# Copyright 2018 The TensorFlow Authors. All Rights Reserved.
#
# 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.
# ==============================================================================
r"""A script that builds boosted trees over higgs data.

If you haven't, please run data_download.py beforehand to prepare the data.

For some more details on this example, please refer to README.md as well.

Note that the model_dir is cleaned up before starting the training.

Usage:
$ python train_higgs.py --n_trees=100 --max_depth=6 --learning_rate=0.1 \
    --model_dir=/tmp/higgs_model

Note that BoostedTreesClassifier is available since Tensorflow 1.8.0.
So you need to install recent enough version of Tensorflow to use this example.

The training data is by default the first million examples out of 11M examples,
and eval data is by default the last million examples.
They are controlled by --train_start, --train_count, --eval_start, --eval_count.
e.g. to train over the first 10 million examples instead of 1 million:
$ python train_higgs.py --n_trees=100 --max_depth=6 --learning_rate=0.1 \
    --model_dir=/tmp/higgs_model --train_count=10000000

Training history and metrics can be inspected using tensorboard.
Set --logdir as the --model_dir set by flag when training
(or the default /tmp/higgs_model).
$ tensorboard --logdir=/tmp/higgs_model
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import os

from absl import app as absl_app
from absl import flags
import numpy as np
import tensorflow as tf

from official.r1.utils.logs import logger
from official.utils.flags import core as flags_core
from official.utils.flags._conventions import help_wrap

NPZ_FILE = "HIGGS.csv.gz.npz"  # numpy compressed file containing "data" array


def read_higgs_data(data_dir, train_start, train_count, eval_start, eval_count):
  """Reads higgs data from csv and returns train and eval data.

  Args:
    data_dir: A string, the directory of higgs dataset.
    train_start: An integer, the start index of train examples within the data.
    train_count: An integer, the number of train examples within the data.
    eval_start: An integer, the start index of eval examples within the data.
    eval_count: An integer, the number of eval examples within the data.

  Returns:
    Numpy array of train data and eval data.
  """
  npz_filename = os.path.join(data_dir, NPZ_FILE)
  try:
    # gfile allows numpy to read data from network data sources as well.
    with tf.gfile.Open(npz_filename, "rb") as npz_file:
      with np.load(npz_file) as npz:
        data = npz["data"]
  except tf.errors.NotFoundError as e:
    raise RuntimeError(
        "Error loading data; use data_download.py to prepare the data.\n{}: {}"
        .format(type(e).__name__, e))
  return (data[train_start:train_start+train_count],
          data[eval_start:eval_start+eval_count])


# This showcases how to make input_fn when the input data is available in the
# form of numpy arrays.
def make_inputs_from_np_arrays(features_np, label_np):
  """Makes and returns input_fn and feature_columns from numpy arrays.

  The generated input_fn will return tf.data.Dataset of feature dictionary and a
  label, and feature_columns will consist of the list of
  tf.feature_column.BucketizedColumn.

  Note, for in-memory training, tf.data.Dataset should contain the whole data
  as a single tensor. Don't use batch.

  Args:
    features_np: A numpy ndarray (shape=[batch_size, num_features]) for
        float32 features.
    label_np: A numpy ndarray (shape=[batch_size, 1]) for labels.

  Returns:
    input_fn: A function returning a Dataset of feature dict and label.
    feature_names: A list of feature names.
    feature_column: A list of tf.feature_column.BucketizedColumn.
  """
  num_features = features_np.shape[1]
  features_np_list = np.split(features_np, num_features, axis=1)
  # 1-based feature names.
  feature_names = ["feature_%02d" % (i + 1) for i in range(num_features)]

  # Create source feature_columns and bucketized_columns.
  def get_bucket_boundaries(feature):
    """Returns bucket boundaries for feature by percentiles."""
    return np.unique(np.percentile(feature, range(0, 100))).tolist()
  source_columns = [
      tf.feature_column.numeric_column(
          feature_name, dtype=tf.float32,
          # Although higgs data have no missing values, in general, default
          # could be set as 0 or some reasonable value for missing values.
          default_value=0.0)
      for feature_name in feature_names
  ]
  bucketized_columns = [
      tf.feature_column.bucketized_column(
          source_columns[i],
          boundaries=get_bucket_boundaries(features_np_list[i]))
      for i in range(num_features)
  ]

  # Make an input_fn that extracts source features.
  def input_fn():
    """Returns features as a dictionary of numpy arrays, and a label."""
    features = {
        feature_name: tf.constant(features_np_list[i])
        for i, feature_name in enumerate(feature_names)
    }
    return tf.data.Dataset.zip((tf.data.Dataset.from_tensors(features),
                                tf.data.Dataset.from_tensors(label_np),))

  return input_fn, feature_names, bucketized_columns


def make_eval_inputs_from_np_arrays(features_np, label_np):
  """Makes eval input as streaming batches."""
  num_features = features_np.shape[1]
  features_np_list = np.split(features_np, num_features, axis=1)
  # 1-based feature names.
  feature_names = ["feature_%02d" % (i + 1) for i in range(num_features)]

  def input_fn():
    features = {
        feature_name: tf.constant(features_np_list[i])
        for i, feature_name in enumerate(feature_names)
    }
    return tf.data.Dataset.zip((
        tf.data.Dataset.from_tensor_slices(features),
        tf.data.Dataset.from_tensor_slices(label_np),)).batch(1000)

  return input_fn


def _make_csv_serving_input_receiver_fn(column_names, column_defaults):
  """Returns serving_input_receiver_fn for csv.

