# coding=utf-8
# copied from hugginface github
# Copyright 2018 The Google AI Language Team Authors and The HuggingFace Inc.
# team.
# Copyright (c) 2018, NVIDIA CORPORATION.  All rights reserved.
#
# 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.
"""BERT pre-training runner."""
import argparse
import json
import os
from os.path import exists, join
import pickle
from time import time

import torch
from torch.nn import functional as F
from torch.nn.utils import clip_grad_norm_
from torch.utils.data import DataLoader

from apex import amp
from horovod import torch as hvd

from tqdm import tqdm

from data import (TokenBucketSampler, PrefetchLoader,
                  DetectFeatLmdb, TxtTokLmdb,
                  VeDataset, VeEvalDataset,
                  ve_collate, ve_eval_collate)
from model import UniterForVisualEntailment
from optim import get_lr_sched
from optim.misc import build_optimizer

from utils.logger import LOGGER, TB_LOGGER, RunningMeter, add_log_to_file
from utils.distributed import (all_reduce_and_rescale_tensors, all_gather_list,
                               broadcast_tensors)
from utils.save import ModelSaver, save_training_meta
from utils.misc import NoOp, parse_with_config, set_dropout, set_random_seed
from utils.misc import VE_ENT2IDX as ans2label
from utils.misc import VE_IDX2ENT as label2ans
from utils.const import IMG_DIM, BUCKET_SIZE


def create_dataloader(img_path, txt_path, batch_size, is_train,
                      dset_cls, collate_fn, opts):
    img_db = DetectFeatLmdb(img_path, opts.conf_th, opts.max_bb, opts.min_bb,
                            opts.num_bb, opts.compressed_db)
    txt_db = TxtTokLmdb(txt_path, opts.max_txt_len if is_train else -1)
    dset = dset_cls(txt_db, img_db)
    sampler = TokenBucketSampler(dset.lens, bucket_size=BUCKET_SIZE,
                                 batch_size=batch_size, droplast=is_train)
    loader = DataLoader(dset, batch_sampler=sampler,
                        num_workers=opts.n_workers, pin_memory=opts.pin_mem,
                        collate_fn=collate_fn)
    return PrefetchLoader(loader)


def main(opts):
    hvd.init()
    n_gpu = hvd.size()
    device = torch.device("cuda", hvd.local_rank())
    torch.cuda.set_device(hvd.local_rank())
    rank = hvd.rank()
    opts.rank = rank
    LOGGER.info("device: {} n_gpu: {}, rank: {}, "
                "16-bits training: {}".format(
                    device, n_gpu, hvd.rank(), opts.fp16))

    if opts.gradient_accumulation_steps < 1:
        raise ValueError("Invalid gradient_accumulation_steps parameter: {}, "
                         "should be >= 1".format(
                            opts.gradient_accumulation_steps))

    set_random_seed(opts.seed)

    # train_examples = None
    LOGGER.info(f"Loading Train Dataset {opts.train_txt_db}, "
                f"{opts.train_img_db}")
    train_dataloader = create_dataloader(opts.train_img_db, opts.train_txt_db,
                                         opts.train_batch_size, True,
                                         VeDataset, ve_collate, opts)
    val_dataloader = create_dataloader(opts.val_img_db, opts.val_txt_db,
                                       opts.val_batch_size, False,
                                       VeEvalDataset, ve_eval_collate, opts)
    test_dataloader = create_dataloader(opts.test_img_db, opts.test_txt_db,
                                        opts.val_batch_size, False,
                                        VeEvalDataset, ve_eval_collate, opts)

