#!/usr/bin/env python
# coding: utf-8

# # 3. GloVe: Global Vectors for Word Representation

# I recommend you take a look at these material first.

# * http://web.stanford.edu/class/cs224n/lectures/cs224n-2017-lecture3.pdf
# * https://nlp.stanford.edu/pubs/glove.pdf

# In[1]:


import torch
import torch.nn as nn
from torch.autograd import Variable
import torch.optim as optim
import torch.nn.functional as F
import nltk
import random
import numpy as np
from collections import Counter
flatten = lambda l: [item for sublist in l for item in sublist]
random.seed(1024)


# In[2]:


print(torch.__version__)
print(nltk.__version__)


# In[3]:


USE_CUDA = torch.cuda.is_available()
gpus = [0]
torch.cuda.set_device(gpus[0])

FloatTensor = torch.cuda.FloatTensor if USE_CUDA else torch.FloatTensor
LongTensor = torch.cuda.LongTensor if USE_CUDA else torch.LongTensor
ByteTensor = torch.cuda.ByteTensor if USE_CUDA else torch.ByteTensor


# In[4]:


def getBatch(batch_size, train_data):
    random.shuffle(train_data)
    sindex = 0
    eindex = batch_size
    while eindex < len(train_data):
        batch = train_data[sindex:eindex]
        temp = eindex
        eindex = eindex + batch_size
        sindex = temp
        yield batch
    
    if eindex >= len(train_data):
        batch = train_data[sindex:]
        yield batch


# In[5]:


def prepare_sequence(seq, word2index):
    idxs = list(map(lambda w: word2index[w] if word2index.get(w) is not None else word2index["<UNK>"], seq))
    return Variable(LongTensor(idxs))

def prepare_word(word, word2index):
    return Variable(LongTensor([word2index[word]]) if word2index.get(word) is not None else LongTensor([word2index["<UNK>"]]))


# ## Data load and Preprocessing 

# In[6]:


corpus = list(nltk.corpus.gutenberg.sents('melville-moby_dick.txt'))[:500]
corpus = [[word.lower() for word in sent] for sent in corpus]


# ### Build vocab

# In[7]:


vocab = list(set(flatten(corpus)))


# In[8]:


word2index = {}
for vo in vocab:
    if word2index.get(vo) is None:
        word2index[vo] = len(word2index)
        
index2word={v:k for k, v in word2index.items()}


# In[9]:


WINDOW_SIZE = 5
windows =  flatten([list(nltk.ngrams(['<DUMMY>'] * WINDOW_SIZE + c + ['<DUMMY>'] * WINDOW_SIZE, WINDOW_SIZE * 2 + 1)) for c in corpus])

window_data = []

for window in windows:
    for i in range(WINDOW_SIZE * 2 + 1):
        if i == WINDOW_SIZE or window[i] == '<DUMMY>': 
            continue
        window_data.append((window[WINDOW_SIZE], window[i]))


# ### Weighting Function 

# <img src="../images/03.glove-weighting-function.png">
# <center>borrowed image from https://nlp.stanford.edu/pubs/glove.pdf</center>

# In[10]:


def weighting(w_i, w_j):
    try:
        x_ij = X_ik[(w_i, w_j)]
    except:
        x_ij = 1
        
    x_max = 100 #100 # fixed in paper
    alpha = 0.75
    
    if x_ij < x_max:
        result = (x_ij/x_max)**alpha
    else:
        result = 1
    
    return result


# ### Build Co-occurence Matrix X

# Because of model complexity, It is important to determine whether a tighter bound can be placed on the number of nonzero elements of X.

# In[11]:


X_i = Counter(flatten(corpus)) # X_i


# In[12]:


X_ik_window_5 = Counter(window_data) # Co-occurece in window size 5


# In[13]:


X_ik = {}
weighting_dic = {}


# In[14]:


from itertools import combinations_with_replacement


# In[15]:


for bigram in combinations_with_replacement(vocab, 2):
    if X_ik_window_5.get(bigram) is not None: # nonzero elements
        co_occer = X_ik_window_5[bigram]
        X_ik[bigram] = co_occer + 1 # log(Xik) -> log(Xik+1) to prevent divergence
        X_ik[(bigram[1],bigram[0])] = co_occer+1
    else:
        pass
        
    weighting_dic[bigram] = weighting(bigram[0], bigram[1])
    weighting_dic[(bigram[1], bigram[0])] = weighting(bigram[1], bigram[0])


# In[16]:


test = random.choice(window_data)
print(test)
try:
    print(X_ik[(test[0], test[1])] == X_ik[(test[1], test[0])])
except:
    1


