#   Copyright (c) 2018 PaddlePaddle Authors. 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.


from __future__ import division
from __future__ import absolute_import
from __future__ import print_function
from __future__ import unicode_literals

import sys
import re
import argparse
import logging
import json
import numpy as np
from collections import namedtuple

import paddle.fluid as F
import paddle.fluid.layers as L
import paddle.fluid.dygraph as D

from ernie.modeling_ernie import ErnieModel, ErnieModelForPretraining
from ernie.modeling_ernie import _build_linear, _build_ln, append_name
from ernie.tokenizing_ernie import ErnieTokenizer

from experimental.seq2seq.modeling_ernie_gen import ErnieModelForGeneration

from propeller import log
import propeller.paddle as propeller

logging.getLogger().handlers[0]=log.handlers[0]
logging.getLogger().setLevel(logging.DEBUG)
log = logging.getLogger() 

@np.vectorize
def rev_lookup(i):
    return rev_dict[i]


def gen_bias(encoder_inputs, decoder_inputs, step):
    decoder_bsz, decoder_seqlen = decoder_inputs.shape[:2]
    attn_bias = L.reshape(L.range(0, decoder_seqlen, 1, dtype='float32') + 1, [1, -1, 1])
    decoder_bias = L.cast((L.matmul(attn_bias, 1. / attn_bias, transpose_y=True) >= 1.) , 'float32') #[1, 1, decoderlen, decoderlen]
    encoder_bias = L.unsqueeze(L.cast(L.ones_like(encoder_inputs), 'float32'), [1]) #[bsz, 1, encoderlen]
    encoder_bias = L.expand(encoder_bias, [1,decoder_seqlen, 1])           #[bsz,decoderlen, encoderlen]
    decoder_bias = L.expand(decoder_bias, [decoder_bsz, 1, 1])              #[bsz, decoderlen, decoderlen]
    if step > 0: 
        bias = L.concat([encoder_bias, L.ones([decoder_bsz, decoder_seqlen, step], 'float32'), decoder_bias], -1)
    else:
        bias = L.concat([encoder_bias, decoder_bias], -1)
    return bias


#def make_data(tokenizer, inputs, max_encode_len):
#    all_ids, all_sids = [], []
#    for i in inputs:
#        q_ids, q_sids = tokenizer.build_for_ernie(
#                np.array(
#                    tokenizer.convert_tokens_to_ids(i.split(' '))[: max_encode_len-2],
#                    dtype=np.int64
#                    )
#                )
#        all_ids.append(q_ids)
#        all_sids.append(q_sids)
#    ml = max(map(len, all_ids))
#    all_ids = [np.pad(i, [0, ml-len(i)], mode='constant')for i in all_ids]
#    all_sids = [np.pad(i, [0, ml-len(i)], mode='constant')for i in all_sids]
#    all_ids = np.stack(all_ids, 0)
#    all_sids = np.stack(all_sids, 0)
#    return all_ids, all_sids


@D.no_grad
def greedy_search_infilling(model, q_ids, q_sids, sos_id, eos_id, attn_id, max_encode_len=640, max_decode_len=100, tgt_type_id=3):
    model.eval()
    #log.debug(q_ids.numpy().tolist())
    _, logits, info = model(q_ids, q_sids)
    gen_ids = L.argmax(logits, -1)
    d_batch, d_seqlen = q_ids.shape
    seqlen = L.reduce_sum(L.cast(q_ids != 0, 'int64'), 1, keep_dim=True)
    log.debug(seqlen.numpy())
    log.debug(d_seqlen)
    has_stopped = np.zeros([d_batch], dtype=np.bool) 
    gen_seq_len = np.zeros([d_batch], dtype=np.int64)
    output_ids = []

    past_cache = info['caches']

