//  ================================================================
//
//    graphics.c
//
//  ----------------------------------------------------------------
//
//    (C) 2025 Mitya Selivanov <guattari.tech>
//
//  ================================================================

#ifndef GRAPHICS_HEADER_GUARD_
#define GRAPHICS_HEADER_GUARD_

#ifdef GRAPHICS_HEADER
#define REDUCED_SYSTEM_LAYER_HEADER
#endif

#include "reduced_system_layer.c"

//  ================================================================
//
//    Vector math
//
//  ================================================================

vec3_f32 vec3_from_vec4_f32(vec4_f32 v);
vec4_f32 vec4_from_vec3_f32(vec3_f32 v, f32 w);
vec3_f32 vec3_f32_lerp     (vec3_f32 a, vec3_f32 b, f32 t);
vec4_f32 vec4_f32_lerp     (vec4_f32 a, vec4_f32 b, f32 t);

//  ================================================================

#ifndef EPSILON
#define EPSILON (1e-9)
#endif

typedef struct {
  i64       width;
  i64       height;
  i64       line_size;
  vec4_f32 *pixels;
} Pixel_Buffer;

typedef struct {
  Pixel_Buffer buffer;
  vec2         position;
  vec2         scale;
  b8           quick     : 1;
  b8           alpha     : 1;
  b8           xor_color : 1;
  vec4_f32     color;
} Brush;

vec3_f32 lab_from_rgb(vec3_f32 rgb);
vec3_f32 rgb_from_lab(vec3_f32 lab);
vec3_f32 lab_from_lch(vec3_f32 lch);
vec3_f32 lch_from_lab(vec3_f32 lab);
vec3_f32 rgb_from_lch(vec3_f32 lch);
vec3_f32 lch_from_rgb(vec3_f32 rgb);

vec3_f32 rgb_gamma_add    (vec3_f32 rgb);
vec3_f32 rgb_gamma_remove (vec3_f32 rgb);
vec4_f32 rgba_gamma_add   (vec4_f32 rgb);
vec4_f32 rgba_gamma_remove(vec4_f32 rgb);

vec3_f32 rgb_gamma_lerp (vec3_f32 a, vec3_f32 b, f32 t);
vec4_f32 rgba_gamma_lerp(vec4_f32 a, vec4_f32 b, f32 t);
vec3_f32 rgb_mix        (vec3_f32 a, vec3_f32 b, f32 t);
vec4_f32 rgba_mix       (vec4_f32 a, vec4_f32 b, f32 t);
vec3_f32 lch_mix        (vec3_f32 a, vec3_f32 b, f32 t);
vec3_f32 lch_lerp       (vec3_f32 a, vec3_f32 b, f32 t);

u32      rgb_u32_from_f32(vec3_f32 color);
vec3_f32 rgb_f32_from_u32(u32 color);
u32      rgba_u32_from_f32(vec4_f32 color);
vec4_f32 rgba_f32_from_u32(u32 color);

#define RGB(...)  ((Brush) { .color = { __VA_ARGS__, 1.f } })
#define RGBA(...) ((Brush) { .color = { __VA_ARGS__ } })
#define LCH(...)  ((Brush) { .color = vec4_from_vec3_f32(rgb_from_lch((vec3_f32) { __VA_ARGS__ }), 1.f) } })
#define LCHA(...) ((Brush) { .color = vec4_from_vec3_f32(rgb_from_lch(vec3_from_vec4_f32((vec4_f32) { __VA_ARGS__ })), ((vec4_f32) { __VA_ARGS__ }).w) } })

b8 rectangle_contains(f64 x0, f64 y0, f64 width, f64 height,          f64 px, f64 py);
b8 triangle_contains (f64 x0, f64 y0, f64 x1, f64 y1, f64 x2, f64 y2, f64 px, f64 py);
b8 ellipse_contains  (f64 x0, f64 y0, f64 width, f64 height,          f64 px, f64 py);
b8 line_contains     (f64 x0, f64 y0, f64 x1, f64 y1, f64 width,      f64 px, f64 py);

Pixel_Buffer window_pixels(void);
Pixel_Buffer subimage(Pixel_Buffer image, i64 x, i64 y, i64 width, i64 height);

void put_pixel       (Brush brush, i64 x, i64 y);
void draw_pixels     (Brush brush, f64 x, f64 y, f64 width, f64 height, Pixel_Buffer src);
void fill_rectangle  (Brush brush, f64 x, f64 y, f64 width, f64 height);
void fill_triangle   (Brush brush, f64 x0, f64 y0, f64 x1, f64 y1, f64 x2, f64 y2);
void fill_ellipse    (Brush brush, f64 x, f64 y, f64 width, f64 height);
void fill_line       (Brush brush, f64 x0, f64 y0, f64 x1, f64 y1, f64 width);
void draw_text_area  (Brush brush, f64 x, f64 y, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 num_chars, c32 *text);
void draw_text_cursor(Brush brush, f64 x, f64 y, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 cursor, i64 selection, i64 num_chars, c32 *text);

