#!/usr/bin/env python3

# Copyright (c) Facebook, Inc. and its affiliates.
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.

from typing import Optional
from parlai.core.params import ParlaiParser
from parlai.core.opt import Opt
import json
import math
import os
import torch
import torch.nn.functional as F
from collections import defaultdict, Counter
from nltk import ngrams

from parlai.core.torch_generator_agent import PPLMetric
from parlai.agents.image_seq2seq.image_seq2seq import ImageSeq2seqAgent
from parlai.agents.transformer.transformer import TransformerGeneratorAgent
from parlai.core.metrics import AverageMetric, SumMetric, GlobalAverageMetric
from parlai.utils.misc import round_sigfigs
from parlai.utils.io import PathManager


def div(x, y):
    if y == 0:
        return x
    else:
        return x / y


class NGramIterator:
    """
    N-Gram iterator for a list.
    """

    def __init__(self, lst, n):
        self.lst = lst
        self.n = n
        self.max = len(lst) - n

    def __iter__(self):
        self.counter = -1
        return self

    def __next__(self):
        self.counter += 1
        if self.counter > self.max:
            raise StopIteration
        return tuple(self.lst[self.counter : self.counter + self.n])


class RewardUnlikelihoodAgentTrait(object):
    """
    Abstract Trait.

    Applies unlikelihood loss based on the presence of negative rewards in the task.
    """

    @classmethod
    def add_cmdline_args(
        cls, parser: ParlaiParser, partial_opt: Optional[Opt] = None
    ) -> ParlaiParser:
        grp = super().add_cmdline_args(parser, partial_opt=partial_opt)
        grp.add_argument('--alpha', default=1.0, type=float)
        return parser

    def _dummy_batch(self, batchsize, maxlen):
        batch = super()._dummy_batch(batchsize, maxlen)
        batch['rewards'] = torch.ones(batchsize, dtype=torch.long).cuda()
        return batch

    def compute_loss(self, batch, return_output=False):
        if batch.label_vec is None:
            raise ValueError('Cannot compute loss without a label.')

        model_output = self.model(*self._model_input(batch), ys=batch.label_vec)
        scores, preds, *_ = model_output  # scores is bsz x time x vocab

        scores = F.log_softmax(scores, dim=-1)
        scores_view = scores.view(-1, scores.size(-1))
        targets = batch.label_vec
        targets_view = targets.view(-1)

        notnull = targets.ne(self.NULL_IDX)
        if self.is_training:
            # note it's >= because convai2 and other teachers all provide a 0 reward
            mle_notnull = notnull & (batch.rewards >= 0).unsqueeze(1).expand_as(notnull)
        else:
            mle_notnull = notnull

        mle_loss = (
            F.nll_loss(
                scores_view, targets_view, ignore_index=self.NULL_IDX, reduction='none'
            ).view_as(mle_notnull)
            * mle_notnull.float()
        ).sum()

        # limit loss to only the positive rewards
        mle_target_tokens = mle_notnull.long().sum()
        correct = ((targets == preds) * mle_notnull).sum()
        self.global_metrics.add('token_acc', AverageMetric(correct, mle_target_tokens))
        self.global_metrics.add('nll_loss', AverageMetric(mle_loss, mle_target_tokens))
        self.global_metrics.add('ppl', PPLMetric(mle_loss, mle_target_tokens))
        if mle_target_tokens > 0:
            mle_loss /= mle_target_tokens  # average loss per token

        if not self.is_training:
            if return_output:
                return (mle_loss, model_output)
            else:
                return mle_loss

        # and now we want the unlikelihood loss on the negative examples
        ul_notnull = notnull & (batch.rewards < 0).unsqueeze(1).expand_as(notnull)
        ul_target_tokens = ul_notnull.long().sum()
        range_ = torch.arange(targets_view.size(0)).to(batch.label_vec.device)
        ul_scores = scores_view[range_, targets_view]
        clamp_min = 1e-6 if self.opt['fp16'] else 1e-20
        ul_loss = (
            -torch.log(torch.clamp(1.0 - ul_scores.exp(), min=clamp_min)).view_as(
                ul_notnull
            )
            * ul_notnull.float()
        ).sum()
        self.global_metrics.add('ul_loss', AverageMetric(ul_loss, ul_target_tokens))
        if ul_target_tokens > 0:
            ul_loss /= ul_target_tokens

        loss = mle_loss + self.opt['alpha'] * ul_loss

        if return_output:
            return (loss, model_output)
        else:
            return loss


class RepetitionUnlikelihoodAgentTrait(object):
    """
    Abstract Trait.

