# -*- coding: utf-8 -*- #
# Copyright 2016 Google Inc. 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.
"""Module for labels API support.

Typical usage (create command):

  # When defining arguments
  labels_util.AddCreateLabelsFlags(parser)
  # When running the command
  new_resource.labels = labels_util.ParseCreateArgs(args, labels_cls)
  Create(..., new_resource)

Typical usage (update command):

  # When defining arguments
  labels_util.AddUpdateLabelsFlags(parser)
  # When running the command
  labels_diff = labels_util.Diff.FromUpdateArgs(args)
  if labels_diff.MayHaveUpdates():
    orig_resource = Get(...)  # to prevent unnecessary Get calls
    new_resource.labels = labels_diff.Apply(
        labels_cls, orig_resource.labels).GetOrNone()
  Update(..., new_resource)
"""

from __future__ import absolute_import
from __future__ import division
from __future__ import unicode_literals

from googlecloudsdk.calliope import arg_parsers
from googlecloudsdk.calliope import base
from googlecloudsdk.calliope import exceptions as calliope_exceptions

import six


def _IsLower(c):
  """Returns True if c is lower case or a caseless ideograph."""
  return c.isalpha() and (c.islower() or not c.isupper())


def _IsValueOrSubsequent(c):
  """Returns True if c is a valid value or subsequent (not first) character."""
  return c in ('_', '-') or c.isdigit() or _IsLower(c)


def IsValidLabelValue(value):
  r"""Implements the PCRE r'[\p{Ll}\p{Lo}\p{N}_-]{0,63}'.

  Only hyphens (-), underscores (_), lowercase characters, and numbers are
  allowed. International characters are allowed.

  Args:
    value: The label value, a string.

  Returns:
    True is the value is valid; False if not.
  """
  if value is None or len(value) > 63:
    return False
  return all(_IsValueOrSubsequent(c) for c in value)


def IsValidLabelKey(key):
  r"""Implements the PCRE r'[\p{Ll}\p{Lo}][\p{Ll}\p{Lo}\p{N}_-]{0,62}'.

  The key must start with a lowercase character and must be a valid label value.

  Args:
    key: The label key, a string.

  Returns:
    True if the key is valid; False if not.
  """
  if not key or not _IsLower(key[0]):
    return False
  return IsValidLabelValue(key)


KEY_FORMAT_ERROR = (
    'Only hyphens (-), underscores (_), lowercase characters, and numbers are '
    'allowed. Keys must start with a lowercase character. International '
    'characters are allowed.')
KEY_FORMAT_HELP = (
    'Keys must start with a lowercase character and contain only hyphens '
    '(`-`), underscores (```_```), lowercase characters, and numbers.')

VALUE_FORMAT_ERROR = (
    'Only hyphens (-), underscores (_), lowercase characters, and numbers are '
    'allowed. International characters are allowed.')
VALUE_FORMAT_HELP = (
    'Values must contain only hyphens (`-`), underscores (```_```), lowercase '
    'characters, and numbers.')

KEY_FORMAT_VALIDATOR = arg_parsers.CustomFunctionValidator(
    IsValidLabelKey, KEY_FORMAT_ERROR)

VALUE_FORMAT_VALIDATOR = arg_parsers.CustomFunctionValidator(
    IsValidLabelValue, VALUE_FORMAT_ERROR)


def GetCreateLabelsFlag(extra_message='', labels_name='labels',
                        validate_values=True):
  """Makes the base.Argument for --labels flag."""
  value_type = VALUE_FORMAT_VALIDATOR if validate_values else None
  format_help = [KEY_FORMAT_HELP]
  if validate_values:
    format_help.append(VALUE_FORMAT_HELP)
  help_parts = ['List of label KEY=VALUE pairs to add.',
                ' '.join(format_help)]
  if extra_message:
    help_parts.append(extra_message)

  return base.Argument(
      '--{}'.format(labels_name),
      metavar='KEY=VALUE',
      type=arg_parsers.ArgDict(
          key_type=KEY_FORMAT_VALIDATOR, value_type=value_type),
      action=arg_parsers.UpdateAction,
      help=('\n\n'.join(help_parts)))


def GetClearLabelsFlag(labels_name='labels'):
  return base.Argument(
      '--clear-{}'.format(labels_name),
      action='store_true',
      # TODO(b/113682642): Update text to be compliant with the style guide.
      help="""\
          Removes all labels. If `--update-{labels}` is also specified then
          `--clear-{labels}` is applied first.

