/*
 * Copyright (C) 2019-2021 Collabora, Ltd.
 * Copyright (C) 2019 Alyssa Rosenzweig
 * SPDX-License-Identifier: MIT
 */

#include "genxml/gen_macros.h"

#include <string.h>
#include "util/format_srgb.h"
#include "util/rounding.h"
#include "util/u_pack_color.h"
#include "pan_format.h"
#include "pan_util.h"

/* Clear colours are packed as the internal format of the tilebuffer, looked up
 * in the blendable formats table given the render target format.
 *
 * Raw formats may emulate arbitrary formats with blend shaders. For these, we
 * defer to util_pack_colour to pack in the API format.
 *
 * Blendable formats, on the other hand, include extra "fractional" bits in the
 * tilebuffer for dithering. These have a packed fixed-point representation:
 * for a channel with m integer bits and n fractional bits, multiply by ((2^m)
 * - 1) * 2^n and round to the nearest even.
 */

/* Replicate a 32-bit value to fill 128-bit */

static void
pan_pack_color_32(uint32_t *packed, uint32_t v)
{
   for (unsigned i = 0; i < 4; ++i)
      packed[i] = v;
}

/* For m integer bits and n fractional bits, calculate the conversion factor,
 * multiply the source value, and convert to integer rounding to even. When
 * dithering, the fractional bits are used. When not dithered, only the integer
 * bits are used and the fractional bits must remain zero. */

static inline uint32_t
float_to_fixed(float f, unsigned bits_int, unsigned bits_frac, bool dither)
{
   uint32_t m = (1 << bits_int) - 1;

   if (dither) {
      float factor = m << bits_frac;
      return _mesa_roundevenf(f * factor);
   } else {
      uint32_t v = _mesa_roundevenf(f * (float)m);
      return v << bits_frac;
   }
}

struct mali_tib_layout {
   unsigned int_r, frac_r;
   unsigned int_g, frac_g;
   unsigned int_b, frac_b;
   unsigned int_a, frac_a;
};

/* clang-format off */
static const struct mali_tib_layout tib_layouts[] = {
   [MALI_COLOR_BUFFER_INTERNAL_FORMAT_R8G8B8A8]    = {  8, 0,  8, 0,  8, 0, 8, 0 },
   [MALI_COLOR_BUFFER_INTERNAL_FORMAT_R10G10B10A2] = { 10, 0, 10, 0, 10, 0, 2, 0 },
   [MALI_COLOR_BUFFER_INTERNAL_FORMAT_R8G8B8A2]    = {  8, 2,  8, 2,  8, 2, 2, 0 },
   [MALI_COLOR_BUFFER_INTERNAL_FORMAT_R4G4B4A4]    = {  4, 4,  4, 4,  4, 4, 4, 4 },
   [MALI_COLOR_BUFFER_INTERNAL_FORMAT_R5G6B5A0]    = {  5, 5,  6, 4,  5, 5, 0, 2 },
   [MALI_COLOR_BUFFER_INTERNAL_FORMAT_R5G5B5A1]    = {  5, 5,  5, 5,  5, 5, 1, 1 },
};
/* clang-format on */

/* Raw values are stored as-is but replicated for multisampling */

static void
pan_pack_raw(uint32_t *packed, const union pipe_color_union *color,
             enum pipe_format format)
{
   union util_color out = {0};
   unsigned size = util_format_get_blocksize(format);
   assert(size <= 16);

   util_pack_color(color->f, format, &out);

   if (size == 1) {
      unsigned b = out.ui[0] & 0xff;
      unsigned w = b | (b << 8);
      pan_pack_color_32(packed, w | (w << 16));
   } else if (size == 2) {
      unsigned w = out.ui[0] & 0xffff;
      pan_pack_color_32(packed, w | (w << 16));
   } else if (size <= 4) {
      pan_pack_color_32(packed, out.ui[0]);
   } else if (size <= 8) {
      memcpy(packed + 0, out.ui, 8);
      memcpy(packed + 2, out.ui, 8);
   } else {
      memcpy(packed, out.ui, 16);
   }
}

void
pan_pack_color(const struct pan_blendable_format *blendable_formats,
               uint32_t *packed, const union pipe_color_union *color,
               enum pipe_format format, bool dithered)
{
   enum mali_color_buffer_internal_format internal =
      blendable_formats[format].internal;

   if (util_format_is_float(format) ||
       internal == MALI_COLOR_BUFFER_INTERNAL_FORMAT_RAW_VALUE) {
      pan_pack_raw(packed, color, format);
      return;
   }

   /* Saturate to [0, 1] by definition of UNORM. Prevents overflow. */
   float r = SATURATE(color->f[0]);
   float g = SATURATE(color->f[1]);
   float b = SATURATE(color->f[2]);
   float a = SATURATE(color->f[3]);

   /* Fill in alpha = 1.0 by default */
   if (!util_format_has_alpha(format))
      a = 1.0;

   /* Convert colourspace while we still have floats */
   if (util_format_is_srgb(format)) {
      r = util_format_linear_to_srgb_float(r);
      g = util_format_linear_to_srgb_float(g);
      b = util_format_linear_to_srgb_float(b);
   }

   /* Look up the layout of the tilebuffer */
   assert(internal < ARRAY_SIZE(tib_layouts));
   struct mali_tib_layout l = tib_layouts[internal];

   unsigned count_r = l.int_r + l.frac_r;
   unsigned count_g = l.int_g + l.frac_g + count_r;
   unsigned count_b = l.int_b + l.frac_b + count_g;
   ASSERTED unsigned count_a = l.int_a + l.frac_a + count_b;

   /* Must fill the word */
   assert(count_a == 32);

   /* Convert the transformed float colour to the given layout */
   uint32_t ur = float_to_fixed(r, l.int_r, l.frac_r, dithered) << 0;
   uint32_t ug = float_to_fixed(g, l.int_g, l.frac_g, dithered) << count_r;
   uint32_t ub = float_to_fixed(b, l.int_b, l.frac_b, dithered) << count_g;
   uint32_t ua = float_to_fixed(a, l.int_a, l.frac_a, dithered) << count_b;

   pan_pack_color_32(packed, ur | ug | ub | ua);
}
