local numutil = require 'numutil'

local function ensure_equipped(ptype, item)
	local cur = peripheral.getType"left"
	print(cur)
	if cur == ptype then return true end
	for i = 1,16 do
		local det = turtle.getItemDetail(i)
		if det and det.name == item then
			turtle.select(i)
			return turtle.equipLeft()
		end
	end
	return false, "couldn't find "..item
end

local function ensure_modem() return ensure_equipped("modem","computercraft:wireless_modem_normal") end

local POS, FACING
local function turtle_pos_init()
	assert(ensure_modem())

	POS = vector.new(gps.locate())

	while turtle.detect() do turtle.turnRight() end
	turtle.forward()
	local newpos = vector.new(gps.locate())
	turtle.back()
	FACING = newpos - POS
	print("init with",POS,FACING)
end


local function moveby_y(delta)
	local fn = turtle.up
	if delta < 0 then fn = turtle.down  delta = -delta  end
	for i=1,delta do fn() end
	POS.y = POS.y + delta
end

local function rotatev(v,nq)
	-- rotates v by n quarters, clockwise (rightwards)
	nq = nq%4
	if nq == 0     then return vector.new( v.x,  v.y,  v.z)
	elseif nq == 1 then return vector.new(-v.z,  v.y,  v.x)
	elseif nq == 2 then return vector.new(-v.x,  v.y, -v.z)
	elseif nq == 3 then return vector.new( v.z,  v.y, -v.x)
	end
end

local function turn_right()
	FACING = rotatev(FACING,1)
	turtle.turnRight()
end
local function turn_left()
	FACING = rotatev(FACING,-1)
	turtle.turnLeft()
end

local function turn_to_face(newfacing)
	if newfacing == FACING then return
	elseif newfacing == -FACING then turn_right() turn_right()
	elseif newfacing == rotatev(FACING,1) then turn_right()
	elseif newfacing == rotatev(FACING,-1) then turn_left()
	else error("invalid facing "..tostring(newfacing),2)
	end
end

local function move_linear(n)
	local dir = turtle.forward
	if n < 0 then dir = turtle.back end
	for i = 1,math.abs(n) do dir() end
	POS = POS + FACING*n
end

local function moveby_xz(dv)
	if FACING.x ~= 0 then
		move_linear(dv:dot(FACING))
		if dv.z ~= 0 then
			turn_to_face(vector.new(0,0,numutil.sign(dv.z)))
			move_linear(dv:dot(FACING))
		end
	elseif FACING.z ~= 0 then
		move_linear(dv:dot(FACING))
		if dv.x ~= 0 then
			turn_to_face(vector.new(numutil.sign(dv.x),0,0))
			move_linear(dv:dot(FACING))
		end
	end
end

local function moveby(delta)
	moveby_y(delta.y)
	moveby_xz(delta)
end
local function moveto(target)
	print("moving to",target)
	moveby(target - POS)
end

local function do_column()
	if turtle.detectDown() then
		turtle.digDown()
		turtle.down()
		turtle.digDown()
		turtle.up()
	end
end

local function dump_and_refuel()
	print("dumping produce")
	os.sleep(1)
	local modem = peripheral.wrap"top"
	local self = modem.getNameLocal()
	print("i am",self)
	local ch = peripheral.find"sc-goodies:diamond_barrel"
	for i=1,16 do
		ch.pullItems(self, i)
	end
	while turtle.getFuelLevel() < 2000 do
		print("refuelling")
		for k,v in pairs(ch.list()) do
			if v.name == "minecraft:lava_bucket" then
				ch.pushItems(self, k, 1, 1)
				turtle.select(1)
				turtle.refuel()
				ch.pullItems(self, 1)
				goto nextfuel
			end
			goto nofuel
		end
		::nextfuel::
	end
	::nofuel::
end
	
local datum = vector.new(-18, 128, -1837)

local function setup()
	turtle_pos_init()
	print("i am at",POS,"facing",FACING)

	moveto(datum)
	turn_to_face(vector.new(0,0,1))
	dump_and_refuel()

end

local function loop()
	print("harvesting")
	repeat
		repeat
			do_column()
			move_linear(1)
		until POS.z == -1826
		do_column()
		turn_right()
		move_linear(1)
		turn_right()

		repeat
			do_column()
			move_linear(1)
		until POS.z == datum.z
		do_column()
		turn_left()
		move_linear(1)
		turn_left()

	until POS.x <= -29

	moveto(datum)
	turn_to_face(vector.new(0,0,1))

	dump_and_refuel()

	os.sleep(120)
end

local function main()
	setup()
	while true do loop() end
end

while true do
	local ok, err = pcall(main)
	if not ok then print("err",err) end
	os.sleep(5)
end