    Applies unliikelihood loss to repetition some proportion of train steps by
    generating, marking repeats, and calculating loss accordingly.
    """

    def __init__(self, opt, shared=None):
        super().__init__(opt, shared)
        self.pred_logsoftmax = torch.nn.LogSoftmax(dim=2)

    @classmethod
    def add_cmdline_args(
        cls, parser: ParlaiParser, partial_opt: Optional[Opt] = None
    ) -> ParlaiParser:
        grp = super().add_cmdline_args(parser, partial_opt=partial_opt)
        grp.add_argument('--seq-ul-ratio', default=0.5, type=float)
        grp.add_argument('--seq-ul-n', default=4, type=int)
        grp.add_argument('--mask-n', default=100, type=int)
        grp.add_argument('--ctxt-beta', default=0.5, type=float)
        grp.add_argument('--crep-pen', default='crep', type=str)
        return parser

    def _init_cuda_buffer(self, batchsize, maxlen, force=False):
        pass

    def _count_n_grams(self, token_lst, n):
        n_grams = defaultdict(int)
        for n_gram in NGramIterator(token_lst, n):
            n_grams[n_gram] += 1
        return n_grams

    def compute_loss(self, batch, return_output=False):
        if self.is_training and (torch.rand(1).item() >= self.opt['seq_ul_ratio']):
            total_loss, model_output = super().compute_loss(batch, return_output=True)
            # No sequence level unlikelihood
            if return_output:
                return total_loss, model_output
            else:
                return total_loss

        # Generate
        clamp_min = 1e-6 if self.opt['fp16'] else 1e-20
        maxlen = self.label_truncate or 256
        with torch.no_grad():
            beam_pred_scores, _ = self._generate(batch, self.beam_size, maxlen)

        # forward pass to create graph for beam search case
        generations = [g[1:] for (g, s) in beam_pred_scores]
        pred_toks = torch.nn.utils.rnn.pad_sequence(generations, batch_first=True)
        model_output = self.model(*self._model_input(batch), ys=pred_toks)
        logits, preds, _ = model_output

        # construct mask marking repeats
        n = self.opt['seq_ul_n']  # label n-grams
        crep_mask = torch.zeros_like(pred_toks).type_as(logits)
        lrep_mask = torch.zeros_like(pred_toks).type_as(logits)

        for i, gen in enumerate(generations):
            gen_i = gen.tolist()

            # Collect context ngrams
            context_i = batch.text_vec[i].tolist()
            context_n_grams = self._count_n_grams(context_i, n)

            seen_n_grams = defaultdict(int)

            # penalize if there is a context repeat
            for j, n_gram in enumerate(NGramIterator(gen_i, n)):
                if context_n_grams[n_gram] > 0:
                    crep_mask[i, j : j + n] = 1

            # penalize if there is a label repeat
            for j, n_gram in enumerate(NGramIterator(gen_i, n)):
                if seen_n_grams[n_gram] > 0:
                    lrep_mask[i, j : j + n] = 1
                seen_n_grams[n_gram] += 1

