gazprea-fuzzer-python/ast_generator/ast_generator.py

import string
import warnings

from english_words import get_english_words_set

from ast_generator.tiny_py_unparse import TinyPyUnparser
from ast_generator.utils import *
from ast_generator.utils import filter_options, _choose_option
from constants import *

import keyword


class AstGenerator:
    """
    Generates an AST from a grammar based on given settings

    Originally the intention was to use the ISLa library to generate
    the AST, however I found that ISLa is like taking a buldozer to
    a sledgehammer's job, so I decided to write a procedural generator
    instead.

    The way we select elements is we take all the settings in their
    category and assign them a range on a number line. Then we
    pick a random number in that range and whichever category it
    falls into will be selected.
    """

    ### INITIALIZATION ###
    def __init__(self, settings: dict):
        """
        This class is designed to get  the settings from some wrapper class that
        better defines the precise constraints of the language being generated

        the necessary settings are in the .yaml file and #TODO this is not generalizable yet

        @param settings: settings for weights and probabilities and lengths
        """
        self.settings = settings

        self.symbol_table = []
        global_scope = Scope(None, None)
        self.symbol_table.append(global_scope)  # NOTE for debug
        self.current_scope = global_scope

        self._init_names()

        self.ast: ET.Element or None = None
        self.current_ast_element: ET.Element or None = None
        self.current_nesting_depth = 0
        self.current_control_flow_nesting_depth = 0

        self._init_numlines()

    def _init_numlines(self):
        # Numberlines - For computing probabilities
        self.int_op_options, self.int_op_cutoffs, self.int_op_numline = (
            get_numberlines('expression-weights', ['brackets', 'arithmetic', 'unary'], [[], [], ['not']],
                            self.settings))
        self.int_unary = ['negation', 'noop']
        self.bool_op_options, self.bool_op_cutoffs, self.bool_op_numline = (
            get_numberlines('expression-weights', ['brackets', 'comparison', 'logical', 'unary'],
                            excluded_values=[[], ['less-than-or-equal', 'greater-than-or-equal', 'less-than',
                                                  'greater-than'], [], ['noop', 'negation']],
                            settings=self.settings))
        self.bool_unary = ['not']
        self.float_op_options, self.float_op_cutoffs, self.float_op_numline = (
            get_numberlines('expression-weights', ['brackets', 'arithmetic', 'unary'], [[], [], ['not']],
                            self.settings))
        self.float_unary = ['negation', 'noop']
        self.char_op_options, self.char_op_cutoffs, self.char_op_numline = (
            get_numberlines('expression-weights', ['brackets', 'comparison'],
                            [[], ['less-than', 'greater-than', 'less-than-or-equal', 'greater-than-or-equal']],
                            self.settings))
        self.comp_op_options, self.comp_op_cutoffs, self.comp_op_numline = (
            get_numberlines('expression-weights', ['brackets', 'comparison'], [[], []], self.settings))

        self.type_options, self.type_cutoffs, self.type_numline = (
            get_numberlines('type-weights', ['composite', 'atomic'], [[], []], self.settings))

        self.atomic_type_options, self.atomic_type_cutoffs, self.atomic_type_numline = (
            get_numberlines('type-weights', ['atomic-types'], [[]], self.settings))

        self.composite_type_options, self.composite_type_cutoffs, self.composite_type_numline = (
            get_numberlines('type-weights', ['composite-types'], [[]], self.settings))

    def _init_names(self):
        names = get_english_words_set(['web2'], alpha=True)
        possible_names = filter(lambda x: (self.settings['properties']['id-length']['max'] <= len(x) <=
                                           self.settings['properties']['id-length']['max']) and not keyword.iskeyword(x),
                                names)
        var_name_list = list(possible_names)
        var_name_len = len(var_name_list)
        self.variable_names = var_name_list[0:var_name_len // 2]
        self.routine_names = var_name_list[var_name_len // 2:var_name_len]

