from __future__ import annotations
import ast
import random

class OpaquePredicateInjector(ast.NodeTransformer):

    def __init__(self, rng: random.Random, seed_name: str, prob: float=0.5):
        self.rng = rng
        self.seed_name = seed_name
        self.prob = prob
        self.injected = False

    def visit_If(self, node: ast.If) -> ast.AST:
        self.generic_visit(node)
        if self.rng.random() < self.prob:
            node.test = self._wrap(node.test)
            self.injected = True
        return node

    def visit_While(self, node: ast.While) -> ast.AST:
        self.generic_visit(node)
        if self.rng.random() < self.prob * 0.4:
            node.test = self._wrap(node.test)
            self.injected = True
        return node

    def _wrap(self, test: ast.expr) -> ast.expr:
        return ast.BoolOp(op=ast.And(), values=[test, self._tautology()])

    def _tautology(self) -> ast.expr:
        s = self.seed_name
        kind = self.rng.choice(('parity', 'flt3', 'flt5'))
        if kind == 'parity':
            src = f'({s} * ({s} + 1)) % 2 == 0'
        elif kind == 'flt3':
            src = f'({s} * {s} * {s} - {s}) % 3 == 0'
        else:
            src = f'({s} * {s} * {s} * {s} * {s} - {s}) % 5 == 0'
        return ast.parse(src, mode='eval').body

def build_seed_stmt(seed_name: str) -> ast.stmt:
    return ast.parse(f'{seed_name} = id(int) & 0xFFFFFFFF').body[0]