# -*- coding: utf-8 -*-

# Copyright (c) 2020 Detlev Offenbach <detlev@die-offenbachs.de>
#

"""
Module implementing a context class for security related checks.
"""

#
# This code is a modified version of the one in 'bandit'.
#
# Original Copyright 2014 Hewlett-Packard Development Company, L.P.
#
# SPDX-License-Identifier: Apache-2.0
#

import ast
import copy
import sys

import AstUtilities

from . import SecurityUtils


class SecurityContext(object):
    """
    Class implementing a context class for security related checks.
    """
    def __init__(self, contextObject=None):
        """
        Constructor
        
        Initialize the class with a context dictionary or an empty
        dictionary.
        
        @param contextObject context dictionary to be used to populate the
            class
        @type dict
        """
        if contextObject is not None:
            self.__context = copy.copy(contextObject)
        else:
            self.__context = {}
    
    def __repr__(self):
        """
        Special method to generate representation of object for printing or
        interactive use.
        
        @return string representation of the object
        @rtype str
        """
        return "<SecurityContext {0}>".formar(self.__context)
    
    @property
    def callArgs(self):
        """
        Public method to get a list of function args.
        
        @return list of function args
        @rtype list
        """
        args = []
        if (
            'call' in self.__context and
            hasattr(self.__context['call'], 'args')
        ):
            for arg in self.__context['call'].args:
                if hasattr(arg, 'attr'):
                    args.append(arg.attr)
                else:
                    args.append(self.__getLiteralValue(arg))
        return args
    
    @property
    def callArgsCount(self):
        """
        Public method to get the number of args a function call has.
        
        @return number of args a function call has
        @rtype int
        """
        if (
            'call' in self.__context and
            hasattr(self.__context['call'], 'args')
        ):
            return len(self.__context['call'].args)
        else:
            return None
    
    @property
    def callFunctionName(self):
        """
        Public method to get the name (not FQ) of a function call.
        
        @return name (not FQ) of a function call
        @rtype str
        """
        return self.__context.get('name')
    
    @property
    def callFunctionNameQual(self):
        """
        Public method to get the FQ name of a function call.
        
        @return FQ name of a function call
        @rtype str
        """
        return self.__context.get('qualname')
    
    @property
    def callKeywords(self):
        """
        Public method to get a dictionary of keyword parameters.
        
        @return dictionary of keyword parameters
        @rtype dict
        """
        if (
            'call' in self.__context and
            hasattr(self.__context['call'], 'keywords')
        ):
            returnDict = {}
            for kw in self.__context['call'].keywords:
                if hasattr(kw.value, 'attr'):
                    returnDict[kw.arg] = kw.value.attr
                else:
                    returnDict[kw.arg] = self.__getLiteralValue(kw.value)
            return returnDict
        
        else:
            return None
    
    @property
    def node(self):
        """
        Public method to get the raw AST node associated with the context.
        
        @return raw AST node associated with the context
        @rtype ast.AST
        """
        return self.__context.get('node')
    
    @property
    def stringVal(self):
        """
        Public method to get the value of a standalone unicode or string
        object.
        
        @return value of a standalone unicode or string object
        @rtype str
        """
        return self.__context.get('str')
    
    @property
    def bytesVal(self):
        """
        Public method to get the value of a standalone bytes object.
        
        @return value of a standalone bytes object
        @rtype bytes
        """
        return self.__context.get('bytes')
    
    @property
    def stringValAsEscapedBytes(self):
        r"""
        Public method to get the escaped value of the object.
        
        Turn the value of a string or bytes object into a byte sequence with
        unknown, control, and \\ characters escaped.

        This function should be used when looking for a known sequence in a
        potentially badly encoded string in the code.
        
        @return sequence of printable ascii bytes representing original string
        @rtype str
        """
        val = self.stringVal
        if val is not None:
            return val.encode('unicode_escape')
        
        val = self.bytesVal
        if val is not None:
            return SecurityUtils.escapedBytesRepresentation(val)
        
        return None
    
    @property
    def statement(self):
        """
        Public method to get the raw AST for the current statement.
        
        @return raw AST for the current statement
        @rtype ast.AST
        """
        return self.__context.get('statement')
    
    @property
    def functionDefDefaultsQual(self):
        """
        Public method to get a list of fully qualified default values in a
        function def.
        
        @return list of fully qualified default values in a function def
        @rtype list
        """
        defaults = []
        if (
            'node' in self.__context and
            hasattr(self.__context['node'], 'args') and
            hasattr(self.__context['node'].args, 'defaults')
        ):
            for default in self.__context['node'].args.defaults:
                defaults.append(SecurityUtils.getQualAttr(
                    default,
                    self.__context['import_aliases']))
        
        return defaults
    
    def __getLiteralValue(self, literal):
        """
        Private method to turn AST literals into native Python types.
        