    ### GENERATION ###
    def generate_ast(self):
        """
        @brief generates an AST from a grammar
        """
        self.generate_top_level_block()

    def generate_top_level_block(self):
        """
        @brief creates the top-level block containing the whole program
        """
        element = self.make_element(GAZ_BLOCK_TAG, [])
        self.ast = element

        for i in range(random.randint(0, self.settings['generation-options']['max-globals'])):
            self.generate_global()
        for i in range(self.settings['generation-options']['max-number-of-routines']):
            if random.random() < self.settings['block-termination-probability']:
                break
            self.generate_routine()

        self.generate_main()
        pass

    def generate_main(self):
        main_args = [  # TODO refactor these into constants
            (GAZ_NAME_KEY, "main"),
            (GAZ_RETURN_KEY, GAZ_INT_KEY),
        ]

        parent = self.make_scoped_element(GAZ_PROCEDURE_TAG, main_args)

        self.generate_block(return_stmt=True, return_value="0", return_type=GAZ_INT_KEY, block_type=GAZ_PROCEDURE_TAG)

        self.exit_scoped_element(parent)

    def generate_block(self, tag=None, return_stmt=False, return_value=None, return_type=None, block_type=None,
                       loop_var=None):
        # TODO this should be broken into many functions depending on the block requirements

        if tag is None:
            tag = []
        parent = self.current_ast_element
        self.push_scope()
        element = build_xml_element(tag, name=GAZ_BLOCK_TAG)
        self.current_ast_element.append(element)
        self.current_ast_element = element

        # Generate the loop condition increment if we are in a loop
        if block_type == GAZ_LOOP_TAG:
            self.generate_loop_condition_check(loop_var)
            self.generate_loop_condition_increment(loop_var)

        if block_type not in [GAZ_PROCEDURE_TAG, GAZ_FUNCTION_TAG]:
            self.generate_statements()
        else:
            self.generate_statements(include='declaration')
            self.generate_statements(exclude='declaration')

        if return_stmt:
            self.generate_return(return_type=return_type, return_value=return_value)
        if self.settings['generation-options']['generate-dead-code']:
            self.generate_statements(exclude='declaration')

        self.print_all_current_scope_vars()
        self.pop_scope()
        self.current_ast_element = parent

    def generate_return(self, return_type=None, return_value=None):
        """
        @brief generates a return statement

        @param return_type: the type to be returned (if None -> any)
        @param return_value: value to be returned (if None -> expr[return_type])
        """
        if return_type is None or return_type == GAZ_VOID_TYPE:
            self.current_ast_element.append(self.make_element(GAZ_RETURN_TAG, []))
        else:
            # store the parent
            parent = self.current_ast_element

            # initialize element
            keys = [("type", return_type)]
            self.make_element(GAZ_RETURN_TAG, keys)

            # make either a literal or a random expression based on choice
            if return_value is None:
                self.generate_expression(return_type)
            else:
                self.generate_literal(return_type, return_value)

            # return to the parent
            self.current_ast_element = parent

    def generate_routine(self, routine_type=None):
        """
        @brief generate a random routine

        @param return_type: the type to be returned (if None -> any (including void))
        """
        if routine_type is None:
            routine_type = self.get_routine_type()  # get a random type
        else:
            pass

        # initialize random variables
        args = self.generate_routine_args()
        name = self.get_name(routine_type)
        return_type = self.get_type(routine_type)

        # initialize the routine
        routine = Routine(name, routine_type, return_type, args)
        routine_args = [
            ("name", routine.name),
            ("return_type", routine.return_type),
        ]

        # Generation
        parent = self.current_ast_element
        self.make_scoped_element(routine.type, routine_args)

        self.define_args(routine.arguments)

        self.generate_block(return_stmt=True, return_type=routine.return_type)

        self.exit_scoped_element(parent)

    def define_args(self, args):
        """
        @brief Generate the argument tags in a routine