        # Compute unlikelihood loss
        lprobs = self.pred_logsoftmax(logits)
        pred_lprobs = lprobs.view(-1, lprobs.size(2)).gather(1, pred_toks.view(-1, 1))
        one_minus_probs = torch.clamp((1.0 - pred_lprobs.exp()), min=clamp_min).view(
            pred_toks.size(0), pred_toks.size(1)
        )

        mask = ((1 - self.opt['ctxt_beta']) * lrep_mask) + (
            self.opt['ctxt_beta'] * crep_mask
        )

        ul_loss = -(torch.log(one_minus_probs)) * mask
        total_loss = div(ul_loss.sum(), mask.sum())
        self.record_local_metric(
            'ul_loss', AverageMetric.many(ul_loss.sum(dim=-1), mask.sum(dim=-1))
        )

        if not self.is_training:
            # in eval mode, we want metrics (e.g. PPL) provided by tga's compute_loss
            _, _ = super().compute_loss(batch, return_output=True)

        if return_output:
            return total_loss, model_output
        return total_loss

    def _add_generation_metrics(self, batch, preds):
        self._ngram_metrics(batch, preds)

    def _ngram_metrics(self, batch, preds):
        text_vecs_cpu = batch.text_vec.cpu()
        lrep, crep = 0, 0
        total_pred_ngs = 0
        n = self.opt['seq_ul_n']
        for i, pred in enumerate(preds):
            pred_token_list = pred.tolist()
            if self.END_IDX in pred_token_list:
                pred_token_list = pred_token_list[
                    : pred_token_list.index(self.END_IDX)
                ]  # remove possible padding
            if self.START_IDX in pred_token_list:
                pred_token_list = pred_token_list[
                    pred_token_list.index(self.START_IDX) :
                ]
            pred_ngs = [ng for ng in ngrams(pred_token_list, n)]
            pred_counter = Counter(pred_ngs)
            total_pred_ngs += len(pred_ngs)
            lrep += len(pred_ngs) - len(pred_counter)

            text_token_list = text_vecs_cpu[i].tolist()
            if self.NULL_IDX in text_token_list:
                text_token_list = text_token_list[
                    : text_token_list.index(self.NULL_IDX)
                ]  # remove possible padding
            context_counter = Counter([ng for ng in ngrams(text_token_list, n)])

            for ng in pred_counter:
                if ng in context_counter:
                    crep += pred_counter[ng]

        self.global_metrics.add(
            'lrep_%dgrams' % n, GlobalAverageMetric(lrep, total_pred_ngs)
        )
        self.global_metrics.add(
            'crep_%dgrams' % n, GlobalAverageMetric(crep, total_pred_ngs)
        )


class _VocabUnlikelihoodTrait(object):
    def reset_metrics(self):
        super().reset_metrics()
        self.metrics['high_freq'] = 0
        self.metrics['gold_high'] = 0

    def _kldiv(self, p_counter, q_counter) -> float:
        ptotal = sum(p_counter.values())
        qtotal = sum(q_counter.values())
        kldiv = 0.0
        for word, _ in p_counter.items():
            prob_p = p_counter[word] / ptotal
            prob_q = q_counter[word] / qtotal
            kldiv += prob_p * math.log(1e-20 + (prob_q / prob_p))
        return -kldiv

    def _jsdiv(self, dist1: Counter, dist2: Counter) -> float:
        half = dist1 + dist2
        return 0.5 * self._kldiv(dist1, half) + 0.5 * self._kldiv(dist2, half)

    def report(self):
        report = super().report()
        report['kldiv_humgen'] = self._kldiv(
            self.running_human, self.running_generation
        )
        report['kldiv_genhum'] = self._kldiv(
            self.running_generation, self.running_human
        )
        report['jsdiv'] = self._jsdiv(self.running_human, self.running_generation)
        return report


class SequenceVocabUnlikelihoodAgentTrait(_VocabUnlikelihoodTrait):
    """
    Abstract Trait.