        @param literal AST literal to be converted
        @type ast.AST
        @return converted Python object
        @rtype Any
        """
        if AstUtilities.isNumber(literal):
            literalValue = literal.n
        
        elif AstUtilities.isString(literal):
            literalValue = literal.s
        
        elif isinstance(literal, ast.List):
            returnList = []
            for li in literal.elts:
                returnList.append(self.__getLiteralValue(li))
            literalValue = returnList
        
        elif isinstance(literal, ast.Tuple):
            returnTuple = ()
            for ti in literal.elts:
                returnTuple = returnTuple + (self.__getLiteralValue(ti),)
            literalValue = returnTuple
        
        elif isinstance(literal, ast.Set):
            returnSet = set()
            for si in literal.elts:
                returnSet.add(self.__getLiteralValue(si))
            literalValue = returnSet
        
        elif isinstance(literal, ast.Dict):
            literalValue = dict(zip(literal.keys, literal.values))
        
        elif (
            sys.version_info <= (3, 8, 0) and
            isinstance(literal, ast.Ellipsis)
        ):
            # what do we want to do with this?
            literalValue = None
        
        elif isinstance(literal, ast.Name):
            literalValue = literal.id
        
        elif AstUtilities.isNameConstant(literal):
            literalValue = str(literal.value)
        
        elif AstUtilities.isBytes(literal):
            literalValue = literal.s
        
        else:
            literalValue = None
        
        return literalValue
    
    def getCallArgValue(self, argumentName):
        """
        Public method to get the value of a named argument in a function call.
        
        @param argumentName name of the argument to get the value for
        @type str
        @return value of the named argument
        @rtype Any
        """
        kwdValues = self.callKeywords
        if kwdValues is not None and argumentName in kwdValues:
            return kwdValues[argumentName]
        
        return None
    
    def checkCallArgValue(self, argumentName, argumentValues=None):
        """
        Public method to check for a value of a named argument in a function
        call.
        
        @param argumentName name of the argument to be checked
        @type str
        @param argumentValues value or list of values to test against
        @type Any or list of Any
        @return True if argument found and matched, False if found and not
            matched, None if argument not found at all
        @rtype bool or None
        """
        argValue = self.getCallArgValue(argumentName)
        if argValue is not None:
            if not isinstance(argumentValues, list):
                # if passed a single value, or a tuple, convert to a list
                argumentValues = [argumentValues]
            for val in argumentValues:
                if argValue == val:
                    return True
            return False
        else:
            # argument name not found, return None to allow testing for this
            # eventuality
            return None
    
    def getLinenoForCallArg(self, argumentName):
        """
        Public method to get the line number for a specific named argument.
        
        @param argumentName name of the argument to get the line number for
        @type str
        @return line number of the found argument or -1
        @rtype int
        """
        if hasattr(self.node, 'keywords'):
            for key in self.node.keywords:
                if key.arg == argumentName:
                    return key.value.lineno
        
        return -1
    
    def getOffsetForCallArg(self, argumentName):
        """
        Public method to get the offset for a specific named argument.
        
        @param argumentName name of the argument to get the line number for
        @type str
        @return offset of the found argument or -1
        @rtype int
        """
        if hasattr(self.node, 'keywords'):
            for key in self.node.keywords:
                if key.arg == argumentName:
                    return key.value.col_offset
        
        return -1
    
    def getCallArgAtPosition(self, positionNum):
        """
        Public method to get a positional argument at the specified position
        (if it exists).
        
        @param positionNum index of the argument to get the value for
        @type int
        @return value of the argument at the specified position if it exists
        @rtype Any or None
        """
        maxArgs = self.callArgsCount
        if maxArgs and positionNum < maxArgs:
            return self.__getLiteralValue(
                self.__context['call'].args[positionNum]
            )
        else:
            return None
    
    def isModuleBeingImported(self, module):
        """
        Public method to check for the given module is currently being
        imported.
        
        @param module module name to look for
        @type str
        @return flag indicating the given module was found
        @rtype bool
        """
        return self.__context.get('module') == module
    
    def isModuleImportedExact(self, module):
        """
        Public method to check if a given module has been imported; only exact
        matches.
        
        @param module module name to look for
        @type str
        @return flag indicating the given module was found
        @rtype bool
        """
        return module in self.__context.get('imports', [])
    
    def isModuleImportedLike(self, module):
        """
        Public method to check if a given module has been imported; given
        module exists.
        
        @param module module name to look for
        @type str
        @return flag indicating the given module was found
        @rtype bool
        """
        if 'imports' in self.__context:
            for imp in self.__context['imports']:
                if module in imp:
                    return True
        
        return False