# ### Prepare train data

# In[17]:


u_p = [] # center vec
v_p = [] # context vec
co_p = [] # log(x_ij)
weight_p = [] # f(x_ij)

for pair in window_data: 
    u_p.append(prepare_word(pair[0], word2index).view(1, -1))
    v_p.append(prepare_word(pair[1], word2index).view(1, -1))
    
    try:
        cooc = X_ik[pair]
    except:
        cooc = 1

    co_p.append(torch.log(Variable(FloatTensor([cooc]))).view(1, -1))
    weight_p.append(Variable(FloatTensor([weighting_dic[pair]])).view(1, -1))
                                  
train_data = list(zip(u_p, v_p, co_p, weight_p))
del u_p
del v_p
del co_p
del weight_p
print(train_data[0]) # tuple (center vec i, context vec j log(x_ij), weight f(w_ij))


# ## Modeling 

# <img src="../images/03.glove-objective.png">
# <center>borrowed image from https://nlp.stanford.edu/pubs/glove.pdf</center>

# In[19]:


class GloVe(nn.Module):
    
    def __init__(self, vocab_size,projection_dim):
        super(GloVe,self).__init__()
        self.embedding_v = nn.Embedding(vocab_size, projection_dim) # center embedding
        self.embedding_u = nn.Embedding(vocab_size, projection_dim) # out embedding
        
        self.v_bias = nn.Embedding(vocab_size, 1)
        self.u_bias = nn.Embedding(vocab_size, 1)
        
        initrange = (2.0 / (vocab_size + projection_dim))**0.5 # Xavier init
        self.embedding_v.weight.data.uniform_(-initrange, initrange) # init
        self.embedding_u.weight.data.uniform_(-initrange, initrange) # init
        self.v_bias.weight.data.uniform_(-initrange, initrange) # init
        self.u_bias.weight.data.uniform_(-initrange, initrange) # init
        
    def forward(self, center_words, target_words, coocs, weights):
        center_embeds = self.embedding_v(center_words) # B x 1 x D
        target_embeds = self.embedding_u(target_words) # B x 1 x D
        
        center_bias = self.v_bias(center_words).squeeze(1)
        target_bias = self.u_bias(target_words).squeeze(1)
        
        inner_product = target_embeds.bmm(center_embeds.transpose(1, 2)).squeeze(2) # Bx1
        
        loss = weights*torch.pow(inner_product +center_bias + target_bias - coocs, 2)
        
        return torch.sum(loss)
    
    def prediction(self, inputs):
        v_embeds = self.embedding_v(inputs) # B x 1 x D
        u_embeds = self.embedding_u(inputs) # B x 1 x D
                
        return v_embeds+u_embeds # final embed


# ## Train 

# In[22]:


EMBEDDING_SIZE = 50
BATCH_SIZE = 256
EPOCH = 50


# In[23]:


losses = []
model = GloVe(len(word2index), EMBEDDING_SIZE)
if USE_CUDA:
    model = model.cuda()
optimizer = optim.Adam(model.parameters(), lr=0.001)


# In[24]:


for epoch in range(EPOCH):
    for i,batch in enumerate(getBatch(BATCH_SIZE, train_data)):
        
        inputs, targets, coocs, weights = zip(*batch)
        
        inputs = torch.cat(inputs) # B x 1
        targets = torch.cat(targets) # B x 1
        coocs = torch.cat(coocs)
        weights = torch.cat(weights)
        model.zero_grad()

        loss = model(inputs, targets, coocs, weights)
        
        loss.backward()
        optimizer.step()
    
        losses.append(loss.data.tolist()[0])
    if epoch % 10 == 0:
        print("Epoch : %d, mean_loss : %.02f" % (epoch, np.mean(losses)))
        losses = []


# ## Test 

# In[25]:


def word_similarity(target, vocab):
    if USE_CUDA:
        target_V = model.prediction(prepare_word(target, word2index))
    else:
        target_V = model.prediction(prepare_word(target, word2index))
    similarities = []
    for i in range(len(vocab)):
        if vocab[i] == target: 
            continue
        
        if USE_CUDA:
            vector = model.prediction(prepare_word(list(vocab)[i], word2index))
        else:
            vector = model.prediction(prepare_word(list(vocab)[i], word2index))
        
        cosine_sim = F.cosine_similarity(target_V, vector).data.tolist()[0] 
        similarities.append([vocab[i], cosine_sim])
    return sorted(similarities, key=lambda x: x[1], reverse=True)[:10]


# In[86]:


test = random.choice(list(vocab))
test


# In[87]:


word_similarity(test, vocab)


# ## TODO

# * Use <a href="https://docs.scipy.org/doc/scipy/reference/sparse.html">sparse-matrix</a> to build co-occurence matrix for memory efficiency

# ## Suggested Readings

# * <a href="http://ruder.io/word-embeddings-2017/?utm_campaign=Revue%20newsletter&utm_medium=Newsletter&utm_source=The%20Wild%20Week%20in%20AI">Word embeddings in 2017: Trends and future directions</a>