function refuel()
    if turtle.getFuelLevel() < 15 then
        print("Fuel level is ", turtle.getFuelLevel(), "refueling...")
        turtle.select(1)
        turtle.refuel(1)
    end
end

function forceForward()
    while not turtle.forward() do
        refuel()
        a, b = turtle.inspect()
        if a then
            if a.name == "minecraft:leaves" then
                turtle.dig()
            end
        end
    end
end

function interactTree(right)
    print("Interacting with tree planting spot...")
    a, b = turtle.inspect()
    if a then
        if b.name == "minecraft:sapling" then
            print("Tree is planted but not mature, ignoring")
        elseif b.name == "minecraft:log" then
            mineTree(right)
            plantSaplings(right)
        else
            print("WARNING: Unknown block found: ", b.name)
            turtle.dig()
            plantSaplings(right)
        end
    else
        plantSaplings(right)
    end
end

function plantSaplings(right)
    print("Planting saplings...")
    refuel()
    findItem("minecraft:sapling")
    if right then
        forceForward()
        forceForward()
        turtle.turnLeft()
        turtle.place()
        turtle.turnRight()
        turtle.back()
        turtle.place()
        turtle.turnLeft()
        turtle.place()
        turtle.turnRight()
        turtle.back()
        turtle.place()
    else
        forceForward()
        forceForward()
        turtle.turnRight()
        turtle.place()
        turtle.turnLeft()
        turtle.back()
        turtle.place()
        turtle.turnRight()
        turtle.place()
        turtle.turnLeft()
        turtle.back()
        turtle.place()
    end
end

function findItem(item)
    for i=1, 16 do
        turtle.select(i)
        if turtle.getItemCount() > 1 then
            local data = turtle.getItemDetail()
            if data.name == item then
                break
            end
        end
    end
end

function mineTree(right)
    print("Chopping down tree")
    refuel()
    turtle.dig()
    forceForward()
    local blocksLeft = 0
    while true do
        refuel()
        turtle.dig()
        turtle.digUp()
        if turtle.up() then
            blocksLeft = blocksLeft + 1
        end
        a, b = turtle.inspectUp()
        if a then
            if not b.name == "minecraft:log" then
                break
            end
        else
            break
        end
    end
    turtle.digUp()
    turtle.up()
    turtle.dig()
    print("Got to top of tree, tree height: ", blocksLeft)
    if right then
        turtle.turnLeft()
        turtle.dig()
        forceForward()
        turtle.turnRight()
    else
        turtle.turnRight()
        turtle.dig()
        forceForward()
        turtle.turnLeft()
    end

    while blocksLeft + 1 > 0 do
        refuel()
        while not turtle.down() do
            turtle.digDown()
        end
        turtle.dig()
        blocksLeft = blocksLeft - 1
    end

    if right then
        turtle.turnRight()
        forceForward()
        turtle.turnLeft()
        turtle.back()
    else
        turtle.turnLeft()
        forceForward()
        turtle.turnRight()
        turtle.back()
    end
end

function startup()
    print("Getting out of starting position...")
    refuel()
    forceForward()
    forceForward()
    forceForward()
end

function harvest()
    -- Go forward one lane
    for i=1, 7 do
        refuel()
        turtle.turnLeft()
        interactTree(false)
        turtle.turnRight()
        turtle.turnRight()
        interactTree(true)
        turtle.turnLeft()
        forceForward()
        forceForward()
        forceForward()
    end

    -- Switch to right next lane

    turtle.turnRight()
    for i=1, 6 do
        refuel()
        forceForward()
    end
    turtle.turnRight()

    forceForward()
    forceForward()

    -- Go forward one lane

    for i=1, 7 do
        refuel()
        turtle.turnLeft()
        interactTree()
        turtle.turnRight()
        turtle.turnRight()
        interactTree()
        turtle.turnLeft()
        forceForward()
        forceForward()
        forceForward()
    end

    -- Switch to left next lane

    turtle.turnLeft()
    for i=1, 6 do
        refuel()
        forceForward()
    end
    turtle.turnLeft()

    forceForward()
    forceForward()

    -- Go forward one lane

    for i=1, 7 do
        refuel()
        turtle.turnLeft()
        interactTree()
        turtle.turnRight()
        turtle.turnRight()
        interactTree()
        turtle.turnLeft()
        forceForward()
        forceForward()
        forceForward()
    end

    -- Switch to right next lane

    turtle.turnRight()
    forceForward()
    forceForward()
    forceForward()
    turtle.turnRight()
    forceForward()
    forceForward()

    -- Go forward one lane

    for i=1, 7 do
        refuel()
        turtle.turnLeft()
        interactTree()
        turtle.turnRight()
        forceForward()
        forceForward()
        forceForward()
    end
    turtle.turnRight()
    for i=1, 15 do
        refuel()
        forceForward()
    end
    turtle.turnLeft()
    forceForward()

    for i=2, 16 do
        turtle.select(i)
        turtle.drop()
    end
end

startup()
harvest()