# --------------------------------------------------------
# Tensorflow Faster R-CNN
# Licensed under The MIT License [see LICENSE for details]
# Written by Zheqi He and Xinlei Chen
# --------------------------------------------------------
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import tensorflow as tf
import tensorflow.contrib.slim as slim
from tensorflow.contrib.slim import losses
from tensorflow.contrib.slim import arg_scope
from tensorflow.contrib.slim.python.slim.nets import resnet_utils
from tensorflow.contrib.slim.python.slim.nets import resnet_v1
from tensorflow.contrib.slim.python.slim.nets.resnet_v1 import resnet_v1_block
import numpy as np

from ..nets.network import Network
from ..model.config import cfg

def resnet_arg_scope(is_training=True,
                     batch_norm_decay=0.997,
                     batch_norm_epsilon=1e-5,
                     batch_norm_scale=True):
  batch_norm_params = {
    'is_training': False,
    'decay': batch_norm_decay,
    'epsilon': batch_norm_epsilon,
    'scale': batch_norm_scale,
    'trainable': False,
    'updates_collections': tf.GraphKeys.UPDATE_OPS
  }

  with arg_scope(
      [slim.conv2d],
      weights_regularizer=slim.l2_regularizer(cfg.TRAIN.WEIGHT_DECAY),
      weights_initializer=slim.variance_scaling_initializer(),
      trainable=is_training,
      activation_fn=tf.nn.relu,
      normalizer_fn=slim.batch_norm,
      normalizer_params=batch_norm_params):
    with arg_scope([slim.batch_norm], **batch_norm_params) as arg_sc:
      return arg_sc

class resnetv1(Network):
  def __init__(self, num_layers=50):
    Network.__init__(self)
    self._feat_stride = [16, ]
    self._feat_compress = [1. / float(self._feat_stride[0]), ]
    self._num_layers = num_layers
    self._scope = 'resnet_v1_%d' % num_layers
    self._decide_blocks()

  def _crop_pool_layer(self, bottom, rois, name):
    with tf.variable_scope(name) as scope:
      batch_ids = tf.squeeze(tf.slice(rois, [0, 0], [-1, 1], name="batch_id"), [1])
      # Get the normalized coordinates of bboxes
      bottom_shape = tf.shape(bottom)
      height = (tf.to_float(bottom_shape[1]) - 1.) * np.float32(self._feat_stride[0])
      width = (tf.to_float(bottom_shape[2]) - 1.) * np.float32(self._feat_stride[0])
      x1 = tf.slice(rois, [0, 1], [-1, 1], name="x1") / width
      y1 = tf.slice(rois, [0, 2], [-1, 1], name="y1") / height
      x2 = tf.slice(rois, [0, 3], [-1, 1], name="x2") / width
      y2 = tf.slice(rois, [0, 4], [-1, 1], name="y2") / height
      # Won't be back-propagated to rois anyway, but to save time
      bboxes = tf.stop_gradient(tf.concat([y1, x1, y2, x2], 1))
      if cfg.RESNET.MAX_POOL:
        pre_pool_size = cfg.POOLING_SIZE * 2
        crops = tf.image.crop_and_resize(bottom, bboxes, tf.to_int32(batch_ids), [pre_pool_size, pre_pool_size],
                                         name="crops")
        crops = slim.max_pool2d(crops, [2, 2], padding='SAME')
      else:
        crops = tf.image.crop_and_resize(bottom, bboxes, tf.to_int32(batch_ids), [cfg.POOLING_SIZE, cfg.POOLING_SIZE],
                                         name="crops")
    return crops