  The input arguments are relevant to `tf.decode_csv()`.

  Args:
    column_names: a list of column names in the order within input csv.
    column_defaults: a list of default values with the same size of
        column_names. Each entity must be either a list of one scalar, or an
        empty list to denote the corresponding column is required.
        e.g. [[""], [2.5], []] indicates the third column is required while
            the first column must be string and the second must be float/double.

  Returns:
    a serving_input_receiver_fn that handles csv for serving.
  """
  def serving_input_receiver_fn():
    csv = tf.placeholder(dtype=tf.string, shape=[None], name="csv")
    features = dict(zip(column_names, tf.decode_csv(csv, column_defaults)))
    receiver_tensors = {"inputs": csv}
    return tf.estimator.export.ServingInputReceiver(features, receiver_tensors)

  return serving_input_receiver_fn


def train_boosted_trees(flags_obj):
  """Train boosted_trees estimator on HIGGS data.

  Args:
    flags_obj: An object containing parsed flag values.
  """
  # Clean up the model directory if present.
  if tf.gfile.Exists(flags_obj.model_dir):
    tf.gfile.DeleteRecursively(flags_obj.model_dir)
  tf.logging.info("## Data loading...")
  train_data, eval_data = read_higgs_data(
      flags_obj.data_dir, flags_obj.train_start, flags_obj.train_count,
      flags_obj.eval_start, flags_obj.eval_count)
  tf.logging.info("## Data loaded; train: {}{}, eval: {}{}".format(
      train_data.dtype, train_data.shape, eval_data.dtype, eval_data.shape))
  # Data consists of one label column followed by 28 feature columns.
  train_input_fn, feature_names, feature_columns = make_inputs_from_np_arrays(
      features_np=train_data[:, 1:], label_np=train_data[:, 0:1])
  eval_input_fn = make_eval_inputs_from_np_arrays(
      features_np=eval_data[:, 1:], label_np=eval_data[:, 0:1])
  tf.logging.info("## Features prepared. Training starts...")

  # Create benchmark logger to log info about the training and metric values
  run_params = {
      "train_start": flags_obj.train_start,
      "train_count": flags_obj.train_count,
      "eval_start": flags_obj.eval_start,
      "eval_count": flags_obj.eval_count,
      "n_trees": flags_obj.n_trees,
      "max_depth": flags_obj.max_depth,
  }
  benchmark_logger = logger.config_benchmark_logger(flags_obj)
  benchmark_logger.log_run_info(
      model_name="boosted_trees",
      dataset_name="higgs",
      run_params=run_params,
      test_id=flags_obj.benchmark_test_id)

  # Though BoostedTreesClassifier is under tf.estimator, faster in-memory
  # training is yet provided as a contrib library.
  from tensorflow.contrib import estimator as contrib_estimator  # pylint: disable=g-import-not-at-top
  classifier = contrib_estimator.boosted_trees_classifier_train_in_memory(
      train_input_fn,
      feature_columns,
      model_dir=flags_obj.model_dir or None,
      n_trees=flags_obj.n_trees,
      max_depth=flags_obj.max_depth,
      learning_rate=flags_obj.learning_rate)

  # Evaluation.
  eval_results = classifier.evaluate(eval_input_fn)
  # Benchmark the evaluation results
  benchmark_logger.log_evaluation_result(eval_results)

  # Exporting the savedmodel with csv parsing.
  if flags_obj.export_dir is not None:
    classifier.export_savedmodel(
        flags_obj.export_dir,
        _make_csv_serving_input_receiver_fn(
            column_names=feature_names,
            # columns are all floats.
            column_defaults=[[0.0]] * len(feature_names)),
        strip_default_attrs=True)


def main(_):
  train_boosted_trees(flags.FLAGS)


def define_train_higgs_flags():
  """Add tree related flags as well as training/eval configuration."""
  flags_core.define_base(clean=False, stop_threshold=False, batch_size=False,
                         num_gpu=False, export_dir=True)
  flags_core.define_benchmark()
  flags.adopt_module_key_flags(flags_core)

  flags.DEFINE_integer(
      name="train_start", default=0,
      help=help_wrap("Start index of train examples within the data."))
  flags.DEFINE_integer(
      name="train_count", default=1000000,
      help=help_wrap("Number of train examples within the data."))
  flags.DEFINE_integer(
      name="eval_start", default=10000000,
      help=help_wrap("Start index of eval examples within the data."))
  flags.DEFINE_integer(
      name="eval_count", default=1000000,
      help=help_wrap("Number of eval examples within the data."))

  flags.DEFINE_integer(
      "n_trees", default=100, help=help_wrap("Number of trees to build."))
  flags.DEFINE_integer(
      "max_depth", default=6, help=help_wrap("Maximum depths of each tree."))
  flags.DEFINE_float(
      "learning_rate", default=0.1,
      help=help_wrap("The learning rate."))

  flags_core.set_defaults(data_dir="/tmp/higgs_data",
                          model_dir="/tmp/higgs_model")


if __name__ == "__main__":
  # Training progress and eval results are shown as logging.INFO; so enables it.
  tf.logging.set_verbosity(tf.logging.INFO)
  define_train_higgs_flags()
  absl_app.run(main)
