# Copyright 2017 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.
# ==============================================================================
"""The TensorBoard Scalars plugin.

See `http_api.md` in this directory for specifications of the routes for
this plugin.
"""

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import collections
import csv

import six
from six import StringIO
from werkzeug import wrappers

import numpy as np
import tensorflow as tf
from tensorboard import plugin_util
from tensorboard.backend import http_util
from tensorboard.plugins import base_plugin
from tensorboard.plugins.scalar import metadata


class OutputFormat(object):
  """An enum used to list the valid output formats for API calls."""
  JSON = 'json'
  CSV = 'csv'


class ScalarsPlugin(base_plugin.TBPlugin):
  """Scalars Plugin for TensorBoard."""

  plugin_name = metadata.PLUGIN_NAME

  def __init__(self, context):
    """Instantiates ScalarsPlugin via TensorBoard core.

    Args:
      context: A base_plugin.TBContext instance.
    """
    self._multiplexer = context.multiplexer
    self._db_connection_provider = context.db_connection_provider

  def get_plugin_apps(self):
    return {
        '/scalars': self.scalars_route,
        '/tags': self.tags_route,
    }

  def is_active(self):
    """The scalars plugin is active iff any run has at least one scalar tag."""
    if self._db_connection_provider:
      # The plugin is active if one relevant tag can be found in the database.
      db = self._db_connection_provider()
      cursor = db.execute('''
        SELECT
          1
        FROM Tags
        WHERE Tags.plugin_name = ?
        LIMIT 1
      ''', (metadata.PLUGIN_NAME,))
      return bool(list(cursor))

    if not self._multiplexer:
      return False

    return bool(self._multiplexer.PluginRunToTagToContent(metadata.PLUGIN_NAME))

  def index_impl(self):
    """Return {runName: {tagName: {displayName: ..., description: ...}}}."""
    if self._db_connection_provider:
      # Read tags from the database.
      db = self._db_connection_provider()
      cursor = db.execute('''
        SELECT
          Tags.tag_name,
          Tags.display_name,
          Runs.run_name
        FROM Tags
        JOIN Runs
          ON Tags.run_id = Runs.run_id
        WHERE
          Tags.plugin_name = ?
      ''', (metadata.PLUGIN_NAME,))
      result = collections.defaultdict(dict)
      for row in cursor:
        tag_name, display_name, run_name = row
        result[run_name][tag_name] = {
            'displayName': display_name,
            # TODO(chihuahua): Populate the description. Currently, the tags
            # table does not link with the description table.
            'description': '',
        }
      return result

    runs = self._multiplexer.Runs()
    result = {run: {} for run in runs}

    mapping = self._multiplexer.PluginRunToTagToContent(metadata.PLUGIN_NAME)
    for (run, tag_to_content) in six.iteritems(mapping):
      for (tag, content) in six.iteritems(tag_to_content):
        content = metadata.parse_plugin_metadata(content)
        summary_metadata = self._multiplexer.SummaryMetadata(run, tag)
        result[run][tag] = {'displayName': summary_metadata.display_name,
                            'description': plugin_util.markdown_to_safe_html(
                                summary_metadata.summary_description)}

    return result

  def scalars_impl(self, tag, run, output_format):
    """Result of the form `(body, mime_type)`."""
    if self._db_connection_provider:
      db = self._db_connection_provider()
      # We select for steps greater than -1 because the writer inserts
      # placeholder rows en masse. The check for step filters out those rows.
      cursor = db.execute('''
        SELECT
          Tensors.step,
          Tensors.computed_time,
          Tensors.data,
          Tensors.dtype
        FROM Tensors
        JOIN Tags
          ON Tensors.series = Tags.tag_id
        JOIN Runs
          ON Tags.run_id = Runs.run_id
        WHERE
          Runs.run_name = ?
          AND Tags.tag_name = ?
          AND Tags.plugin_name = ?
          AND Tensors.shape = ''
          AND Tensors.step > -1
        ORDER BY Tensors.step
      ''', (run, tag, metadata.PLUGIN_NAME))
      values = [(wall_time, step, self._get_value(data, dtype_enum))
                for (step, wall_time, data, dtype_enum) in cursor]
    else:
      tensor_events = self._multiplexer.Tensors(run, tag)
      values = [(tensor_event.wall_time,
                 tensor_event.step,
                 tf.make_ndarray(tensor_event.tensor_proto).item())
                for tensor_event in tensor_events]

    if output_format == OutputFormat.CSV:
      string_io = StringIO()
      writer = csv.writer(string_io)
      writer.writerow(['Wall time', 'Step', 'Value'])
      writer.writerows(values)
      return (string_io.getvalue(), 'text/csv')
    else:
      return (values, 'application/json')

  def _get_value(self, scalar_data_blob, dtype_enum):
    """Obtains value for scalar event given blob and dtype enum.

    Args:
      scalar_data_blob: The blob obtained from the database.
      dtype_enum: The enum representing the dtype.

    Returns:
      The scalar value.
    """
    tensorflow_dtype = tf.DType(dtype_enum)
    buf = np.frombuffer(scalar_data_blob, dtype=tensorflow_dtype.as_numpy_dtype)
    return np.asscalar(buf)

  @wrappers.Request.application
  def tags_route(self, request):
    index = self.index_impl()
    return http_util.Respond(request, index, 'application/json')

  @wrappers.Request.application
  def scalars_route(self, request):
    """Given a tag and single run, return array of ScalarEvents."""
    # TODO: return HTTP status code for malformed requests
    tag = request.args.get('tag')
    run = request.args.get('run')
    output_format = request.args.get('format')
    (body, mime_type) = self.scalars_impl(tag, run, output_format)
    return http_util.Respond(request, body, mime_type)
