--[[
	Crater MG - Crater Map Generator for Minetest
	(c) Pierre-Yves Rollo

	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Lesser General Public License as published
	by the Free Software Foundation, either version 2.1 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program.  If not, see <http://www.gnu.org/licenses/>.
--]]

local ores = {}

local nscale = 8

-- Simplification of math.fuctions call
local floor, random = math.floor, math.random

local function ncoord(xyz)
	return floor(xyz/nscale)
end

local function npos(pos)
	return {
		x = floor(pos.x/nscale),
		y = floor(pos.y/nscale),
		z = floor(pos.z/nscale),
	}
end

local function get_and_check_cid(node_name)
	local cid = minetest.get_content_id(node_name)
	assert(cid ~= 127, string.format("Unknown node \"%s\"", node_name))
	return cid
end

function cratermg.register_ore(def)
	local def = table.copy(def)
	def.c_spawns_in = get_and_check_cid(def.spawns_in)
	def.c_ore = get_and_check_cid(def.ore)
	assert(type(def.noise) == 'table',
		"Ore definition should have a 'noise' def table")

	def.noise.spread = def.noise.spread or {x=256, y=256, z=256}
	def.noise.seed = def.noise.seed or #ores + 2345
	def.noise.spread = vector.divide(def.noise.spread, nscale)

	def.nmap = {}

	ores[#ores+1] = def
end

local nores, spawns_in, ore, nmap

local function pre_generate()
	if nores then return end
	nores = #ores
	spawns_in = {}
	ore = {}
	nmap = {}
	for index = 1, nores do
		spawns_in[index] = ores[index].c_spawns_in
		ore[index] = ores[index].c_ore
		nmap[index] = ores[index].nmap
	end
end

function cratermg.ore_generate(minp, maxp, mapdata, area, p)
	pre_generate()

	local p = cratermg.profile

	local nlens3d = {
		x=ncoord(maxp.x) - ncoord(minp.x) + 1,
		y=ncoord(maxp.y) - ncoord(minp.y) + 1,
		z=ncoord(maxp.z) - ncoord(minp.z) + 1,
	}

	local nminp = npos(minp)

	p.start('oregen noises')
	for index = 1, nores do
		ores[index].nobj = ores[index].nobj or
			minetest.get_perlin_map(ores[index].noise, nlens3d)
		ores[index].nobj:get_3d_map_flat(nminp, ores[index].nmap)
	end
	p.stop('oregen noises')

	p.start('oregen loop')
	local nix = 1
	local l_cid = minetest.get_content_id("default:lava_source")
	for z = minp.z, maxp.z do
		local nixz = ncoord(z-minp.z) * nlens3d.x * nlens3d.y
		for y = minp.y, maxp.y do
			local nixy = ncoord(y-minp.y) * nlens3d.x + nixz
			local vmi = area:index(minp.x, y, z)
			for x = minp.x, maxp.x do
				local nix = ncoord(x-minp.x) + nixy + 1
				local cid = mapdata[vmi]
				for index = 1, nores do
					if minp.y < -500 then
						mapdata[vmi] = l_cid
					end
					if spawns_in[index] == cid and
							random() < nmap[index][nix] then
						mapdata[vmi] = ore[index]
						break
					end
				end
				vmi = vmi + 1
			end
		end
	end
	p.stop('oregen loop')
end