# !pip install -r requirements.txt

# # 以下代码在colab下不会被注释
# #
# !pip install -q torchdata==0.3.0 torchtext==0.12 spacy==3.2 altair GPUtil
# !python -m spacy download de_core_news_sm
# !python -m spacy download en_core_web_sm

import os
from os.path import exists
import torch
import torch.nn as nn
from torch.nn.functional import log_softmax, pad
import math
import copy
import time
from torch.optim.lr_scheduler import LambdaLR
import pandas as pd
import altair as alt
from torchtext.data.functional import to_map_style_dataset
from torch.utils.data import DataLoader
from torchtext.vocab import build_vocab_from_iterator
import torchtext.datasets as datasets
import spacy
import GPUtil
import warnings
from torch.utils.data.distributed import DistributedSampler
import torch.distributed as dist
import torch.multiprocessing as mp
from torch.nn.parallel import DistributedDataParallel as DDP

# 设置为False以跳过测试示例 (例如用于调试)
warnings.filterwarnings("ignore")
RUN_EXAMPLES = True

# 这是一些全局的便捷辅助函数

def is_interactive_notebook():  # 是否为交互式笔记本
    return __name__ == "__main__"


def show_example(fn, args=[]):  # 显示示例
    if __name__ == "__main__" and RUN_EXAMPLES:
        return fn(*args)


def execute_example(fn, args=[]):  # 执行示例
    if __name__ == "__main__" and RUN_EXAMPLES:
        fn(*args)


class DummyOptimizer(torch.optim.Optimizer):  # 虚拟优化器
    def __init__(self):
        self.param_groups = [{"lr": 0}]
        None

    def step(self):
        None

    def zero_grad(self, set_to_none=False):
        None


class DummyScheduler:  # 虚拟调度器
    def step(self):
        None

class EncoderDecoder(nn.Module):
    """
    一个标准的编码器-解码器框架。作为Transformer及许多其他模型的基础。
    """

    def __init__(self, encoder, decoder, src_embed, tgt_embed, generator):
        super(EncoderDecoder, self).__init__()
        self.encoder = encoder # 编码器（尚未实现）
        self.decoder = decoder # 解码器（尚未实现）
        self.src_embed = src_embed # 源词嵌入层
        self.tgt_embed = tgt_embed # 目标词嵌入层
        self.generator = generator # 生成器（后面有解释）

    def forward(self, src, tgt, src_mask, tgt_mask):
        "输入并且处理带掩码的源序列与目标序列."
        return self.decode(self.encode(src, src_mask), src_mask, tgt, tgt_mask)

    def encode(self, src, src_mask):
        return self.encoder(self.src_embed(src), src_mask)

    def decode(self, memory, src_mask, tgt, tgt_mask):
        return self.decoder(self.tgt_embed(tgt), memory, src_mask, tgt_mask)

class Generator(nn.Module):
    "定义标准的线性层与softmax层（用于处理每一步最后的结果，将隐状态转换为最终的词的编号）"

    def __init__(self, d_model, vocab):
        super(Generator, self).__init__()
        self.proj = nn.Linear(d_model, vocab)

    def forward(self, x):
        return log_softmax(self.proj(x), dim=-1)

def clones(module, N):
    "创建 N 个相同的层"
    return nn.ModuleList([copy.deepcopy(module) for _ in range(N)])

class Encoder(nn.Module):
    "核心的编码器是由N层的神经网络堆叠而来"

    def __init__(self, layer, N):
        super(Encoder, self).__init__()
        self.layers = clones(layer, N)
        self.norm = LayerNorm(layer.size)

    def forward(self, x, mask):
        "逐层传递输入（和掩码）"
        for layer in self.layers:
            x = layer(x, mask)
        return self.norm(x)

class LayerNorm(nn.Module):
    "构建一个层归一化模块（详细信息请参见解释信息）。"

    def __init__(self, features, eps=1e-6):
        super(LayerNorm, self).__init__()
        self.a_2 = nn.Parameter(torch.ones(features))
        self.b_2 = nn.Parameter(torch.zeros(features))
        self.eps = eps

    def forward(self, x):
        mean = x.mean(-1, keepdim=True)
        std = x.std(-1, keepdim=True)
        return self.a_2 * (x - mean) / (std + self.eps) + self.b_2

class SublayerConnection(nn.Module): # 对应图中的 Add & Norm
    """
    一个残差连接，后面跟着一个层归一化。
    为了简化代码，我们先进行归一化，然后再进行残差连接。
    """