    cls_ids =  L.ones([d_batch], dtype='int64') * sos_id
    attn_ids = L.ones([d_batch], dtype='int64') * attn_id
    ids = L.stack([cls_ids, attn_ids], -1)
    for step in range(max_decode_len):
        log.debug('decode step %d' % step)
        bias = gen_bias(q_ids, ids, step)
        pos_ids = D.to_variable(np.tile(np.array([[step, step + 1]], dtype=np.int64), [d_batch, 1]))
        pos_ids += seqlen
        _, logits, info = model(ids, L.ones_like(ids) * tgt_type_id, pos_ids=pos_ids, attn_bias=bias, past_cache=past_cache)
        gen_ids = L.argmax(logits, -1)

        past_cached_k, past_cached_v = past_cache
        cached_k, cached_v = info['caches']
        cached_k = [L.concat([pk, k[:, :1, :]], 1) for pk, k in zip(past_cached_k, cached_k)] # concat cached 
        cached_v = [L.concat([pv, v[:, :1, :]], 1) for pv, v in zip(past_cached_v, cached_v)]
        past_cache = (cached_k, cached_v)

        gen_ids = gen_ids[:, 1]
        ids = L.stack([gen_ids, attn_ids], 1)

        gen_ids = gen_ids.numpy()
        has_stopped |= (gen_ids == eos_id).astype(np.bool)
        gen_seq_len += (1 - has_stopped.astype(np.int64))
        output_ids.append(gen_ids.tolist())
        if has_stopped.all():
            #log.debug('exit because all done')
            break
        #if step == 1: break
    output_ids = np.array(output_ids).transpose([1, 0])
    return output_ids


BeamSearchState = namedtuple('BeamSearchState', ['log_probs', 'lengths', 'finished'])
BeamSearchOutput = namedtuple('BeamSearchOutput', ['scores', 'predicted_ids', 'beam_parent_ids'])


def log_softmax(x):
    e_x = np.exp(x - np.max(x))
    return np.log(e_x / e_x.sum())


def mask_prob(p, onehot_eos, finished):
    is_finished = L.cast(L.reshape(finished, [-1, 1]) != 0, 'float32')
    p = is_finished * (1. - L.cast(onehot_eos, 'float32')) * -9999. + (1. - is_finished) * p
    return p


def hyp_score(log_probs, length, length_penalty):
    lp = L.pow((5.+L.cast(length, 'float32')) / 6., length_penalty)
    return log_probs / lp


def beam_search_step(state, logits, eos_id, beam_width, is_first_step, length_penalty):
    """logits.shape == [B*W, V]"""
    _, vocab_size = logits.shape

    bsz, beam_width = state.log_probs.shape
    onehot_eos = L.cast(F.one_hot(L.ones([1], 'int64') * eos_id, vocab_size), 'int64') #[1, V]

    probs = L.log(L.softmax(logits)) #[B*W, V]
    probs = mask_prob(probs, onehot_eos, state.finished) #[B*W, V]
    allprobs = L.reshape(state.log_probs, [-1, 1]) + probs #[B*W, V]

    not_finished = 1 - L.reshape(state.finished, [-1, 1]) #[B*W,1]
    not_eos = 1 - onehot_eos
    length_to_add = not_finished * not_eos   #[B*W,V]
    alllen = L.reshape(state.lengths, [-1, 1]) + length_to_add

    allprobs = L.reshape(allprobs, [-1, beam_width * vocab_size])
    alllen = L.reshape(alllen, [-1, beam_width * vocab_size])
    allscore = hyp_score(allprobs, alllen, length_penalty)
    if is_first_step:
        allscore = L.reshape(allscore, [bsz, beam_width, -1])[:,0,:] # first step only consiter beam 0
    scores, idx = L.topk(allscore, k=beam_width) #[B, W]
    next_beam_id = idx // vocab_size #[B, W]
    next_word_id = idx % vocab_size

    gather_idx = L.concat([L.where(idx!=-1)[:, :1], L.reshape(idx, [-1, 1])], 1)
    next_probs = L.reshape(L.gather_nd(allprobs, gather_idx), idx.shape)
    next_len = L.reshape(L.gather_nd(alllen, gather_idx), idx.shape)

    gather_idx = L.concat([L.where(next_beam_id!=-1)[:, :1], L.reshape(next_beam_id, [-1, 1])], 1)
    next_finished = L.reshape(L.gather_nd(state.finished, gather_idx), state.finished.shape) #[gather new beam state according to new beam id]
    #log.debug(gather_idx.numpy())
    #log.debug(state.finished.numpy())
    #log.debug(next_finished.numpy())

    next_finished += L.cast(next_word_id==eos_id, 'int64')
    next_finished = L.cast(next_finished > 0, 'int64')

