local farmWidth -- number
local farmLength -- number
local farmSpacing -- number, blocks between each tree

local farmField -- table

local farmXOffset -- number
local farmYOffset -- number
local farmZOffset -- number

-- gets all global variables
function init( global )
	setfenv(1,global)
end

function distance( x1,z1,x2,z2 )
	local dx = x1-x2
	local dz = z1-z2
	return math.sqrt(dx^2+dz^2)
end

function findNearestSpot( x,z )
	local nearX,nearZ = x,z
	local nearestDistance = math.huge
	local turtleX,_,turtleZ = gps.getPosition()
	local direction
	-- direction is from the nearest position towards the x,z

	for xOffset = -1,1 do
		for zOffset = -1,1 do
			if (xOffset==0 or zOffset==0) and zOffset~=xOffset then

				-- distance from the turtle to the tree
				local tmpDistance = distance(x+xOffset,z+zOffset,turtleX,turtleZ)
				if tmpDistance < nearestDistance then
					nearX = x + xOffset
					nearZ = z + zOffset
					nearestDistance = tmpDistance

					if xOffset == 1 then
						direction = gps.west
					elseif xOffset == -1 then
						direction = gps.east
					elseif zOffset == 1 then
						direction = gps.north
					elseif zOffset == -1 then
						direction = gps.south
					end
				end
				
			end
		end
	end

	return nearX,nearZ,direction
end

function findNearestCorner( x1,z1,x2,z2 )
	local nearX,nearZ
	local nearestDistance = math.huge
	local turtleX,_,turtleZ = gps.getPosition()

	for x = x1,x2,x2-x1 do
		for z = z1,z2,z2-z1 do
			
			-- distance from the turtle to the corner
			local tmpDistance = distance(x,z,turtleX,turtleZ)
			if tmpDistance < nearestDistance then
				nearX = x
				nearZ = z
				nearestDistance = tmpDistance
			end

		end
	end

	return nearX,nearZ
end

-- will dig til it reaches the surface
-- instead of comparing log
-- more consistant and easier with a big farm
-- This does move the turtle 1 block forward
function chop( clearDirt,x,z )
	if not x or not z then
		x,_,z = gps.getPosition(1,gps.absPos.dir)
	end
	gps.moveForward(1,killMobs,true)
	if turtle.detectUp() then
		-- tree in front
		
		-- begin chop down the tree
		-- keep count on the trees height
		local height = 0
		while turtle.detectUp() do
			gps.moveUp(1,killMobs,true)
			height = height + 1
		end

		-- get back down to the "ground"
		gps.moveDown(height,killMobs,true)
	else
		-- no tree in front
	end
	if clearDirt then
		dig.down(killMobs,true)
	end
end

function chopAll( clearDirt )
	if type(farmWidth) == "number"
	and type(farmLength) == "number"
	and type(farmSpacing) == "number"
	and type(farmXOffset) == "number"
	and type(farmYOffset) == "number"
	and type(farmZOffset) == "number"
	then

		-- find nearest corner of farm
		
		local homeX,homeY,homeZ = gps.getHome()	

		local corner1x = homeX + farmXOffset
		local corner1z = homeZ + farmZOffset
		local corner2x = homeX + farmXOffset + (farmWidth-mult(farmWidth)) * farmSpacing
		local corner2z = homeZ + farmZOffset + (farmLength-mult(farmLength)) * farmSpacing

		-- loop through the trees
		local startX,startZ = findNearestCorner( corner1x,corner1z,corner2x,corner2z )
		local stopX = corner1x; if stopX==startX then stopX = corner2x end
		local stopZ = corner1z; if stopZ==startZ then stopZ = corner2z end

		for x = startX,stopX,farmSpacing*mult(stopX-startX) do
			-- to alternate so you zig zag through the farm to save fuel and time
			local iteration = (x-startX+farmSpacing)/farmSpacing
			local A,B = startZ,stopZ
			if iteration%2==0 then A,B = stopZ,startZ end
			--print("i="..iteration.." start at "..A.." stop at "..B)
			for z = A,B,farmSpacing*mult(B-A) do
				--write(z.." ")
				local treeX,treeZ,dir = findNearestSpot(x,z)
				gps.goto(treeX,homeY+farmYOffset,treeZ,dir)
				chop(clearDirt)
			end
			--print()
		end
	end
end

