"""
KG Sparse embedding
"""
import os
import numpy as np

import torch as th
import torch.nn as nn
import torch.nn.functional as functional
import torch.nn.init as INIT

import torch.multiprocessing as mp
from torch.multiprocessing import Queue
from _thread import start_new_thread
import traceback
from functools import wraps

from .. import *

logsigmoid = functional.logsigmoid

def get_device(args):
    return th.device('cpu') if args.gpu[0] < 0 else th.device('cuda:' + str(args.gpu[0]))

norm = lambda x, p: x.norm(p=p)**p
get_scalar = lambda x: x.detach().item()
reshape = lambda arr, x, y: arr.view(x, y)
cuda = lambda arr, gpu: arr.cuda(gpu)

def thread_wrapped_func(func):
    """Wrapped func for torch.multiprocessing.Process.

    With this wrapper we can use OMP threads in subprocesses
    otherwise, OMP_NUM_THREADS=1 is mandatory.

    How to use:
    @thread_wrapped_func
    def func_to_wrap(args ...):
    """
    @wraps(func)
    def decorated_function(*args, **kwargs):
        queue = Queue()
        def _queue_result():
            exception, trace, res = None, None, None
            try:
                res = func(*args, **kwargs)
            except Exception as e:
                exception = e
                trace = traceback.format_exc()
            queue.put((res, exception, trace))

        start_new_thread(_queue_result, ())
        result, exception, trace = queue.get()
        if exception is None:
            return result
        else:
            assert isinstance(exception, Exception)
            raise exception.__class__(trace)
    return decorated_function

@thread_wrapped_func
def async_update(args, emb, queue):
    """Asynchronous embedding update for entity embeddings.
    How it works:
        1. trainer process push entity embedding update requests into the queue.
        2. async_update process pull requests from the queue, calculate 
           the gradient state and gradient and write it into entity embeddings.

    Parameters
    ----------
    args :
        Global confis.
    emb : ExternalEmbedding
        The entity embeddings.
    queue:
        The request queue.
    """
    th.set_num_threads(args.num_thread)
    while True:
        (grad_indices, grad_values, gpu_id) = queue.get()
        clr = emb.args.lr
        if grad_indices is None:
            return
        with th.no_grad():
            grad_sum = (grad_values * grad_values).mean(1)
            device = emb.state_sum.device
            if device != grad_indices.device:
                grad_indices = grad_indices.to(device)
            if device != grad_sum.device:
                grad_sum = grad_sum.to(device)

            emb.state_sum.index_add_(0, grad_indices, grad_sum)
            std = emb.state_sum[grad_indices]  # _sparse_mask
            if gpu_id >= 0:
                std = std.cuda(gpu_id)
            std_values = std.sqrt_().add_(1e-10).unsqueeze(1)
            tmp = (-clr * grad_values / std_values)
            if tmp.device != device:
                tmp = tmp.to(device)
            emb.emb.index_add_(0, grad_indices, tmp)

class ExternalEmbedding:
    """Sparse Embedding for Knowledge Graph
    It is used to store both entity embeddings and relation embeddings.

    Parameters
    ----------
    args :
        Global configs.
    num : int
        Number of embeddings.
    dim : int
        Embedding dimention size.
    device : th.device
        Device to store the embedding.
    """
    def __init__(self, args, num, dim, device):
        self.gpu = args.gpu
        self.args = args
        self.trace = []

        self.emb = th.empty(num, dim, dtype=th.float32, device=device)
        self.state_sum = self.emb.new().resize_(self.emb.size(0)).zero_()
        self.state_step = 0
        # queue used by asynchronous update
        self.async_q = None
        # asynchronous update process
        self.async_p = None

    def init(self, emb_init):
        """Initializing the embeddings.

        Parameters
        ----------
        emb_init : float
            The intial embedding range should be [-emb_init, emb_init].
        """
        INIT.uniform_(self.emb, -emb_init, emb_init)
        INIT.zeros_(self.state_sum)

    def share_memory(self):
        """Use torch.tensor.share_memory_() to allow cross process tensor access
        """
        self.emb.share_memory_()
        self.state_sum.share_memory_()

    def __call__(self, idx, gpu_id=-1, trace=True):
        """ Return sliced tensor.

        Parameters
        ----------
        idx : th.tensor
            Slicing index
        gpu_id : int
            Which gpu to put sliced data in.
        trace : bool
            If True, trace the computation. This is required in training.
            If False, do not trace the computation.
            Default: True
        """
        s = self.emb[idx]
        if gpu_id >= 0:
            s = s.cuda(gpu_id)
        # During the training, we need to trace the computation.
        # In this case, we need to record the computation path and compute the gradients.
        if trace:
            data = s.clone().detach().requires_grad_(True)
            self.trace.append((idx, data))
        else:
            data = s
        return data

    def update(self, gpu_id=-1):
        """ Update embeddings in a sparse manner
        Sparse embeddings are updated in mini batches. we maintains gradient states for 
        each embedding so they can be updated separately.

        Parameters
        ----------
        gpu_id : int
            Which gpu to accelerate the calculation. if -1 is provided, cpu is used.
        """
        self.state_step += 1
        with th.no_grad():
            for idx, data in self.trace:
                grad = data.grad.data

                clr = self.args.lr
                #clr = self.args.lr / (1 + (self.state_step - 1) * group['lr_decay'])

                # the update is non-linear so indices must be unique
                grad_indices = idx
                grad_values = grad
                if self.async_q is not None:
                    grad_indices.share_memory_()
                    grad_values.share_memory_()
                    self.async_q.put((grad_indices, grad_values, gpu_id))
                else:
                    grad_sum = (grad_values * grad_values).mean(1)
                    device = self.state_sum.device
                    if device != grad_indices.device:
                        grad_indices = grad_indices.to(device)
                    if device != grad_sum.device:
                        grad_sum = grad_sum.to(device)
                    self.state_sum.index_add_(0, grad_indices, grad_sum)
                    std = self.state_sum[grad_indices]  # _sparse_mask
                    if gpu_id >= 0:
                        std = std.cuda(gpu_id)
                    std_values = std.sqrt_().add_(1e-10).unsqueeze(1)
                    tmp = (-clr * grad_values / std_values)
                    if tmp.device != device:
                        tmp = tmp.to(device)
                    # TODO(zhengda) the overhead is here.
                    self.emb.index_add_(0, grad_indices, tmp)
        self.trace = []

    def create_async_update(self):
        """Set up the async update subprocess.
        """
        self.async_q = Queue(1)
        self.async_p = mp.Process(target=async_update, args=(self.args, self, self.async_q))
        self.async_p.start()

    def finish_async_update(self):
        """Notify the async update subprocess to quit.
        """
        self.async_q.put((None, None, None))
        self.async_p.join()

    def curr_emb(self):
        """Return embeddings in trace.
        """
        data = [data for _, data in self.trace]
        return th.cat(data, 0)

    def save(self, path, name):
        """Save embeddings.

        Parameters
        ----------
        path : str
            Directory to save the embedding.
        name : str
            Embedding name.
        """
        file_name = os.path.join(path, name+'.npy')
        np.save(file_name, self.emb.cpu().detach().numpy())

    def load(self, path, name):
        """Load embeddings.

        Parameters
        ----------
        path : str
            Directory to load the embedding.
        name : str
            Embedding name.
        """
        file_name = os.path.join(path, name+'.npy')
        self.emb = th.Tensor(np.load(file_name))