#endif // GRAPHICS_HEADER_GUARD_

//  ================================================================

#ifndef GRAPHICS_HEADER
#ifndef GRAPHICS_IMPL_GUARD_
#define GRAPHICS_IMPL_GUARD_

static u64 _bitfont[] = {
  0xbc0000000000, 0xc00300000, 0x5fd5040093f24fc9, 0xa00a2c2a1a280105, 0xc000415e6f, 0x400000020be0000, 0x1c38a8400000007d, 0x40002043e1020215, 0x408102000000010, 0x9800000000020002, 0xf913e00000033, 0x53200000207c8800, 0x3654880000099, 0x54b800000f840e00, 0xe953c000001a, 0x953e000000674080, 0x1e54b800000f, 0x490000000000240, 0x88a08000000, 0x20a220050a142850, 0x6520800000, 0x912f801eab260be, 0x800034952bf0001f, 0xc850bf0000921427, 0xf00010a54afc0003, 0xd29427800002142b, 0x840007e1023f0000, 0x7d09100000217e, 0x3f000188a08fc000, 0xc30c0cfc00000810, 0x27803f101013f00f, 0xc244bf0000f214, 0x4bf0002f21427800, 0xc254a480006c24, 0x407c00102fc08100, 0xf208080f0000fa0, 0x531007d81c607c0, 0xc208288c031141, 0x83fc00046954b10, 0x180e03000000, 0x41040000000ff04, 0x8102040810000404, 0x2a54600000000101, 0x309123e0000e, 0xc912180000a22447, 0x8000062a54700007, 0xe52a4300000029f0, 0xa0000602043e0001, 0x1d48000002074, 0x1f000003610f8000, 0x13e04f800000010, 0x470000780813e00f, 0x184893e0000e224, 0x23e0001f12243000, 0x82a54100000008, 0x40780000009f0200, 0xe208080e0001f20, 0xa22007981860780, 0x82082888022282, 0x16c200004ca95320, 0x7f000004, 0x408200000086d04, 0x8204,
};

enum {
  CHAR_NUM_BITS_X_ = 6,
  CHAR_NUM_BITS_Y_ = 7,
  CHAR_NUM_BITS_   = CHAR_NUM_BITS_X_ * CHAR_NUM_BITS_Y_,
};

static f64 min3_(f64 a, f64 b, f64 c) {
  if (a < b && a < c)
    return a;
  if (b < c)
    return b;
  return c;
}

static f64 max3_(f64 a, f64 b, f64 c) {
  if (a > b && a > c)
    return a;
  if (b > c)
    return b;
  return c;
}

static b8 same_sign_(f64 a, f64 b) {
  if (a >=  EPSILON && b <= -EPSILON) return 0;
  if (a <= -EPSILON && b >=  EPSILON) return 0;
  return 1;
}

static f64 gamma_(f64 x) {
  if (x >= 0.0031308)
    return 1.055 * pow(x, 1.0 / 2.4) - 0.055;
  return 12.92 * x;
}

static f64 gamma_re_(f64 x) {
  if (x >= 0.04045)
    return pow((x + 0.055) / 1.055, 2.4);
  return x / 12.92;
}

static void put_pixel_color_(Brush brush, i64 x, i64 y) {
  brush.buffer.pixels[y * brush.buffer.line_size + x] = brush.color;
}

static void put_pixel_alpha_(Brush brush, i64 x, i64 y) {
  i64 n = y * brush.buffer.line_size + x;

  vec4_f32 dst = brush.buffer.pixels[n];
  f64      a   = brush.color.w;

  brush.buffer.pixels[n] = (vec4_f32) {
    .x = (f32) (dst.x * (1. - a) + brush.color.x * a),
    .y = (f32) (dst.y * (1. - a) + brush.color.y * a),
    .z = (f32) (dst.z * (1. - a) + brush.color.z * a),
    .w = 1.f,
  };
}

static void put_pixel_xor_(Brush brush, i64 x, i64 y) {
  i64 n = y * brush.buffer.line_size + x;

  vec3_f32 c = rgb_f32_from_u32(
      rgb_u32_from_f32(vec3_from_vec4_f32(brush.buffer.pixels[n]))
    ^ rgb_u32_from_f32(vec3_from_vec4_f32(brush.color))
  );

  brush.color = vec4_from_vec3_f32(c, brush.color.w);

  if (brush.alpha)
    put_pixel_alpha_(brush, x, y);
  else
    brush.buffer.pixels[n] = brush.color;
}

static void put_pixel_(Brush brush, i64 x, i64 y) {
  if (brush.xor_color)
    put_pixel_xor_(brush, x, y);
  else if (brush.alpha)
    put_pixel_alpha_(brush, x, y);
  else
    put_pixel_color_(brush, x, y);
}

void fill_rectangle_(Brush brush, f64 x, f64 y, f64 width, f64 height) {
  if (width < EPSILON || height < EPSILON)
    return;

  f64 x0, y0, x1, y1;

  if (brush.scale.x < 0) {
    x1 = brush.position.x + x * brush.scale.x;
    x0 = x1 + width * brush.scale.x;
  } else {
    x0 = brush.position.x + x * brush.scale.x;
    x1 = x0 + width * brush.scale.x;
  }

  if (brush.scale.y < 0) {
    y1 = brush.position.y + y * brush.scale.y;
    y0 = y1 + height * brush.scale.y;
  } else {
    y0 = brush.position.y + y * brush.scale.y;
    y1 = y0 + height * brush.scale.y;
  }

  if (!brush.quick) {
    i64 i0 = (i64) ceil (x0);
    i64 i1 = (i64) floor(x1);
    i64 j0 = (i64) ceil (y0);
    i64 j1 = (i64) floor(y1);

    i64 i00 = i0;
    i64 j00 = j0;
    i64 i10 = i1;
    i64 j10 = j1;

    if (i0 < 0)                   i0 = 0;
    if (i1 > brush.buffer.width)  i1 = brush.buffer.width;
    if (j0 < 0)                   j0 = 0;
    if (j1 > brush.buffer.height) j1 = brush.buffer.height;

    f64 kx0 = i00 - x0;
    f64 kx1 = x1  - i10;
    f64 ky0 = j00 - y0;
    f64 ky1 = y1  - j10;

    for (i64 j = j0; j < j1; ++j)
      for (i64 i = i0; i < i1; ++i)
        put_pixel_(brush, i, j);