          For example, to remove all labels:

              $ {{command}} --clear-{labels}

          To set the labels to exactly "foo" and "baz":

              $ {{command}} --clear-{labels} --update-{labels} foo=bar,baz=qux
          """.format(labels=labels_name))


def GetUpdateLabelsFlag(extra_message, labels_name='labels',
                        validate_values=True):
  """Makes a base.Argument for the `--update-labels` flag."""
  value_type = VALUE_FORMAT_VALIDATOR if validate_values else None
  format_help = [KEY_FORMAT_HELP]
  if validate_values:
    format_help.append(VALUE_FORMAT_HELP)
  help_parts = [
      ('A list of label KEY=VALUE pairs to update. If a label exists its value '
       'is modified, otherwise a new label is created.'),
      ' '.join(format_help)]
  if extra_message:
    help_parts.append(extra_message)

  return base.Argument(
      '--update-{}'.format(labels_name),
      metavar='KEY=VALUE',
      type=arg_parsers.ArgDict(
          key_type=KEY_FORMAT_VALIDATOR, value_type=value_type),
      action=arg_parsers.UpdateAction,
      help='\n\n'.join(help_parts))


def GetRemoveLabelsFlag(extra_message, labels_name='labels'):
  return base.Argument(
      '--remove-{}'.format(labels_name),
      metavar='KEY',
      type=arg_parsers.ArgList(),
      action=arg_parsers.UpdateAction,
      help="""\
      A list of label keys to remove. If a label does not exist it is
      silently ignored.""" + extra_message)


def AddCreateLabelsFlags(parser):
  """Adds create command labels flags to an argparse parser.

  Args:
    parser: The argparse parser to add the flags to.
  """
  GetCreateLabelsFlag().AddToParser(parser)


def AddUpdateLabelsFlags(
    parser, extra_update_message='', extra_remove_message='',
    enable_clear=True):
  """Adds update command labels flags to an argparse parser.

  Args:
    parser: The argparse parser to add the flags to.
    extra_update_message: str, extra message to append to help text for
                          --update-labels flag.
    extra_remove_message: str, extra message to append to help text for
                          --delete-labels flag.
    enable_clear: bool, whether to include the --clear-labels flag.
  """
  GetUpdateLabelsFlag(extra_update_message).AddToParser(parser)
  if enable_clear:
    remove_group = parser.add_mutually_exclusive_group()
    GetClearLabelsFlag().AddToParser(remove_group)
    GetRemoveLabelsFlag(extra_remove_message).AddToParser(remove_group)
  else:
    GetRemoveLabelsFlag(extra_remove_message).AddToParser(parser)


def GetUpdateLabelsDictFromArgs(args):
  """Returns the update labels dict from the parsed args.

  Args:
    args: The parsed args.

  Returns:
    The update labels dict from the parsed args.
  """
  return args.labels if hasattr(args, 'labels') else args.update_labels


def GetRemoveLabelsListFromArgs(args):
  """Returns the remove labels list from the parsed args.

  Args:
    args: The parsed args.

  Returns:
    The remove labels list from the parsed args.
  """
  return args.remove_labels


def GetAndValidateOpsFromArgs(parsed_args):
  """Validates and returns labels specific args for update.

  At least one of --update-labels, --clear-labels or --remove-labels must be
  provided. The --clear-labels flag *must* be a declared argument, whether it
  was specified on the command line or not.

  Args:
    parsed_args: The parsed args.

  Returns:
    (update_labels, remove_labels)
    update_labels contains values from --labels and --update-labels flags
    respectively.
    remove_labels contains values from --remove-labels flag

  Raises:
    RequiredArgumentException: if all labels arguments are absent.
    AttributeError: if the --clear-labels flag is absent.
  """
  diff = Diff.FromUpdateArgs(parsed_args)
  if not diff.MayHaveUpdates():
    raise calliope_exceptions.RequiredArgumentException(
        'LABELS',
        'At least one of --update-labels, --remove-labels, or --clear-labels '
        'must be specified.')

  return diff


def _PackageLabels(labels_cls, labels):
  # Sorted for test stability
  return labels_cls(additionalProperties=[
      labels_cls.AdditionalProperty(key=key, value=value)
      for key, value in sorted(six.iteritems(labels))])


def _GetExistingLabelsDict(labels):
  if not labels:
    return {}
  return {l.key: l.value for l in labels.additionalProperties}


class UpdateResult(object):
  """Result type for Diff application.

  Attributes:
    needs_update: bool, whether the diff resulted in any changes to the existing
      labels proto.
    _labels: LabelsValue, the new populated LabelsValue object. If needs_update
      is False, this is identical to the original LabelValue object.
  """

  def __init__(self, needs_update, labels):
    self.needs_update = needs_update
    self._labels = labels

  @property
  def labels(self):
    """Returns the new labels.

