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

# Copyright (c) 2019 - 2023 Detlev Offenbach <detlev@die-offenbachs.de>
#

"""
Module implementing some utility and compatibility functions for working with
the ast module.
"""

import ast
import sys

if sys.version_info >= (3, 8, 0):
    # functions for Python >= 3.8

    import numbers

    def isNumber(node):
        """
        Function to check that a node is a number.

        @param node reference to the node to check
        @type ast.AST
        @return flag indicating a number
        @rtype bool
        """
        return isinstance(node, ast.Constant) and isinstance(node.value, numbers.Number)

    def isString(node):
        """
        Function to check that a node is a string.

        @param node reference to the node to check
        @type ast.AST
        @return flag indicating a string
        @rtype bool
        """
        return isinstance(node, ast.Constant) and isinstance(node.value, str)

    def isBytes(node):
        """
        Function to check that a node is a bytes.

        @param node reference to the node to check
        @type ast.AST
        @return flag indicating a bytes
        @rtype bool
        """
        return isinstance(node, ast.Constant) and isinstance(node.value, bytes)

    def isBaseString(node):
        """
        Function to check that a node is a bytes or string.

        @param node reference to the node to check
        @type ast.AST
        @return flag indicating a bytes or string
        @rtype bool
        """
        return isinstance(node, ast.Constant) and isinstance(node.value, (bytes, str))

    def isNameConstant(node):
        """
        Function to check that a node is a name constant.

        @param node reference to the node to check
        @type ast.AST
        @return flag indicating a name constant
        @rtype bool
        """
        return isinstance(node, ast.Constant) and not isinstance(
            node.value, (bytes, str, numbers.Number)
        )

    def getValue(node):
        """
        Function to extract the value of a node.

        @param node reference to the node to extract the value from
        @type ast.Constant
        @return value of the node
        @rtype any
        @exception TypeError raised to indicate an unsupported type
        """
        if not isinstance(node, ast.Constant):
            raise TypeError("Illegal node type passed.")

        return node.value

else:
    # functions for Python < 3.8

    def isNumber(node):
        """
        Function to check that a node is a number.

        @param node reference to the node to check
        @type ast.AST
        @return flag indicating a number
        @rtype bool
        """
        return isinstance(node, ast.Num)

    def isString(node):
        """
        Function to check that a node is a string.

        @param node reference to the node to check
        @type ast.AST
        @return flag indicating a string
        @rtype bool
        """
        return isinstance(node, ast.Str)

    def isBytes(node):
        """
        Function to check that a node is a bytes.

        @param node reference to the node to check
        @type ast.AST
        @return flag indicating a bytes
        @rtype bool
        """
        return isinstance(node, ast.Bytes)

    def isBaseString(node):
        """
        Function to check that a node is a bytes or string.

        @param node reference to the node to check
        @type ast.AST
        @return flag indicating a bytes or string
        @rtype bool
        """
        return isinstance(node, (ast.Str, ast.Bytes))

    def isNameConstant(node):
        """
        Function to check that a node is a name constant.

        @param node reference to the node to check
        @type ast.AST
        @return flag indicating a name constant
        @rtype bool
        """
        return isinstance(node, ast.NameConstant)

    def getValue(node):
        """
        Function to extract the value of a node.

        @param node reference to the node to extract the value from
        @type one of ast.Num, ast.Str, ast.Bytes or ast.NameConstant
        @return value of the node
        @rtype one of str, bytes, int
        @exception TypeError raised to indicate an unsupported type
        """
        if not isinstance(node, (ast.Num, ast.Str, ast.Bytes, ast.NameConstant)):
            raise TypeError("Illegal node type passed.")

        if isinstance(node, ast.Num):
            return node.n

        elif isinstance(node, (ast.Str, ast.Bytes)):
            return node.s

        elif isinstance(node, ast.NameConstant):
            return node.value

        return None