    if (i00 > i10) {
      kx0 *= kx1;
      kx1 = 0.;
    }

    if (j00 > j10) {
      ky0 *= ky1;
      ky1 = 0.;
    }

    f64 alpha   = brush.alpha ? brush.color.w : 1.;
    brush.alpha = 1;

    if (i00 - 1 >= 0 && i00 - 1 < brush.buffer.width) {
      brush.color.w = gamma_(gamma_re_(alpha) * kx0);
      for (i64 j = j0; j < j1; ++j)
        put_pixel_(brush, i00 - 1, j);
    }

    if (i10 >= 0 && i10 < brush.buffer.width) {
      brush.color.w = gamma_(gamma_re_(alpha) * kx1);
      for (i64 j = j0; j < j1; ++j)
        put_pixel_(brush, i10, j);
    }

    if (j00 - 1 >= 0 && j00 - 1 < brush.buffer.height) {
      brush.color.w = gamma_(gamma_re_(alpha) * ky0);
      for (i64 i = i0; i < i1; ++i)
        put_pixel_(brush, i, j00 - 1);
    }

    if (j10 >= 0 && j10 < brush.buffer.height) {
      brush.color.w = gamma_(gamma_re_(alpha) * ky1);
      for (i64 i = i0; i < i1; ++i)
        put_pixel_(brush, i, j10);
    }

    if (   i00 - 1 >= 0 && i00 - 1 < brush.buffer.width
        && j00 - 1 >= 0 && j00 - 1 < brush.buffer.height) {
      brush.color.w = gamma_(gamma_re_(alpha) * kx0 * ky0);
      put_pixel_(brush, i00 - 1, j00 - 1);
    }

    if (   i10     >= 0 && i10     < brush.buffer.width
        && j00 - 1 >= 0 && j00 - 1 < brush.buffer.height) {
      brush.color.w = gamma_(gamma_re_(alpha) * kx1 * ky0);
      put_pixel_(brush, i10, j00 - 1);
    }

    if (   i00 - 1 >= 0 && i00 - 1 < brush.buffer.width
        && j10     >= 0 && j10     < brush.buffer.height) {
      brush.color.w = gamma_(gamma_re_(alpha) * kx0 * ky1);
      put_pixel_(brush, i00 - 1, j10);
    }

    if (   i10 >= 0 && i10 < brush.buffer.width
        && j10 >= 0 && j10 < brush.buffer.height) {
      brush.color.w = gamma_(gamma_re_(alpha) * kx1 * ky1);
      put_pixel_(brush, i10, j10);
    }
  } else {
    i64 i0 = (i64) floor(x0);
    i64 i1 = (i64) ceil (x1);
    i64 j0 = (i64) floor(y0);
    i64 j1 = (i64) ceil (y1);

    if (i0 < 0)                   i0 = 0;
    if (i1 > brush.buffer.width)  i1 = brush.buffer.width;
    if (j0 < 0)                   j0 = 0;
    if (j1 > brush.buffer.height) j1 = brush.buffer.height;

    if (brush.xor_color)
      for (i64 j = j0; j < j1; ++j)
        for (i64 i = i0; i < i1; ++i)
          put_pixel_xor_(brush, i, j);
    else if (brush.alpha)
      for (i64 j = j0; j < j1; ++j)
        for (i64 i = i0; i < i1; ++i)
          put_pixel_alpha_(brush, i, j);
    else
      for (i64 j = j0; j < j1; ++j)
        for (i64 i = i0; i < i1; ++i)
          put_pixel_color_(brush, i, j);
  }
}

void fill_triangle_(Brush brush, f64 x0, f64 y0, f64 x1, f64 y1, f64 x2, f64 y2) {
  //  FIXME PERF:
  //  Implement better algorithm.

  x0 = brush.position.x + x0 * brush.scale.x;
  y0 = brush.position.y + y0 * brush.scale.y;

  x1 = brush.position.x + x1 * brush.scale.x;
  y1 = brush.position.y + y1 * brush.scale.y;

  x2 = brush.position.x + x2 * brush.scale.x;
  y2 = brush.position.y + y2 * brush.scale.y;

  i64 i0 = (i64) floor(min3_(x0, x1, x2));
  i64 j0 = (i64) floor(min3_(y0, y1, y2));
  i64 i1 = (i64) ceil (max3_(x0, x1, x2));
  i64 j1 = (i64) ceil (max3_(y0, y1, y2));

  if (j0 < 0)                    j0 = 0;
  if (j1 >= brush.buffer.height) j1 = brush.buffer.height - 1;

  for (i64 j = j0; j <= j1; ++j) {
    i64 left  = i1;
    i64 right = i0;

    for (i64 i = i0; i <= i1; ++i)
      if (triangle_contains(x0, y0, x1, y1, x2, y2, (f64) i, (f64) j)) {
        left = i;
        break;
      }

    for (i64 i = i1; i >= i0; --i)
      if (triangle_contains(x0, y0, x1, y1, x2, y2, (f64) i, (f64) j)) {
        right = i;
        break;
      }

    if (left  <  0)                  left  = 0;
    if (right >= brush.buffer.width) right = brush.buffer.width - 1;

    for (i64 i = left; i <= right; ++i)
      put_pixel_(brush, i, j);
  }
}

static i64 char_column_offset_(c32 c, i64 column_index) {
  if (column_index < 0 || column_index >= CHAR_NUM_BITS_X_)
    return -1;
  return (c - 32) * CHAR_NUM_BITS_ + column_index * CHAR_NUM_BITS_Y_;
}

static b8 char_bit_(i64 column_offset, i64 row_index) {
  if (column_offset < 0 || row_index < 0 || row_index >= CHAR_NUM_BITS_Y_)
    return 0;

