/*
    Copyright (C) 2011 Sebastian Pancratz

    This file is part of FLINT.

    FLINT 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 <https://www.gnu.org/licenses/>.
*/

#include "padic.h"

#define PADIC_RANDTEST_TRIES  10

void padic_randtest(padic_t rop, flint_rand_t state, const padic_ctx_t ctx)
{
    const slong N = padic_prec(rop);

    slong min, max;
    fmpz_t pow;
    int alloc;

    if (N > 0)
    {
        min = - ((N + 9) / 10);
        max = N;
    }
    else if (N < 0)
    {
        min = N - ((-N + 9) / 10);
        max = N;
    }
    else  /* ctx->N == 0 */
    {
        min = -10;
        max = 0;
    }

    padic_val(rop) = n_randint(state, max - min) + min;

    alloc = _padic_ctx_pow_ui(pow, N - padic_val(rop), ctx);
    fmpz_randm(padic_unit(rop), state, pow);
    _padic_canonicalise(rop, ctx);
    if (alloc)
        fmpz_clear(pow);
}

void padic_randtest_not_zero(padic_t rop, flint_rand_t state, 
                             const padic_ctx_t ctx)
{
    slong i;

    padic_randtest(rop, state, ctx);

    for (i = 1; !padic_is_zero(rop) && i < PADIC_RANDTEST_TRIES; i++)
        padic_randtest(rop, state, ctx);

    if (padic_is_zero(rop))
    {
        fmpz_one(padic_unit(rop));
        padic_val(rop) = padic_prec(rop) - 1;
    }
}

void padic_randtest_int(padic_t rop, flint_rand_t state, 
                        const padic_ctx_t ctx)
{
    const slong N = padic_prec(rop);

    if (N <= 0)
    {
        padic_zero(rop);
    }
    else
    {
        fmpz_t pow;
        int alloc;

        padic_val(rop) = n_randint(state, N);

        alloc = _padic_ctx_pow_ui(pow, N - padic_val(rop), ctx);
        fmpz_randm(padic_unit(rop), state, pow);
        _padic_canonicalise(rop, ctx);
        if (alloc)
            fmpz_clear(pow);
    }
}