        @param args: a list of arguments
        """
        for arg in args:
            self.current_ast_element.append(arg.xml)
            self.current_scope.append(arg.name, arg)

    def generate_statements(self, include=None, exclude=None):

        opts = ['declaration', 'routine_call', 'conditional', 'loop', 'assignment', 'out_stream', 'in_stream']

        # Number line
        number_line = 180  # TODO fix the numberline stuff to reflect the settings
        cutoffs = [10, 30, 50, 80, 100, 140, 180]
        options = {
            0: self.generate_declaration,
            1: self.generate_routine_call,
            2: self.generate_conditional,
            3: self.generate_loop,
            4: self.generate_assignment,
            5: self.generate_out_stream,
            6: self.generate_in_stream,
        }

        # Filter unwanted options
        filter_options(exclude, include, options, opts)

        # Generate the statements
        self._generate_from_options(cutoffs, number_line, options)

    def _generate_expression(self, expr_type: list[str], number_line,
                             cutoffs, options, unary=None, comparison: bool = False):
        """
        @brief Generate an expression

        @param expr_type: a list of types to be used
        @param number_line: number line for probability computation
        @param cutoffs: cutoffs to be used
        @param options: options to be used
        @param unary: a list of unary operators in options
        """
        if unary is None:
            unary = []

        parent = self.current_ast_element
        self.current_nesting_depth += 1

        # Check the expression depth against settings
        if self.current_nesting_depth > self.settings['generation-options']['max-nesting-depth'] or random.random() < \
                self.settings['block-termination-probability']:
            self.generate_literal(random.choice(expr_type))
            self.current_nesting_depth -= 1
            return

        # Generate
        op = _choose_option(cutoffs, number_line, options)
        self._generate_expr(comparison, expr_type, op, unary)

        # Return to parent
        self.current_nesting_depth -= 1
        self.current_ast_element = parent

    def generate_declaration(self, mut=None):  # TODO change this to a bool
        """
        @brief Generate a declaration

        @param mut: the mutability of the variable ('const' or 'var')
        """
        # Initialize the variable
        parent = self.current_ast_element
        decl_type = self.get_type(GAZ_VAR_TAG)
        decl_args = [
            ("type", decl_type),
        ]
        self.make_element(GAZ_DECLARATION_TAG, decl_args)

        # Generate the variable
        variable = self.generate_variable(decl_type, mut=mut)
        self.current_ast_element.append(variable.xml)
        self.current_scope.append(variable.name, variable)  # make sure the variable is in scope

        # Generate the initialization of the variable
        self.generate_xhs(GAZ_RHS_TAG, decl_type)

        # Return to parent
        self.current_ast_element = parent

    def generate_binary(self, op, op_type):
        """
        @brief Generate a binary operation

        @param op: the operator
        @param op_type: the type of the expression
        """
        parent = self.current_ast_element

        # Check if the operator is valid
        if op == "":
            raise ValueError("op is empty!")
        args = [
            ("op", op),
            ("type", op_type),
        ]
        self.make_element(GAZ_OPERATOR_TAG, args)

        # Gnereate lhs and rhs
        self.generate_xhs(GAZ_LHS_TAG, op_type)
        self.generate_xhs(GAZ_RHS_TAG, op_type)

        # Return to parent
        self.current_ast_element = parent

    def generate_bracket(self, op_type):
        """
        @brief Generate a bracket operation

        @param op_type: the type of the expression
        """
        parent = self.current_ast_element

        args = [("type", op_type)]
        self.make_element(GAZ_BRACKET_TAG, args)

        # Generate the expression in the brackets
        self.generate_xhs(GAZ_RHS_TAG, op_type)

        # Return to parent
        self.current_ast_element = parent

    def generate_xhs(self, handedness, op_type, is_zero=False):
        """
        @brief generate a lhs or a rhs depending on handedness