    def __init__(self, size, dropout):
        super(SublayerConnection, self).__init__()
        self.norm = LayerNorm(size)
        self.dropout = nn.Dropout(dropout)

    def forward(self, x, sublayer):
        "对于任何与输入数据相同词元大小的子层都应用残差连接。"
        return x + self.dropout(sublayer(self.norm(x)))

class EncoderLayer(nn.Module):
    "编码器由自注意力和前馈网络组成"

    def __init__(self, size, self_attn, feed_forward, dropout):
        super(EncoderLayer, self).__init__()
        self.self_attn = self_attn # 多头自注意力
        self.feed_forward = feed_forward # 前馈网络
        self.sublayer = clones(SublayerConnection(size, dropout), 2)
        self.size = size

    def forward(self, x, mask):
        "下面是图1（左）的连接方式"
        x = self.sublayer[0](x, lambda x: self.self_attn(x, x, x, mask))
        return self.sublayer[1](x, self.feed_forward)

class Decoder(nn.Module):
    "带掩码的N层解码器。"

    def __init__(self, layer, N):
        super(Decoder, self).__init__()
        self.layers = clones(layer, N)
        self.norm = LayerNorm(layer.size)

    def forward(self, x, memory, src_mask, tgt_mask):
        for layer in self.layers:
            x = layer(x, memory, src_mask, tgt_mask)
        return self.norm(x)

class DecoderLayer(nn.Module):
    "解码器由自注意力，源注意力（就是新引入的那一层，不是完全的自注意力）和前馈网络组成"

    def __init__(self, size, self_attn, src_attn, feed_forward, dropout):
        super(DecoderLayer, self).__init__()
        self.size = size
        self.self_attn = self_attn
        self.src_attn = src_attn
        self.feed_forward = feed_forward
        self.sublayer = clones(SublayerConnection(size, dropout), 3)

    def forward(self, x, memory, src_mask, tgt_mask):
        "下面是图1（右）的连接方式"
        m = memory
        x = self.sublayer[0](x, lambda x: self.self_attn(x, x, x, tgt_mask))
        x = self.sublayer[1](x, lambda x: self.src_attn(x, m, m, src_mask))
        return self.sublayer[2](x, self.feed_forward)

def subsequent_mask(size): # 生成一个上三角矩阵，对角线及其右上角元素为1，其余为0
    "用掩码遮挡掉后续位置"
    attn_shape = (1, size, size)
    subsequent_mask = torch.triu(torch.ones(attn_shape), diagonal=1).type(
        torch.uint8
    )
    return subsequent_mask == 0

def attention(query, key, value, mask=None, dropout=None):
    "计算 '缩放点积注意力'"
    d_k = query.size(-1)
    scores = torch.matmul(query, key.transpose(-2, -1)) / math.sqrt(d_k)
    if mask is not None:
        scores = scores.masked_fill(mask == 0, -1e9)
    p_attn = scores.softmax(dim=-1)
    if dropout is not None:
        p_attn = dropout(p_attn)
    return torch.matmul(p_attn, value), p_attn

class MultiHeadedAttention(nn.Module):
    def __init__(self, h, d_model, dropout=0.1):
        "输入模型大小和注意力头的数量"
        super(MultiHeadedAttention, self).__init__()
        assert d_model % h == 0
        # 我们假设 d_v 总是等于 d_k
        self.d_k = d_model // h
        self.h = h
        self.linears = clones(nn.Linear(d_model, d_model), 4) # 4个线性层 Q, K, V, O
        self.attn = None
        self.dropout = nn.Dropout(p=dropout)

    def forward(self, query, key, value, mask=None):
        "图2的实现"
        if mask is not None:
            # 所有的注意力头都使用相同的掩码
            mask = mask.unsqueeze(1)
        nbatches = query.size(0)

        # 1) 将所有(前三个)的线性层拆分进批处理中 d_model => h x d_k
        query, key, value = [
            lin(x).view(nbatches, -1, self.h, self.d_k).transpose(1, 2)
            for lin, x in zip(self.linears, (query, key, value))
        ]

        # 2) 在所有batch中的向量上应用注意力机制
        x, self.attn = attention(
            query, key, value, mask=mask, dropout=self.dropout
        )

        # 3) 使用view进行“拼接”，然后应用最终的线性层(第四个)
        x = (
            x.transpose(1, 2)
            .contiguous()
            .view(nbatches, -1, self.h * self.d_k)
        )
        del query
        del key
        del value
        return self.linears[-1](x)

class PositionwiseFeedForward(nn.Module):
    "前馈神经网络的实现."

