"""Console logger utilities.

Copied from https://github.com/HazyResearch/transformers/blob/master/src/utils/utils.py
Copied from https://docs.python.org/3/howto/logging-cookbook.html#using-a-context-manager-for-selective-logging
"""

import argparse
import logging
import os
import sys
import pickle
import time
import math
from typing import List

import fsspec
import lightning
import numpy as np
import torch
from scipy.integrate import quad
from scipy.stats import norm
from timm.scheduler import CosineLRScheduler


def _save_tensor(tensor, filename):
  if os.path.exists(filename):
    _logits_saved = torch.load(filename)
    _logits_saved = torch.cat([_logits_saved, tensor], dim=0)
  else:
    _logits_saved = tensor
  torch.save(_logits_saved, filename)


class WarmupCosineLR(torch.optim.lr_scheduler._LRScheduler):
  """
  Global-step scheduler: linear warmup -> cosine decay.

  Args:
    optimizer: torch optimizer
    total_steps: total number of optimizer steps in the entire training run
    warmup_steps: linear warmup steps from 0 -> base lr
    min_lr: final learning rate at the end of decay (per group)
    last_epoch: DO NOT pass directly; Lightning manages stepping. Left for state restoration.

  Notes:
    - `last_epoch` here tracks *optimizer steps taken* (i.e., global steps within the scheduler).
    - Works with Lightning when you set scheduler dict {"interval": "step"}.
  """
  def __init__(
    self,
    optimizer: torch.optim.Optimizer,
    total_steps: int,
    warmup_steps: int = 2000,
    min_lr: float = 0.0,
    last_epoch: int = -1):
    assert total_steps > 0, 'total_steps must be > 0'
    assert 0 < warmup_steps < total_steps, 'warmup_steps must be in (0, total_steps)'
    self.total_steps = total_steps
    self.warmup_steps = int(warmup_steps)
    self.min_lr = min_lr
    super().__init__(optimizer, last_epoch)

  def _lr_at(self, step: int, base_lr: float) -> float:
    # step is 0-based after super().__init__,
    # self.last_epoch starts at -1
    if step < self.warmup_steps:
        return base_lr * (step + 1) / self.warmup_steps
    progress = (step - self.warmup_steps) / (
      self.total_steps - self.warmup_steps)
    cosine = 0.5 * (1 + math.cos(math.pi * min(1.0, progress)))
    return self.min_lr + (base_lr - self.min_lr) * cosine

  def get_lr(self) -> List[float]:
    step = max(0, self.last_epoch)  # last_epoch counts calls to step()
    return [self._lr_at(step, base_lr=group['initial_lr'])
            for group in self.optimizer.param_groups]


def count_parameters(model):
  return sum(p.numel()
             for p in model.parameters()
             if p.requires_grad)

def fsspec_exists(filename):
  """Check if a file exists using fsspec."""
  fs, _ = fsspec.core.url_to_fs(filename)
  return fs.exists(filename)


def fsspec_listdir(dirname):
  """Listdir in manner compatible with fsspec."""
  fs, _ = fsspec.core.url_to_fs(dirname)
  return fs.ls(dirname)


def fsspec_mkdirs(dirname, exist_ok=True):
  """Mkdirs in manner compatible with fsspec."""
  fs, _ = fsspec.core.url_to_fs(dirname)
  fs.makedirs(dirname, exist_ok=exist_ok)


def print_nans(tensor, name):
  if torch.isnan(tensor).any():
    print(name, tensor)


def flops_to_max_steps(target_flops_1e18, global_batch_size,
                       json_path):
  with fsspec.open(json_path) as f:
    config = json.load(f)
  return int(target_flops_1e18 * 1e18
             / config['flops'] / global_batch_size / 3)


class LRHalveScheduler:
  def __init__(self, warmup_steps, n_halve_steps):
    self.warmup_steps = warmup_steps
    self.n_halve_steps = n_halve_steps
  