  i64 bit_index   = column_offset + row_index;
  i64 qword_index = bit_index / 64;
  if (qword_index < 0 || qword_index >= (i64) (sizeof _bitfont / sizeof *_bitfont))
    return 0;
  u64 mask        = 1ull << (bit_index % 64);
  return !!(_bitfont[qword_index] & mask);
}

static u64 char_column_convolved_(c32 c, i64 column_index) {
  if (column_index < 0 || column_index >= CHAR_NUM_BITS_X_)
    return 0;

  u64 column = 0;
  i64 offset = char_column_offset_(c, column_index);

  for (i64 y = 0; y < CHAR_NUM_BITS_Y_; ++y)
    if (char_bit_(offset, y))
      column |= 3ull << y;

  return column;
}

static b8 char_column_empty_(c32 c, i64 column_index) {
  if (column_index < 0 || column_index >= CHAR_NUM_BITS_X_)
    return 1;

  i64 offset = char_column_offset_(c, column_index);

  for (i64 y = 0; y < CHAR_NUM_BITS_Y_; ++y)
    if (char_bit_(offset, y))
      return 0;

  return 1;
}

static i64 char_width_(c32 c) {
  if (c < 32)
    return 0;
  if (c == ' ' || c > 127)
    return 4;

  i64 width = 0;

  for (; width < CHAR_NUM_BITS_X_; ++width)
    if (char_column_empty_(c, width) && char_column_empty_(c, width + 1))
      break;

  return width;
}

static i64 char_spacing_(i64 num_chars, c32 *text, i64 index) {
  if (text == NULL)
    return 0;

  if (index < 0 || index + 1 >= num_chars)
    return 0;

  u64 a = char_column_convolved_(text[index], char_width_(text[index]) - 1);
  u64 b = char_column_convolved_(text[index + 1], 0);

  if (!!(a & b))
    return 1;

  return 0;
}

static i64 text_cursor_(i64 num_chars, c32 *text) {
  if (text == NULL)
    return 0;

  i64 cursor = 0;

  for (i64 i = 0; i < num_chars; ++i) {
    if (text[i] <= ' ') {
      if (text[i] == '\n')
        cursor = 0;
      else if (text[i] == '\b' && i > 0)
        cursor -= char_width_(text[i - 1]) + char_spacing_(num_chars, text, i - 1);
      else if (text[i] == '\r')
        cursor = 0;
      else
        cursor += char_width_(' ') + char_spacing_(num_chars, text, i);
      continue;
    }
    cursor += char_width_(text[i]) + char_spacing_(num_chars, text, i);
  }

  return cursor;
}

static i64 enum_text_columns_(i64 num_chars, c32 *text) {
  if (text == NULL)
    return 0;

  i64 cols = 0;
  i64 n    = 0;

  for (i64 i = 0; i < num_chars; ++i) {
    if (text[i] <= ' ') {
      if (text[i] == '\n') {
        if (cols < n)
          cols = n;
        n = 0;
      } else if (text[i] == '\b' && i > 0) {
        if (cols < n)
          cols = n;
        n -= char_width_(text[i - 1]) + char_spacing_(num_chars, text, i - 1);
      } else if (text[i] == '\r') {
        if (cols < n)
          cols = n;
        n = 0;
      } else
        n += char_width_(' ') + char_spacing_(num_chars, text, i);
      continue;
    }
    n += char_width_(text[i]) + char_spacing_(num_chars, text, i);
  }

  if (cols < n)
    cols = n;

  return cols;
}

static i64 enum_text_rows_(i64 num_chars, c32 *text) {
  if (text == NULL)
    return 0;

  i64 rows = 0;

  for (i64 i = 0; i <= num_chars; ++i)
    if (i == num_chars || text[i] == '\n') {
      if (rows > 0)
        ++rows;
      rows += CHAR_NUM_BITS_Y_;
    }

  return rows;
}

static void draw_text_(Brush brush, f64 x0, f64 y0, f64 scale_x, f64 scale_y, i64 num_chars, c32 *text) {
  x0 = brush.position.x + x0 * brush.scale.x;
  y0 = brush.position.y + y0 * brush.scale.y;

  if (brush.scale.x < 0) scale_x *= -brush.scale.x;
  else                   scale_x *=  brush.scale.x;
  if (brush.scale.y < 0) scale_y *= -brush.scale.y;
  else                   scale_y *=  brush.scale.y;

  f64 kx = scale_x;
  f64 h  = scale_y * CHAR_NUM_BITS_Y_;

  if (h < EPSILON)
    return;

  f64 x = x0;
  f64 y = y0;

  for (i64 n = 0; n < num_chars; ++n) {
    if (text[n] <= ' ') {
      if (text[n] == '\n') {
        x  = x0;
        y += scale_y * (CHAR_NUM_BITS_Y_ + 1);
      }
      else if (text[n] == '\b' && n > 0)
        x -= kx * (char_width_(text[n - 1]) + char_spacing_(num_chars, text, n - 1));
      else if (text[n] == '\r')
        x  = x0;
      else
        x += kx * (char_width_(' ') + char_spacing_(num_chars, text, n));
      continue;
    }

    i64 num_cols = char_width_(text[n]);
    f64 w        = num_cols * kx;

    if (w >= EPSILON) {
      i64 i0 = (i64) floor(x);
      i64 i1 = (i64) ceil (x + w);
      i64 j0 = (i64) floor(y);
      i64 j1 = (i64) ceil (y + h);

      if (i0 <  0)                   i0 = 0;
      if (i1 >= brush.buffer.width)  i1 = brush.buffer.width - 1;
      if (j0 <  0)                   j0 = 0;
      if (j1 >= brush.buffer.height) j1 = brush.buffer.height - 1;

      for (i64 i = i0; i <= i1; ++i) {
        i64 column = (i64) floor(((i - x) * num_cols) / w + .5);
        i64 offset = char_column_offset_(text[n], column);

