# Copyright (c) 2016, GohighSec
# 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.

import ast
import re
import six

import pep8


"""
Guidelines for writing new hacking checks

 - Use only for Barbican specific tests. OpenStack general tests
   should be submitted to the common 'hacking' module.
 - Pick numbers in the range B3xx. Find the current test with
   the highest allocated number and then pick the next value.
 - Keep the test method code in the source file ordered based
   on the B3xx value.
 - List the new rule in the top level HACKING.rst file
 - Add test cases for each new rule to barbican/tests/test_hacking.py

"""

oslo_namespace_imports = re.compile(r"from[\s]*oslo[.](.*)")
dict_constructor_with_list_copy_re = re.compile(r".*\bdict\((\[)?(\(|\[)")
assert_no_xrange_re = re.compile(r"\s*xrange\s*\(")
assert_True = re.compile(r".*assertEqual\(True, .*\)")
assert_None = re.compile(r".*assertEqual\(None, .*\)")
assert_Not_Equal = re.compile(r".*assertNotEqual\(None, .*\)")
assert_Is_Not = re.compile(r".*assertIsNot\(None, .*\)")
no_log_warn = re.compile(r".*LOG.warn\(.*\)")


class BaseASTChecker(ast.NodeVisitor):
    """Provides a simple framework for writing AST-based checks.

    Subclasses should implement visit_* methods like any other AST visitor
    implementation. When they detect an error for a particular node the
    method should call ``self.add_error(offending_node)``. Details about
    where in the code the error occurred will be pulled from the node
    object.

    Subclasses should also provide a class variable named CHECK_DESC to
    be used for the human readable error message.

    """

    CHECK_DESC = 'No check message specified'

    def __init__(self, tree, filename):
        """This object is created automatically by pep8.

        :param tree: an AST tree
        :param filename: name of the file being analyzed
                         (ignored by our checks)
        """
        self._tree = tree
        self._errors = []

    def run(self):
        """Called automatically by pep8."""
        self.visit(self._tree)
        return self._errors

    def add_error(self, node, message=None):
        """Add an error caused by a node to the list of errors for pep8."""
        message = message or self.CHECK_DESC
        error = (node.lineno, node.col_offset, message, self.__class__)
        self._errors.append(error)

    def _check_call_names(self, call_node, names):
        if isinstance(call_node, ast.Call):
            if isinstance(call_node.func, ast.Name):
                if call_node.func.id in names:
                    return True
        return False


class CheckLoggingFormatArgs(BaseASTChecker):
    """Check for improper use of logging format arguments.

    LOG.debug("Volume %s caught fire and is at %d degrees C and climbing.",
              ('volume1', 500))

    The format arguments should not be a tuple as it is easy to miss.

    """

    CHECK_DESC = 'B310 Log method arguments should not be a tuple.'
    LOG_METHODS = [
        'debug', 'info',
        'warn', 'warning',
        'error', 'exception',
        'critical', 'fatal',
        'trace', 'log'
    ]

    def _find_name(self, node):
        """Return the fully qualified name or a Name or Attribute."""
        if isinstance(node, ast.Name):
            return node.id
        elif (isinstance(node, ast.Attribute)
                and isinstance(node.value, (ast.Name, ast.Attribute))):
            method_name = node.attr
            obj_name = self._find_name(node.value)
            if obj_name is None:
                return None
            return obj_name + '.' + method_name
        elif isinstance(node, six.string_types):
            return node
        else:  # could be Subscript, Call or many more
            return None

    def visit_Call(self, node):
        """Look for the 'LOG.*' calls."""
        # extract the obj_name and method_name
        if isinstance(node.func, ast.Attribute):
            obj_name = self._find_name(node.func.value)
            if isinstance(node.func.value, ast.Name):
                method_name = node.func.attr
            elif isinstance(node.func.value, ast.Attribute):
                obj_name = self._find_name(node.func.value)
                method_name = node.func.attr
            else:  # could be Subscript, Call or many more
                return super(CheckLoggingFormatArgs, self).generic_visit(node)

            # obj must be a logger instance and method must be a log helper
            if (obj_name != 'LOG'
                    or method_name not in self.LOG_METHODS):
                return super(CheckLoggingFormatArgs, self).generic_visit(node)

            # the call must have arguments
            if not len(node.args):
                return super(CheckLoggingFormatArgs, self).generic_visit(node)

            # any argument should not be a tuple
            for arg in node.args:
                if isinstance(arg, ast.Tuple):
                    self.add_error(arg)

        return super(CheckLoggingFormatArgs, self).generic_visit(node)


class CheckForStrUnicodeExc(BaseASTChecker):
    """Checks for the use of str() or unicode() on an exception.