  def __call__(self, current_step):
    if current_step < self.warmup_steps:
      return current_step / self.warmup_steps
    return 0.5 ** ((current_step - self.warmup_steps)
                   // self.n_halve_steps)


class CosineDecayWarmupLRScheduler(
  CosineLRScheduler,
  torch.optim.lr_scheduler._LRScheduler):
  """Wrap timm.scheduler.CosineLRScheduler
  Enables calling scheduler.step() without passing in epoch.
  Supports resuming as well.
  Adapted from:
    https://github.com/HazyResearch/hyena-dna/blob/main/src/utils/optim/schedulers.py
  """

  def __init__(self, *args, **kwargs):
    super().__init__(*args, **kwargs)
    self._last_epoch = -1
    self.step(epoch=0)

  def step(self, epoch=None):
    if epoch is None:
      self._last_epoch += 1
    else:
      self._last_epoch = epoch
    # We call either step or step_update, depending on
    # whether we're using the scheduler every epoch or every
    # step.
    # Otherwise, lightning will always call step (i.e.,
    # meant for each epoch), and if we set scheduler
    # interval to "step", then the learning rate update will
    # be wrong.
    if self.t_in_epochs:
      super().step(epoch=self._last_epoch)
    else:
      super().step_update(num_updates=self._last_epoch)


class LoggingContext:
  """Context manager for selective logging."""
  def __init__(self, logger, level=None, handler=None, close=True):
    self.logger = logger
    self.level = level
    self.handler = handler
    self.close = close

  def __enter__(self):
    if self.level is not None:
      self.old_level = self.logger.level
      self.logger.setLevel(self.level)
    if self.handler:
      self.logger.addHandler(self.handler)

  def __exit__(self, et, ev, tb):
    if self.level is not None:
      self.logger.setLevel(self.old_level)
    if self.handler:
      self.logger.removeHandler(self.handler)
    if self.handler and self.close:
      self.handler.close()


class GradientInspectionCallback(lightning.Callback):
    def __init__(self, num_grads_log):
        self.num_grads_log = 10

    def on_before_optimizer_step(self, trainer, pl_module, optimizer):
      gradients = []
      for name, param in pl_module.backbone.blocks.named_parameters():
          gradients.append(param.grad.view(-1))

      if gradients:
        grads = torch.cat((gradients))
        if not hasattr(pl_module, 'grad_accum_buffer'):
          pl_module.grad_step = torch.tensor(
            0, device=pl_module.device)
          pl_module.grad_accum_buffer = torch.zeros(
            self.num_grads_log,
            grads.shape[0],
            device=pl_module.device)
        pl_module.grad_accum_buffer[pl_module.grad_step] = grads
        pl_module.grad_step += 1

      if (hasattr(pl_module, 'grad_accum_buffer') 
          and pl_module.grad_step == self.num_grads_log):
        grads = pl_module.grad_accum_buffer
        grad_var = grads.std(0).mean()
        pl_module.log(name='trainer/grad_var',
                      value=grad_var.item(),
                      on_step=True,
                      on_epoch=False,
                      sync_dist=True)
        # import ipdb; ipdb.set_trace()
        # should save the grads tensor as a numpy array
        # and visualize mean, median, top-k
        pl_module.grad_accum_buffer.zero_()
        pl_module.grad_step = 0


def get_logger(name=__name__, level=logging.INFO) -> logging.Logger:
  """Initializes multi-GPU-friendly python logger."""

  logger = logging.getLogger(name)
  logger.setLevel(level)

  # this ensures all logging levels get marked with the rank zero decorator
  # otherwise logs would get multiplied for each GPU process in multi-GPU setup
  for level in ('debug', 'info', 'warning', 'error',
                'exception', 'fatal', 'critical'):
    setattr(logger,
            level,
            lightning.pytorch.utilities.rank_zero_only(
              getattr(logger, level)))

  return logger


# Copied from https://github.com/jdeschena/sdtt/blob/bbc54d5b3c5fcffd79602cff17ed34dde1f3eff6/src/sdtt/core/sampling/utils.py#L10
def top_k_top_p_filtering(
    logits,
    top_k=0,
    top_p=0.0,
    filter_value=-float("Inf"),
    dim=-1):
    """Filter a distribution of logits using top-k/top-p (nucleus) filtering.
    Adapted from https://gist.github.com/thomwolf/1a5a29f6962089e871b94cbd09daf317