    # Prepare model
    if opts.checkpoint:
        checkpoint = torch.load(opts.checkpoint)
    else:
        checkpoint = {}
    bert_model = json.load(open(f'{opts.train_txt_db}/meta.json'))['bert']
    if 'bert' not in bert_model:
        bert_model = 'bert-large-cased'  # quick hack for glove exp
    model = UniterForVisualEntailment.from_pretrained(
        opts.model_config, state_dict=checkpoint, img_dim=IMG_DIM)
    model.to(device)
    # make sure every process has same model parameters in the beginning
    broadcast_tensors([p.data for p in model.parameters()], 0)
    set_dropout(model, opts.dropout)

    # Prepare optimizer
    optimizer = build_optimizer(model, opts)
    model, optimizer = amp.initialize(model, optimizer,
                                      enabled=opts.fp16, opt_level='O2')

    global_step = 0
    if rank == 0:
        save_training_meta(opts)
        TB_LOGGER.create(join(opts.output_dir, 'log'))
        pbar = tqdm(total=opts.num_train_steps)
        model_saver = ModelSaver(join(opts.output_dir, 'ckpt'))
        pickle.dump(ans2label,
                    open(join(opts.output_dir, 'ckpt', 'ans2label.pkl'), 'wb'))
        os.makedirs(join(opts.output_dir, 'results'))  # store VQA predictions
        add_log_to_file(join(opts.output_dir, 'log', 'log.txt'))
    else:
        LOGGER.disabled = True
        pbar = NoOp()
        model_saver = NoOp()

    LOGGER.info(f"***** Running training with {n_gpu} GPUs *****")
    LOGGER.info("  Num examples = %d", len(train_dataloader.dataset))
    LOGGER.info("  Batch size = %d", opts.train_batch_size)
    LOGGER.info("  Accumulate steps = %d", opts.gradient_accumulation_steps)
    LOGGER.info("  Num steps = %d", opts.num_train_steps)

    running_loss = RunningMeter('loss')
    model.train()
    n_examples = 0
    n_epoch = 0
    start = time()
    # quick hack for amp delay_unscale bug
    optimizer.zero_grad()
    optimizer.step()
    while True:
        for step, batch in enumerate(train_dataloader):
            n_examples += batch['input_ids'].size(0)

            loss = model(batch, compute_loss=True)
            loss = loss.mean() * batch['targets'].size(1)  # instance-leval bce
            delay_unscale = (step+1) % opts.gradient_accumulation_steps != 0
            with amp.scale_loss(loss, optimizer, delay_unscale=delay_unscale
                                ) as scaled_loss:
                scaled_loss.backward()
                if not delay_unscale:
                    # gather gradients from every processes
                    # do this before unscaling to make sure every process uses
                    # the same gradient scale
                    grads = [p.grad.data for p in model.parameters()
                             if p.requires_grad and p.grad is not None]
                    all_reduce_and_rescale_tensors(grads, float(1))

            running_loss(loss.item())

            if (step + 1) % opts.gradient_accumulation_steps == 0:
                global_step += 1

                # learning rate scheduling
                lr_this_step = get_lr_sched(global_step, opts)
                for param_group in optimizer.param_groups:
                    param_group['lr'] = lr_this_step
                TB_LOGGER.add_scalar('lr', lr_this_step, global_step)

                # log loss
                losses = all_gather_list(running_loss)
                running_loss = RunningMeter(
                    'loss', sum(l.val for l in losses)/len(losses))
                TB_LOGGER.add_scalar('loss', running_loss.val, global_step)
                TB_LOGGER.step()

                # update model params
                if opts.grad_norm != -1:
                    grad_norm = clip_grad_norm_(amp.master_params(optimizer),
                                                opts.grad_norm)
                    TB_LOGGER.add_scalar('grad_norm', grad_norm, global_step)
                optimizer.step()
                optimizer.zero_grad()
                pbar.update(1)

                if global_step % 100 == 0:
                    # monitor training throughput
                    LOGGER.info(f'============Step {global_step}=============')
                    tot_ex = sum(all_gather_list(n_examples))
                    ex_per_sec = int(tot_ex / (time()-start))
                    LOGGER.info(f'{tot_ex} examples trained at '
                                f'{ex_per_sec} ex/s')
                    TB_LOGGER.add_scalar('perf/ex_per_s',
                                         ex_per_sec, global_step)
                    LOGGER.info(f'===========================================')

