--[[
Lua implementation of HSLuv and HPLuv color spaces
Homepage: http://www.hsluv.org/

Copyright (C) 2019 Alexei Boronine

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.
]]

hsluv = {}

hexChars = "0123456789abcdef"


distance_line_from_origin = function(line)
  return math.abs(line.intercept) / math.sqrt((line.slope ^ 2) + 1)
end

length_of_ray_until_intersect = function(theta, line)
  return line.intercept / (math.sin(theta) - line.slope * math.cos(theta))
end

hsluv.get_bounds = function(l)
  local result = {};
  local sub2;
  local sub1 = ((l + 16) ^ 3) / 1560896;
  if sub1 > hsluv.epsilon then
    sub2 = sub1;
  else
    sub2 = l / hsluv.kappa;
  end

  for i = 1, 3 do
    local m1 = hsluv.m[i][1];
    local m2 = hsluv.m[i][2];
    local m3 = hsluv.m[i][3];

    for t = 0, 1 do
      local top1 = (284517 * m1 - 94839 * m3) * sub2;
      local top2 = (838422 * m3 + 769860 * m2 + 731718 * m1) * l * sub2 - 769860 * t * l;
      local bottom = (632260 * m3 - 126452 * m2) * sub2 + 126452 * t;
      table.insert(result, {
        slope = top1 / bottom,
        intercept = top2 / bottom
      })
    end;
  end;
  return result
end

hsluv.max_safe_chroma_for_l = function(l)
  local bounds = hsluv.get_bounds(l);
  local min = 1.7976931348623157e+308;

  for i = 1, 6 do
    local length = distance_line_from_origin(bounds[i]);
    if length >= 0 then
      min = math.min(min, length);
    end;
  end;
  return min;
end

hsluv.max_safe_chroma_for_lh = function(l, h)
  local hrad = h / 360 * math.pi * 2;
  local bounds = hsluv.get_bounds(l);
  local min = 1.7976931348623157e+308;

  for i = 1, 6 do
    local bound = bounds[i];
    local length = length_of_ray_until_intersect(hrad, bound);
    if length >= 0 then
      min = math.min(min, length);
    end;
  end;
  return min
end

hsluv.dot_product = function(a, b)
  local sum = 0;
  for i = 1, 3 do
    sum = sum + a[i] * b[i];
  end;
  return sum
end

hsluv.from_linear = function(c)
  if c <= 0.0031308 then
    return 12.92 * c
  else
    return 1.055 * (c ^ 0.416666666666666685) - 0.055
  end;
end

hsluv.to_linear = function(c)
  if c > 0.04045 then
    return ((c + 0.055) / 1.055) ^ 2.4
  else
    return c / 12.92
  end;
end

hsluv.xyz_to_rgb = function(tuple)
  return {
    hsluv.from_linear(hsluv.dot_product(hsluv.m[1], tuple)),
    hsluv.from_linear(hsluv.dot_product(hsluv.m[2], tuple)),
    hsluv.from_linear(hsluv.dot_product(hsluv.m[3], tuple))
  }
end

hsluv.rgb_to_xyz = function(tuple)
  local rgbl = {
    hsluv.to_linear(tuple[1]),
    hsluv.to_linear(tuple[2]),
    hsluv.to_linear(tuple[3])
  };
  return {
    hsluv.dot_product(hsluv.minv[1], rgbl),
    hsluv.dot_product(hsluv.minv[2], rgbl),
    hsluv.dot_product(hsluv.minv[3], rgbl)
  }
end

hsluv.y_to_l = function(Y)
  if Y <= hsluv.epsilon then
    return Y / hsluv.refY * hsluv.kappa
  else
    return 116 * ((Y / hsluv.refY) ^ 0.333333333333333315) - 16
  end;
end

hsluv.l_to_y = function(L)
  if L <= 8 then
    return hsluv.refY * L / hsluv.kappa
  else
    return hsluv.refY * (((L + 16) / 116) ^ 3)
  end;
end

hsluv.xyz_to_luv = function(tuple)
  local X = tuple[1];
  local Y = tuple[2];
  local divider = X + 15 * Y + 3 * tuple[3];
  local varU = 4 * X;
  local varV = 9 * Y;
  if divider ~= 0 then
    varU = varU / divider;
    varV = varV / divider;
  else
    varU = 0;
    varV = 0;
  end
  local L = hsluv.y_to_l(Y);
  if L == 0 then
    return { 0, 0, 0 }
  end;
  return { L, 13 * L * (varU - hsluv.refU), 13 * L * (varV - hsluv.refV) }
end

hsluv.luv_to_xyz = function(tuple)
  local L = tuple[1];
  local U = tuple[2];
  local V = tuple[3];
  if L == 0 then
    return { 0, 0, 0 }
  end;
  local varU = U / (13 * L) + hsluv.refU;
  local varV = V / (13 * L) + hsluv.refV;
  local Y = hsluv.l_to_y(L);
  local X = 0 - (9 * Y * varU) / ((((varU - 4) * varV) - varU * varV));
  return { X, Y, (9 * Y - 15 * varV * Y - varV * X) / (3 * varV) }
end

hsluv.luv_to_lch = function(tuple)
  local L = tuple[1];
  local U = tuple[2];
  local V = tuple[3];
  local C = math.sqrt(U * U + V * V);
  local H
  if C < 0.00000001 then
    H = 0;
  else
    H = math.atan2(V, U) * 180.0 / 3.1415926535897932;
    if H < 0 then
      H = 360 + H;
    end;
  end;
  return { L, C, H }
end

