-- Parameters

local WALK = true -- Walkable paths
local YMAXMINP = 48 -- Maximum minp.y of generated chunks
					-- (-32 for default mapgen v6. 48, 128, 208 for higher)
local HSAMP = 0.85 -- Height select amplitude. Maximum steepness of paths
local HSOFF = -0.2 -- Height select noise offset.
					-- Bias paths towards base (-) or higher (+) terrain
local TCOL = 0.3 -- Column noise threshold. Bridge column density


-- Mapgen v6 parameters

-- 2D noise for base terrain

local np_base = {
	offset = -4,
	scale = 20,
	spread = {x = 250, y = 250, z = 250},
	seed = 82341,
	octaves = 5,
	persist = 0.6
}

-- 2D noise for higher terrain

local np_higher = {
	offset = 20,
	scale = 16,
	spread = {x = 500, y = 500, z = 500},
	seed = 85039,
	octaves = 5,
	persist = 0.6
}

-- 2D noise for height select

local np_hselect = {
	offset = 0.5,
	scale = 1,
	spread = {x = 250, y = 250, z = 250},
	seed = 4213,
	octaves = 5,
	persist = 0.4 -- default = 0.69
}

-- 2D noise for mud

local np_mud = {
	offset = 4,
	scale = 2,
	spread = {x = 200, y = 200, z = 200},
	seed = 91013,
	octaves = 3,
	persist = 0.55
}

-- Mod path parameters

-- 2D noise for patha

local np_patha = {
	offset = 0,
	scale = 1,
	spread = {x = 1024, y = 1024, z = 1024},
	seed = 11711,
	octaves = 3,
	persist = 0.4
}

-- 2D noise for pathb

local np_pathb = {
	offset = 0,
	scale = 1,
	spread = {x = 2048, y = 2048, z = 2048},
	seed = -8017,
	octaves = 4,
	persist = 0.4
}

-- 2D noise for pathc

local np_pathc = {
	offset = 0,
	scale = 1,
	spread = {x = 4096, y = 4096, z = 4096},
	seed = 300707,
	octaves = 5,
	persist = 0.4
}

-- 2D noise for pathd

local np_pathd = {
	offset = 0,
	scale = 1,
	spread = {x = 8192, y = 8192, z = 8192},
	seed = -80033,
	octaves = 6,
	persist = 0.4
}

-- 2D noise for columns

local np_column = {
	offset = 0,
	scale = 1,
	spread = {x = 8, y = 8, z = 8},
	seed = 1728833,
	octaves = 3,
	persist = 2
}


-- Do files

dofile(minetest.get_modpath("pathv6alt") .. "/nodes.lua")


-- Initialize noise objects to nil

local nobj_base = nil
local nobj_higher = nil
local nobj_hselect = nil
local nobj_mud = nil
local nobj_patha = nil
local nobj_pathb = nil
local nobj_pathc = nil
local nobj_pathd = nil
local nobj_column = nil


-- On generated function

minetest.register_on_generated(function(minp, maxp, seed)
	if minp.y < -32 or minp.y > YMAXMINP then
		return
	end

	local t1 = os.clock()
	local x1 = maxp.x
	local y1 = maxp.y
	local z1 = maxp.z
	local x0 = minp.x
	local y0 = minp.y
	local z0 = minp.z
	
	local c_air = minetest.get_content_id("air")
	local c_ignore = minetest.get_content_id("ignore")
	local c_tree = minetest.get_content_id("default:tree")
	local c_sand = minetest.get_content_id("default:sand")
	local c_dirt = minetest.get_content_id("default:dirt")
	local c_grass = minetest.get_content_id("default:dirt_with_grass")
	local c_desand = minetest.get_content_id("default:desert_sand")
	local c_stone = minetest.get_content_id("default:stone")
	local c_destone = minetest.get_content_id("default:desert_stone")

	local c_wood = minetest.get_content_id("pathv6alt:junglewood")
	local c_path = minetest.get_content_id("pathv6alt:path")
	local c_column = minetest.get_content_id("pathv6alt:bridgewood")

	local c_stairn = minetest.get_content_id("pathv6alt:stairn")
	local c_stairs = minetest.get_content_id("pathv6alt:stairs")
	local c_staire = minetest.get_content_id("pathv6alt:staire")
	local c_stairw = minetest.get_content_id("pathv6alt:stairw")
	local c_stairne = minetest.get_content_id("pathv6alt:stairne")
	local c_stairnw = minetest.get_content_id("pathv6alt:stairnw")
	local c_stairse = minetest.get_content_id("pathv6alt:stairse")
	local c_stairsw = minetest.get_content_id("pathv6alt:stairsw")
	
