farming

local x=0
local y=0
local dir=0
local field=0
local homeX=0
local homeY=0
local stop=false

--Fields (H for home):
--  1       3
--      H
--  2       4
-- Only 1 and 2 are done for now

local function harvest()
    if turtle.detectDown() then
        turtle.digDown()
    end
end

local function plant()
    if not turtle.detectDown() and turtle.getItemCount(1)>1 then
        turtle.select(1)
        turtle.placeDown()
    end
end

local function turn(direction)
    if direction == "left" then
        turtle.turnLeft()
        dir = (dir-1)%4
    elseif direction == "right" then
        turtle.turnRight()
        dir = (dir+1)%4
    end
end

local function forward()
    if dir == 0 then
        if turtle.forward() then
            x = x+1
            homeX = homeX+1
        end
    elseif dir == 2 then
        if turtle.forward() then
            x = x-1
            homeX = homeX-1
        end
    elseif dir == 1 then
        if turtle.forward() then
            y = y+1
            homeY = homeY+1
        end
    elseif dir == 3 then
        if turtle.forward() then
            y = y-1
            homeY = homeY-1
        end
    end
end

local function setDir(newDir)
    while not (newDir == dir) do
        turn("right")
    end
end

local function move()
    if x==0 and y~=0 then
        turn("left")
    elseif x==8 and y~=8 then
        turn("right")
    elseif x==8 and y==8 then
        return false
    end
    forward()
    return true
end

local function returnHome()
    if homeX > 0 then
        setDir(2)
        while homeX ~=0 do
            forward()
        end
    elseif homeX < 0 then
        setDir(0)
        while homeX ~=0 do
            forward()
        end
    end

    if homeY > 0 then
        setDir(3)
        while homeY ~=0 do
            forward()
        end
    elseif homeY < 0 then
        setDir(1)
        while homeY ~=0 do
            forward()
        end
    end
    setDir(0)
    print("Returned home")
end

local function gotoField()
    if homeX ~=0 or homeY ~=0 or dir~=0 then
        returnHome()
    end
    if field == 1 then
        turn("right")
        forward()

        turn("left")
        forward()
    elseif field == 2 then
        turn("left")
        for i=1, 9 do
            forward()
        end

        turn("right")
            forward()
    end
    -- Reset x and y
    x=0
    y=0
    write("Starting harvesting field ")
    write(field)
    print("...")
end

local function manageInventory()
    local fuelCount
    for i=3,15 do
        turtle.select(i)
        turtle.dropDown()
    end
    turtle.select(16)
    if turtle.getFuelLevel() < 100 and turtle.suckUp() then
        fuelCount = turtle.getItemCount()
        turtle.refuel(fuelCunt-1)
    end
end

local function harvestLoop(fieldNum)
    field = fieldNum
    stop=false
    turtle.select(1)
    gotoField()
    while not stop do
        harvest()
        plant()
        if not move() then
            stop = true
        end
    end
    returnHome()
    manageInventory()
end

local function mainLoop()
    harvestLoop(1)
    harvestLoop(2)
end

mainLoop()