        for (i64 j = j0; j <= j1; ++j) {
          i64 row = (i64) floor(((j - y) * CHAR_NUM_BITS_Y_) / h + .5);

          if (char_bit_(offset, row))
            put_pixel_(brush, i, j);
        }
      }
    }

    x += kx * (num_cols + char_spacing_(num_chars, text, n));
  }
}

static Brush brush_defaults_(Brush b) {
  if (g_platform.frame_width > 0) {
    if (b.scale.x == 0.) b.scale.x = ((f64) g_platform.frame_width)  / g_platform.real_width;
    if (b.scale.y == 0.) b.scale.y = ((f64) g_platform.frame_height) / g_platform.real_height;
  }

  if (b.buffer.pixels == NULL)
    b.buffer = window_pixels();

  if (b.buffer.line_size == 0)
    b.buffer.line_size = b.buffer.width;

  return b;
}

//  ================================================================

vec3_f32 vec3_from_vec4_f32(vec4_f32 v) {
  return (vec3_f32) {
    .x = v.x,
    .y = v.y,
    .z = v.z,
  };
}

vec4_f32 vec4_from_vec3_f32(vec3_f32 v, f32 w) {
  return (vec4_f32) {
    .x = v.x,
    .y = v.y,
    .z = v.z,
    .w = w,
  };
}

vec3_f32 vec3_f32_lerp(vec3_f32 a, vec3_f32 b, f32 t) {
  return (vec3_f32) {
    .x = a.x + (b.x - a.x) * t,
    .y = a.y + (b.y - a.y) * t,
    .z = a.z + (b.z - a.z) * t,
  };
}

vec4_f32 vec4_f32_lerp(vec4_f32 a, vec4_f32 b, f32 t) {
  return (vec4_f32) {
    .x = a.x + (b.x - a.x) * t,
    .y = a.y + (b.y - a.y) * t,
    .z = a.z + (b.z - a.z) * t,
    .w = a.w + (b.w - a.w) * t,
  };
}

//  ================================================================

vec3_f32 rgb_gamma_add(vec3_f32 rgb) {
  return (vec3_f32) {
    .x = (f32) gamma_(rgb.x),
    .y = (f32) gamma_(rgb.y),
    .z = (f32) gamma_(rgb.z),
  };
}

vec3_f32 rgb_gamma_remove(vec3_f32 rgb) {
  return (vec3_f32) {
    .x = (f32) gamma_re_(rgb.x),
    .y = (f32) gamma_re_(rgb.y),
    .z = (f32) gamma_re_(rgb.z),
  };
}

vec4_f32 rgba_gamma_add(vec4_f32 rgba) {
  return (vec4_f32) {
    .x = (f32) gamma_(rgba.x),
    .y = (f32) gamma_(rgba.y),
    .z = (f32) gamma_(rgba.z),
    .w = (f32) gamma_(rgba.w),
  };
}

vec4_f32 rgba_gamma_remove(vec4_f32 rgba) {
  return (vec4_f32) {
    .x = (f32) gamma_re_(rgba.x),
    .y = (f32) gamma_re_(rgba.y),
    .z = (f32) gamma_re_(rgba.z),
    .w = (f32) gamma_re_(rgba.w),
  };
}

vec3_f32 lab_from_rgb(vec3_f32 rgb) {
  f64 l = 0.4122214708 * rgb.x + 0.5363325363 * rgb.y + 0.0514459929 * rgb.z;
  f64 m = 0.2119034982 * rgb.x + 0.6806995451 * rgb.y + 0.1073969566 * rgb.z;
  f64 s = 0.0883024619 * rgb.x + 0.2817188376 * rgb.y + 0.6299787005 * rgb.z;

  f64 l_ = cbrt(l);
  f64 m_ = cbrt(m);
  f64 s_ = cbrt(s);

  return (vec3_f32) {
    .x = (f32) (0.2104542553f * l_ + 0.7936177850f * m_ - 0.0040720468f * s_),
    .y = (f32) (1.9779984951f * l_ - 2.4285922050f * m_ + 0.4505937099f * s_),
    .z = (f32) (0.0259040371f * l_ + 0.7827717662f * m_ - 0.8086757660f * s_),
  };
}

vec3_f32 rgb_from_lab(vec3_f32 lab) {
  f64 l_ = lab.x + 0.3963377774 * lab.y + 0.2158037573 * lab.z;
  f64 m_ = lab.x - 0.1055613458 * lab.y - 0.0638541728 * lab.z;
  f64 s_ = lab.x - 0.0894841775 * lab.y - 1.2914855480 * lab.z;

  f64 l = l_ * l_ * l_;
  f64 m = m_ * m_ * m_;
  f64 s = s_ * s_ * s_;

  return (vec3_f32) {
    .x = (f32) (+4.0767416621 * l - 3.3077115913 * m + 0.2309699292 * s),
    .y = (f32) (-1.2684380046 * l + 2.6097574011 * m - 0.3413193965 * s),
    .z = (f32) (-0.0041960863 * l - 0.7034186147 * m + 1.7076147010 * s),
  };
}

vec3_f32 lch_from_lab(vec3_f32 lab) {
  f64 a = lab.y;
  f64 b = lab.z;

  return (vec3_f32) {
    .x = lab.x,
    .y = (f32) sqrt (a * a + b * b),
    .z = (f32) atan2(b, a),
  };
}

vec3_f32 lab_from_lch(vec3_f32 lch) {
  return (vec3_f32) {
    .x = lch.x,
    .y = (f32) (lch.y * cos(lch.z)),
    .z = (f32) (lch.y * sin(lch.z)),
  };
}

vec3_f32 rgb_from_lch(vec3_f32 lch) {
  return rgb_from_lab(lab_from_lch(lch));
}