    Raises:
      ValueError: if needs_update is False.
    """
    if not self.needs_update:
      raise ValueError(
          'If no update is needed (self.needs_update == False), '
          'checking labels is unnecessary.')
    return self._labels

  def GetOrNone(self):
    """Returns the new labels if an update is needed or None otherwise."""
    try:
      return self.labels
    except ValueError:
      return None


class Diff(object):
  """A change to the labels on a resource."""

  def __init__(self, additions=None, subtractions=None, clear=False):
    """Initialize a Diff.

    Only one of [subtractions, clear] may be specified.

    Args:
      additions: {str: str}, any label values to be updated
      subtractions: List[str], any labels to be removed
      clear: bool, whether to clear the labels

    Returns:
      Diff.

    Raises:
      ValueError: if both subtractions and clear are specified.
    """
    self._additions = additions or {}
    self._subtractions = subtractions or []
    self._clear = clear
    if self._subtractions and self._clear:
      raise ValueError('Only one of [subtractions, clear] may be specified.')

  def _RemoveLabels(self, existing_labels, new_labels):
    """Remove labels."""
    del existing_labels  # Unused in _RemoveLabels; needed by subclass
    new_labels = new_labels.copy()
    for key in self._subtractions:
      new_labels.pop(key, None)
    return new_labels

  def _ClearLabels(self, existing_labels):
    del existing_labels  # Unused in _ClearLabels; needed by subclass
    return {}

  def _AddLabels(self, new_labels):
    new_labels = new_labels.copy()
    new_labels.update(self._additions)
    return new_labels

  def Apply(self, labels_cls, labels=None):
    """Apply this Diff to the (possibly non-existing) labels.

    First, makes any additions. Then, removes any labels.

    Args:
      labels_cls: type, the LabelsValue class for the resource.
      labels: LabelsValue, the existing LabelsValue object for the original
        resource (or None, which is treated the same as empty labels)

    Returns:
      labels_cls, the instantiated LabelsValue message with the new set up
        labels, or None if there are no changes.
    """
    # Add pre-existing labels.
    existing_labels = _GetExistingLabelsDict(labels)
    new_labels = existing_labels.copy()

    if self._clear:
      new_labels = self._ClearLabels(existing_labels)

    if self._additions:
      new_labels = self._AddLabels(new_labels)

    if self._subtractions:
      new_labels = self._RemoveLabels(existing_labels, new_labels)

    needs_update = new_labels != existing_labels
    return UpdateResult(needs_update, _PackageLabels(labels_cls, new_labels))

  def MayHaveUpdates(self):
    """Returns true if this Diff is non-empty."""
    return any([self._additions, self._subtractions, self._clear])

  @classmethod
  def FromUpdateArgs(cls, args, enable_clear=True):
    """Initializes a Diff based on the arguments in AddUpdateLabelsFlags."""
    if enable_clear:
      clear = args.clear_labels
    else:
      clear = None
    return cls(args.update_labels, args.remove_labels, clear)


def ProcessUpdateArgsLazy(args, labels_cls, orig_labels_thunk):
  """Returns the result of applying the diff constructed from args.

  Lazily fetches the original labels value if needed.

  Args:
    args: argparse.Namespace, the parsed arguments with update_labels,
      remove_labels, and clear_labels
    labels_cls: type, the LabelsValue class for the new labels.
    orig_labels_thunk: callable, a thunk which will return the original labels
      object (of type LabelsValue) when evaluated.

  Returns:
    UpdateResult: the result of applying the diff.

  """
  diff = Diff.FromUpdateArgs(args)
  orig_labels = orig_labels_thunk() if diff.MayHaveUpdates() else None
  return diff.Apply(labels_cls, orig_labels)


def ParseCreateArgs(args, labels_cls, labels_dest='labels'):
  """Initializes labels based on args and the given class."""
  labels = getattr(args, labels_dest)
  if labels is None:
    return None
  return _PackageLabels(labels_cls, labels)


class ExplicitNullificationDiff(Diff):
  """A change to labels for resources where API requires explicit nullification.

  That is, to clear a label {'foo': 'bar'}, you must pass {'foo': None} to the
  API.
  """

  def _RemoveLabels(self, existing_labels, new_labels):
    """Remove labels."""
    new_labels = new_labels.copy()
    for key in self._subtractions:
      if key in existing_labels:
        new_labels[key] = None
      elif key in new_labels:
        del new_labels[key]
    return new_labels

  def _ClearLabels(self, existing_labels):
    return {key: None for key in existing_labels}