    This currently only handles the case where str() or unicode()
    is used in the scope of an exception handler.  If the exception
    is passed into a function, returned from an assertRaises, or
    used on an exception created in the same scope, this does not
    catch it.
    """

    CHECK_DESC = ('B314 str() and unicode() cannot be used on an '
                  'exception.  Remove or use six.text_type()')

    def __init__(self, tree, filename):
        super(CheckForStrUnicodeExc, self).__init__(tree, filename)
        self.name = []
        self.already_checked = []

    # Python 2
    def visit_TryExcept(self, node):
        for handler in node.handlers:
            if handler.name:
                self.name.append(handler.name.id)
                super(CheckForStrUnicodeExc, self).generic_visit(node)
                self.name = self.name[:-1]
            else:
                super(CheckForStrUnicodeExc, self).generic_visit(node)

    # Python 3
    def visit_ExceptHandler(self, node):
        if node.name:
            self.name.append(node.name)
            super(CheckForStrUnicodeExc, self).generic_visit(node)
            self.name = self.name[:-1]
        else:
            super(CheckForStrUnicodeExc, self).generic_visit(node)

    def visit_Call(self, node):
        if self._check_call_names(node, ['str', 'unicode']):
            if node not in self.already_checked:
                self.already_checked.append(node)
                if isinstance(node.args[0], ast.Name):
                    if node.args[0].id in self.name:
                        self.add_error(node.args[0])
        super(CheckForStrUnicodeExc, self).generic_visit(node)


def check_oslo_namespace_imports(logical_line, physical_line, filename):
    """'oslo_' should be used instead of 'oslo.'

    B317
    """
    if pep8.noqa(physical_line):
        return
    if re.match(oslo_namespace_imports, logical_line):
        msg = ("B317: '%s' must be used instead of '%s'.") % (
            logical_line.replace('oslo.', 'oslo_'),
            logical_line)
        yield(0, msg)


def dict_constructor_with_list_copy(logical_line):
    """Use a dict comprehension instead of a dict constructor

    B318
    """
    msg = ("B318: Must use a dict comprehension instead of a dict constructor"
           " with a sequence of key-value pairs."
           )
    if dict_constructor_with_list_copy_re.match(logical_line):
        yield (0, msg)


def no_xrange(logical_line):
    """Do not use 'xrange'

    B319
    """
    if assert_no_xrange_re.match(logical_line):
        yield(0, "B319: Do not use xrange().")


def validate_assertTrue(logical_line):
    """Use 'assertTrue' instead of 'assertEqual'

    B312
    """
    if re.match(assert_True, logical_line):
        msg = ("B312: Unit tests should use assertTrue(value) instead"
               " of using assertEqual(True, value).")
        yield(0, msg)


def validate_assertIsNone(logical_line):
    """Use 'assertIsNone' instead of 'assertEqual'

    B311
    """
    if re.match(assert_None, logical_line):
        msg = ("B311: Unit tests should use assertIsNone(value) instead"
               " of using assertEqual(None, value).")
        yield(0, msg)


def no_log_warn_check(logical_line):
    """Disallow 'LOG.warn'

    B320
    """
    msg = ("B320: LOG.warn is deprecated, please use LOG.warning!")
    if re.match(no_log_warn, logical_line):
        yield(0, msg)


def validate_assertIsNotNone(logical_line):
    """Use 'assertIsNotNone'

    B321
    """
    if re.match(assert_Not_Equal, logical_line) or \
       re.match(assert_Is_Not, logical_line):
        msg = ("B321: Unit tests should use assertIsNotNone(value) instead"
               " of using assertNotEqual(None, value) or"
               " assertIsNot(None, value).")
        yield(0, msg)


def factory(register):
    register(CheckForStrUnicodeExc)
    register(CheckLoggingFormatArgs)
    register(check_oslo_namespace_imports)
    register(dict_constructor_with_list_copy)
    register(no_xrange)
    register(validate_assertTrue)
    register(validate_assertIsNone)
    register(no_log_warn_check)
    register(validate_assertIsNotNone)