        @param handedness: the handedness
        @param op_type: the type of the expression
        @param is_zero: if the expression is zero
        """
        parent = self.current_ast_element

        self.make_element(handedness, [])

        self.generate_expression(op_type, is_zero=is_zero)

        self.current_ast_element = parent

    def generate_unary(self, op, op_type=ANY_TYPE):
        """
        @brief Generate a unary operation

        @param op_type: the type of the expression
        """
        parent = self.current_ast_element
        args = [
            ("op", op),
            ("type", op_type),
        ]
        self.make_element(GAZ_UNARY_OPERATOR_TAG, args)

        self.generate_xhs(GAZ_RHS_TAG, op_type)

        self.current_ast_element = parent

    def generate_routine_call(self):  # we should generate a test case with arbitrary number of args
        pass

    def generate_conditional(self):
        """
        @brief generate a conditional statement

        @effects: modifies the current_ast_element

        @return: None
        """
        if self.current_control_flow_nesting_depth >= self.settings['generation-options']['max-nesting-depth']:
            return

        if self.current_control_flow_nesting_depth > 0 and random.random() < self.settings[
            'block-termination-probability']:
            return

        parent = self.current_ast_element

        self.make_scoped_element(GAZ_IF_TAG, [])
        self.current_control_flow_nesting_depth += 1

        self.generate_expression(GAZ_BOOL_KEY)

        self.generate_block(tag=[("type", GAZ_TRUE_BLOCK_TAG)])  # FIXME this inhibits elif blocks
        self.generate_block(tag=[("type", GAZ_FALSE_BLOCK_TAG)])

        self.current_control_flow_nesting_depth -= 1
        self.exit_scoped_element(parent)

    def generate_loop(self):
        """
        @brief generate a loop

        @return: None
        """
        # FIXME make sure that loop conditions are evaluated at least once (assert true or make a config param)
        if self.current_control_flow_nesting_depth >= self.settings['generation-options']['max-nesting-depth']:
            return

        if self.current_control_flow_nesting_depth > 0 and random.random() < self.settings[
            'block-termination-probability']:
            return

        init_var = self.generate_zero_declaration()
        parent = self.current_ast_element

        self.make_scoped_element(GAZ_LOOP_TAG, [])
        self.current_control_flow_nesting_depth += 1

        truthiness = self.get_truthiness()

        while True:
            self.generate_expression(GAZ_BOOL_KEY)  # the loop entry condition  #TODO force true, if false, generate a simple block and return, no need to nest code we won't use

            iterator = self.current_ast_element.iter()
            next(iterator)
            conditional = next(iterator)
            if not self.truth_check(conditional, truthiness):
                self.current_ast_element.remove(conditional)
            else:
                break

        self.generate_block(block_type=GAZ_LOOP_TAG,
                            loop_var=init_var)  # append a variable increment and prepend a break statement if var is > max loop iterations

        self.current_control_flow_nesting_depth -= 1
        self.exit_scoped_element(parent)

    def get_truthiness(self):
        return random.random() < self.settings['misc-weights']['truthiness']

    def truth_check(self, element: ET.Element, truthiness: bool):
        # evaluate the element
        uncompiled = self.unparse_conditional_statement(element)
        substr1 = uncompiled.find("**")
        substr2 = uncompiled.find("**", substr1 + 1)

        if -1 not in [substr1, substr2]:
            return False

        # print(uncompiled)
        try:
            res = eval(uncompiled)
        except (OverflowError, ZeroDivisionError):
            res = False

        # check it against truthiness and return the comparison
        return res == truthiness

    def unparse_conditional_statement(self, element: ET.Element):
        py_unparse = TinyPyUnparser(element, True)
        unparsed = ""
        if element.tag == GAZ_LIT_TAG:
            py_unparse.unparse_literal(element)
            unparsed = py_unparse.source
        elif element.tag == GAZ_OPERATOR_TAG:
            py_unparse.unparse_operator(element)
            unparsed = py_unparse.source
        elif element.tag == GAZ_VAR_TAG:
            xml = self.current_scope.resolve(element.get("name"))
            py_unparse.unparse_variable(xml)
            unparsed = py_unparse.source
        elif element.tag == GAZ_BRACKET_TAG:
            py_unparse.unparse_brackets(element)
            unparsed = py_unparse.source
        else:
            raise ValueError("Unknown element type for conditional argument: " + element.tag)
        return unparsed

    def generate_zero_declaration(self):
        """
        @brief generate a declaration int a = 0 for some a

