"""References:

Szegedy, Christian, Wei Liu, Yangqing Jia, Pierre Sermanet, Scott Reed, Dragomir
Anguelov, Dumitru Erhan, Vincent Vanhoucke, and Andrew Rabinovich. "Going deeper
with convolutions." arXiv preprint arXiv:1409.4842 (2014).

"""

import mxnet as mx

def ConvFactory(data, num_filter, kernel, stride=(1,1), pad=(0, 0), name=None, suffix=''):
    conv = mx.symbol.Convolution(data=data, num_filter=num_filter, kernel=kernel, stride=stride, pad=pad, name='conv_%s%s' %(name, suffix))
    act = mx.symbol.Activation(data=conv, act_type='relu', name='relu_%s%s' %(name, suffix))
    return act

def InceptionFactory(data, num_1x1, num_3x3red, num_3x3, num_d5x5red, num_d5x5, pool, proj, name):
    # 1x1
    c1x1 = ConvFactory(data=data, num_filter=num_1x1, kernel=(1, 1), name=('%s_1x1' % name))
    # 3x3 reduce + 3x3
    c3x3r = ConvFactory(data=data, num_filter=num_3x3red, kernel=(1, 1), name=('%s_3x3' % name), suffix='_reduce')
    c3x3 = ConvFactory(data=c3x3r, num_filter=num_3x3, kernel=(3, 3), pad=(1, 1), name=('%s_3x3' % name))
    # double 3x3 reduce + double 3x3
    cd5x5r = ConvFactory(data=data, num_filter=num_d5x5red, kernel=(1, 1), name=('%s_5x5' % name), suffix='_reduce')
    cd5x5 = ConvFactory(data=cd5x5r, num_filter=num_d5x5, kernel=(5, 5), pad=(2, 2), name=('%s_5x5' % name))
    # pool + proj
    pooling = mx.symbol.Pooling(data=data, kernel=(3, 3), stride=(1, 1), pad=(1, 1), pool_type=pool, name=('%s_pool_%s_pool' % (pool, name)))
    cproj = ConvFactory(data=pooling, num_filter=proj, kernel=(1, 1), name=('%s_proj' %  name))
    # concat
    concat = mx.symbol.Concat(*[c1x1, c3x3, cd5x5, cproj], name='ch_concat_%s_chconcat' % name)
    return concat

def get_symbol(num_classes = 1000, **kwargs):
    data = mx.sym.Variable("data")
    conv1 = ConvFactory(data, 64, kernel=(7, 7), stride=(2,2), pad=(3, 3), name="conv1")
    pool1 = mx.sym.Pooling(conv1, kernel=(3, 3), stride=(2, 2), pool_type="max")
    conv2 = ConvFactory(pool1, 64, kernel=(1, 1), stride=(1,1), name="conv2")
    conv3 = ConvFactory(conv2, 192, kernel=(3, 3), stride=(1, 1), pad=(1,1), name="conv3")
    pool3 = mx.sym.Pooling(conv3, kernel=(3, 3), stride=(2, 2), pool_type="max")

    in3a = InceptionFactory(pool3, 64, 96, 128, 16, 32, "max", 32, name="in3a")
    in3b = InceptionFactory(in3a, 128, 128, 192, 32, 96, "max", 64, name="in3b")
    pool4 = mx.sym.Pooling(in3b, kernel=(3, 3), stride=(2, 2), pool_type="max")
    in4a = InceptionFactory(pool4, 192, 96, 208, 16, 48, "max", 64, name="in4a")
    in4b = InceptionFactory(in4a, 160, 112, 224, 24, 64, "max", 64, name="in4b")
    in4c = InceptionFactory(in4b, 128, 128, 256, 24, 64, "max", 64, name="in4c")
    in4d = InceptionFactory(in4c, 112, 144, 288, 32, 64, "max", 64, name="in4d")
    in4e = InceptionFactory(in4d, 256, 160, 320, 32, 128, "max", 128, name="in4e")
    pool5 = mx.sym.Pooling(in4e, kernel=(3, 3), stride=(2, 2), pool_type="max")
    in5a = InceptionFactory(pool5, 256, 160, 320, 32, 128, "max", 128, name="in5a")
    in5b = InceptionFactory(in5a, 384, 192, 384, 48, 128, "max", 128, name="in5b")
    pool6 = mx.sym.Pooling(in5b, kernel=(7, 7), stride=(1,1), pool_type="avg")
    flatten = mx.sym.Flatten(data=pool6)
    fc1 = mx.sym.FullyConnected(data=flatten, num_hidden=num_classes)
    softmax = mx.symbol.SoftmaxOutput(data=fc1, name='softmax')
    return softmax