/******************************************************************************
 * Top contributors (to current version):
 *   Aina Niemetz, Liana Hadarean, Makai Mann
 *
 * This file is part of the cvc5 project.
 *
 * Copyright (c) 2009-2021 by the authors listed in the file AUTHORS
 * in the top-level source directory and their institutional affiliations.
 * All rights reserved.  See the file COPYING in the top-level source
 * directory for licensing information.
 * ****************************************************************************
 *
 * A simple demonstration of the solving capabilities of the cvc5
 * bit-vector solver.
 *
 */

import io.github.cvc5.api.*;
import java.util.*;

public class BitVectorsAndArrays
{
  private static int log2(int n)
  {
    return (int) Math.round(Math.log(n) / Math.log(2));
  }

  public static void main(String[] args) throws CVC5ApiException
  {
    Solver slv = new Solver();
    slv.setOption("produce-models", "true"); // Produce Models
    slv.setOption("output-language", "smtlib"); // output-language
    slv.setLogic("QF_AUFBV"); // Set the logic

    // Consider the following code (where size is some previously defined constant):
    //
    //
    //   Assert (current_array[0] > 0);
    //   for (unsigned i = 1; i < k; ++i) {
    //     current_array[i] = 2 * current_array[i - 1];
    //     Assert (current_array[i-1] < current_array[i]);
    //     }
    //
    // We want to check whether the assertion in the body of the for loop holds
    // throughout the loop.

    // Setting up the problem parameters
    int k = 4; // number of unrollings (should be a power of 2)
    int index_size = log2(k); // size of the index

    // Sorts
    Sort elementSort = slv.mkBitVectorSort(32);
    Sort indexSort = slv.mkBitVectorSort(index_size);
    Sort arraySort = slv.mkArraySort(indexSort, elementSort);

    // Variables
    Term current_array = slv.mkConst(arraySort, "current_array");

    // Making a bit-vector constant
    Term zero = slv.mkBitVector(index_size, 0);

    // Asserting that current_array[0] > 0
    Term current_array0 = slv.mkTerm(Kind.SELECT, current_array, zero);
    Term current_array0_gt_0 =
        slv.mkTerm(Kind.BITVECTOR_SGT, current_array0, slv.mkBitVector(32, 0));
    slv.assertFormula(current_array0_gt_0);

    // Building the assertions in the loop unrolling
    Term index = slv.mkBitVector(index_size, 0);
    Term old_current = slv.mkTerm(Kind.SELECT, current_array, index);
    Term two = slv.mkBitVector(32, 2);

    List<Term> assertions = new ArrayList<Term>();
    for (int i = 1; i < k; ++i)
    {
      index = slv.mkBitVector(index_size, i);
      Term new_current = slv.mkTerm(Kind.BITVECTOR_MULT, two, old_current);
      // current[i] = 2 * current[i-1]
      current_array = slv.mkTerm(Kind.STORE, current_array, index, new_current);
      // current[i-1] < current [i]
      Term current_slt_new_current = slv.mkTerm(Kind.BITVECTOR_SLT, old_current, new_current);
      assertions.add(current_slt_new_current);

      old_current = slv.mkTerm(Kind.SELECT, current_array, index);
    }

    Term query = slv.mkTerm(Kind.NOT, slv.mkTerm(Kind.AND, assertions.toArray(new Term[0])));

    System.out.println("Asserting " + query + " to cvc5 ");
    slv.assertFormula(query);
    System.out.println("Expect sat. ");
    System.out.println("cvc5: " + slv.checkSatAssuming(slv.mkTrue()));

    // Getting the model
    System.out.println("The satisfying model is: ");
    System.out.println("  current_array = " + slv.getValue(current_array));
    System.out.println("  current_array[0] = " + slv.getValue(current_array0));
  }
}