  # Do the first few layers manually, because 'SAME' padding can behave inconsistently
  # for images of different sizes: sometimes 0, sometimes 1
  def _build_base(self):
    with tf.variable_scope(self._scope, self._scope):
      net = resnet_utils.conv2d_same(self._image, 64, 7, stride=2, scope='conv1')
      net = tf.pad(net, [[0, 0], [1, 1], [1, 1], [0, 0]])
      net = slim.max_pool2d(net, [3, 3], stride=2, padding='VALID', scope='pool1')

    return net

  def _image_to_head(self, is_training, reuse=None):
    assert (0 <= cfg.RESNET.FIXED_BLOCKS <= 3)
    # Now the base is always fixed during training
    with slim.arg_scope(resnet_arg_scope(is_training=False)):
      net_conv = self._build_base()
    if cfg.RESNET.FIXED_BLOCKS > 0:
      with slim.arg_scope(resnet_arg_scope(is_training=False)):
        net_conv, _ = resnet_v1.resnet_v1(net_conv,
                                           self._blocks[0:cfg.RESNET.FIXED_BLOCKS],
                                           global_pool=False,
                                           include_root_block=False,
                                           reuse=reuse,
                                           scope=self._scope)
    if cfg.RESNET.FIXED_BLOCKS < 3:
      with slim.arg_scope(resnet_arg_scope(is_training=is_training)):
        net_conv, _ = resnet_v1.resnet_v1(net_conv,
                                           self._blocks[cfg.RESNET.FIXED_BLOCKS:-1],
                                           global_pool=False,
                                           include_root_block=False,
                                           reuse=reuse,
                                           scope=self._scope)

    self._act_summaries.append(net_conv)
    self._layers['head'] = net_conv

    return net_conv

  def _head_to_tail(self, pool5, is_training, reuse=None):
    with slim.arg_scope(resnet_arg_scope(is_training=is_training)):
      fc7, _ = resnet_v1.resnet_v1(pool5,
                                   self._blocks[-1:],
                                   global_pool=False,
                                   include_root_block=False,
                                   reuse=reuse,
                                   scope=self._scope)
      # average pooling done by reduce_mean
      fc7 = tf.reduce_mean(fc7, axis=[1, 2])
    return fc7

  def _decide_blocks(self):
    # choose different blocks for different number of layers
    if self._num_layers == 50:
      self._blocks = [resnet_v1_block('block1', base_depth=64, num_units=3, stride=2),
                      resnet_v1_block('block2', base_depth=128, num_units=4, stride=2),
                      # use stride 1 for the last conv4 layer
                      resnet_v1_block('block3', base_depth=256, num_units=6, stride=1),
                      resnet_v1_block('block4', base_depth=512, num_units=3, stride=1)]

    elif self._num_layers == 101:
      self._blocks = [resnet_v1_block('block1', base_depth=64, num_units=3, stride=2),
                      resnet_v1_block('block2', base_depth=128, num_units=4, stride=2),
                      # use stride 1 for the last conv4 layer
                      resnet_v1_block('block3', base_depth=256, num_units=23, stride=1),
                      resnet_v1_block('block4', base_depth=512, num_units=3, stride=1)]

    elif self._num_layers == 152:
      self._blocks = [resnet_v1_block('block1', base_depth=64, num_units=3, stride=2),
                      resnet_v1_block('block2', base_depth=128, num_units=8, stride=2),
                      # use stride 1 for the last conv4 layer
                      resnet_v1_block('block3', base_depth=256, num_units=36, stride=1),
                      resnet_v1_block('block4', base_depth=512, num_units=3, stride=1)]

    else:
      # other numbers are not supported
      raise NotImplementedError

  def get_variables_to_restore(self, variables, var_keep_dic):
    variables_to_restore = []

    for v in variables:
      # exclude the first conv layer to swap RGB to BGR
      if v.name == (self._scope + '/conv1/weights:0'):
        self._variables_to_fix[v.name] = v
        continue
      if v.name.split(':')[0] in var_keep_dic:
        print('Variables restored: %s' % v.name)
        variables_to_restore.append(v)

    return variables_to_restore

  def fix_variables(self, sess, pretrained_model):
    print('Fix Resnet V1 layers..')
    with tf.variable_scope('Fix_Resnet_V1') as scope:
      with tf.device("/cpu:0"):
        # fix RGB to BGR
        conv1_rgb = tf.get_variable("conv1_rgb", [7, 7, 3, 64], trainable=False)
        restorer_fc = tf.train.Saver({self._scope + "/conv1/weights": conv1_rgb})
        restorer_fc.restore(sess, pretrained_model)

        sess.run(tf.assign(self._variables_to_fix[self._scope + '/conv1/weights:0'], 
                           tf.reverse(conv1_rgb, [2])))