    Applies unlikelihood loss to vocabulary distributiion by generating, calculating
    proportion of tokens per vocabulary frequency bin, and computing loss accordingly
    """

    def __init__(self, opt, shared=None):
        super().__init__(opt, shared)
        self.NUM_STEPS = opt['queue_size']
        if shared is None:
            self._reset_running_histories()
            self._last_was_training = True
            self.truebins = {}
            counts_file = self.opt['counts_file']
            if counts_file is None:
                counts_file = os.path.join(
                    os.path.dirname(self.opt['model_file']), 'counts.txt'
                )
                if not PathManager.exists(counts_file):
                    raise RuntimeError(
                        'Please give a --counts-file to use vocab unlikelihood'
                    )
            with PathManager.open(counts_file) as f:
                for line in f:
                    record = json.loads(line)
                    self.truebins[record['word_id']] = record['bin']

    def reset(self):
        super().reset()
        self._reset_running_histories()

    def _reset_running_histories(self):
        self.generation_history = []
        self.running_generation = Counter()
        self.human_history = []
        self.running_human = Counter()

    @classmethod
    def add_cmdline_args(
        cls, parser: ParlaiParser, partial_opt: Optional[Opt] = None
    ) -> ParlaiParser:
        grp = super().add_cmdline_args(parser, partial_opt=partial_opt)
        grp.add_argument('--alpha', default=1.0, type=float)
        grp.add_argument('--queue-size', default=32, type=int)
        grp.add_argument(
            '--weighting', choices={'uniform', 'logdiff', 'kldiv'}, default='uniform'
        )
        grp.add_argument('--threshold', type=float, default=1e-3)
        grp.add_argument('--counts-file', type=str, default=None)
        return parser

    def _init_cuda_buffer(self, *args, **kwargs):
        pass

    def reset_metrics(self):
        super().reset_metrics()
        self.metrics['num_penalize'] = 0
        self.metrics['steps'] = 0
        self.metrics['hum_toks'] = 0
        self.metrics['gen_toks'] = 0
        self.metrics['ul_weights'] = 0
        # better clean our statistics so not to leak test statistics into train

    def _get_bins(self, counts: Counter):
        c = Counter()
        for k, v in counts.items():
            c.update({self.truebins.get(k, 'never'): v})
        t = sum(c.values())
        return {k: round_sigfigs(v / t, 4) for k, v in c.items()}

    def _l2dist(self, bins):
        return (
            (bins.get('frequent', 0) - 0.4) ** 2
            + (bins.get('medium', 0) - 0.3) ** 2
            + (bins.get('rare', 0) - 0.2) ** 2
            + (bins.get('veryrare', 0) - 0.1) ** 2
            + (bins.get('never', 0) - 0.0) ** 2
        )

    def report(self):
        r = super().report()
        if self.running_generation and self.running_human:
            for k, v in self._get_bins(self.running_human).items():
                r[f'humdist_{k}'] = v
            gendist = self._get_bins(self.running_generation)
            for k, v in gendist.items():
                r[f'gendist_{k}'] = v
            r['dist_l2'] = self._l2dist(gendist)

        return r

    def compute_loss(self, batch, return_output=False):
        if self._last_was_training is not self.is_training:
            self._reset_running_histories()
            self._last_was_training = self.is_training

        nll_loss, model_output = super().compute_loss(batch, True)
        scores, preds, *_ = model_output  # scores is bsz x time x vocab
        targets = batch.label_vec
        notnull = targets != self.NULL_IDX

        with torch.no_grad():
            beam_pred_scores, _ = self._generate(
                batch, self.beam_size, self.opt['label_truncate']
            )

            # forward pass to create graph for beam search case
            generations = [g for (g, s) in beam_pred_scores]
            gentoks = torch.nn.utils.rnn.pad_sequence(
                generations, batch_first=True, padding_value=self.NULL_IDX
            )
            # strip the BOS tokens
            gentoks = gentoks[:, 1:]

        # find everything we oversampled
        gen_mask = gentoks != self.NULL_IDX
        self.generation_history.append(Counter(gentoks[gen_mask].view(-1).tolist()))
        self.human_history.append(Counter(targets[notnull].view(-1).tolist()))
        self.running_generation += self.generation_history[-1]
        self.running_human += self.human_history[-1]

        if len(self.generation_history) > self.NUM_STEPS:
            if not self.is_training:
                # we want a running history of word usage
                self.running_generation -= self.generation_history.pop(0)
                self.running_human -= self.human_history.pop(0)
        else:
            if return_output:
                return nll_loss, model_output
            else:
                return nll_loss

        gen_sum = sum(self.running_generation.values())
        hum_sum = sum(self.running_human.values())

