// SPDX-License-Identifier: MIT
//
// Copyright 2024 Advanced Micro Devices, Inc.

#include "spl_debug.h"
#include "spl_custom_float.h"

static bool spl_build_custom_float(struct spl_fixed31_32 value,
                               const struct spl_custom_float_format *format,
                               bool *negative,
                               uint32_t *mantissa,
                               uint32_t *exponenta)
{
        uint32_t exp_offset = (1 << (format->exponenta_bits - 1)) - 1;

        const struct spl_fixed31_32 mantissa_constant_plus_max_fraction =
                SPL_NAMESPACE(spl_fixpt_from_fraction((1LL << (format->mantissa_bits + 1)) - 1,
                                       1LL << format->mantissa_bits));

        struct spl_fixed31_32 mantiss;

        if (spl_fixpt_eq(value, spl_fixpt_zero)) {
                *negative = false;
                *mantissa = 0;
                *exponenta = 0;
                return true;
        }

        if (spl_fixpt_lt(value, spl_fixpt_zero)) {
                *negative = format->sign;
                value = spl_fixpt_neg(value);
        } else {
                *negative = false;
        }

        if (spl_fixpt_lt(value, spl_fixpt_one)) {
                uint32_t i = 1;

                do {
                        value = spl_fixpt_shl(value, 1);
                        ++i;
                } while (spl_fixpt_lt(value, spl_fixpt_one));

                --i;

                if (exp_offset <= i) {
                        *mantissa = 0;
                        *exponenta = 0;
                        return true;
                }

                *exponenta = exp_offset - i;
        } else if (spl_fixpt_le(mantissa_constant_plus_max_fraction, value)) {
                uint32_t i = 1;

                do {
                        value = spl_fixpt_shr(value, 1);
                        ++i;
                } while (spl_fixpt_lt(mantissa_constant_plus_max_fraction, value));

                *exponenta = exp_offset + i - 1;
        } else {
                *exponenta = exp_offset;
        }

        mantiss = spl_fixpt_sub(value, spl_fixpt_one);

        if (spl_fixpt_lt(mantiss, spl_fixpt_zero) ||
            spl_fixpt_lt(spl_fixpt_one, mantiss))
                mantiss = spl_fixpt_zero;
        else
                mantiss = spl_fixpt_shl(mantiss, format->mantissa_bits);

        *mantissa = spl_fixpt_floor(mantiss);

        return true;
}

static bool spl_setup_custom_float(const struct spl_custom_float_format *format,
                               bool negative,
                               uint32_t mantissa,
                               uint32_t exponenta,
                               uint32_t *result)
{
        uint32_t i = 0;
        uint32_t j = 0;
        uint32_t value = 0;

        /* verification code:
         * once calculation is ok we can remove it
         */

        const uint32_t mantissa_mask =
                (1 << (format->mantissa_bits + 1)) - 1;

        const uint32_t exponenta_mask =
                (1 << (format->exponenta_bits + 1)) - 1;

        if (mantissa & ~mantissa_mask) {
                SPL_BREAK_TO_DEBUGGER();
                mantissa = mantissa_mask;
        }

        if (exponenta & ~exponenta_mask) {
                SPL_BREAK_TO_DEBUGGER();
                exponenta = exponenta_mask;
        }

        /* end of verification code */

        while (i < format->mantissa_bits) {
                uint32_t mask = 1 << i;

                if (mantissa & mask)
                        value |= mask;

                ++i;
        }

        while (j < format->exponenta_bits) {
                uint32_t mask = 1 << j;

                if (exponenta & mask)
                        value |= mask << i;

                ++j;
        }

        if (negative && format->sign)
                value |= 1 << (i + j);

        *result = value;

        return true;
}

bool SPL_NAMESPACE(spl_convert_to_custom_float_format(
        struct spl_fixed31_32 value,
        const struct spl_custom_float_format *format,
        uint32_t *result))
{
        uint32_t mantissa;
        uint32_t exponenta;
        bool negative;

        return spl_build_custom_float(value, format, &negative, &mantissa, &exponenta) &&
                                  spl_setup_custom_float(format,
                                                     negative,
                                                     mantissa,
                                                     exponenta,
                                                     result);
}