/*
 * lut.h
 * Copyright (c) 2025 Christopher Herb
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#pragma once

#include <cmath>
#include <cstdint>

namespace trnr {

// Fixed-point log lookup table (Q12)
constexpr int32_t LOG_TABLE_SIZE = 256;
constexpr int32_t LOG_FRACTIONAL_BITS = 12;
constexpr int32_t LOG_TABLE[LOG_TABLE_SIZE] = {
	-37726, -22594, -19806, -18163, -16993, -16084, -15341, -14712, -14167, -13686,
	-13256, -12866, -12511, -12183, -11880, -11598, -11334, -11086, -10853, -10632,
	-10422, -10222, -10032, -9850,	-9676,	-9509,	-9348,	-9194,	-9045,	-8901,
	-8763,	-8628,	-8499,	-8373,	-8250,	-8132,	-8016,	-7904,	-7795,	-7689,
	-7585,	-7484,	-7385,	-7289,	-7195,	-7103,	-7013,	-6925,	-6839,	-6754,
	-6672,	-6591,	-6511,	-6433,	-6357,	-6281,	-6208,	-6135,	-6064,	-5994,
	-5925,	-5858,	-5791,	-5725,	-5661,	-5598,	-5535,	-5473,	-5413,	-5353,
	-5294,	-5236,	-5179,	-5122,	-5067,	-5012,	-4957,	-4904,	-4851,	-4799,
	-4747,	-4696,	-4646,	-4597,	-4548,	-4499,	-4451,	-4404,	-4357,	-4311,
	-4265,	-4220,	-4175,	-4131,	-4087,	-4044,	-4001,	-3958,	-3916,	-3875,
	-3834,	-3793,	-3753,	-3713,	-3673,	-3634,	-3595,	-3557,	-3518,	-3481,
	-3443,	-3406,	-3370,	-3333,	-3297,	-3261,	-3226,	-3191,	-3156,	-3121,
	-3087,	-3053,	-3019,	-2986,	-2953,	-2920,	-2887,	-2855,	-2823,	-2791,
	-2759,	-2728,	-2697,	-2666,	-2635,	-2605,	-2574,	-2544,	-2515,	-2485,
	-2456,	-2427,	-2398,	-2369,	-2340,	-2312,	-2284,	-2256,	-2228,	-2201,
	-2173,	-2146,	-2119,	-2092,	-2065,	-2039,	-2013,	-1986,	-1960,	-1935,
	-1909,	-1883,	-1858,	-1833,	-1808,	-1783,	-1758,	-1733,	-1709,	-1685,
	-1661,	-1637,	-1613,	-1589,	-1565,	-1542,	-1519,	-1495,	-1472,	-1449,
	-1426,	-1404,	-1381,	-1359,	-1336,	-1314,	-1292,	-1270,	-1248,	-1227,
	-1205,	-1184,	-1162,	-1141,	-1120,	-1099,	-1078,	-1057,	-1036,	-1016,
	-995,	-975,	-954,	-934,	-914,	-894,	-874,	-854,	-834,	-815,
	-795,	-776,	-756,	-737,	-718,	-699,	-680,	-661,	-642,	-623,
	-605,	-586,	-568,	-549,	-531,	-513,	-494,	-476,	-458,	-440,
	-423,	-405,	-387,	-370,	-352,	-335,	-317,	-300,	-283,	-265,
	-248,	-231,	-214,	-197,	-181,	-164,	-147,	-131,	-114,	-98,
	-81,	-65,	-48,	-32,	-16,	0,
};

