/*
    Copyright (C) 2014 Fredrik Johansson

    This file is part of Arb.

    Arb is free software: you can redistribute it and/or modify it under
    the terms of the GNU Lesser General Public License (LGPL) as published
    by the Free Software Foundation; either version 2.1 of the License, or
    (at your option) any later version.  See <http://www.gnu.org/licenses/>.
*/

#include "arb.h"

static void
bsplit(fmpz_t P, fmpz_t T, fmpz_t Q, flint_bitcnt_t * Qexp, const fmpz_t x,
    slong r, slong a, slong b, int cont)
{
    if (b - a == 1)
    {
        fmpz_set(P, x);
        fmpz_set_ui(Q, a + 1);
        *Qexp = r;
        fmpz_set(T, P);
    }
    else
    {
        slong m;
        flint_bitcnt_t Q2exp[1];
        fmpz_t P2, Q2, T2;

        m = a + (b - a) / 2;

        fmpz_init(P2);
        fmpz_init(Q2);
        fmpz_init(T2);

        bsplit(P,  T,  Q,  Qexp,  x, r, a, m, 1);
        bsplit(P2, T2, Q2, Q2exp, x, r, m, b, 1);

        fmpz_mul(T, T, Q2);
        fmpz_mul_2exp(T, T, *Q2exp);
        fmpz_addmul(T, P, T2);

        fmpz_mul(Q, Q, Q2);
        *Qexp = *Qexp + *Q2exp;

        if (cont)
            fmpz_mul(P, P, P2);

        fmpz_clear(P2);
        fmpz_clear(Q2);
        fmpz_clear(T2);
    }
}

void
_arb_exp_sum_bs_simple(fmpz_t T, fmpz_t Q, flint_bitcnt_t * Qexp,
    const fmpz_t x, flint_bitcnt_t r, slong N)
{
    fmpz_t P;
    fmpz_init(P);
    bsplit(P, T, Q, Qexp, x, r, 0, N, 0);
    fmpz_clear(P);
}