    def __init__(self, d_model, d_ff, dropout=0.1):
        super(PositionwiseFeedForward, self).__init__()
        self.w_1 = nn.Linear(d_model, d_ff)
        self.w_2 = nn.Linear(d_ff, d_model)
        self.dropout = nn.Dropout(dropout)

    def forward(self, x):
        return self.w_2(self.dropout(self.w_1(x).relu()))

class Embeddings(nn.Module):
    def __init__(self, d_model, vocab):
        super(Embeddings, self).__init__()
        self.lut = nn.Embedding(vocab, d_model)
        self.d_model = d_model

    def forward(self, x):
        return self.lut(x) * math.sqrt(self.d_model)

class PositionalEncoding(nn.Module):
    "位置编码层的实现"

    def __init__(self, d_model, dropout, max_len=5000):
        super(PositionalEncoding, self).__init__()
        self.dropout = nn.Dropout(p=dropout)

        # 计算位置编码
        pe = torch.zeros(max_len, d_model)
        position = torch.arange(0, max_len).unsqueeze(1)
        div_term = torch.exp(
            torch.arange(0, d_model, 2) * -(math.log(10000.0) / d_model) # 换底公式
        )
        pe[:, 0::2] = torch.sin(position * div_term)
        pe[:, 1::2] = torch.cos(position * div_term)
        pe = pe.unsqueeze(0)
        self.register_buffer("pe", pe)

    def forward(self, x):
        x = x + self.pe[:, : x.size(1)].requires_grad_(False)
        return self.dropout(x)

def make_model(
        src_vocab, tgt_vocab, N=6, d_model=512, d_ff=2048, h=8, dropout=0.1
):
    "助手：根据超参数构造模型。"
    c = copy.deepcopy
    attn = MultiHeadedAttention(h, d_model)
    ff = PositionwiseFeedForward(d_model, d_ff, dropout)
    position = PositionalEncoding(d_model, dropout)
    model = EncoderDecoder(
        Encoder(EncoderLayer(d_model, c(attn), c(ff), dropout), N),
        Decoder(DecoderLayer(d_model, c(attn), c(attn), c(ff), dropout), N),
        nn.Sequential(Embeddings(d_model, src_vocab), c(position)),
        nn.Sequential(Embeddings(d_model, tgt_vocab), c(position)),
        Generator(d_model, tgt_vocab),
    )

    # 这是他们的代码中很重要的一部分。
    # 使用Glorot / fan_avg初始化参数。
    
    """
    nn.init.xavier_uniform_(p) 是一个函数调用，它使用 Xavier (又称为 Glorot) 初始化方法来填充参数 p 的值。Xavier 初始化是一种常用的权重初始化技巧，旨在保持网络各层间输入和输出的方差一致，从而有助于防止梯度消失或爆炸问题，促进神经网络在训练初期的稳定收敛。

    具体而言，Xavier 初始化根据权重矩阵的输入和输出维度计算一个合适的均匀分布范围，并从中随机采样值来填充权重矩阵。在 PyTorch 中，nn.init.xavier_uniform_() 版本使用的是均匀分布。"fan_avg" 指的是在计算分布范围时采用输入和输出维度的平均值（“均方根”Fan-in和Fan-out），这是 Xavier 初始化的默认行为。
    """
    
    for p in model.parameters():
        if p.dim() > 1:
            nn.init.xavier_uniform_(p)
    return model

class Batch:
    """用于在训练过程中生成带掩码的批数据的对象"""


    def __init__(self, src, tgt=None, pad=2):  # 2 = <blank>
        self.src = src
        self.src_mask = (src != pad).unsqueeze(-2)
        if tgt is not None:
            self.tgt = tgt[:, :-1]
            self.tgt_y = tgt[:, 1:]
            self.tgt_mask = self.make_std_mask(self.tgt, pad)
            self.ntokens = (self.tgt_y != pad).data.sum()

    @staticmethod
    def make_std_mask(tgt, pad):
        "构造一个掩码去挡住pad词元和尚未生成的词元。"
        tgt_mask = (tgt != pad).unsqueeze(-2)
        tgt_mask = tgt_mask & subsequent_mask(tgt.size(-1)).type_as(
            tgt_mask.data
        ) # 这里利用到了广播机制
        return tgt_mask

class TrainState:
    """记录计算过的步数，样例数和词元数"""

    step: int = 0  # 当前轮的步数
    accum_step: int = 0  # 优化器调整参数的次数
    samples: int = 0  # 处理过的样例数
    tokens: int = 0  # 处理过的词元数

