-- Original implementation taken from here https://github.com/thenumbernine/lua-simplexnoise/blob/master/2d.lua

local public, this = {}, {}
local _global = require("utils.global")
local _common = require(".common")
_global.register(this, function(t) this = t end)

this.perm = {}
this.seed = 0
this.grad3 = {
   {1, 1, 0}, {-1, 1, 0}, {1, -1, 0}, {-1, -1 ,0},
   {1, 0, 1}, {-1, 0, 1}, {1, 0, -1}, {-1, 0, -1},
   {0, 1, 1}, {0, -1, 1}, {0, 1, -1}, {0, -1, -1}
}
this.p = {
   151, 160, 137, 91, 90, 15, 131, 13, 201,
   95, 96, 53, 194, 233, 7, 225, 140, 36,
   103, 30, 69, 142, 8, 99, 37, 240, 21, 10,
   23, 190, 6, 148, 247, 120, 234, 75, 0, 26,
   197, 62, 94, 252, 219, 203, 117, 35, 11,
   32, 57, 177, 33, 88, 237, 149, 56, 87,
   174, 20, 125, 136, 171, 168, 68, 175, 74,
   165, 71, 134, 139, 48, 27, 166, 77, 146,
   158, 231, 83, 111, 229, 122, 60, 211, 133,
   230, 220, 105, 92, 41, 55, 46, 245, 40,
   244, 102, 143, 54, 65, 25, 63, 161, 1,
   216, 80, 73, 209, 76, 132, 187, 208, 89,
   18, 169, 200, 196, 135, 130, 116, 188,
   159, 86, 164, 100, 109, 198, 173, 186,
   3, 64, 52, 217, 226, 250, 124, 123, 5, 202,
   38, 147, 118, 126, 255, 82, 85, 212, 207,
   206, 59, 227, 47, 16, 58, 17, 182, 189,
   28, 42, 223, 183, 170, 213, 119, 248, 152,
   2, 44, 154, 163, 70, 221, 153, 101, 155,
   167, 43, 172, 9, 129, 22, 39, 253, 19,
   98, 108, 110, 79, 113, 224, 232, 178, 185,
   112, 104, 218, 246, 97, 228, 251, 34, 242,
   193, 238, 210, 144, 12, 191, 179, 162, 241,
   81, 51, 145, 235, 249, 14, 239, 107, 49, 192,
   214, 31, 181, 199, 106, 157, 184, 84, 204,
   176, 115, 121, 50, 45, 127, 4, 150, 254,
   138, 236, 205, 93, 222, 114, 67, 29, 24, 72,
   243, 141, 128, 195, 78, 66, 215, 61, 156, 180
}

local function dot(a, b)
   local sum = 0
   for i = 1, #b do
      sum = sum + (a[i] * b[i])
   end

   return sum
end

public.init = function()
   local rng = game.create_random_generator()
   this.seed = rng(1, 4294967295)
   for i = 0, 511 do
      this.perm[i + 1] = this.p[bit32.band(i, 255) + 1]
   end
end

public.get = function(pos, resolution)
   local x = (_common.get_axis(pos, 'x') + this.seed) * resolution
   local y = (_common.get_axis(pos, 'y') + this.seed) * resolution
   local n0, n1, n2
   local F2 = 0.5*(math.sqrt(3.0)-1.0)
   local s = (x + y) * F2;
   local i = math.floor(x + s)
   local j = math.floor(y + s)
   local G2 = (3.0-math.sqrt(3.0))/6.0
   local t = (i+j)*G2
   local X0 = i-t
   local Y0 = j-t
   local x0 = x - X0
   local y0 = y -Y0
   local i1, j1
   if x0 > y0 then
      i1 = 1
      j1 = 0
   else
      i1 = 0
      j1 = 1
   end

   local x1 = x0 - i1 + G2
   local y1 = y0 - j1 + G2
   local x2 = x0 - 1 + 2 * G2
   local y2 = y0 - 1 + 2 * G2
   local ii = bit32.band(i, 255)
   local jj = bit32.band(j, 255)
   local gi0 = this.perm[ii + this.perm[jj+1]+1] % 12
   local gi1 = this.perm[ii + i1 + this.perm[jj + j1+1]+1] % 12
   local gi2 = this.perm[ii + 1 + this.perm[jj + 1+1]+1] % 12

   -- Calculate the contribution from the three corners
   local t0 = 0.5 - x0 * x0 - y0 * y0
   if t0 < 0 then
      n0 = 0.0
   else
      t0 = t0 * t0
      n0 = t0 * t0 * dot(this.grad3[gi0+1], {x0, y0})
   end

   local t1 = 0.5 - x1 * x1 - y1 * y1
   if t1 < 0 then
      n1 = 0.0
   else
      t1 = t1 * t1
      n1 = t1 * t1 * dot(this.grad3[gi1+1], {x1, y1})
   end

   local t2 = 0.5 - x2 * x2 - y2 * y2
   if t2 < 0 then
      n2 = 0.0
   else
      t2 = t2 * t2
      n2 = t2 * t2 * dot(this.grad3[gi2+1], {x2, y2})
   end

   return 70.0 * (n0 + n1 + n2)
end

return public