    Args:
      logits (Tensor): Tensor of logits
      top_k (int, optional): Number of top values to keep.
          Deactivated if k is 0. Defaults to 0.
      top_p (float, optional): Cumulative mass to retain.
          Deactivated if p = 0. Defaults to 0.0.
      filter_value (float, optional): Fill value to replace
          the entries removed by top-k/top-p filtering.
          Defaults to -float('Inf').
      dim (int, optional): Dimension of the filtering. Defaults to -1.

    Returns:
        logits: Tensor whose axis `dim` was filtered.
    """
    if dim != -1:
      logits = torch.transpose(logits, dim, -1)

    assert top_k < logits.size(dim)
    if top_k > 0:
      # Remove all tokens with a probability less than
      # the last token of the top-k
      values, _ = torch.topk(logits, k=top_k, dim=-1)
      to_remove_mask = (
          logits < torch.min(values, dim=-1, keepdim=True)[0]
      )  # min returns a tuple (values, indices)
      logits[to_remove_mask] = filter_value

    if top_p > 0.0:
      sorted_logits, sorted_indices = torch.sort(
        logits, descending=True, dim=-1)
      cum_probs = torch.cumsum(
        torch.softmax(sorted_logits, dim=-1), dim=-1)

      sorted_indices_to_remove = cum_probs > top_p
      # Ensures at least one token is kept
      sorted_indices_to_remove[..., 1:] = \
        sorted_indices_to_remove[..., :-1].clone()
      sorted_indices_to_remove[..., 0] = 0

      mask_to_remove = torch.empty_like(sorted_indices_to_remove)
      mask_to_remove.scatter_(dim=-1,
                              index=sorted_indices,
                              src=sorted_indices_to_remove)
      logits[mask_to_remove] = filter_value

    if dim != -1:
      logits = torch.transpose(logits, dim, -1)

    return logits


def _discrete_prob_map(gamma_t, N=10):
  snr_sqrt = np.exp(-gamma_t / 2)
  def value(x):
    cdf = norm.cdf(x, scale=1) ** (N - 1)
    pdf = norm.pdf(x, loc=snr_sqrt, scale=1)
    return pdf * cdf
  return value


def _discrete_prob_grad(gamma_t, N=10):
  snr_sqrt = np.exp(-gamma_t / 2)
  def value(x):
    coef = -0.5 * snr_sqrt * (x - snr_sqrt)
    cdf = norm.cdf(x, scale=1) ** (N - 1)
    pdf = norm.pdf(x, loc=snr_sqrt, scale=1)
    return coef * pdf * cdf
  return value


def _cache_prob_usdm_in_partition(
  vocab_size=30522, partition_index=0, num_partitions=1,
  log10_num_points=5):
  print(f'Caching partition:{partition_index} / {num_partitions}')
  path = 'integral'
  gamma_min = -5
  gamma_max = -1
  num_points = 10 ** log10_num_points
  p_cache = []
  grad_p_cache = []
  start_time = time.time()
  gammas = np.linspace(gamma_min, gamma_max, num_points)
  n = num_points // num_partitions
  for gamma in gammas[partition_index * n:
                      (partition_index + 1) * n]:
    pt, _ = quad(_discrete_prob_map(gamma, vocab_size),
                 -np.inf, np.inf)
    p_cache.append(pt)
    grad_pt, _ = quad(_discrete_prob_grad(gamma, vocab_size),
                      -np.inf, np.inf)
    grad_p_cache.append(grad_pt)
    if len(p_cache) % 100 == 0:
      print('{}% completed. Time elapsed:{:.2f} mins'.format(
        int(100 * len(p_cache) / num_points),
        (time.time() - start_time) / 60))