	local c_pstairn = minetest.get_content_id("pathv6alt:pstairn")
	local c_pstairs = minetest.get_content_id("pathv6alt:pstairs")
	local c_pstaire = minetest.get_content_id("pathv6alt:pstaire")
	local c_pstairw = minetest.get_content_id("pathv6alt:pstairw")
	local c_pstairne = minetest.get_content_id("pathv6alt:pstairne")
	local c_pstairnw = minetest.get_content_id("pathv6alt:pstairnw")
	local c_pstairse = minetest.get_content_id("pathv6alt:pstairse")
	local c_pstairsw = minetest.get_content_id("pathv6alt:pstairsw")

	local sidelen = x1 - x0 + 1
	local overlen = sidelen + 5 -- noisemap x, z from minp-3 to maxp+2
	local chulens = {x = overlen, y = overlen, z = 1}
	local minpos = {x = x0 - 3, y = z0 - 3}

	nobj_base = nobj_base or minetest.get_perlin_map(np_base, chulens)
	nobj_higher = nobj_higher or minetest.get_perlin_map(np_higher, chulens)
	nobj_hselect = nobj_hselect or minetest.get_perlin_map(np_hselect, chulens)
	nobj_mud = nobj_mud or minetest.get_perlin_map(np_mud, chulens)

	nobj_patha = nobj_patha or minetest.get_perlin_map(np_patha, chulens)
	nobj_pathb = nobj_pathb or minetest.get_perlin_map(np_pathb, chulens)
	nobj_pathc = nobj_pathc or minetest.get_perlin_map(np_pathc, chulens)
	nobj_pathd = nobj_pathd or minetest.get_perlin_map(np_pathd, chulens)
	nobj_column = nobj_column or minetest.get_perlin_map(np_column, chulens)
	
	-- these 4 minpos are mgv6 noise offsets - 3
	local nvals_base = nobj_base:get2dMap_flat({x = x0 + 122, y = z0 + 122})
	local nvals_higher = nobj_higher:get2dMap_flat({x = x0 + 247, y = z0 + 247})
	local nvals_hselect = nobj_hselect:get2dMap_flat({x = x0 + 122, y = z0 + 122})
	local nvals_mud = nobj_mud:get2dMap_flat({x = x0 + 97, y = z0 + 97})

	local nvals_patha = nobj_patha:get2dMap_flat(minpos)
	local nvals_pathb = nobj_pathb:get2dMap_flat(minpos)
	local nvals_pathc = nobj_pathc:get2dMap_flat(minpos)
	local nvals_pathd = nobj_pathd:get2dMap_flat(minpos)
	local nvals_column = nobj_column:get2dMap_flat(minpos)
	
	local vm, emin, emax = minetest.get_mapgen_object("voxelmanip")
	local area = VoxelArea:new({MinEdge = emin, MaxEdge = emax})
	local data = vm:get_data()
	local emerlen = sidelen + 32

	local ni = 1
	local stable = {}
	for z = z0 - 3, z1 + 2 do
		local n_xprepatha = false
		local n_xprepathb = false
		local n_xprepathc = false
		local n_xprepathd = false
		-- x0-3, z0-3 is to setup initial values of 'xprepath_', 'zprepath_'
		for x = x0 - 3, x1 + 2 do
			local n_patha = nvals_patha[ni]
			local n_zprepatha = nvals_patha[(ni - overlen)]

			local n_pathb = nvals_pathb[ni]
			local n_zprepathb = nvals_pathb[(ni - overlen)]
			
			local n_pathc = nvals_pathc[ni]
			local n_zprepathc = nvals_pathc[(ni - overlen)]

			local n_pathd = nvals_pathd[ni]
			local n_zprepathd = nvals_pathd[(ni - overlen)]

			-- paths overgenerate by 2 nodes to erase mudflow griefing
			if x >= x0 - 2 and z >= z0 - 2 then
				local abscol = math.abs(nvals_column[ni])
				local base = nvals_base[ni]
				local higher = nvals_higher[ni]
				local hselect = nvals_hselect[ni]
				local mudadd = nvals_mud[ni] / 2 + 0.5
				if higher < base then
					higher = base
				end
				local tblend = 0.5 + HSAMP * (hselect + HSOFF)
				tblend = math.min(math.max(tblend, 0), 1)
				local tlevel = base * (1 - tblend) + higher * tblend + mudadd
				local pathy = math.floor(math.max(tlevel, 6))