        # what did we oversample?
        if self.opt['weighting'] == 'logdiff':
            to_penalize = {
                w: (v / gen_sum) - (self.running_human.get(w, 0) / hum_sum)
                for w, v in self.running_generation.items()
            }
            to_penalize = {
                w: v for w, v in to_penalize.items() if v >= self.opt['threshold']
            }
            to_penalize = {w: math.log(v / 0.001) for w, v in to_penalize.items()}
        elif self.opt['weighting'] == 'uniform':
            to_penalize = {
                w: (v / gen_sum) - (self.running_human.get(w, 0) / hum_sum)
                for w, v in self.running_generation.items()
            }
            to_penalize = {
                w: 1 for w, v in to_penalize.items() if v >= self.opt['threshold']
            }
        elif self.opt['weighting'] == 'kldiv':
            to_penalize = {
                w: (
                    self.running_generation[w] / gen_sum,
                    self.running_human[w] / hum_sum,
                )
                for w, v in self.running_human.items()
                if w in self.running_generation
            }
            to_penalize = {
                w: (p_gen, p_hum)
                for w, (p_gen, p_hum) in to_penalize.items()
                if p_gen > p_hum
            }
            to_penalize = {
                w: p_gen * (math.log(p_gen) - math.log(p_hum))
                for w, (p_gen, p_hum) in to_penalize.items()
            }
            to_penalize = {
                k: v for k, v in to_penalize.items() if v > self.opt['threshold']
            }
        else:
            raise ValueError

        self.global_metrics.add('num_penalize', SumMetric(len(to_penalize)))

        ul_weights = torch.zeros(gen_mask.shape)
        ul_mask = torch.zeros_like(gen_mask)
        for wordid, weight in to_penalize.items():
            ul_mask = ul_mask | (gentoks == wordid)
            ul_weights[gentoks == wordid] = weight
        ul_weights = ul_weights.to(gen_mask.device)
        self.global_metrics.add('ul_weights', AverageMetric(ul_weights[ul_mask].mean()))

        # and whack it
        model_output = self.model(*self._model_input(batch), ys=gentoks)
        scores, *_ = model_output
        downweight = gentoks[ul_mask]

        almost_scores = F.log_softmax(scores[ul_mask], dim=-1)
        ul_scores = almost_scores[torch.arange(len(downweight)), downweight]

        clamp_min = 1e-6 if self.opt['fp16'] else 1e-20

        ul_loss = (
            -(torch.log(torch.clamp(1 - ul_scores.exp(), min=clamp_min)))
            * ul_weights[ul_mask]
        ).sum()
        num_ul = ul_mask.sum()

        self.global_metrics.add('ul_loss', AverageMetric(ul_loss, num_ul))
        self.global_metrics.add('ul_num_tokens', SumMetric(num_ul))

        ul_loss = div(ul_loss, num_ul)

        if len(self.generation_history) < self.NUM_STEPS:
            loss = nll_loss
        else:
            loss = nll_loss + self.opt['alpha'] * ul_loss

        if return_output:
            return (loss, model_output)
        else:
            return loss


class TransformerSequenceVocabUnlikelihoodAgent(
    SequenceVocabUnlikelihoodAgentTrait, TransformerGeneratorAgent
):
    """
    Example usage:

    -t convai2 -m parlai_internal.projects.dontsaythat.agents:TransformerSequenceVocabUnlikelihoodAgent
    """

    pass


class TransformerUnlikelihoodAgent(
    RewardUnlikelihoodAgentTrait, TransformerGeneratorAgent
):
    """
    Example usage:

    -t convai2 -m parlai_internal.projects.dontsaythat.agents:TransformerUnlikelihoodAgent
    """

    pass


class RepetitionUnlikelihoodAgent(RepetitionUnlikelihoodAgentTrait, ImageSeq2seqAgent):
    """
    Example usage:

    -t convai2 -m parlai_internal.projects.dontsaythat.agents:RepetitionUnlikelihoodAgent
    """

    pass