vec3_f32 lch_from_rgb(vec3_f32 rgb) {
  return lch_from_lab(lab_from_rgb(rgb));
}

vec3_f32 rgb_gamma_lerp (vec3_f32 a, vec3_f32 b, f32 t) {
  return rgb_gamma_add(vec3_f32_lerp(
    rgb_gamma_remove(a),
    rgb_gamma_remove(b),
    t
  ));
}

vec4_f32 rgba_gamma_lerp(vec4_f32 a, vec4_f32 b, f32 t) {
  return rgba_gamma_add(vec4_f32_lerp(
    rgba_gamma_remove(a),
    rgba_gamma_remove(b),
    t
  ));
}

vec3_f32 rgb_mix(vec3_f32 a, vec3_f32 b, f32 t) {
  vec3_f32 a_lch = lch_from_rgb(a);
  vec3_f32 b_lch = lch_from_rgb(b);

  return rgb_from_lch((vec3_f32) {
    a_lch.x + (b_lch.x - a_lch.x) * t,
    a_lch.y + (b_lch.y - a_lch.y) * t,
    lch_from_rgb(rgb_gamma_lerp(a, b, t)).z,
  });
}

vec4_f32 rgba_mix(vec4_f32 a, vec4_f32 b, f32 t) {
  vec3_f32 a_lch = lch_from_rgb(vec3_from_vec4_f32(a));
  vec3_f32 b_lch = lch_from_rgb(vec3_from_vec4_f32(b));
  vec4_f32 ab    = rgba_gamma_lerp(a, b, t);

  return vec4_from_vec3_f32(rgb_from_lch((vec3_f32) {
    a_lch.x + (b_lch.x - a_lch.x) * t,
    a_lch.y + (b_lch.y - a_lch.y) * t,
    lch_from_rgb(vec3_from_vec4_f32(ab)).z,
  }), ab.w);
}

vec3_f32 lch_mix(vec3_f32 a, vec3_f32 b, f32 t) {
  return (vec3_f32) {
    a.x + (b.x - a.x) * t,
    a.y + (b.y - a.y) * t,
    lch_from_rgb(rgb_gamma_lerp(rgb_from_lch(a), rgb_from_lch(b), t)).z,
  };
}

vec3_f32 lch_lerp(vec3_f32 a, vec3_f32 b, f32 t) {
  f32 delta_hue = b.z - a.z;
  if (delta_hue >  M_PI) delta_hue -= M_PI * 2;
  if (delta_hue < -M_PI) delta_hue += M_PI * 2;

  return (vec3_f32) {
    .x = a.x + (b.x - a.x) * t,
    .y = a.y + (b.y - a.y) * t,
    .z = a.z +  delta_hue  * t,
  };
}

u32 rgb_u32_from_f32(vec3_f32 color) {
  i32 ir = (i32) floor(color.x * 255. + .5);
  i32 ig = (i32) floor(color.y * 255. + .5);
  i32 ib = (i32) floor(color.z * 255. + .5);

  u32 r = ir < 0 ? 0u : ir > 255 ? 255u : (u32) ir;
  u32 g = ig < 0 ? 0u : ig > 255 ? 255u : (u32) ig;
  u32 b = ib < 0 ? 0u : ib > 255 ? 255u : (u32) ib;

  return (r << 16) | (g << 8) | b;
}

vec3_f32 rgb_f32_from_u32(u32 color) {
  return (vec3_f32) {
    .x = ((color & 0xff0000) >> 16) / 255.f,
    .y = ((color & 0x00ff00) >>  8) / 255.f,
    .z =  (color & 0x0000ff)        / 255.f,
  };
}

u32 rgba_u32_from_f32(vec4_f32 color) {
  i32 ir = (i32) floor(color.x * 255. + .5);
  i32 ig = (i32) floor(color.y * 255. + .5);
  i32 ib = (i32) floor(color.z * 255. + .5);
  i32 ia = (i32) floor(color.w * 255. + .5);

  u32 r = ir < 0 ? 0u : ir > 255 ? 255u : (u32) ir;
  u32 g = ig < 0 ? 0u : ig > 255 ? 255u : (u32) ig;
  u32 b = ib < 0 ? 0u : ib > 255 ? 255u : (u32) ib;
  u32 a = ia < 0 ? 0u : ia > 255 ? 255u : (u32) ia;

  return (a << 24) | (r << 16) | (g << 8) | b;
}

vec4_f32 rgba_f32_from_u32(u32 color) {
  return (vec4_f32) {
    .x = ((color & 0x00ff0000) >> 16) / 255.f,
    .y = ((color & 0x0000ff00) >>  8) / 255.f,
    .z =  (color & 0x000000ff)        / 255.f,
    .w = ((color & 0xff000000) >> 24) / 255.f,
  };
}

b8 rectangle_contains(f64 x0, f64 y0, f64 width, f64 height, f64 px, f64 py) {
  return px >= x0 && px < x0 + width && py >= y0 && py < y0 + height;
}

b8 triangle_contains(f64 x0, f64 y0, f64 x1, f64 y1, f64 x2, f64 y2, f64 px, f64 py) {
  //  Z-components of cross-products
  //

  f64 x10 = x1 - x0;
  f64 x21 = x2 - x1;
  f64 x02 = x0 - x2;

  f64 y10 = y1 - y0;
  f64 y21 = y2 - y1;
  f64 y02 = y0 - y2;

  f64 z0  = x02 * y10 - x10 * y02;
  f64 z1  = x10 * y21 - x21 * y10;
  f64 z2  = x21 * y02 - x02 * y21;

  f64 pz0 = x02 * (py - y0) - (px - x0) * y02;
  f64 pz1 = x10 * (py - y1) - (px - x1) * y10;
  f64 pz2 = x21 * (py - y2) - (px - x2) * y21;