        @return: None
        """
        parent = self.current_ast_element

        self.make_element(GAZ_DECLARATION_TAG, [])

        # Initialize variable
        variable = self.generate_variable(GAZ_INT_KEY, 'var')
        self.current_ast_element.append(variable.xml)
        self.current_scope.append(variable.name, variable)

        self.generate_xhs(GAZ_RHS_TAG, variable.type, is_zero=True)

        self.current_ast_element = parent

        return variable

    def generate_assignment(self):
        """
        @brief generate an assignment

        @return: None
        """
        possible_vars = self.current_scope.get_all_defined_mutable_vars()
        if len(possible_vars) == 0:
            raise ValueError("No possible variables to assign to!")

        # same structure as a declaration
        parent = self.current_ast_element

        self.make_element(GAZ_ASSIGNMENT_TAG, [])

        variable = random.choice(possible_vars)

        self.current_ast_element.append(variable.xml)
        self.generate_xhs(GAZ_RHS_TAG, variable.type)

        self.current_ast_element = parent

    def generate_out_stream(self):
        self.generate_stream(GAZ_OUT_STREAM)

    def generate_in_stream(self):
        self.generate_stream(GAZ_IN_STREAM)

    def generate_stream(self, stream_type):
        """
        @brief generate a stream statment from a stream type

        @param stream_type: whether the stream is an input or output
        @return:
        """
        parent = self.current_ast_element

        args = [
            ("type", stream_type),
        ]
        self.make_element(GAZ_STREAM_TAG, args)
        self.generate_expression(ANY_TYPE)

        self.current_ast_element = parent

    def generate_variable(self, var_type: str, mut=None):
        """
        @brief generate a variable

        @param var_type: they type of the variable
        @param mut: mutability of the variable
        @return: None
        """
        if mut is None:
            return Variable(self.get_name(GAZ_VAR_TAG), var_type, self.get_qualifier())
        else:
            return Variable(self.get_name(GAZ_VAR_TAG), var_type, mut)

    def generate_literal(self, var_type: str, value=None):
        """
        @brief generate a literal

        @param var_type: Type of the literal
        @param value: optional value of the literal
        @return: None
        """
        if value is None:
            value = self.get_value(var_type)
        else:
            value = value

        args = [
            ("type", var_type),
            ("value", str(value)),
        ]
        element = build_xml_element(args, name=GAZ_LIT_TAG)
        self.current_ast_element.append(element)

    def make_literal(self, type, value):  # TODO eliminate this function
        args = [
            ("type", type),
            ("value", value),
        ]
        element = build_xml_element(args, name=GAZ_LIT_TAG)
        return element

    def generate_global(self):
        """
        @brief generate a global const declaration

        @return: None
        """
        current_scope = self.current_scope
        current_element = self.current_ast_element

        self.current_scope = self.current_scope.get_top_scope()
        self.current_ast_element = self.ast

        self.generate_declaration(mut='const')

        self.current_scope = current_scope
        self.current_ast_element = current_element

    def generate_expression(self, expr_type: str, is_zero=False):
        """
        @brief generate an expression