				-- paths a and b
				if (n_patha >= 0 and n_xprepatha < 0)
				or (n_patha < 0 and n_xprepatha >= 0)
				or (n_patha >= 0 and n_zprepatha < 0)
				or (n_patha < 0 and n_zprepatha >= 0)
				or (n_pathb >= 0 and n_xprepathb < 0)
				or (n_pathb < 0 and n_xprepathb >= 0)
				or (n_pathb >= 0 and n_zprepathb < 0)
				or (n_pathb < 0 and n_zprepathb >= 0) then
					if pathy > y1 then -- build columns through this chunk
						if abscol < TCOL then
							local vi = area:index(x, y1, z)
							for y = 1, sidelen do
								local nodid = data[vi]
								if nodid == c_stone
								or nodid == c_destone then
									break
								else
									data[vi] = c_column
								end
								vi = vi - emerlen
							end
						end
					elseif pathy >= y0 then -- path in chunk, place path node brush
						local wood = true -- scan disk at path level for ground
						for k = -1, 1 do
							local vi = area:index(x - 1, pathy, z + k)
							for i = -1, 1 do
								local nodid = data[vi]
								if nodid == c_sand
								or nodid == c_desand
								or nodid == c_dirt
								or nodid == c_grass
								or nodid == c_stone
								or nodid == c_destone then
									wood = false -- use dirt path node
								end
								vi = vi + 1
							end
						end

						local tunnel = false -- scan disk above path for stone
						local excatop
						for k = -1, 1 do
							local vi = area:index(x - 1, pathy + 5, z + k)
							for i = -1, 1 do
								local nodid = data[vi]
								if nodid == c_stone
								or nodid == c_destone then
									tunnel = true
								end
								vi = vi + 1
							end
						end
						if tunnel then
							excatop = pathy + 5 -- tunnel
						else
							excatop = y1 -- excavate to chunk top
						end

						if WALK then
							if wood then
								local vi = area:index(x - 1, pathy, z - 1)
								if data[vi] ~= c_wood
								and data[vi] ~= c_path then
									data[vi] = c_stairne
								end
								vi = vi + 1
								if data[vi] ~= c_wood
								and data[vi] ~= c_path then
									data[vi] = c_stairn
								end
								vi = vi + 1
								if data[vi] ~= c_wood
								and data[vi] ~= c_path then
									data[vi] = c_stairnw
								end
	
								local vi = area:index(x - 1, pathy, z)
								if data[vi] ~= c_wood
								and data[vi] ~= c_path then
									data[vi] = c_staire
								end
								vi = vi + 1
								data[vi] = c_wood
								vi = vi + 1
								if data[vi] ~= c_wood
								and data[vi] ~= c_path then
									data[vi] = c_stairw
								end
	
								local vi = area:index(x - 1, pathy, z + 1)
								if data[vi] ~= c_wood
								and data[vi] ~= c_path then
									data[vi] = c_stairse
								end
								vi = vi + 1
								if data[vi] ~= c_wood
								and data[vi] ~= c_path then
									data[vi] = c_stairs
								end
								vi = vi + 1
								if data[vi] ~= c_wood
								and data[vi] ~= c_path then
									data[vi] = c_stairsw
								end
							else
								local vi = area:index(x - 1, pathy, z - 1)
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_pstairne
								end
								vi = vi + 1
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_pstairn
								end
								vi = vi + 1
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_pstairnw
								end
	
								local vi = area:index(x - 1, pathy, z)
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_pstaire
								end
								vi = vi + 1
								data[vi] = c_path
								vi = vi + 1
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_pstairw
								end
	
								local vi = area:index(x - 1, pathy, z + 1)
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_pstairse
								end
								vi = vi + 1
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_pstairs
								end
								vi = vi + 1
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_pstairsw
								end
							end

