/*
 * This file is part of the DXX-Rebirth project <https://www.dxx-rebirth.com/>.
 * It is copyright by its individual contributors, as recorded in the
 * project's Git history.  See COPYING.txt at the top level for license
 * terms and a link to the Git history.
 */
#include "mve_audio.h"
#include "dxxsconf.h"
#include <array>
#include "d_enumerate.h"
#include "backports-ranges.h"

constexpr std::array<int, 256> audio_exp_table{
{
         0,      1,      2,      3,      4,      5,      6,      7,      8,      9,     10,     11,     12,     13,     14,     15,
        16,     17,     18,     19,     20,     21,     22,     23,     24,     25,     26,     27,     28,     29,     30,     31,
        32,     33,     34,     35,     36,     37,     38,     39,     40,     41,     42,     43,     47,     51,     56,     61,
        66,     72,     79,     86,     94,    102,    112,    122,    133,    145,    158,    173,    189,    206,    225,    245,
       267,    292,    318,    348,    379,    414,    452,    493,    538,    587,    640,    699,    763,    832,    908,    991,
      1081,   1180,   1288,   1405,   1534,   1673,   1826,   1993,   2175,   2373,   2590,   2826,   3084,   3365,   3672,   4008,
      4373,   4772,   5208,   5683,   6202,   6767,   7385,   8059,   8794,   9597,  10472,  11428,  12471,  13609,  14851,  16206,
     17685,  19298,  21060,  22981,  25078,  27367,  29864,  32589, -29973, -26728, -23186, -19322, -15105, -10503,  -5481,     -1,
         1,      1,   5481,  10503,  15105,  19322,  23186,  26728,  29973, -32589, -29864, -27367, -25078, -22981, -21060, -19298,
    -17685, -16206, -14851, -13609, -12471, -11428, -10472,  -9597,  -8794,  -8059,  -7385,  -6767,  -6202,  -5683,  -5208,  -4772,
     -4373,  -4008,  -3672,  -3365,  -3084,  -2826,  -2590,  -2373,  -2175,  -1993,  -1826,  -1673,  -1534,  -1405,  -1288,  -1180,
     -1081,   -991,   -908,   -832,   -763,   -699,   -640,   -587,   -538,   -493,   -452,   -414,   -379,   -348,   -318,   -292,
      -267,   -245,   -225,   -206,   -189,   -173,   -158,   -145,   -133,   -122,   -112,   -102,    -94,    -86,    -79,    -72,
       -66,    -61,    -56,    -51,    -47,    -43,    -42,    -41,    -40,    -39,    -38,    -37,    -36,    -35,    -34,    -33,
       -32,    -31,    -30,    -29,    -28,    -27,    -26,    -25,    -24,    -23,    -22,    -21,    -20,    -19,    -18,    -17,
       -16,    -15,    -14,    -13,    -12,    -11,    -10,     -9,     -8,     -7,     -6,     -5,     -4,     -3,     -2,     -1
}
};

static void processSwath(std::span<int16_t> fout, const uint8_t *const data, std::array<int32_t, 2> offsets)
{
	for (const auto &&[i, d] : enumerate(ranges::subrange(data, std::next(data, fout.size()))))
    {
		auto &o = offsets[i & 1];
		o += audio_exp_table[d];
		fout.front() = o;
		fout = fout.subspan<1>();
    }
}

void mveaudio_uncompress(std::span<int16_t> buffer, const uint8_t *data)
{
	/* Skip 4 bytes.  Then, skip over the swath value in the input, since the
	 * caller provided that value as the extent of `buffer`.
	 */
	data += 6;
	const uint16_t c0 = data[0] | (data[1] << 8);
	data += 2;
	const uint16_t c1 = data[0] | (data[1] << 8);
	data += 2;
	buffer.front() = c0;
	buffer = buffer.subspan<1>();
	buffer.front() = c1;
	buffer = buffer.subspan<1>();
	processSwath(buffer, data, {{c0, c1}});
}