        @param expr_type: the type of the expression
        @param is_zero: if the expression should eval to 0
        @return: None
        """
        if is_zero:
            self.generate_literal(expr_type, value=0)
            return
        elif expr_type == GAZ_INT_KEY or expr_type == GAZ_FLOAT_KEY:
            self.generate_int_expr()
        elif expr_type == GAZ_BOOL_KEY:
            if random.random() < 0.5:
                self.generate_bool_expr()
            else:
                self.generate_comp_expr()
        elif expr_type == GAZ_CHAR_KEY:
            self.generate_char_expr()
        elif expr_type == GAZ_FLOAT_KEY:
            self.generate_float_expr()
        elif expr_type == ANY_TYPE:  # TODO implement the choice of any type
            ty = self.get_type(GAZ_RHS_TAG)
            self.generate_expression(ty)
        else:
            raise NotImplementedError(f"Expression type {expr_type} not implemented")

    def generate_routine_args(self) -> list[Argument]:
        """
        @brief generate a list of arguments for a routine

        @return: a list of arguments
        """
        number = random.randint(self.settings['properties']['number-of-arguments']['min'],
                                self.settings['properties']['number-of-arguments']['max'])
        args = []
        for i in range(number):
            arg = self.generate_arg()
            args.append(arg)
            self.current_scope.append(arg.name, arg)
        return args

    def generate_arg(self):
        return Argument(self.get_name(GAZ_VAR_TAG), self.get_type(GAZ_VAR_TAG))

    def generate_int_expr(self):
        self._generate_expression([GAZ_INT_KEY],
                                  self.int_op_numline,
                                  self.int_op_cutoffs,
                                  self.int_op_options,
                                  self.int_unary)

    def generate_float_expr(self):
        self._generate_expression([GAZ_FLOAT_KEY, GAZ_INT_KEY],
                                  self.float_op_numline,
                                  self.float_op_cutoffs,
                                  self.float_op_options,
                                  self.float_unary)

    def generate_bool_expr(self):
        self._generate_expression([GAZ_BOOL_KEY],
                                  self.bool_op_numline,
                                  self.bool_op_cutoffs,
                                  self.bool_op_options,
                                  self.bool_unary)

    def generate_char_expr(self):
        self._generate_expression([GAZ_CHAR_KEY],
                                  self.char_op_numline,
                                  self.char_op_cutoffs,
                                  self.char_op_options)

    def generate_comp_expr(self):
        self._generate_expression([GAZ_BOOL_KEY],
                                  self.comp_op_numline,
                                  self.comp_op_cutoffs,
                                  self.comp_op_options,
                                  comparison=True)  #, evals=self.get_truth())

    def push_scope(self, xml_element: ET.Element = None):
        scope = Scope(self.current_scope)
        self.symbol_table.append(scope)
        self.current_scope = scope

    def pop_scope(self):
        self.current_scope = self.current_scope.enclosing_scope

    # TODO revamp the random value generations
    def get_qualifier(self):
        """
        @brief get a random qualifier from the list of possible qualifiers

        @return a qualifier as a string
        """
        number_line = (self.settings["misc-weights"]["type-qualifier-weights"]["const"] +
                       self.settings["misc-weights"]["type-qualifier-weights"]["var"] - 1)

        res = random.randint(0, number_line)
        if res in range(0, self.settings["misc-weights"]["type-qualifier-weights"]["const"]):
            return 'const'
        elif res in range(self.settings["misc-weights"]["type-qualifier-weights"]["const"],
                          self.settings["misc-weights"]["type-qualifier-weights"]["const"] +
                          self.settings["misc-weights"]["type-qualifier-weights"]["var"]):
            return 'var'
        else:
            raise ValueError("Internal Error, please report the stack trace to me")

    def get_routine_type(self):
        cutoffs = []
        values = []
        ops = []
        for key, value in self.settings["routine-weights"].items():
            cutoffs.append(value + sum(cutoffs))
            values.append(value)
            ops.append(key)

        res = random.randint(0, sum(values))
        for i in range(len(cutoffs)):
            if res < cutoffs[i]:
                return ops[i]  # TODO everything should be fast faied

    def get_value(self, type):
        if type == GAZ_INT_KEY:
            if self.settings["properties"]["generate-max-int"]:
                return random.randint(-2147483648, 2147483647)
            else:
                return random.randint(-1000, 1000)
        elif type == GAZ_FLOAT_KEY:
            return random.uniform(-1000, 1000)
        elif type == GAZ_BOOL_KEY:
            return random.choice([True, False])
        elif type == GAZ_CHAR_KEY:
            return "'" + random.choice(string.ascii_letters) + "'"
        else:
            raise TypeError("Unimplemented generator for type: " + type)

    def get_name(self, name_type):
        """
        @brief get a random name from the list of possible names and add it to the current scope

