local x
local y
local z
local r

local minFuel = 150

local mx = 9
local mz = 5

function readNumber(inputFile)

  local returnVal
  local nextLine = inputFile.readLine()
  if (nextLine ~= nil) then
    returnVal = tonumber(nextLine)
  end

  return returnVal
end

function updateCoords()
    local fl = fs.open("coords", "w")
    fl.write(x)
    fl.write("\n")
    fl.write(y)
    fl.write("\n")
    fl.write(z)
    fl.write("\n")
    fl.write(r)
    fl.close()
end

function turnRight()
    turtle.turnRight()
    r = r + 1
    if r == 4 then r = r - 4 end
    updateCoords()
end

function turnLeft()
    turtle.turnLeft()
    r = r - 1
    if r == -1 then r = r + 4 end
    updateCoords()
end

function updateForward()
    if r == 0 then
        z = z + 1
    elseif r == 1 then
        x = x - 1
    elseif r == 2 then
        z = z - 1
    elseif r == 3 then
        x = x + 1
    end
    updateCoords()
end

function treeFeller()
    if not turtle.forward() then
        turtle.select(1)
        if turtle.compare() then
            turtle.dig()
            turtle.forward()
            updateForward()
            turtle.digDown()
            while turtle.digUp() do
                turtle.up()
                y = y + 1
                updateCoords()
            end
            while y > 0 do
                turtle.digDown()
                turtle.down()
                y = y - 1
                updateCoords()
            end
        else
            turtle.dig()
            turtle.forward()
            updateForward()
        end
    else
        updateForward()
    end
        turtle.select(16)
        turtle.suckDown()
        turtle.placeDown()
end

function dropWood()
    for i = 2, 15, 1 do
        turtle.select(i)
        turtle.dropDown()
    end
end

function getCoords()
    local f = fs.open("coords", "r")
    if f ~= nil then
        x = readNumber(f)
        y = readNumber(f)
        z = readNumber(f)
        r = readNumber(f)
        fl.close()
    else
        x = 0
        y = 0
        z = 0
        r = 0
        updateCoords()
    end
end

function returnHome()

    while r ~= 1 do turnLeft() end
    while x > 0 do treeFeller() end
    while r ~= 2 do turnRight() end
    while z > 0 do treeFeller() end
end

-- main

getCoords()
returnHome()
dropWood()
while true do
    while turtle.getFuelLevel() < minFuel do
        print("Waiting for fuel in slot 1")
        turtle.select(1)
        turtle.refuel()
    end
    turnRight()
    while z < mz do
        while x < mx do
            treeFeller()
        end
        turnRight()
        treeFeller()
        turnRight()
        while x > 0 do
            treeFeller()
        end
        if z == mz then
            break
        else
            turnLeft()
            treeFeller()
            turnLeft()
        end
    end
    returnHome()
    dropWood()
    sleep(120)
end