145 lines
4.3 KiB
Python
145 lines
4.3 KiB
Python
# -*- coding: utf-8 -*-
|
|
#
|
|
# Copyright 2013 - Mirantis, Inc.
|
|
#
|
|
# 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 abc
|
|
import re
|
|
import yaql
|
|
import six
|
|
|
|
from mistral.openstack.common import log as logging
|
|
|
|
LOG = logging.getLogger(__name__)
|
|
|
|
|
|
class Evaluator(object):
|
|
"""Expression evaluator interface.
|
|
|
|
Having this interface gives the flexibility to change the actual expression
|
|
language used in Mistral DSL for conditions, output calculation etc.
|
|
"""
|
|
|
|
@classmethod
|
|
@abc.abstractmethod
|
|
def evaluate(cls, expression, context):
|
|
"""Evaluates the expression against the given data context.
|
|
|
|
:param expression: Expression string
|
|
:param context: Data context
|
|
:return: Expression result
|
|
"""
|
|
pass
|
|
|
|
@classmethod
|
|
@abc.abstractmethod
|
|
def is_expression(cls, expression):
|
|
"""
|
|
Check expression string and decide whether it is expression or not.
|
|
|
|
:param expression: Expression string
|
|
:return: True if string is expression
|
|
"""
|
|
pass
|
|
|
|
|
|
class YAQLEvaluator(Evaluator):
|
|
@classmethod
|
|
def evaluate(cls, expression, context):
|
|
LOG.debug("Evaluating YAQL expression [expression='%s', context=%s]"
|
|
% (expression, context))
|
|
|
|
return yaql.parse(expression).evaluate(context)
|
|
|
|
@classmethod
|
|
def is_expression(cls, s):
|
|
# TODO(rakhmerov): It should be generalized since it may not be YAQL.
|
|
return s and s.startswith('$')
|
|
|
|
|
|
class InlineYAQLEvaluator(YAQLEvaluator):
|
|
# Put YAQL-specific regexp pattern here.
|
|
# Use form {$.any_symbols_except'}'} to find an expression.
|
|
find_expression_pattern = re.compile("\{\$\.*[^\}]*\}")
|
|
|
|
@classmethod
|
|
def evaluate(cls, expression, context):
|
|
if super(InlineYAQLEvaluator, cls).is_expression(expression):
|
|
return super(InlineYAQLEvaluator,
|
|
cls).evaluate(expression, context)
|
|
|
|
result = expression
|
|
found_expressions = cls.find_inline_expressions(expression)
|
|
|
|
if found_expressions:
|
|
for expr in found_expressions:
|
|
trim_expr = expr.strip("{}")
|
|
evaluated = super(InlineYAQLEvaluator,
|
|
cls).evaluate(trim_expr, context)
|
|
|
|
replacement = str(evaluated) if evaluated else expr
|
|
result = result.replace(expr, replacement)
|
|
|
|
return result
|
|
|
|
@classmethod
|
|
def is_expression(cls, s):
|
|
return s
|
|
|
|
@classmethod
|
|
def find_inline_expressions(cls, s):
|
|
return cls.find_expression_pattern.findall(s)
|
|
|
|
|
|
# TODO(rakhmerov): Make it configurable.
|
|
_EVALUATOR = InlineYAQLEvaluator
|
|
|
|
|
|
def evaluate(expression, context):
|
|
# Check if the passed value is expression so we don't need to do this
|
|
# every time on a caller side.
|
|
if not isinstance(expression, six.string_types) or \
|
|
not _EVALUATOR.is_expression(expression):
|
|
return expression
|
|
|
|
return _EVALUATOR.evaluate(expression, context)
|
|
|
|
|
|
def _evaluate_item(item, context):
|
|
if isinstance(item, six.string_types):
|
|
try:
|
|
return evaluate(item, context)
|
|
except AttributeError as e:
|
|
LOG.debug("Expression %s is not evaluated, [context=%s]: %s"
|
|
% (item, context, e))
|
|
return item
|
|
else:
|
|
return evaluate_recursively(item, context)
|
|
|
|
|
|
def evaluate_recursively(data, context):
|
|
if not context:
|
|
return data
|
|
|
|
if isinstance(data, dict):
|
|
for key in data:
|
|
data[key] = _evaluate_item(data[key], context)
|
|
elif isinstance(data, list):
|
|
for index, item in enumerate(data):
|
|
data[index] = _evaluate_item(item, context)
|
|
elif isinstance(data, six.string_types):
|
|
return _evaluate_item(data, context)
|
|
|
|
return data
|