        @param name_type:
        @return:
        """
        if not self.settings['properties']['use-english-words']:
            length = random.randint(self.settings['properties']['id-length']['min'],
                                    self.settings['properties']['id-length']['max'])
            name = ''.join(random.choices(string.ascii_letters, k=length))
            return name
        else:
            try:
                if name_type == GAZ_VAR_TAG:
                    choice = random.choice(self.variable_names)
                    self.variable_names.remove(choice)
                    return choice
                else:
                    choice = random.choice(self.routine_names)
                    self.routine_names.remove(choice)
                    return choice
            except IndexError:  # if we run out of variable names
                length = random.randint(self.settings['properties']['id-length']['min'],
                                        self.settings['properties']['id-length']['max'])
                name = ''.join(random.choices(string.ascii_letters, k=length))
                return name

    def get_type(self, tag) -> str:  # TODO Add support for composite types
        """
        @brief get a random type from the list of possible types

        @param tag:
        @return: a type as a string
        """
        comp_atom = self.get_choice(self.type_options, self.type_numline, self.type_cutoffs)
        choice = ""
        if comp_atom == GAZ_ATOMIC_TYPE_KEY:
            choice = self.get_choice(self.atomic_type_options, self.atomic_type_numline, self.atomic_type_cutoffs)
        elif comp_atom == GAZ_COMPOSITE_TYPE_KEY:
            choice = self.get_choice(self.composite_type_options, self.composite_type_numline, self.composite_type_cutoffs)
        else:
            raise NotImplementedError(f"Unimplemented generator for type: {comp_atom}")

        if tag not in [GAZ_PROCEDURE_TAG]:
            if choice != GAZ_VOID_TYPE:
                return choice
            else:
                return self.get_type(tag)
        else:
            return choice

    def get_choice(self, options, numline, cutoffs):
        res = random.randint(0, numline - 1)
        for i in range(len(cutoffs)):
            if res < cutoffs[i]:
                try:
                    return options[i]
                except Exception as e:
                    raise ValueError(str(e) + "Internal Error, please report the stack trace to me")

    ### LOOP HELPERS ###

    def generate_loop_condition_check(self, loop_var: Variable):
        """
        @brief generates the loop condition check

        Ensures that the loop does not iterate more than max-loop-iterations times

        @param loop_var:
        @return:
        """
        # loop var is always an int
        assert loop_var.type == GAZ_INT_KEY

        # create a conditional xml tag
        if_stmt = build_xml_element([], name=GAZ_IF_TAG)
        self.current_ast_element.append(if_stmt)
        parent = self.current_ast_element
        self.current_ast_element = if_stmt

        # add the check 'if loop_var >= self.settings['generation_options']['max-loop-iterations']: break'
        operation = build_xml_element([("op", ">=")], name=GAZ_OPERATOR_TAG)
        rhs = self._loop_heloper(loop_var, operation)
        rhs.append(  # TODO refactor this to use generate_literal instead of make_literal
            self.make_literal(GAZ_INT_KEY, "'" + str(self.settings['generation-options']['max-loop-iterations']) + "'"))

        true_block = build_xml_element([], name=GAZ_BLOCK_TAG)
        if_stmt.append(true_block)
        self.current_ast_element = true_block
        break_stmt = build_xml_element([], name=GAZ_BREAK_TAG)
        true_block.append(break_stmt)