  filename = os.path.join(
    path, '{}_{}_{}-{}.pkl'.format(
      vocab_size, log10_num_points, partition_index,
      num_partitions))
  with open(filename, 'wb') as f:
    pickle.dump({
      'vocab_size': vocab_size,
      'gamma_min': gamma_min,
      'gamma_max': gamma_max,
      'num_points': num_points,
      'pt': np.asarray(p_cache),
      'grad_pt': np.asarray(grad_p_cache)}, f)


def test_cache_prob_usdm_in_partition(
  partition_index=0, num_partitions=1, vocab_size=30522,
  log10_num_points=5):
  path = 'integral/{}_{}_{}-{}.pkl'.format(
    vocab_size, log10_num_points, partition_index,
    num_partitions)
  with open(path, 'rb') as f:
    data = pickle.load(f)
  num_points = data['num_points']
  def _get_index(x):
    return round((num_points - 1) * (x - data['gamma_min']) / (
      data['gamma_max'] - data['gamma_min']))

  pt_errors = []
  grad_pt_errors = []
  gammas = np.linspace(data['gamma_min'],
                       data['gamma_max'],
                       num_points)
  n = num_points // num_partitions
  for gamma in gammas[partition_index * n:
                      (partition_index + 1) * n]:
    pt, _ = quad(
      _discrete_prob_map(gamma, data['vocab_size']),
      -np.inf, np.inf)
    grad_pt, _ = quad(
      _discrete_prob_grad(gamma, data['vocab_size']),
      -np.inf, np.inf)
    idx = _get_index(gamma)
    print(idx)
    pt_errors.append((pt - data['pt'][idx]) ** 2)
    grad_pt_errors.append((grad_pt - data['grad_pt'][idx]) ** 2)
  print('Integral MSE:{} Integral Squared:{:.4f}'.format(
    np.mean(pt_errors), np.mean(data['pt'] ** 2)))
  print('Integral Grad MSE:{} Integral Grad Squared:{:.4f}'.format(
    np.mean(grad_pt_errors), np.mean(data['grad_pt'] ** 2)))


if __name__ == "__main__":
  # Usage: python utils.py --vocab_size=N
  parser = argparse.ArgumentParser(
    description='Caches the integral appearing in the '
                'Diffusion Transformation operator.')
  parser.add_argument(
    '--vocab_size',
    type=int,
    default=50257,  # For the gpt2 tokenizer
    help='Vocabulary size (default: 50257)')
  parser.add_argument(
    '--partition_index',
    type=int,
    default=0,
    help='Helps parallelize caching')
  parser.add_argument(
    '--num_partitions',
    type=int,
    default=1,
    help='Helps parallelize caching')
  parser.add_argument(
    '--log10_num_points',
    type=int,
    default=5,
    help=('The integral is function that needs to be '
          'evaluated for inputs with a range [-5, 1]. '
          'This argument represents the logarithm base 10 '
          'of number of bins of discretization.'))
  args = parser.parse_args()

  # Computing the integral over [-5, 1] can be slow,
  # so one might prefer splitting it into `num_partitions`
  # bins and compute each separately and merge them later.
  _cache_prob_usdm_in_partition(
    partition_index=args.partition_index,
    num_partitions=args.num_partitions,
    vocab_size=args.vocab_size,
    log10_num_points=args.log10_num_points)
  
  test_cache_prob_usdm_in_partition(
    partition_index=args.partition_index,
    num_partitions=args.num_partitions,
    vocab_size=args.vocab_size,
    log10_num_points=args.log10_num_points)


def get_reverse_indices(indices):
  """
  indices: LongTensor of shape [B, N] representing permutations
  returns: LongTensor of shape [B, N] representing the inverse permutations
  """
  B, N = indices.shape
  reverse_indices = torch.empty_like(indices)
  arange = torch.arange(N, device=indices.device).unsqueeze(0).expand(B, -1)
  reverse_indices.scatter_(1, indices, arange)
  return reverse_indices