/*
    Copyright (C) 2011 Sebastian Pancratz
    Copyright (C) 2010 William Hart

    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 <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "fmpz_poly.h"
#include "fmpz_mod_poly.h"

void _fmpz_mod_poly_sqr(fmpz *res, const fmpz *poly, slong len, const fmpz_t p)
{
    _fmpz_poly_sqr(res, poly, len);
    _fmpz_vec_scalar_mod_fmpz(res, res, 2 * len - 1, p);
}

void fmpz_mod_poly_sqr(fmpz_mod_poly_t res, const fmpz_mod_poly_t poly,
                                                      const fmpz_mod_ctx_t ctx)
{
    const slong len = poly->length;

    if (len == 0)
    {
        fmpz_mod_poly_zero(res, ctx);
        return;
    }

    if (res == poly)
    {
        fmpz *t = flint_calloc(2 * len - 1, sizeof(fmpz));

        _fmpz_mod_poly_sqr(t, poly->coeffs, len, fmpz_mod_ctx_modulus(ctx));

        _fmpz_vec_clear(res->coeffs, res->alloc);
        res->alloc  = 2 * len - 1;
        res->length = 2 * len - 1;
        res->coeffs = t;
        _fmpz_mod_poly_normalise(res);
    }
    else
    {
        fmpz_mod_poly_fit_length(res, 2*len - 1, ctx);
    
        _fmpz_mod_poly_sqr(res->coeffs, poly->coeffs, len,
                                                    fmpz_mod_ctx_modulus(ctx));

        _fmpz_mod_poly_set_length(res, 2 * len - 1);
        _fmpz_mod_poly_normalise(res);
    }
}