							for y = pathy + 1, excatop do
								for k = -1, 1 do
									local vi = area:index(x - 1, y, z + k)
									for i = -1, 1 do
										local nodid = data[vi]
										if y == excatop then
											if nodid == c_dirt
											or nodid == c_grass then
												data[vi] = c_stone
											elseif nodid == c_desand then
												data[vi] = c_destone
											end
										else
											if nodid ~= c_wood
											and nodid ~= c_path
											and nodid ~= c_stairn
											and nodid ~= c_stairs
											and nodid ~= c_staire
											and nodid ~= c_stairw
											and nodid ~= c_stairne
											and nodid ~= c_stairnw
											and nodid ~= c_stairse
											and nodid ~= c_stairsw
											and nodid ~= c_pstairn
											and nodid ~= c_pstairs
											and nodid ~= c_pstaire
											and nodid ~= c_pstairw
											and nodid ~= c_pstairne
											and nodid ~= c_pstairnw
											and nodid ~= c_pstairse
											and nodid ~= c_pstairsw then
												data[vi] = c_air
											end
										end
										vi = vi + 1
									end
								end
							end
						else -- non walkable option
							for y = pathy, excatop do
								for k = -1, 1 do
									local vi = area:index(x - 1, y, z + k)
									for i = -1, 1 do
										local nodid = data[vi]
										if y == pathy then
											if wood then
												data[vi] = c_wood
											else
												data[vi] = c_path
											end
										elseif nodid ~= c_wood
										and nodid ~= c_path then
											data[vi] = c_air
										end
										vi = vi + 1
									end
								end
							end
						end

						if wood then
							local vi = area:index(x, pathy - 1, z) -- bridge structure
							data[vi] = c_column
							vi = vi - emerlen
							data[vi] = c_column

							if abscol < TCOL then -- columns
								local vi = area:index(x, pathy - 3, z)
								for y = pathy - 3, y0, -1 do
									local nodid = data[vi]
									if nodid == c_stone
									or nodid == c_destone then
										break
									else
										data[vi] = c_column
									end
									vi = vi - emerlen
								end
							end
						end
					end
				-- paths c and d
				elseif (n_pathc >= 0 and n_xprepathc < 0)
				or (n_pathc < 0 and n_xprepathc >= 0)
				or (n_pathc >= 0 and n_zprepathc < 0)
				or (n_pathc < 0 and n_zprepathc >= 0)
				or (n_pathd >= 0 and n_xprepathd < 0)
				or (n_pathd < 0 and n_xprepathd >= 0)
				or (n_pathd >= 0 and n_zprepathd < 0)
				or (n_pathd < 0 and n_zprepathd >= 0) then
					if pathy > y1 then -- build columns through this chunk
						if abscol < TCOL then
							for i = -1, 1, 2 do
							for k = -1, 1, 2 do
								local vi = area:index(x + i, y1, z + k)
								for y = 1, sidelen do
									local nodid = data[vi]
									if nodid == c_stone
									or nodid == c_destone then
										break
									else
										data[vi] = c_column
									end
									vi = vi - emerlen
								end
							end
							end
						end
					elseif pathy >= y0 then -- path in chunk, place path node brush
						local wood = true -- scan disk at path level for ground
						for k = -2, 2 do
							local vi = area:index(x - 2, pathy, z + k)
							for i = -2, 2 do
								local nodid = data[vi]
								if nodid == c_sand
								or nodid == c_desand
								or nodid == c_dirt
								or nodid == c_grass
								or nodid == c_stone
								or nodid == c_destone then
									wood = false
								end
								vi = vi + 1
							end
						end

						local tunnel = false -- scan disk above path for stone
						local excatop
						for k = -2, 2 do
							local vi = area:index(x - 2, pathy + 5, z + k)
							for i = -2, 2 do
								local nodid = data[vi]
								if nodid == c_stone
								or nodid == c_destone then
									tunnel = true
								end
								vi = vi + 1
							end
						end

						if tunnel then
							excatop = pathy + 5 -- tunnel
						else
							excatop = y1 -- excavate to chunk top
						end

						if WALK then
							if wood then
								local vi = area:index(x - 2, pathy, z - 2)
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_stairne
								end
								for iter = 1, 3 do
									vi = vi + 1
									if data[vi] ~= c_path
									and data[vi] ~= c_wood then
										data[vi] = c_stairn
									end
								end
								vi = vi + 1
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_stairnw
								end
	
								for k = -1, 1 do
									local vi = area:index(x - 2, pathy, z + k)
									if data[vi] ~= c_path
									and data[vi] ~= c_wood then
										data[vi] = c_staire
									end
									for iter = 1, 3 do
										vi = vi + 1
										data[vi] = c_wood
									end
									vi = vi + 1
									if data[vi] ~= c_path
									and data[vi] ~= c_wood then
										data[vi] = c_stairw
									end
								end
	
