions.csv", index=False)

    accelerator.wait_for_everyone()
    # Option1: Pushing the model to Hugging Face Hub
    # model.push_to_hub(
    #     f"{dataset_name}_{model_name_or_path}_{peft_config.peft_type}_{peft_config.task_type}".replace("/", "_"),
    #     token = "hf_..."
    # )
    # token (`bool` or `str`, *optional*):
    #     `token` is to be used for HTTP Bearer authorization when accessing remote files. If `True`, will use the token generated
    #     when running `huggingface-cli login` (stored in `~/.huggingface`). Will default to `True` if `repo_url`
    #     is not specified.
    #     Or you can get your token from https://huggingface.co/settings/token

    # Option2: Saving the model locally
    peft_model_id = f"{dataset_name}_{model_name_or_path}_{peft_config.peft_type}_{peft_config.task_type}".replace(
        "/", "_"
    )
    model.save_pretrained(peft_model_id)
    accelerator.wait_for_everyone()


if __name__ == "__main__":
    main()