                if global_step % opts.valid_steps == 0:
                    for split, loader in [("val", val_dataloader),
                                          ("test", test_dataloader)]:
                        LOGGER.info(f"Step {global_step}: start running "
                                    f"validation on {split} split...")
                        val_log, results = validate(
                            model, loader, label2ans, split)
                        with open(f'{opts.output_dir}/results/'
                                  f'{split}_results_{global_step}_'
                                  f'rank{rank}.json', 'w') as f:
                            json.dump(results, f)
                        TB_LOGGER.log_scaler_dict(val_log)
                    model_saver.save(model, global_step)
            if global_step >= opts.num_train_steps:
                break
        if global_step >= opts.num_train_steps:
            break
        n_epoch += 1
        LOGGER.info(f"Step {global_step}: finished {n_epoch} epochs")
    for split, loader in [("val", val_dataloader),
                          ("test", test_dataloader)]:
        LOGGER.info(f"Step {global_step}: start running "
                    f"validation on {split} split...")
        val_log, results = validate(model, loader, label2ans, split)
        with open(f'{opts.output_dir}/results/'
                  f'{split}_results_{global_step}_'
                  f'rank{rank}_final.json', 'w') as f:
            json.dump(results, f)
        TB_LOGGER.log_scaler_dict(val_log)
    model_saver.save(model, f'{global_step}_final')


@torch.no_grad()
def validate(model, val_loader, label2ans, split='val'):
    model.eval()
    val_loss = 0
    tot_score = 0
    n_ex = 0
    st = time()
    results = {}
    for i, batch in enumerate(val_loader):
        scores = model(batch, compute_loss=False)
        targets = batch['targets']
        loss = F.binary_cross_entropy_with_logits(
            scores, targets, reduction='sum')
        val_loss += loss.item()
        tot_score += compute_score_with_logits(scores, targets).sum().item()
        answers = [label2ans[i]
                   for i in scores.max(dim=-1, keepdim=False
                                       )[1].cpu().tolist()]
        qids = batch['qids']
        for qid, answer in zip(qids, answers):
            results[qid] = answer
        n_ex += len(qids)
    val_loss = sum(all_gather_list(val_loss))
    tot_score = sum(all_gather_list(tot_score))
    n_ex = sum(all_gather_list(n_ex))
    tot_time = time()-st
    val_loss /= n_ex
    val_acc = tot_score / n_ex
    val_log = {f'valid/{split}_loss': val_loss,
               f'valid/{split}_acc': val_acc,
               f'valid/{split}_ex_per_s': n_ex/tot_time}
    model.train()
    LOGGER.info(f"validation finished in {int(tot_time)} seconds, "
                f"score: {val_acc*100:.2f}")
    return val_log, results


def compute_score_with_logits(logits, labels):
    logits = torch.max(logits, 1)[1]  # argmax
    one_hots = torch.zeros(*labels.size(), device=labels.device)
    one_hots.scatter_(1, logits.view(-1, 1), 1)
    scores = (one_hots * labels)
    return scores


if __name__ == "__main__":
    parser = argparse.ArgumentParser()

    # Required parameters
    parser.add_argument("--train_txt_db",
                        default=None, type=str,
                        help="The input train corpus. (LMDB)")
    parser.add_argument("--train_img_db",
                        default=None, type=str,
                        help="The input train images.")
    parser.add_argument("--val_txt_db",
                        default=None, type=str,
                        help="The input validation corpus. (LMDB)")
    parser.add_argument("--val_img_db",
                        default=None, type=str,
                        help="The input validation images.")
    parser.add_argument("--test_txt_db",
                        default=None, type=str,
                        help="The input test corpus. (LMDB)")
    parser.add_argument("--test_img_db",
                        default=None, type=str,
                        help="The input test images.")
    parser.add_argument('--compressed_db', action='store_true',
                        help='use compressed LMDB')
    parser.add_argument("--model_config",
                        default=None, type=str,
                        help="json file for model architecture")
    parser.add_argument("--checkpoint",
                        default=None, type=str,
                        help="pretrained model (can take 'google-bert') ")

    parser.add_argument(
        "--output_dir", default=None, type=str,
        help="The output directory where the model checkpoints will be "
             "written.")

