local circles = {}
-- Calculate the values for the segments of the circles
do
	local sqrt2 = math.sqrt(2) * 0.5
	local rad90 = math.rad(90)
	local pos = vector.new(sqrt2, 0, sqrt2)
	local vel = vector.new((1 - sqrt2) * 2, 0, -sqrt2)
	local acc = vector.new((1 - sqrt2) * -2, 0, 0)
	local axes = {
		x = vector.new(1, 0, 0),
		y = vector.new(0, 1, 0),
		z = vector.new(0, 0, 1),
	}
	for _,axis in ipairs({"y", "x", "z"}) do  -- This order is important
		circles[axis] = {}
		if axis == "x" then
			pos = vector.rotate_around_axis(pos, axes.z, rad90)
			vel = vector.rotate_around_axis(vel, axes.z, rad90)
			acc = vector.rotate_around_axis(acc, axes.z, rad90)
		elseif axis == "z" then
			pos = vector.rotate_around_axis(pos, axes.y, rad90)
			vel = vector.rotate_around_axis(vel, axes.y, rad90)
			acc = vector.rotate_around_axis(acc, axes.y, rad90)
		end
		for i=1, 4 do
			circles[axis][i] = {
				pos = vector.rotate_around_axis(pos, axes[axis], rad90 * i),
				vel = vector.rotate_around_axis(vel, axes[axis], rad90 * i),
				acc = vector.rotate_around_axis(acc, axes[axis], rad90 * i),
			}
		end
	end
end

local function get_valid_options(options)
	if type(options) ~= "table" then
		options = {}
	end
	local color = options.color or vizlib.default_color
	for _,c in ipairs(vizlib.colors) do
		if c.name == color then
			color = c.hex
		end
	end
	local time = options.infinite and 0 or 10
	local density = options.infinite and 1 or 10
	local name
	local t = type(options.player)
	if t == "string" then
		name = options.player
	elseif t == "userdata" or t == "table" then
		name = options.player:get_player_name()
	end
	return color, name, time, density
end

local function make_shape(name, time, ids)
	local shape = {name = name}
	if time > 0 then
		shape.expiry = os.time() + time
	end
	if type(ids) ~= "table" then
		shape.ids = {ids}
	else
		shape.ids = ids
	end
	return shape
end

local function make_arc(arc, pos, radius, color, name, time, density)
	pos = vector.add(pos, vector.multiply(arc.pos, radius))
	local vel = vector.multiply(arc.vel, radius)
	local acc = vector.multiply(arc.acc, radius)
	return minetest.add_particlespawner({
		playername = name,
		time = time,
		amount = math.ceil(radius * density * 6.0),
		minpos = pos,
		maxpos = pos,
		minvel = vel,
		maxvel = vel,
		minacc = acc,
		maxacc = acc,
		minexptime = 2,
		maxexptime = 2,
		texture = "vizlib_particle.png^[multiply:"..color,
		glow = 14,
	})
end

local function make_line(pos1, pos2, color, name, time, density)
	local distance = vector.distance(pos1, pos2)
	local dir = vector.direction(pos1, pos2)
	local vel = vector.multiply(dir, math.min(distance, 10.0))
	local expt = math.max(distance / 10.0, 1.0)
	return minetest.add_particlespawner({
		playername = name,
		time = time,
		amount = math.ceil(math.min(distance, 10.0) * density * 3.0),
		minpos = pos1,
		maxpos = pos1,
		minvel = vel,
		maxvel = vel,
		minexptime = expt,
		maxexptime = expt,
		texture = "vizlib_particle.png^[multiply:"..color,
		glow = 14,
	})
end

local function make_point(pos, color, name, time, density)
	return minetest.add_particlespawner({
		playername = name,
		time = time,
		amount = density * 2,
		minpos = pos,
		maxpos = pos,
		minexptime = 2.0,
		maxexptime = 2.0,
		texture = "vizlib_particle.png^[multiply:"..color,
		glow = 14,
		size = 1.5,
	})
end

--------------------------------------------------
-- API Functions. See API.md for details.
--------------------------------------------------

function vizlib.select_color()
	return vizlib.colors[math.random(24)].hex
end

function vizlib.random_color()
	local r = math.random(0, 255)
	local g = math.random(0, 255)
	local b = math.random(0, 255)
	return string.format("#%02x%02x%02x", r, g, b)
end

function vizlib.draw_point(pos, options)
	local color, name, time, density = get_valid_options(options)
	local ids = make_point(pos, color, name, time, density)
	return make_shape(name, time, ids)
end

function vizlib.draw_circle(pos, radius, axis, options)
	local color, name, time, density = get_valid_options(options)
	local ids = {}
	for _,arc in pairs(circles[axis]) do
		table.insert(ids, make_arc(arc, pos, radius, color, name, time, density))
	end
	return make_shape(name, time, ids)
end

function vizlib.draw_sphere(pos, radius, options)
	local color, name, time, density = get_valid_options(options)
	local ids = {}
	for _,circle in pairs(circles) do
		for _,arc in pairs(circle) do
			table.insert(ids, make_arc(arc, pos, radius, color, name, time, density))
		end
	end
	return make_shape(name, time, ids)
end