        # return everything to normalcy
        self.current_ast_element = parent

    def _loop_heloper(self, loop_var, operation):
        self.current_ast_element.append(operation)
        self.current_ast_element = operation
        lhs = build_xml_element([], name=GAZ_LHS_TAG)
        operation.append(lhs)
        var = build_xml_element([("name", loop_var.name), ("type", loop_var.type)], name=GAZ_VAR_TAG)
        lhs.append(var)
        rhs = build_xml_element([], name=GAZ_RHS_TAG)
        operation.append(rhs)
        return rhs

    def generate_loop_condition_increment(self, loop_var):
        assert loop_var.type == GAZ_INT_KEY

        parent = self.current_ast_element
        assignment = build_xml_element([], name=GAZ_ASSIGNMENT_TAG)
        self.current_ast_element.append(assignment)
        self.current_ast_element = assignment

        # append the variable
        self.current_ast_element.append(loop_var.xml)

        # add the increment 'loop_var += 1'
        assn_rhs = build_xml_element([], name=GAZ_RHS_TAG)
        self.current_ast_element.append(assn_rhs)
        self.current_ast_element = assn_rhs

        operation = build_xml_element([("op", "+")], name=GAZ_OPERATOR_TAG)
        rhs = self._loop_heloper(loop_var, operation)
        rhs.append(self.make_literal(GAZ_INT_KEY, '1'))  # TODO refactor this to use generate_literal instead of make_literal

        # return everything to normalcy
        self.current_ast_element = parent

    ### HELPER FUNCTIONS ###
    def make_element(self, name: str, keys: list[tuple[str, any]]) -> ET.Element:
        """
        @brief make an xml element for the ast

        @effects modifies self.current_ast_element

        @param name: the tag for the element
        @param keys: a list of tuple containing keys for the element
        """
        element = build_xml_element(keys, name=name)
        if self.current_ast_element is not None:
            self.current_ast_element.append(element)
        self.current_ast_element = element

        return element

    def make_scoped_element(self, name, keys) -> ET.Element:
        """
        @brief make an xml element for the ast with a scope

        @param name: the tag for the element
        @param keys: a list of tuple containing keys for the element
        """
        parent = self.current_ast_element
        self.push_scope()
        self.make_element(name, keys)
        return parent

    def exit_scoped_element(self, parent):
        """
        @brief leave the current element and return to parent

        @param parent: the enclosing element to return to
        """
        self.pop_scope()
        self.current_ast_element = parent

    def _generate_from_options(self, cutoffs, number_line, options):
        while True:
            if random.random() < self.settings['block-termination-probability']:
                break

            a = random.randint(0, number_line)
            i = 0
            for i in range(len(cutoffs) - 1):
                if cutoffs[i] < a < cutoffs[i + 1]:
                    try:
                        options[i]()
                    except KeyError:  # if the key is not in the options (due to exclusion)
                        continue
                    except ValueError:
                        break
                    break

    def _generate_expr(self, comparison, expr_type, op, unary):
        if op in unary:
            self.generate_unary(op, random.choice(expr_type))
        elif op == GAZ_BRACKET_TAG:
            self.generate_bracket(random.choice(expr_type))
        elif comparison:
            if op in ['equality', 'inequality']:
                self.generate_binary(op, random.choice([GAZ_INT_KEY, GAZ_FLOAT_KEY, GAZ_CHAR_KEY]))
            else:
                self.generate_binary(op, random.choice([GAZ_INT_KEY, GAZ_FLOAT_KEY]))
        else:
            self.generate_binary(op, random.choice(expr_type))

    def print_all_current_scope_vars(self):
        for key, value in self.current_scope.symbols.items():
            if isinstance(value, Variable):
                self.print_variable(value)

    def print_variable(self, var: Variable):
        """
        @brief generate an outstream for a variable

        @param var: the variable to print
        @return:
        """
        parent = self.current_ast_element

        args = [
            ("type", GAZ_OUT_STREAM),
        ]
        self.make_element(GAZ_STREAM_TAG, args)
        self.current_ast_element.append(var.xml)

        self.current_ast_element = parent