# 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.
# ==============================================================================
"""Code transformation exceptions."""

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

import collections

from tensorflow.python.autograph.pyct import origin_info


class FrameInfo(
    collections.namedtuple(
        'FrameInfo',
        ('filename', 'lineno', 'function_name', 'code', 'converted'))):
  pass


def _stack_trace_inside_mapped_code(tb, source_map):
  """Summarizes inner traceback frames up to the call to a given function.

  This functions locates the innermost (i.e. most recent) frame that corresponds
  to code that can be mapped by source_map originated from, and returns a
  translated stack trace ending at that frame. If no such frame is found, the
  entire stack trace is summarized.

  For example, the following code:

    def f():
      for i in tf.range(1):
        z = y + i  # z only defined here

  Would generate this traceback:

    <converted code>
        ag__.for_stmt(...)
    <for_stmt>
        return _known_len_tf_for_stmt(iter_, extra_test, body, init_state)
    <_known_len_tf_for_stmt>
        _disallow_undefs_into_loop(*init_state)
    <_disallow_undefs_into_loop>
        raise ...

  Which is then processed into:

    <f>
        for i in tf.range(1):
    <for_stmt>
        return _known_len_tf_for_stmt(iter_, extra_test, body, init_state)
    <_known_len_tf_for_stmt>
        _disallow_undefs_into_loop(*init_state)
    <_disallow_undefs_into_loop>
        raise ...

  Args:
    tb: List[Tuple], the traceback corresponding to an error; typically,
      the output of traceback.extract_tb.
    source_map: Dict[LineLocation, OriginInfo], a source map as created by
      origin_info.create_source_map.

  Returns:
    List[FrameInfo]
  """
  result_frames = []
  for filename, line_number, function_name, text in reversed(tb):

    loc = origin_info.LineLocation(filename=filename, lineno=line_number)
    if loc in source_map:
      origin = source_map[loc]
      origin_frame_info = FrameInfo(
          filename=origin.loc.filename,
          lineno=origin.loc.lineno,
          function_name=origin.function_name,
          code=origin.source_code_line,
          converted=True)
      result_frames.append(origin_frame_info)
      break

    fi = FrameInfo(
        filename=filename,
        lineno=line_number,
        function_name=function_name,
        code=text,
        converted=False)
    result_frames.append(fi)

  return tuple(result_frames)


KNOWN_STRING_CONSTRUCTOR_ERRORS = (
    AssertionError,
    AttributeError,
    NameError,
    NotImplementedError,
    RuntimeError,
    StopIteration,
    TypeError,
    ValueError,
)


# KeyError escapes newlines in strings. We create a special subclass
# that doesn't do that. Overriding the name for display purposes; hopefully
# that won't create too many surprises.
class MultilineMessageKeyError(KeyError):

  def __init__(self, message, original_key):
    super(MultilineMessageKeyError, self).__init__(original_key)
    self.__message = message

  def __str__(self):
    return self.__message

MultilineMessageKeyError.__name__ = KeyError.__name__


class ErrorMetadataBase(object):
  """Container objects attached to exceptions in converted code.

  This metadata allows re-raising exceptions that occur in generated code, with
  a custom error message that includes a stack trace relative to user-readable
  code from which the generated code originated.
  """

  def __init__(self, callsite_tb, cause_metadata, cause_message, source_map):
    translated_stack = _stack_trace_inside_mapped_code(callsite_tb, source_map)

    if cause_metadata is None:
      self.translated_stack = translated_stack
      self.cause_message = cause_message
    else:
      # Daisy chain the translated stacks.
      self.translated_stack = (
          cause_metadata.translated_stack + (translated_stack[-1],))
      self.cause_message = cause_metadata.cause_message

  def get_message(self):
    """Returns the message for the underlying exception."""
    lines = []

    lines.append('in converted code:')
    lines.append('')

    for frame_info in reversed(self.translated_stack):
      lines.append('    {}:{} {}{}'.format(
          frame_info.filename,
          frame_info.lineno,
          frame_info.function_name,
          '  *' if frame_info.converted else '',
      ))
      if frame_info.code is None:
        code_snippet = '<source unavailable>'
      else:
        code_snippet = frame_info.code.strip()
      lines.append('        {}'.format(code_snippet))

    lines.append('')

    message_lines = self.cause_message.split('\n')
    for i in range(len(message_lines)):
      message_lines[i] = '    ' + message_lines[i]
    lines.extend(message_lines)

    lines.append('')

    return '\n'.join(lines)

  def create_exception(self, source_error):
    preferred_type = type(source_error)
    if preferred_type.__init__ is Exception.__init__:
      return preferred_type(self.get_message())
    if preferred_type in KNOWN_STRING_CONSTRUCTOR_ERRORS:
      return preferred_type(self.get_message())
    elif preferred_type is KeyError:
      return MultilineMessageKeyError(self.get_message(), self.cause_message)
    return None

  def to_exception(self, source_error):
    exc = self.create_exception(source_error)
    exc.__suppress_context__ = True
    exc.ag_error_metadata = self
    return exc