								local vi = area:index(x - 2, pathy, z + 2)
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_stairse
								end
								for iter = 1, 3 do
									vi = vi + 1
									if data[vi] ~= c_path
									and data[vi] ~= c_wood then
										data[vi] = c_stairs
									end
								end
								vi = vi + 1
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_stairsw
								end
							else
								local vi = area:index(x - 2, pathy, z - 2)
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_pstairne
								end
								for iter = 1, 3 do
									vi = vi + 1
									if data[vi] ~= c_path
									and data[vi] ~= c_wood then
										data[vi] = c_pstairn
									end
								end
								vi = vi + 1
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_pstairnw
								end
	
								for k = -1, 1 do
									local vi = area:index(x - 2, pathy, z + k)
									if data[vi] ~= c_path
									and data[vi] ~= c_wood then
										data[vi] = c_pstaire
									end
									for iter = 1, 3 do
										vi = vi + 1
										data[vi] = c_path
									end
									vi = vi + 1
									if data[vi] ~= c_path
									and data[vi] ~= c_wood then
										data[vi] = c_pstairw
									end
								end
	
								local vi = area:index(x - 2, pathy, z + 2)
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_pstairse
								end
								for iter = 1, 3 do
									vi = vi + 1
									if data[vi] ~= c_path
									and data[vi] ~= c_wood then
										data[vi] = c_pstairs
									end
								end
								vi = vi + 1
								if data[vi] ~= c_path
								and data[vi] ~= c_wood then
									data[vi] = c_pstairsw
								end
							end

							for y = pathy + 1, excatop do
								for k = -2, 2 do
									local vi = area:index(x - 2, y, z + k)
									for i = -2, 2 do
										local nodid = data[vi]
										if y == excatop then
											if nodid == c_dirt
											or nodid == c_grass then
												data[vi] = c_stone
											elseif nodid == c_desand then
												data[vi] = c_destone
											end
										else
											if nodid ~= c_wood
											and nodid ~= c_path
											and nodid ~= c_stairn
											and nodid ~= c_stairs
											and nodid ~= c_staire
											and nodid ~= c_stairw
											and nodid ~= c_stairne
											and nodid ~= c_stairnw
											and nodid ~= c_stairse
											and nodid ~= c_stairsw
											and nodid ~= c_pstairn
											and nodid ~= c_pstairs
											and nodid ~= c_pstaire
											and nodid ~= c_pstairw
											and nodid ~= c_pstairne
											and nodid ~= c_pstairnw
											and nodid ~= c_pstairse
											and nodid ~= c_pstairsw then
												data[vi] = c_air
											end
										end
										vi = vi + 1
									end
							end
							end
						else -- non walkable option
							for y = pathy, excatop do
								for k = -2, 2 do
									local vi = area:index(x - 2, y, z + k)
									for i = -2, 2 do
										if math.abs(k) + math.abs(i) <= 3 then
											local nodid = data[vi]
											if y == pathy then
												if wood then
													data[vi] = c_wood
												else
													data[vi] = c_path
												end
											elseif nodid ~= c_wood
											and nodid ~= c_path then
												data[vi] = c_air
											end
										end
										vi = vi + 1
									end
								end
							end
						end

						if wood then
							for i = -1, 1 do -- bridge structure
							for k = -1, 1 do
								if not (i == 0 and k == 0) then
									local vi = area:index(x + i, pathy - 1, z + k)
									for y = 1, 2 do
										data[vi] = c_column
										vi = vi - emerlen
									end
								end
							end
							end

							if abscol < TCOL then -- columns
								for i = -1, 1, 2 do
								for k = -1, 1, 2 do
									local vi = area:index(x + i, pathy - 3, z + k)
									for y = pathy - 3, y0, -1 do
										local nodid = data[vi]
										if nodid == c_stone
										or nodid == c_destone then
											break
										else
											data[vi] = c_column
										end
										vi = vi - emerlen
									end
								end
								end
							end
						end
					end
				end
			end

			n_xprepatha = n_patha
			n_xprepathb = n_pathb
			n_xprepathc = n_pathc
			n_xprepathd = n_pathd
			ni = ni + 1
		end
	end
	
	vm:set_data(data)
	vm:set_lighting({day = 0, night = 0})
	vm:calc_lighting()
	vm:write_to_map(data)

	local chugent = math.ceil((os.clock() - t1) * 1000)
	print ("[pathv6alt] " .. chugent .. " ms")
end)