/*
    Copyright (C) 2020, 2021 Fredrik Johansson

    This file is part of Calcium.

    Calcium 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 "ca_poly.h"

void
ca_poly_randtest_same_nf(ca_poly_t res, flint_rand_t state, const ca_t x, slong len, slong bits, slong den_bits, ca_ctx_t ctx)
{
    slong i;
    fmpz_t t;

    ca_poly_fit_length(res, len, ctx);
    for (i = 0; i < len; i++)
        ca_randtest_same_nf(res->coeffs + i, state, x, bits, 1, ctx);
    _ca_poly_set_length(res, len, ctx);
    _ca_poly_normalise(res, ctx);

    fmpz_init(t);
    fmpz_randtest_not_zero(t, state, den_bits);
    ca_poly_div_fmpz(res, res, t, ctx);
    fmpz_clear(t);
}

/* todo */
void
ca_poly_truncate(ca_poly_t poly, slong newlen, ca_ctx_t ctx)
{
    if (poly->length > newlen)
    {
        slong i;
        for (i = newlen; i < poly->length; i++)
            ca_zero(poly->coeffs + i, ctx);
        poly->length = newlen;
        _ca_poly_normalise(poly, ctx);
    }
}

int main()
{
    slong iter;
    flint_rand_t state;

    flint_printf("inv_series....");
    fflush(stdout);

    flint_randinit(state);

    for (iter = 0; iter < 100 * calcium_test_multiplier(); iter++)
    {
        ca_ctx_t ctx;
        ca_poly_t A, B, AB, one;
        slong n1;

        /* Test inv(A) * A == 1 */
        ca_ctx_init(ctx);

        ca_poly_init(A, ctx);
        ca_poly_init(B, ctx);
        ca_poly_init(AB, ctx);
        ca_poly_init(one, ctx);

        if (n_randint(state, 2))
        {
            ca_poly_randtest(A, state, 4, 2, 10, ctx);
            n1 = n_randint(state, 6);
        }
        else
        {
            qqbar_t t;
            ca_t x;

            qqbar_init(t);
            ca_init(x, ctx);

            qqbar_randtest(t, state, 8, 10);
            ca_set_qqbar(x, t, ctx);

            ca_poly_randtest_same_nf(A, state, x, 1 + n_randint(state, 20), 2 + n_randint(state, 100), 2 + n_randint(state, 100), ctx);

            n1 = n_randint(state, 50);

            qqbar_clear(t);
            ca_clear(x, ctx);
        }

        ca_poly_randtest(B, state, 4, 2, 10, ctx);

        if (n_randint(state, 2))
        {
            ca_poly_set(B, A, ctx);
            ca_poly_inv_series(B, B, n1, ctx);
        }
        else
        {
            ca_poly_inv_series(B, A, n1, ctx);
        }

        ca_poly_mullow(AB, A, B, n1, ctx);
        ca_poly_one(one, ctx);
        ca_poly_truncate(one, n1, ctx);

        if (!(A->length == 0 || ca_check_is_zero(A->coeffs, ctx) != T_FALSE))
        {
            if (ca_poly_check_equal(AB, one, ctx) == T_FALSE)
            {
                flint_printf("FAIL\n\n");
                flint_printf("A = "); ca_poly_print(A, ctx); flint_printf("\n");
                flint_printf("B = "); ca_poly_print(B, ctx); flint_printf("\n");
                flint_printf("AB = "); ca_poly_print(AB, ctx); flint_printf("\n");
                flint_abort();
            }
        }

        ca_poly_clear(A, ctx);
        ca_poly_clear(B, ctx);
        ca_poly_clear(AB, ctx);
        ca_poly_clear(one, ctx);

        ca_ctx_clear(ctx);
    }

    flint_randclear(state);
    flint_cleanup();
    flint_printf("PASS\n");
    return EXIT_SUCCESS;
}