// Fixed-point exp lookup table (Q12)
constexpr int32_t EXP_TABLE_SIZE = 256;
constexpr int32_t EXP_FRACTIONAL_BITS = 12;

constexpr int32_t EXP_TABLE[EXP_TABLE_SIZE] = {
	4096,	4169,	4243,	4319,	4396,	4474,	4553,	4635,	4717,	4801,
	4887,	4974,	5062,	5152,	5244,	5337,	5432,	5529,	5627,	5728,
	5830,	5933,	6039,	6147,	6256,	6367,	6481,	6596,	6714,	6833,
	6955,	7079,	7205,	7333,	7463,	7596,	7732,	7869,	8009,	8152,
	8297,	8445,	8595,	8748,	8904,	9062,	9224,	9388,	9555,	9725,
	9898,	10075,	10254,	10436,	10622,	10811,	11004,	11200,	11399,	11602,
	11809,	12019,	12233,	12451,	12672,	12898,	13128,	13361,	13599,	13841,
	14088,	14339,	14594,	14854,	15118,	15387,	15661,	15940,	16224,	16513,
	16807,	17106,	17410,	17720,	18036,	18357,	18684,	19016,	19355,	19700,
	20050,	20407,	20771,	21140,	21517,	21900,	22290,	22687,	23091,	23502,
	23920,	24346,	24779,	25221,	25670,	26127,	26592,	27065,	27547,	28037,
	28537,	29045,	29562,	30088,	30624,	31169,	31724,	32289,	32864,	33449,
	34044,	34650,	35267,	35895,	36534,	37185,	37847,	38520,	39206,	39904,
	40615,	41338,	42074,	42823,	43585,	44361,	45151,	45955,	46773,	47606,
	48453,	49316,	50194,	51088,	51997,	52923,	53865,	54824,	55800,	56794,
	57805,	58834,	59881,	60947,	62032,	63137,	64261,	65405,	66569,	67755,
	68961,	70189,	71438,	72710,	74005,	75322,	76663,	78028,	79417,	80831,
	82270,	83735,	85226,	86743,	88288,	89859,	91459,	93088,	94745,	96432,
	98148,	99896,	101674, 103485, 105327, 107202, 109111, 111053, 113031, 115043,
	117091, 119176, 121298, 123457, 125655, 127892, 130169, 132487, 134845, 137246,
	139690, 142177, 144708, 147284, 149906, 152575, 155292, 158056, 160870, 163735,
	166650, 169617, 172636, 175710, 178838, 182022, 185263, 188561, 191918, 195335,
	198813, 202352, 205955, 209622, 213354, 217152, 221018, 224953, 228958, 233035,
	237184, 241406, 245704, 250079, 254531, 259063, 263675, 268369, 273147, 278010,
	282960, 287998, 293125, 298344, 303655, 309061, 314564, 320164, 325864, 331666,
	337571, 343581, 349698, 355924, 362261, 368710,
};

inline int32_t fixed_log(int32_t x)
{
	if (x <= 0) return LOG_TABLE[0] << 3; // Scale Q12 → Q15
	int32_t max_val = (1 << LOG_FRACTIONAL_BITS);
	int32_t idx = (x * LOG_TABLE_SIZE) / max_val;
	if (idx >= LOG_TABLE_SIZE - 1) idx = LOG_TABLE_SIZE - 2;
	int32_t a = LOG_TABLE[idx] << 3; // Scale Q12 → Q15
	int32_t b = LOG_TABLE[idx + 1] << 3;
	int32_t frac = ((x * LOG_TABLE_SIZE) - (idx * max_val));
	return a + ((b - a) * frac / max_val);
}

inline int32_t fixed_exp(int32_t x)
{
	int32_t max_val = (1 << EXP_FRACTIONAL_BITS);
	int32_t idx = (x * EXP_TABLE_SIZE) / max_val;
	if (idx >= EXP_TABLE_SIZE - 1) idx = EXP_TABLE_SIZE - 2;
	int32_t a = EXP_TABLE[idx] << 3; // Scale Q12 → Q15
	int32_t b = EXP_TABLE[idx + 1] << 3;
	int32_t frac = ((x * EXP_TABLE_SIZE) - (idx * max_val));
	return a + ((b - a) * frac / max_val);
}

} // namespace trnr