-- requires dirt
function replant()
	if type(farmWidth) == "number"
	and type(farmLength) == "number"
	and type(farmSpacing) == "number"
	and type(farmXOffset) == "number"
	and type(farmYOffset) == "number"
	and type(farmZOffset) == "number"
	then

		-- obtain materials
		item.followStoragePath()
		item.dropoff()
		item.getItems({item.types.dirt,item.types.sapling},math.abs(farmWidth*farmLength),true)
		item.followStoragePath(true)

		-- find nearest corner of farm
		
		local homeX,homeY,homeZ = gps.getHome()	

		local corner1x = homeX + farmXOffset
		local corner1z = homeZ + farmZOffset
		local corner2x = homeX + farmXOffset + (farmWidth-mult(farmWidth)) * farmSpacing
		local corner2z = homeZ + farmZOffset + (farmLength-mult(farmLength)) * farmSpacing

		-- loop through the trees
		local startX,startZ = findNearestCorner( corner1x,corner1z,corner2x,corner2z )
		local stopX = corner1x; if stopX==startX then stopX = corner2x end
		local stopZ = corner1z; if stopZ==startZ then stopZ = corner2z end

		for x = startX,stopX,farmSpacing*mult(stopX-startX) do
			-- to alternate so you zig zag through the farm to save fuel and time
			local iteration = (x-startX+farmSpacing)/farmSpacing
			local A,B = startZ,stopZ
			if iteration%2==0 then A,B = stopZ,startZ end
			--print("i="..iteration.." start at "..A.." stop at "..B)
			for z = A,B,farmSpacing*mult(B-A) do

				-- select dirt
				local atStorage = false
				while not item.select(item.types.dirt) do
					if not atStorage then item.followStoragePath() atStorage=true end
					item.getItem(item.types.dirt,_,false)
				end
				if atStorage then item.followStoragePath(true) end

				gps.goto(x,homeY+farmYOffset,z)
				turtle.placeDown()

				-- select sapling
				local atStorage = false
				while not item.select(item.types.sapling) do
					if not atStorage then item.followStoragePath() atStorage=true end
					item.getItem(item.types.sapling,_,false)
				end
				if atStorage then item.followStoragePath(true) end

				gps.goto(x,homeY+farmYOffset+1,z)
				turtle.placeDown()
			end
		end
	end

	item.followStoragePath()
	item.dropoff()
	gps.goto(gps.getHome())
end

function setOffset( xOffset,yOffset,zOffset )
	farmXOffset = xOffset or farmXOffset
	farmYOffset = yOffset or farmYOffset
	farmZOffset = zOffset or farmZOffset
end

function setSize( width,length,spacing )
	farmWidth = width or farmWidth
	farmLength = length or farmLength
	farmSpacing = spacing or farmSpacing
end

-- sets the field forwards to the right
-- z = forward
-- x = right
-- state = (boolean) true/false depends if its grown/harvested
function updateField( state )
	if type(farmWidth) == "number"
	and type(farmLength) == "number"
	and type(farmSpacing) == "number"
	and type(farmZOffset) == "number"
	and type(farmXOffset) == "number"
	then
		-- reset the field
		farmField = {}

		local totalWidth = (farmWidth-1) * farmSpacing + 1
		local totalLength = (farmLength-1) * farmSpacing + 1

		-- loop through the width and length
		for x = 1,totalWidth,farmSpacing do
			for z = 1,totalLength,farmSpacing do
				-- make sure the column exists
				if not farmField[x] then farmField[x] = {} end

				farmField[x][z] = farmField[x][z] or (state or false)
			end
		end

		return true
	else
		return false
	end
end