/*
    Copyright (C) 2018 Daniel Schultz

    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_mpoly.h"


int fmpz_mpoly_pow_fmpz(fmpz_mpoly_t A, const fmpz_mpoly_t B,
                                    const fmpz_t k, const fmpz_mpoly_ctx_t ctx)
{
    slong i;
    fmpz * maxBfields;
    flint_bitcnt_t exp_bits;
    TMP_INIT;

    if (fmpz_sgn(k) < 0)
        flint_throw(FLINT_ERROR, "Negative power in fmpz_mpoly_pow_fmpz");

    if (fmpz_fits_si(k))
        return fmpz_mpoly_pow_ui(A, B, fmpz_get_ui(k), ctx);

    /*
        we are raising a polynomial to an unreasonable exponent
        It must either be zero or a monomial with unit coefficient
    */

    if (B->length == 0)
    {
        fmpz_mpoly_zero(A, ctx);
        return 1;
    }

    if (B->length != 1)
        return 0;

    if (!fmpz_is_pm1(B->coeffs + 0))
        return 0;

    TMP_START;

    maxBfields = (fmpz *) TMP_ALLOC(ctx->minfo->nfields*sizeof(fmpz));
    for (i = 0; i < ctx->minfo->nfields; i++)
        fmpz_init(maxBfields + i);
    mpoly_max_fields_fmpz(maxBfields, B->exps, B->length, B->bits, ctx->minfo);

    _fmpz_vec_scalar_mul_fmpz(maxBfields, maxBfields, ctx->minfo->nfields, k);

    exp_bits = _fmpz_vec_max_bits(maxBfields, ctx->minfo->nfields);
    exp_bits = FLINT_MAX(MPOLY_MIN_BITS, exp_bits + 1);
    exp_bits = mpoly_fix_bits(exp_bits, ctx->minfo);

    fmpz_mpoly_fit_length(A, 1, ctx);
    fmpz_mpoly_fit_bits(A, exp_bits, ctx);
    A->bits = exp_bits;

    fmpz_set_si(A->coeffs + 0,
                     (fmpz_is_one(B->coeffs + 0) || fmpz_is_even(k)) ? 1 : -1);

    mpoly_pack_vec_fmpz(A->exps + 0, maxBfields, exp_bits, ctx->minfo->nfields, 1);

    _fmpz_mpoly_set_length(A, 1, ctx);

    for (i = 0; i < ctx->minfo->nfields; i++)
        fmpz_clear(maxBfields + i);

    TMP_END;

    return 1;
}