  return
       same_sign_(z0, pz0)
    && same_sign_(z1, pz1)
    && same_sign_(z2, pz2);
}

b8 ellipse_contains(f64 x0, f64 y0, f64 width, f64 height, f64 px, f64 py) {
  f64 dw = width  / 2;
  f64 dh = height / 2;

  if (dw < EPSILON || dh < EPSILON)
    return 0;

  f64 cx = x0 + dw;
  f64 cy = y0 + dh;
  f64 kx = 1. / dw;
  f64 ky = 1. / dh;

  f64 dx = (px - cx) * kx;
  f64 dy = (py - cy) * ky;

  return dx * dx + dy * dy - 1.0 < EPSILON;
}

b8 line_contains(f64 x0, f64 y0, f64 x1, f64 y1, f64 width, f64 px, f64 py) {
  f64 dx = x1 - x0;
  f64 dy = y1 - y0;

  //  Tangent
  //
  f64 tx = -dy;
  f64 ty = dx;
  f64 tl = sqrt(tx * tx + ty * ty);
  if (tl >= EPSILON) {
    tx /= tl;
    ty /= tl;
  }
  tx *= width * .5;
  ty *= width * .5;

  return
       triangle_contains(x0 - tx, y0 - ty, x0 + tx, y0 + ty, x1 + tx, y1 + ty, px, py)
    || triangle_contains(x0 - tx, y0 - ty, x1 + tx, y1 + ty, x1 - tx, y1 - ty, px, py);
}

Pixel_Buffer window_pixels(void) {
  return (Pixel_Buffer) {
    .width     = g_platform.frame_width,
    .height    = g_platform.frame_height,
    .line_size = g_platform.frame_width,
    .pixels    = g_platform.pixels,
  };
}

Pixel_Buffer subimage(Pixel_Buffer image, i64 x, i64 y, i64 width, i64 height) {
  if (x < 0 || y < 0 || width < 0 || height < 0 || x + width > image.width || y + height > image.height || image.pixels == NULL)
    return (Pixel_Buffer) {
      .width     = 0,
      .height    = 0,
      .line_size = 0,

      // Set pixels pointer to prevent default initialization.
      .pixels = g_platform.pixels,
    };

  return (Pixel_Buffer) {
    .width     = width,
    .height    = height,
    .line_size = image.line_size,
    .pixels    = image.pixels + (y * image.line_size + x),
  };
}

void put_pixel(Brush brush, i64 x, i64 y) {
  brush = brush_defaults_(brush);

  if (x < 0 || x >= brush.buffer.width || y < 0 || y >= brush.buffer.height)
    return;

  put_pixel_(brush, x, y);
}

void draw_pixels(Brush brush, f64 x, f64 y, f64 width, f64 height, Pixel_Buffer src) {
  //  FIXME PERF

  brush = brush_defaults_(brush);

  f64 x0, y0, x1, y1;

  if (brush.scale.x < 0) {
    x1 = brush.position.x + x * brush.scale.x;
    x0 = x1 + width  * brush.scale.x;
  } else {
    x0 = brush.position.x + x * brush.scale.x;
    x1 = x0 + width  * brush.scale.x;
  }

  if (brush.scale.y < 0) {
    y1 = brush.position.y + y * brush.scale.y;
    y0 = y1 + height * brush.scale.y;
  } else {
    y0 = brush.position.y + y * brush.scale.y;
    y1 = y0 + height * brush.scale.y;
  }

  i64 i0 = (i64) floor(x0);
  i64 i1 = (i64) ceil (x1);
  i64 j0 = (i64) floor(y0);
  i64 j1 = (i64) ceil (y1);

  f64 w = x1 - x0;
  f64 h = y1 - y0;

  if (w < EPSILON || h < EPSILON)
    return;

  if (i0 <  0)                   i0 = 0;
  if (i1 >= brush.buffer.width)  i1 = brush.buffer.width - 1;
  if (j0 <  0)                   j0 = 0;
  if (j1 >= brush.buffer.height) j1 = brush.buffer.height - 1;

  for (i64 j = j0; j <= j1; ++j) {
    i64 src_j = (i64) floor(((j - y0) * src.height) / h + .5);
    if (src_j < 0 || src_j >= src.height) continue;
    for (i64 i = i0; i <= i1; ++i) {
      i64 src_i = (i64) floor(((i - x0) * src.width) / w + .5);
      if (src_i < 0 || src_i >= src.width) continue;
      brush.color = src.pixels[src_j * src.line_size + src_i];
      put_pixel_(brush, i, j);
    }
  }
}

void fill_rectangle(Brush brush, f64 x, f64 y, f64 width, f64 height) {
  fill_rectangle_(brush_defaults_(brush), x, y, width, height);
}

void fill_triangle(Brush brush, f64 x0, f64 y0, f64 x1, f64 y1, f64 x2, f64 y2) {
  fill_triangle_(brush_defaults_(brush), x0, y0, x1, y1, x2, y2);
}

void fill_ellipse(Brush brush, f64 x, f64 y, f64 width, f64 height) {
  //  FIXME PERF:
  //  Implement better algorithm.