def run_epoch(
        data_iter,
        model,
        loss_compute,
        optimizer,
        scheduler,
        mode="train",
        accum_iter=1,
        train_state=TrainState(),
):
    """训练单轮"""
    start = time.time()
    total_tokens = 0
    total_loss = 0
    tokens = 0
    n_accum = 0
    for i, batch in enumerate(data_iter):
        out = model.forward(
            batch.src, batch.tgt, batch.src_mask, batch.tgt_mask
        )
        loss, loss_node = loss_compute(out, batch.tgt_y, batch.ntokens)
        # loss_node = loss_node / accum_iter
        if mode == "train" or mode == "train+log":
            loss_node.backward()
            train_state.step += 1
            train_state.samples += batch.src.shape[0]
            train_state.tokens += batch.ntokens
            if i % accum_iter == 0:
                optimizer.step()
                optimizer.zero_grad(set_to_none=True)
                n_accum += 1
                train_state.accum_step += 1
            scheduler.step()

        total_loss += loss
        total_tokens += batch.ntokens
        tokens += batch.ntokens
        if i % 40 == 1 and (mode == "train" or mode == "train+log"):
            lr = optimizer.param_groups[0]["lr"]
            elapsed = time.time() - start
            print(
                (
                        "Epoch Step: %6d | Accumulation Step: %3d | Loss: %6.2f "
                        + "| Tokens / Sec: %7.1f | Learning Rate: %6.1e"
                )
                % (i, n_accum, loss / batch.ntokens, tokens / elapsed, lr)
            )
            start = time.time()
            tokens = 0
        del loss
        del loss_node
    return total_loss / total_tokens, train_state

def rate(step, model_size, factor, warmup):
    """
    为了避免零值被赋予负指数导致错误，我们必须在LambdaLR函数（本函数就是LambdaLR函数）中将step参数默认设置为1。
    """
    if step == 0:
        step = 1
    return factor * (
            model_size ** (-0.5) * min(step ** (-0.5), step * warmup ** (-1.5))
    )

class LabelSmoothing(nn.Module):
    "标签平滑的实现"

    def __init__(self, size, padding_idx, smoothing=0.0):
        super(LabelSmoothing, self).__init__()
        self.criterion = nn.KLDivLoss(reduction="sum")
        self.padding_idx = padding_idx
        self.confidence = 1.0 - smoothing
        self.smoothing = smoothing
        self.size = size
        self.true_dist = None

    def forward(self, x, target):
        assert x.size(1) == self.size
        true_dist = x.data.clone()
        true_dist.fill_(self.smoothing / (self.size - 1)) # 原文这里是 -2 ，但是译者无法理解其含义，所以将其改为 -1
        true_dist.scatter_(1, target.data.unsqueeze(1), self.confidence) # 将正确词元的概率设置为confidence，这一步其实是将 target序列转换为独热编码（这里是标签平滑）
        true_dist[:, self.padding_idx] = 0
        mask = torch.nonzero(target.data == self.padding_idx)
        if mask.dim() > 0:
            true_dist.index_fill_(0, mask.squeeze(), 0.0)
        self.true_dist = true_dist
        return self.criterion(x, true_dist.clone().detach()) # 计算损失

def data_gen(V, batch_size, nbatches):
    "生成一个随机的源-目标复述任务的数据集"
    for i in range(nbatches):
        data = torch.randint(1, V, size=(batch_size, 10))
        data[:, 0] = 1
        src = data.requires_grad_(False).clone().detach()
        tgt = data.requires_grad_(False).clone().detach()
        yield Batch(src, tgt, 0)

class SimpleLossCompute:
    "一个简单的损失计算和训练函数。"

    def __init__(self, generator, criterion):
        self.generator = generator
        self.criterion = criterion

    def __call__(self, x, y, norm):
        x = self.generator(x)
        sloss = (
                self.criterion(
                    x.contiguous().view(-1, x.size(-1)), y.contiguous().view(-1)
                )
                / norm
        )
        return sloss.data * norm, sloss

def greedy_decode(model, src, src_mask, max_len, start_symbol):
    memory = model.encode(src, src_mask)
    ys = torch.zeros(1, 1).fill_(start_symbol).type_as(src.data)
    for i in range(max_len - 1):
        out = model.decode(
            memory, src_mask, ys, subsequent_mask(ys.size(1)).type_as(src.data)
        )
        prob = model.generator(out[:, -1])
        _, next_word = torch.max(prob, dim=1)
        next_word = next_word.data[0]
        ys = torch.cat(
            [ys, torch.zeros(1, 1).type_as(src.data).fill_(next_word)], dim=1
        )
    return ys