hsluv.lch_to_luv = function(tuple)
  local L = tuple[1];
  local C = tuple[2];
  local Hrad = tuple[3] / 360.0 * 2 * math.pi;
  return { L, math.cos(Hrad) * C, math.sin(Hrad) * C };
end

hsluv.hsluv_to_lch = function(tuple)
  local H = tuple[1];
  local S = tuple[2];
  local L = tuple[3];
  if L > 99.9999999 then
    return { 100, 0, H }
  end;
  if L < 0.00000001 then
    return { 0, 0, H }
  end;
  return { L, hsluv.max_safe_chroma_for_lh(L, H) / 100 * S, H }
end

hsluv.lch_to_hsluv = function(tuple)
  local L = tuple[1];
  local C = tuple[2];
  local H = tuple[3];
  local max_chroma = hsluv.max_safe_chroma_for_lh(L, H)
  if L > 99.9999999 then
    return { H, 0, 100 }
  end;
  if L < 0.00000001 then
    return { H, 0, 0 }
  end;

  return { H, C / max_chroma * 100, L }
end

hsluv.hpluv_to_lch = function(tuple)
  local H = tuple[1];
  local S = tuple[2];
  local L = tuple[3];
  if L > 99.9999999 then
    return { 100, 0, H }
  end;
  if L < 0.00000001 then
    return { 0, 0, H }
  end;
  return { L, hsluv.max_safe_chroma_for_l(L) / 100 * S, H }
end

hsluv.lch_to_hpluv = function(tuple)
  local L = tuple[1];
  local C = tuple[2];
  local H = tuple[3];
  if L > 99.9999999 then
    return { H, 0, 100 }
  end;
  if L < 0.00000001 then
    return { H, 0, 0 }
  end;
  return { H, C / hsluv.max_safe_chroma_for_l(L) * 100, L }
end

hsluv.rgb_to_hex = function(tuple)
  local h = "#";
  for i = 1, 3 do
    local c = math.floor(tuple[i] * 255 + 0.5);
    local digit2 = math.fmod(c, 16);
    local x = (c - digit2) / 16;
    local digit1 = math.floor(x);
    h = h .. string.sub(hexChars, digit1 + 1, digit1 + 1)
    h = h .. string.sub(hexChars, digit2 + 1, digit2 + 1)
  end;
  return h
end

hsluv.hex_to_rgb = function(hex)
  hex = string.lower(hex)
  local ret = {}
  for i = 0, 2 do
    local char1 = string.sub(hex, i * 2 + 2, i * 2 + 2);
    local char2 = string.sub(hex, i * 2 + 3, i * 2 + 3);
    local digit1 = string.find(hexChars, char1) - 1
    local digit2 = string.find(hexChars, char2) - 1
    ret[i + 1] = (digit1 * 16 + digit2) / 255.0;
  end;
  return ret
end

hsluv.lch_to_rgb = function(tuple)
  return hsluv.xyz_to_rgb(hsluv.luv_to_xyz(hsluv.lch_to_luv(tuple)))
end

hsluv.rgb_to_lch = function(tuple)
  return hsluv.luv_to_lch(hsluv.xyz_to_luv(hsluv.rgb_to_xyz(tuple)))
end

hsluv.hsluv_to_rgb = function(tuple)
  return hsluv.lch_to_rgb(hsluv.hsluv_to_lch(tuple))
end

hsluv.rgb_to_hsluv = function(tuple)
  return hsluv.lch_to_hsluv(hsluv.rgb_to_lch(tuple))
end

hsluv.hpluv_to_rgb = function(tuple)
  return hsluv.lch_to_rgb(hsluv.hpluv_to_lch(tuple))
end

hsluv.rgb_to_hpluv = function(tuple)
  return hsluv.lch_to_hpluv(hsluv.rgb_to_lch(tuple))
end

hsluv.hsluv_to_hex = function(tuple)
  return hsluv.rgb_to_hex(hsluv.hsluv_to_rgb(tuple))
end

hsluv.hpluv_to_hex = function(tuple)
  return hsluv.rgb_to_hex(hsluv.hpluv_to_rgb(tuple))
end

hsluv.hex_to_hsluv = function(s)
  return hsluv.rgb_to_hsluv(hsluv.hex_to_rgb(s))
end

hsluv.hex_to_hpluv = function(s)
  return hsluv.rgb_to_hpluv(hsluv.hex_to_rgb(s))
end

hsluv.m = {
  { 3.240969941904521, -1.537383177570093, -0.498610760293 },
  { -0.96924363628087, 1.87596750150772, 0.041555057407175 },
  { 0.055630079696993, -0.20397695888897, 1.056971514242878 }
}
hsluv.minv = {
  { 0.41239079926595, 0.35758433938387, 0.18048078840183 },
  { 0.21263900587151, 0.71516867876775, 0.072192315360733 },
  { 0.019330818715591, 0.11919477979462, 0.95053215224966 }
}
hsluv.refY = 1.0
hsluv.refU = 0.19783000664283
hsluv.refV = 0.46831999493879
hsluv.kappa = 903.2962962
hsluv.epsilon = 0.0088564516

return hsluv