  if (width < EPSILON || height < EPSILON)
    return;

  brush = brush_defaults_(brush);

  f64 x0, y0, x1, y1;

  if (brush.scale.x < 0) {
    x1 = brush.position.x + x * brush.scale.x;
    x0 = x1 + width  * brush.scale.x;
  } else {
    x0 = brush.position.x + x * brush.scale.x;
    x1 = x0 + width  * brush.scale.x;
  }

  if (brush.scale.y < 0) {
    y1 = brush.position.y + y * brush.scale.y;
    y0 = y1 + height * brush.scale.y;
  } else {
    y0 = brush.position.y + y * brush.scale.y;
    y1 = y0 + height * brush.scale.y;
  }

  i64 i0 = (i64) floor(x0);
  i64 i1 = (i64) ceil (x1);
  i64 j0 = (i64) floor(y0);
  i64 j1 = (i64) ceil (y1);

  if (j0 < 0)                    j0 = 0;
  if (j1 >= brush.buffer.height) j1 = brush.buffer.height - 1;

  for (i64 j = j0; j <= j1; ++j) {
    i64 left  = i1;
    i64 right = i0;

    for (i64 i = i0; i <= i1; ++i)
      if (ellipse_contains(x0, y0, x1 - x0, y1 - y0, (f64) i, (f64) j)) {
        left  = i;
        right = (i64) ceil(x0 + x1 - left); // symmetry
        break;
      }

    for (i64 i = right; i >= i0; --i)
      if (ellipse_contains(x0, y0, x1 - x0, y1 - y0, (f64) i, (f64) j)) {
        right = i;
        break;
      }

    if (left  <  0)                  left  = 0;
    if (right >= brush.buffer.width) right = brush.buffer.width - 1;

    for (i64 i = left; i <= right; ++i)
      put_pixel_(brush, i, j);
  }
}

void fill_line(Brush brush, f64 x0, f64 y0, f64 x1, f64 y1, f64 width) {
  if (width < EPSILON)
    return;

  f64 dx = x1 - x0;
  f64 dy = y1 - y0;

  //  Tangent
  //
  f64 tx = -dy;
  f64 ty =  dx;
  f64 tl = sqrt(tx * tx + ty * ty);

  if (tl < EPSILON)
    return;

  tx *= width / (tl * 2.0);
  ty *= width / (tl * 2.0);

  brush = brush_defaults_(brush);
  fill_triangle_(brush, x0 - tx, y0 - ty, x0 + tx, y0 + ty, x1 + tx, y1 + ty);
  fill_triangle_(brush, x0 - tx, y0 - ty, x1 + tx, y1 + ty, x1 - tx, y1 - ty);
}

void draw_text_area(Brush brush, f64 x, f64 y, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 num_chars, c32 *text) {
  if (text == NULL || num_chars <= 0 || max_scale_x < EPSILON || max_scale_y < EPSILON)
    return;

  i64 num_columns = enum_text_columns_(num_chars, text);
  i64 num_rows    = enum_text_rows_(num_chars, text);

  f64 scale_x = width  / num_columns;
  f64 scale_y = height / num_rows;

  f64 kx = scale_x / max_scale_x;
  f64 ky = scale_y / max_scale_y;

  f64 k = kx < ky ? kx : ky;

  kx = k * max_scale_x;
  ky = k * max_scale_y;

  draw_text_(brush_defaults_(brush), x, y, kx, ky, num_chars, text);
}

void draw_text_cursor(Brush brush, f64 x, f64 y, f64 width, f64 height, f64 max_scale_x, f64 max_scale_y, i64 cursor, i64 selection, i64 num_chars, c32 *text) {
  if (max_scale_x < EPSILON || max_scale_y < EPSILON)
    return;

  i64 num_columns = enum_text_columns_(num_chars, text);
  i64 num_rows    = enum_text_rows_(num_chars, text);
  i64 cursor_x    = text_cursor_(cursor, text);
  i64 cursor_y    = enum_text_rows_(cursor, text);

  f64 scale_x = width  / num_columns;
  f64 scale_y = height / num_rows;

  f64 kx = scale_x / max_scale_x;
  f64 ky = scale_y / max_scale_y;

  f64 k = kx < ky ? kx : ky;

  kx = k * max_scale_x;
  ky = k * max_scale_y;

  brush = brush_defaults_(brush);

  if (selection != 0) {
    i64 selection_x, selection_y;

    if (selection > 0) {
      selection_x = text_cursor_(cursor + selection, text);
      selection_y = enum_text_rows_(cursor + selection, text);
    } else {
      selection_x = cursor_x;
      selection_y = cursor_y;
      cursor_x    = text_cursor_(cursor + selection, text);
      cursor_y    = enum_text_rows_(cursor + selection, text);
    }

    if (cursor_y == selection_y)
      fill_rectangle_(
        brush,
        x + kx * cursor_x,
        y + ky * cursor_y - ky * (CHAR_NUM_BITS_Y_ + 1),
        kx * (selection_x - cursor_x),
        ky * (CHAR_NUM_BITS_Y_ + 1)
      );
    else {
      fill_rectangle_(
        brush,
        x + kx * cursor_x,
        y + ky * cursor_y - ky * (CHAR_NUM_BITS_Y_ + 1),
        kx * (num_columns - cursor_x),
        ky * (CHAR_NUM_BITS_Y_ + 1)
      );
      for (i64 j = cursor_y + CHAR_NUM_BITS_Y_ + 1; j < selection_y; j += CHAR_NUM_BITS_Y_ + 1)
        fill_rectangle_(
          brush,
          x,
          y + ky * j - ky * (CHAR_NUM_BITS_Y_ + 1),
          kx * num_columns,
          ky * (CHAR_NUM_BITS_Y_ + 1)
        );
      fill_rectangle_(
        brush,
        x,
        y + ky * selection_y - ky * (CHAR_NUM_BITS_Y_ + 1),
        kx * selection_x,
        ky * (CHAR_NUM_BITS_Y_ + 1)
      );
    }
  } else
    fill_rectangle_(
      brush,
      x + kx * cursor_x,
      y + ky * cursor_y - ky * CHAR_NUM_BITS_Y_,
      kx * .5,
      ky * (CHAR_NUM_BITS_Y_ - 1)
    );
}

#endif // GRAPHICS_IMPL_GUARD_
#endif // GRAPHICS_HEADER