/*
    Copyright (C) 2005-2009 Damien Stehle
    Copyright (C) 2007 David Cade
    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 "fmpz_mat.h"

void
fmpz_mat_randntrulike(fmpz_mat_t mat, flint_rand_t state, flint_bitcnt_t bits, ulong q)
{
    const slong c = mat->c, r = mat->r, d = r / 2;

    slong i, j, k;
    fmpz *h;

    if ((c != r) || (c != 2 * d))
    {
        flint_printf("Exception (fmpz_mat_randntrulike). Ill-formed matrix.\n");
        flint_abort();
    }

    h = _fmpz_vec_init(d);

    for (i = 0; i < d; i++)
        fmpz_randbits(h + i, state, bits);

    for (i = 0; i < d; i++)
    {
        for (j = 0; j < i; j++)
            fmpz_zero(mat->rows[i] + j);
        fmpz_one(mat->rows[i] + i);
        for (j = i + 1; j < d; j++)
            fmpz_zero(mat->rows[i] + j);
    }

    for (i = d; i < r; i++)
        for (j = 0; j < d; j++)
            fmpz_zero(mat->rows[i] + j);

    for (i = d; i < r; i++)
    {
        for (j = d; j < i; j++)
            fmpz_zero(mat->rows[i] + j);
        fmpz_set_ui(mat->rows[i] + i, q);
        for (j = i + 1; j < c; j++)
            fmpz_zero(mat->rows[i] + j);
    }

    for (i = 0; i < d; i++)
    {
        for (j = d; j < c; j++)
        {
            k = j + i;
            while (k >= d)
                k -= d;
            fmpz_set(mat->rows[i] + j, h + k);
        }
    }

    _fmpz_vec_clear(h, d);
}