    # Prepro parameters
    parser.add_argument('--max_txt_len', type=int, default=60,
                        help='max number of tokens in text (BERT BPE)')
    parser.add_argument('--conf_th', type=float, default=0.2,
                        help='threshold for dynamic bounding boxes '
                             '(-1 for fixed)')
    parser.add_argument('--max_bb', type=int, default=100,
                        help='max number of bounding boxes')
    parser.add_argument('--min_bb', type=int, default=10,
                        help='min number of bounding boxes')
    parser.add_argument('--num_bb', type=int, default=36,
                        help='static number of bounding boxes')

    # training parameters
    parser.add_argument("--train_batch_size",
                        default=4096, type=int,
                        help="Total batch size for training. "
                             "(batch by tokens)")
    parser.add_argument("--val_batch_size",
                        default=4096, type=int,
                        help="Total batch size for validation. "
                             "(batch by tokens)")
    parser.add_argument('--gradient_accumulation_steps',
                        type=int,
                        default=16,
                        help="Number of updates steps to accumualte before "
                             "performing a backward/update pass.")
    parser.add_argument("--learning_rate",
                        default=3e-5,
                        type=float,
                        help="The initial learning rate for Adam.")
    parser.add_argument("--valid_steps",
                        default=1000,
                        type=int,
                        help="Run validation every X steps")
    parser.add_argument("--num_train_steps",
                        default=100000,
                        type=int,
                        help="Total number of training updates to perform.")
    parser.add_argument("--optim", default='adam',
                        choices=['adam', 'adamax', 'adamw'],
                        help="optimizer")
    parser.add_argument("--betas", default=[0.9, 0.98], nargs='+',
                        help="beta for adam optimizer")
    parser.add_argument("--decay", default='linear',
                        choices=['linear', 'invsqrt', 'constant'],
                        help="learning rate decay method")
    parser.add_argument("--dropout",
                        default=0.1,
                        type=float,
                        help="tune dropout regularization")
    parser.add_argument("--weight_decay",
                        default=0.0,
                        type=float,
                        help="weight decay (L2) regularization")
    parser.add_argument("--grad_norm",
                        default=0.25,
                        type=float,
                        help="gradient clipping (-1 for no clipping)")
    parser.add_argument("--warmup_steps",
                        default=4000,
                        type=int,
                        help="Number of training steps to perform linear "
                             "learning rate warmup for. (invsqrt decay)")

    # device parameters
    parser.add_argument('--seed',
                        type=int,
                        default=42,
                        help="random seed for initialization")
    parser.add_argument('--fp16',
                        action='store_true',
                        help="Whether to use 16-bit float precision instead "
                             "of 32-bit")
    parser.add_argument('--n_workers', type=int, default=4,
                        help="number of data workers")
    parser.add_argument('--pin_mem', action='store_true',
                        help="pin memory")

    # can use config files
    parser.add_argument('--config', help='JSON config files')

    args = parse_with_config(parser)

    if exists(args.output_dir) and os.listdir(args.output_dir):
        raise ValueError("Output directory ({}) already exists and is not "
                         "empty.".format(args.output_dir))

    # options safe guard
    # TODO

    if args.conf_th == -1:
        assert args.max_bb + args.max_txt_len + 2 <= 512
    else:
        assert args.num_bb + args.max_txt_len + 2 <= 512

    main(args)