    #log.debug(next_word_id.numpy())
    #log.debug(next_beam_id.numpy())
    next_state = BeamSearchState(log_probs=next_probs, lengths=next_len, finished=next_finished)
    output = BeamSearchOutput(scores=scores, predicted_ids=next_word_id, beam_parent_ids=next_beam_id)

    return output, next_state


@D.no_grad
def beam_search_infilling(model, q_ids, q_sids, sos_id, eos_id, attn_id, max_encode_len=640, max_decode_len=100, beam_width=5, tgt_type_id=3, length_penalty=1.0):
    model.eval()
    #log.debug(q_ids.numpy().tolist())
    _, __, info = model(q_ids, q_sids)
    d_batch, d_seqlen = q_ids.shape

    state = BeamSearchState(
            log_probs=L.zeros([d_batch, beam_width], 'float32'), 
            lengths=L.zeros([d_batch, beam_width], 'int64'), 
            finished=L.zeros([d_batch, beam_width], 'int64'))
    outputs = []

    def reorder_(t, parent_id):
        """reorder cache according to parent beam id"""
        gather_idx = L.where(parent_id!=-1)[:, 0] * beam_width + L.reshape(parent_id, [-1]) 
        t = L.gather(t, gather_idx) 
        return t

    def tile_(t, times):
        _shapes = list(t.shape[1:])
        ret = L.reshape(L.expand(L.unsqueeze(t, [1]), [1, times,] + [1,] * len(_shapes)), [-1,] + _shapes)
        return ret

    cached_k, cached_v = info['caches']
    cached_k = [tile_(k, beam_width)for k in cached_k]
    cached_v = [tile_(v, beam_width)for v in cached_v]
    past_cache = (cached_k, cached_v)

    q_ids = tile_(q_ids, beam_width)
    seqlen = L.reduce_sum(L.cast(q_ids != 0, 'int64'), 1, keep_dim=True)
    #log.debug(q_ids.shape)

    cls_ids =  L.ones([d_batch * beam_width], dtype='int64') * sos_id
    attn_ids = L.ones([d_batch * beam_width], dtype='int64') * attn_id # SOS
    ids = L.stack([cls_ids, attn_ids], -1)
    for step in range(max_decode_len):
        #log.debug('decode step %d' % step)
        bias = gen_bias(q_ids, ids, step)
        pos_ids = D.to_variable(np.tile(np.array([[step, step + 1]], dtype=np.int64), [d_batch * beam_width, 1]))
        pos_ids += seqlen
        _, logits, info = model(ids, L.ones_like(ids) * tgt_type_id, pos_ids=pos_ids, attn_bias=bias, past_cache=past_cache)

        
        output, state = beam_search_step(state, logits[:, 1], 
                eos_id=eos_id, 
                beam_width=beam_width, 
                is_first_step=(step==0), 
                length_penalty=length_penalty)
        outputs.append(output)

        past_cached_k, past_cached_v = past_cache
        cached_k, cached_v = info['caches']
        cached_k = [reorder_(L.concat([pk, k[:, :1, :]], 1), output.beam_parent_ids) for pk, k in zip(past_cached_k, cached_k)] # concat cached 
        cached_v = [reorder_(L.concat([pv, v[:, :1, :]], 1), output.beam_parent_ids) for pv, v in zip(past_cached_v, cached_v)]
        past_cache = (cached_k, cached_v)


        pred_ids_flatten = L.reshape(output.predicted_ids, [d_batch * beam_width])
        ids = L.stack([pred_ids_flatten, attn_ids], 1)

        if state.finished.numpy().all():
            #log.debug('exit because all done')
            break
        #if step == 1: break