function vizlib.draw_line(pos1, pos2, options)
	local color, name, time, density = get_valid_options(options)
	local ids = make_line(pos1, pos2, color, name, time, density)
	return make_shape(name, time, ids)
end

function vizlib.draw_square(pos, radius, axis, options)
	local color, name, time, density = get_valid_options(options)
	local p1, p2, p3, p4
	if axis == "x" then
		p1 = vector.add(pos, vector.new(0, -radius, -radius))
		p2 = vector.add(pos, vector.new(0,  radius, -radius))
		p3 = vector.add(pos, vector.new(0,  radius,  radius))
		p4 = vector.add(pos, vector.new(0, -radius,  radius))
	elseif axis == "y" then
		p1 = vector.add(pos, vector.new(-radius, 0, -radius))
		p2 = vector.add(pos, vector.new( radius, 0, -radius))
		p3 = vector.add(pos, vector.new( radius, 0,  radius))
		p4 = vector.add(pos, vector.new(-radius, 0,  radius))
	elseif axis == "z" then
		p1 = vector.add(pos, vector.new(-radius, -radius, 0))
		p2 = vector.add(pos, vector.new( radius, -radius, 0))
		p3 = vector.add(pos, vector.new( radius,  radius, 0))
		p4 = vector.add(pos, vector.new(-radius,  radius, 0))
	end
	local ids = {
		make_line(p1, p2, color, name, time, density),
		make_line(p2, p3, color, name, time, density),
		make_line(p3, p4, color, name, time, density),
		make_line(p4, p1, color, name, time, density),
	}
	return make_shape(name, time, ids)
end

function vizlib.draw_cube(pos, radius, options)
	local color, name, time, density = get_valid_options(options)
	local p1 = vector.add(pos, vector.new(-radius,  radius, -radius))
	local p2 = vector.add(pos, vector.new( radius,  radius, -radius))
	local p3 = vector.add(pos, vector.new( radius,  radius,  radius))
	local p4 = vector.add(pos, vector.new(-radius,  radius,  radius))
	local p5 = vector.add(pos, vector.new(-radius, -radius, -radius))
	local p6 = vector.add(pos, vector.new( radius, -radius, -radius))
	local p7 = vector.add(pos, vector.new( radius, -radius,  radius))
	local p8 = vector.add(pos, vector.new(-radius, -radius,  radius))
	local ids = {
		-- Top
		make_line(p1, p2, color, name, time, density),
		make_line(p2, p3, color, name, time, density),
		make_line(p3, p4, color, name, time, density),
		make_line(p4, p1, color, name, time, density),
		-- Bottom
		make_line(p5, p6, color, name, time, density),
		make_line(p6, p7, color, name, time, density),
		make_line(p7, p8, color, name, time, density),
		make_line(p8, p5, color, name, time, density),
		-- Sides
		make_line(p1, p5, color, name, time, density),
		make_line(p2, p6, color, name, time, density),
		make_line(p3, p7, color, name, time, density),
		make_line(p4, p8, color, name, time, density),
	}
	return make_shape(name, time, ids)
end

function vizlib.draw_area(pos1, pos2, options)
	local color, name, time, density = get_valid_options(options)
	local minp, maxp = {}, {}
	for _,c in pairs({"x", "y", "z"}) do
		minp[c] = math.min(pos1[c], pos2[c])
		maxp[c] = math.max(pos1[c], pos2[c])
	end
	local p1 = vector.new(minp.x, maxp.y, minp.z)
	local p2 = vector.new(maxp.x, maxp.y, minp.z)
	local p3 = vector.new(maxp.x, maxp.y, maxp.z)
	local p4 = vector.new(minp.x, maxp.y, maxp.z)
	local p5 = vector.new(minp.x, minp.y, minp.z)
	local p6 = vector.new(maxp.x, minp.y, minp.z)
	local p7 = vector.new(maxp.x, minp.y, maxp.z)
	local p8 = vector.new(minp.x, minp.y, maxp.z)
	local ids = {
		-- Top
		make_line(p1, p2, color, name, time, density),
		make_line(p2, p3, color, name, time, density),
		make_line(p3, p4, color, name, time, density),
		make_line(p4, p1, color, name, time, density),
		-- Bottom
		make_line(p5, p6, color, name, time, density),
		make_line(p6, p7, color, name, time, density),
		make_line(p7, p8, color, name, time, density),
		make_line(p8, p5, color, name, time, density),
		-- Sides
		make_line(p1, p5, color, name, time, density),
		make_line(p2, p6, color, name, time, density),
		make_line(p3, p7, color, name, time, density),
		make_line(p4, p8, color, name, time, density),
	}
	return make_shape(name, time, ids)
end

function vizlib.erase_shape(shape)
	if type(shape) ~= "table" or not shape.ids then
		return
	end
	for _,id in pairs(shape.ids) do
		minetest.delete_particlespawner(id)
	end
end