#
# Copyright (c) 2017 Intel Corporation 
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

import numpy as np
from annoy import AnnoyIndex


class AnnoyDictionary(object):
    def __init__(self, dict_size, key_width, new_value_shift_coefficient=0.1, batch_size=100, key_error_threshold=0.01):
        self.max_size = dict_size
        self.curr_size = 0
        self.new_value_shift_coefficient = new_value_shift_coefficient

        self.index = AnnoyIndex(key_width, metric='euclidean')
        self.index.set_seed(1)

        self.embeddings = np.zeros((dict_size, key_width))
        self.values = np.zeros(dict_size)

        self.lru_timestamps = np.zeros(dict_size)
        self.current_timestamp = 0.0

        # keys that are in this distance will be considered as the same key
        self.key_error_threshold = key_error_threshold

        self.initial_update_size = batch_size
        self.min_update_size = self.initial_update_size
        self.key_dimension = key_width
        self.value_dimension = 1
        self._reset_buffer()

        self.built_capacity = 0

    def add(self, keys, values):
        # Adds new embeddings and values to the dictionary
        indices = []
        indices_to_remove = []
        for i in range(keys.shape[0]):
            index = self._lookup_key_index(keys[i])
            if index:
                # update existing value
                self.values[index] += self.new_value_shift_coefficient * (values[i] - self.values[index])
                self.lru_timestamps[index] = self.current_timestamp
                indices_to_remove.append(i)
            else:
                # add new
                if self.curr_size >= self.max_size:
                    # find the LRU entry
                    index = np.argmin(self.lru_timestamps)
                else:
                    index = self.curr_size
                    self.curr_size += 1
                self.lru_timestamps[index] = self.current_timestamp
                indices.append(index)

        for i in reversed(indices_to_remove):
            keys = np.delete(keys, i, 0)
            values = np.delete(values, i, 0)

        self.buffered_keys = np.vstack((self.buffered_keys, keys))
        self.buffered_values = np.vstack((self.buffered_values, values))
        self.buffered_indices = self.buffered_indices + indices

        if len(self.buffered_indices) >= self.min_update_size:
            self.min_update_size = max(self.initial_update_size, int(self.curr_size * 0.02))
            self._rebuild_index()

        self.current_timestamp += 1

    # Returns the stored embeddings and values of the closest embeddings
    def query(self, keys, k):
        _, indices = self._get_k_nearest_neighbors_indices(keys, k)

        embeddings = []
        values = []
        for ind in indices:
            self.lru_timestamps[ind] = self.current_timestamp
            embeddings.append(self.embeddings[ind])
            values.append(self.values[ind])

        self.current_timestamp += 1

        return embeddings, values

    def has_enough_entries(self, k):
        return self.curr_size > k and (self.built_capacity > k)

    def _get_k_nearest_neighbors_indices(self, keys, k):
        distances = []
        indices = []
        for key in keys:
            index, distance = self.index.get_nns_by_vector(key, k, include_distances=True)
            distances.append(distance)
            indices.append(index)
        return distances, indices

    def _rebuild_index(self):
        self.index.unbuild()
        self.embeddings[self.buffered_indices] = self.buffered_keys
        self.values[self.buffered_indices] = np.squeeze(self.buffered_values)
        for idx, key in zip(self.buffered_indices, self.buffered_keys):
            self.index.add_item(idx, key)

        self._reset_buffer()

        self.index.build(50)
        self.built_capacity = self.curr_size

    def _reset_buffer(self):
        self.buffered_keys = np.zeros((0, self.key_dimension))
        self.buffered_values = np.zeros((0, self.value_dimension))
        self.buffered_indices = []

    def _lookup_key_index(self, key):
        distance, index = self._get_k_nearest_neighbors_indices([key], 1)
        if distance != [[]] and distance[0][0] <= self.key_error_threshold:
            return index
        return None


class QDND:
    def __init__(self, dict_size, key_width, num_actions, new_value_shift_coefficient=0.1, key_error_threshold=0.01):
        self.num_actions = num_actions
        self.dicts = []

        # create a dict for each action
        for a in range(num_actions):
            new_dict = AnnoyDictionary(dict_size, key_width, new_value_shift_coefficient, key_error_threshold=key_error_threshold)
            self.dicts.append(new_dict)

    def add(self, embeddings, actions, values):
        # add a new set of embeddings and values to each of the underlining dictionaries
        embeddings = np.array(embeddings)
        actions = np.array(actions)
        values = np.array(values)
        for a in range(self.num_actions):
            idx = np.where(actions == a)
            curr_action_embeddings = embeddings[idx]
            curr_action_values = np.expand_dims(values[idx], -1)

            self.dicts[a].add(curr_action_embeddings, curr_action_values)
        return True

    def query(self, embeddings, actions, k):
        # query for nearest neighbors to the given embeddings
        dnd_embeddings = []
        dnd_values = []
        for i, action in enumerate(actions):
            embedding, value = self.dicts[action].query([embeddings[i]], k)
            dnd_embeddings.append(embedding[0])
            dnd_values.append(value[0])

        return dnd_embeddings, dnd_values

    def has_enough_entries(self, k):
        # check if each of the action dictionaries has at least k entries
        for a in range(self.num_actions):
            if not self.dicts[a].has_enough_entries(k):
                return False
        return True