from collections import defaultdict

from math import inf

from tensorflow.python.ops.losses.losses_impl import Reduction

from trainers import trainer_utils

from trainers.AEMODEL import AEMODEL, update_log_dicts, Phase, indicate_early_stopping

from trainers.DLMODEL import *

matplotlib.pyplot.ion()

class VAE(AEMODEL):

    class Config(AEMODEL.Config):

        def __init__(self):

            super().__init__('VAE')

    def __init__(self, sess, config, network=None):

        super().__init__(sess, config, network)

        self.x = tf.placeholder(tf.float32, [None, self.config.outputHeight, self.config.outputWidth, self.config.numChannels], name='x')

        self.outputs = self.network(self.x, dropout_rate=self.dropout_rate, dropout=self.dropout, config=self.config)

        self.reconstruction = self.outputs['x_hat']

        self.z_mu = self.outputs['z_mu']

        self.z_sigma = self.outputs['z_sigma']

        # Print Stats

        self.get_number_of_trainable_params()

        # Instantiate Saver

        self.saver = tf.train.Saver()

    def train(self, dataset):

        # Determine trainable variables

        self.variables = tf.get_collection(tf.GraphKeys.TRAINABLE_VARIABLES)

        # Build losses

        self.losses['L1'] = tf.losses.absolute_difference(self.x, self.reconstruction, reduction=Reduction.NONE)

        rec = tf.reduce_sum(self.losses['L1'], axis=[1, 2, 3])

        kl = 0.5 * tf.reduce_sum(tf.square(self.z_mu) + tf.square(self.z_sigma) - tf.log(tf.square(self.z_sigma)) - 1, axis=1)

        self.losses['reconstructionLoss'] = tf.reduce_mean(rec)

        self.losses['kl'] = tf.reduce_mean(kl)

        self.losses['loss'] = tf.reduce_mean(rec + kl)

        # Set the optimizer

        optim = self.create_optimizer(self.losses['loss'], var_list=self.variables, learningrate=self.config.learningrate,

                                      beta1=self.config.beta1, type=self.config.optimizer)

        # initialize all variables

        tf.global_variables_initializer().run(session=self.sess)

        best_cost = inf

        last_improvement = 0

        last_epoch = self.load_checkpoint()

        # Go go go!

        for epoch in range(last_epoch, self.config.numEpochs):

            ############

            # TRAINING #

            ############

            self.process(dataset, epoch, Phase.TRAIN, optim)

            # Increment last_epoch counter and save model

            last_epoch += 1

            self.save(self.checkpointDir, last_epoch)

            ##############

            # VALIDATION #

            ##############

            val_scalars = self.process(dataset, epoch, Phase.VAL)

            best_cost, last_improvement, stop = indicate_early_stopping(val_scalars['loss'], best_cost, last_improvement)

            if stop:

                print('Early stopping was triggered due to no improvement over the last 5 epochs')

                break

    def process(self, dataset, epoch, phase: Phase, optim=None):

        scalars = defaultdict(list)

        visuals = []

        num_batches = dataset.num_batches(self.config.batchsize, set=phase.value)

        for idx in range(0, num_batches):

            batch, _, _ = dataset.next_batch(self.config.batchsize, set=phase.value)

            fetches = {

                'reconstruction': self.reconstruction,

                **self.losses

            }

            if phase == Phase.TRAIN:

                fetches['optimizer'] = optim

            feed_dict = {

                self.x: batch,

                self.dropout: phase == Phase.TRAIN,

                self.dropout_rate: self.config.dropout_rate

            }

            run = self.sess.run(fetches, feed_dict=feed_dict)

            # Print to console

            print(f'Epoch ({phase.value}): [{epoch:2d}] [{idx:4d}/{num_batches:4d}] loss: {run["loss"]:.8f}')

            update_log_dicts(*trainer_utils.get_summary_dict(batch, run), scalars, visuals)

        self.log_to_tensorboard(epoch, scalars, visuals, phase)

        return scalars

    def reconstruct(self, x, dropout=False):

        if x.ndim < 4:

            x = np.expand_dims(x, 0)

        fetches = {

            'reconstruction': self.reconstruction

        }

        feed_dict = {

            self.x: x,

            self.dropout: dropout,  # apply only during MC sampling.

            self.dropout_rate: self.config.dropout_rate

        }

        results = self.sess.run(fetches, feed_dict=feed_dict)

        results['l1err'] = np.sum(np.abs(x - results['reconstruction']))

        results['l2err'] = np.sum(np.sqrt((x - results['reconstruction']) ** 2))

        return results