    final_ids = L.stack([o.predicted_ids for o in outputs], 0)
    final_parent_ids = L.stack([o.beam_parent_ids for o in outputs], 0)
    final_ids = L.gather_tree(final_ids, final_parent_ids)[:,:,0] #pick best beam
    final_ids = L.transpose(L.reshape(final_ids, [-1, d_batch * 1]), [1, 0])
    return final_ids
    
en_patten = re.compile(r'^[a-zA-Z0-9]*$')

def post_process(token):
    if token.startswith('##'):
        ret = token[2:]
    else:
        if en_patten.match(token):
            ret = ' ' + token
        else:
            ret = token
    return ret


if __name__ == '__main__':
    parser = argparse.ArgumentParser('seq2seq model with ERNIE')
    parser.add_argument('--from_pretrained', type=str, required=True, help='pretrained model directory or tag')
    parser.add_argument('--bsz', type=int, default=8, help='batchsize')
    parser.add_argument('--max_encode_len', type=int, default=640)
    parser.add_argument('--max_decode_len', type=int, default=120)
    parser.add_argument('--tgt_type_id', type=int, default=3)
    parser.add_argument('--beam_width', type=int, default=5)
    parser.add_argument('--attn_token', type=str, default='[ATTN]', help='if [ATTN] not in vocab, you can specified [MAKK] as attn-token')
    parser.add_argument('--length_penalty', type=float, default=1.0)
    parser.add_argument('--save_dir', type=str, required=True, help='model dir to be loaded')

    args = parser.parse_args()

    place = F.CUDAPlace(D.parallel.Env().dev_id)
    D.guard(place).__enter__()

    ernie = ErnieModelForGeneration.from_pretrained(args.from_pretrained, name='')
    tokenizer = ErnieTokenizer.from_pretrained(args.from_pretrained, mask_token=None)
    rev_dict = {v: k for k, v in tokenizer.vocab.items()}
    rev_dict[tokenizer.pad_id] = '' # replace [PAD]
    rev_dict[tokenizer.unk_id] = '' # replace [PAD]

    sd, _ = D.load_dygraph(args.save_dir)
    ernie.set_dict(sd)

    def map_fn(src_ids):
        src_ids = src_ids[: args.max_encode_len]
        src_ids, src_sids = tokenizer.build_for_ernie(src_ids)
        return (src_ids, src_sids)

    feature_column = propeller.data.FeatureColumns([
        propeller.data.TextColumn('seg_a', unk_id=tokenizer.unk_id, vocab_dict=tokenizer.vocab, tokenizer=tokenizer.tokenize),
    ])
    dataset = feature_column.build_dataset_from_stdin('predict').map(map_fn).padded_batch(args.bsz)

    for step, (encoder_ids, encoder_sids) in enumerate(dataset):
        #result_ids = greedy_search_infilling(ernie, D.to_variable(encoder_ids), D.to_variable(encoder_sids), 
        #       eos_id=tokenizer.sep_id,
        #       sos_id=tokenizer.cls_id,
        #       attn_id=tokenizer.vocab[args.attn_id],
        #    max_decode_len=args.max_decode_len, 
        #    max_encode_len=args.max_encode_len, 
        #    beam_width=args.beam_width,
        #    tgt_type_id=args.tgt_type_id)
        result_ids = beam_search_infilling(ernie, D.to_variable(encoder_ids), D.to_variable(encoder_sids), 
                eos_id=tokenizer.sep_id,
                sos_id=tokenizer.cls_id,
                attn_id=tokenizer.vocab[args.attn_token],
                max_decode_len=args.max_decode_len, 
                max_encode_len=args.max_encode_len, 
                beam_width=args.beam_width,
                length_penalty=args.length_penalty,
                tgt_type_id=args.tgt_type_id)

        output_str = rev_lookup(result_ids.numpy())
        for ostr in output_str.tolist():
            if '[SEP]' in ostr:
                ostr = ostr[: ostr.index('[SEP]')]
            
            ostr = ''.join(map(post_process, ostr))
            ostr = ostr.strip()
            print(ostr)