ComputerCraft Witherboss Farmer

--constants
local casing_slot_one = 1
local casing_slot_two = 2
local spike_slot = 3

local wither_skulls_needed = 3
local soul_sand_needed = 4
local casing_needed = 112
local spikes_needed = 9

local redstone_direction = "left"
local chest_direction = "right"

--functions
function show_usage()
    print("wither_farm build --> build the casing for the farm")
    print("wither_farm run ----> run the actual witherboss farm")
end

function pre_boss_builder()
    turtle.up()
    move_direction("forward", 2)
    move_direction("down", 2)
end

function post_boss_builder()
    move_direction("back", 2)
    turtle.down()
end

function move_direction(direction, count)
    direction = string.lower(direction)
    --this is to perform more of a strafe than just moving in a given direction
    --turn left/right before moving
    if direction == "left" then
        turtle.turnLeft()
    elseif direction == "right" then
        turtle.turnRight()
    end

    --move in the requested direction x number of times
    for x = 1, count, 1 do
        if direction == "up" then
            turtle.up()
        elseif direction == "down" then
            turtle.down()
        elseif direction == "left" then
            turtle.forward()
        elseif direction == "right" then
            turtle.forward()
        elseif direction == "forward" then
            turtle.forward()
        elseif direction == "back" then
            turtle.back()
        else
            print("An undefined direction string was entered!")
        end
    end

    --turn back left/right after moving
    if direction == "left" then
        turtle.turnRight()
    elseif direction == "right" then
        turtle.turnLeft()
    end
end

function compare_casing_slots()
    local current = turtle.getSelectedSlot()
    turtle.select(casing_slot_one)
    local result = turtle.compareTo(casing_slot_two)
    turtle.select(current)
    return result
end

function is_case_constructed()
    local current = turtle.getSelectedSlot()
    turtle.select(casing_slot_one)
    local result = turtle.compare()
    if result then
        turtle.select(casing_slot_two)
        result = turtle.compare()
        turtle.select(current)
        return result
    end
    return false
end

function build_casing()
    --first layer
    turtle.select(casing_slot_one)
    turtle.place() --1
    turtle.up()
    turtle.forward()
    turtle.turnLeft()
    turtle.forward()
    turtle.placeDown() --2
    turtle.forward()
    turtle.placeDown() --3
    turtle.turnRight()
    turtle.forward()
    turtle.placeDown() --4
    turtle.forward()
    turtle.placeDown() --5
    turtle.forward()
    turtle.placeDown() --6
    turtle.forward()
    turtle.placeDown() --7
    turtle.turnRight()
    turtle.forward()
    turtle.placeDown() --8
    turtle.turnRight()
    turtle.forward()
    turtle.placeDown() --8
    turtle.forward()
    turtle.placeDown() --9
    turtle.forward()
    turtle.placeDown() --10
    turtle.forward()
    turtle.placeDown() --11
    turtle.turnLeft()
    turtle.forward()
    turtle.turnLeft()
    turtle.forward()
    turtle.placeDown() --12
    turtle.forward()
    turtle.placeDown() --13
    turtle.forward()
    turtle.placeDown() --14
    turtle.forward()
    turtle.placeDown() --15
    turtle.turnRight()
    turtle.forward()
    turtle.placeDown() --16
    turtle.turnRight()
    turtle.forward()
    turtle.placeDown() --17
    turtle.forward()
    turtle.placeDown() --18
    turtle.forward()
    turtle.placeDown() --19
    turtle.forward()
    turtle.placeDown() --20
    turtle.turnLeft()
    turtle.forward()
    turtle.placeDown() --21
    turtle.turnLeft()
    turtle.forward()
    turtle.placeDown() --22
    turtle.forward()
    turtle.placeDown() --23
    turtle.forward()
    turtle.placeDown() --24
    turtle.forward()
    turtle.placeDown() --25

    --second layer -> fifth layer
    for y = 1, 5 do
        turtle.up()
        turtle.placeDown() --26
        --top right corner
        turtle.turnLeft()
        for x = 1, 4 do
            turtle.forward()
            turtle.placeDown() --27-30
        end
        --top left corner
        turtle.turnLeft()
        for x = 1, 4 do
            turtle.forward()
            if turtle.getItemCount(casing_slot_one) == 0 then  --runs out at this point
                turtle.select(casing_slot_two)
            end
            turtle.placeDown() --30-35
        end
        --bottom left corner
        turtle.turnLeft()
        turtle.forward()
        turtle.placeDown() --36
        if y == 2 or y == 4 or y == 5 then  --level 2, 4, and 5 or the hollow part
            turtle.forward()
            turtle.placeDown()
            turtle.forward()
        else
            for x = 1, 2 do
                turtle.forward()
            end
        end
        turtle.placeDown() --37
        turtle.forward()
        turtle.placeDown() --38
        --bottom right corner
        turtle.turnLeft()
        for x = 1, 3 do
            turtle.forward()
            turtle.placeDown() --38-42
        end
        turtle.forward()
    end
    turtle.turnLeft()
    turtle.forward()
    turtle.turnLeft()
    turtle.forward()
    for x = 1, 2 do
        turtle.down()
    end
    turtle.placeUp()
    turtle.forward()
    turtle.placeUp()
    turtle.forward()
    turtle.placeUp()
    turtle.turnRight()
    turtle.forward()
    turtle.placeUp()
    turtle.turnRight()
    turtle.forward()
    turtle.placeUp()
    turtle.forward()
    turtle.placeUp()
    turtle.turnLeft()
    turtle.forward()
    turtle.placeUp()
    turtle.turnLeft()
    turtle.forward()
    turtle.placeUp()
    turtle.forward()
    turtle.placeUp()

    turtle.select(spike_slot)
    turtle.down()
    turtle.placeUp()
    for x = 1, 2 do
        turtle.turnLeft()
    end
    turtle.forward()
    turtle.placeUp()
    turtle.forward()
    turtle.placeUp()
    turtle.turnRight()
    turtle.forward()
    turtle.placeUp()
    turtle.turnRight()
    turtle.forward()
    turtle.placeUp()
    turtle.forward()
    turtle.placeUp()
    turtle.turnLeft()
    turtle.forward()
    turtle.placeUp()
    turtle.turnLeft()
    turtle.forward()
    turtle.placeUp()
    turtle.forward()
    turtle.placeUp()
    turtle.turnLeft()
    turtle.forward()
    turtle.turnLeft()
    for x = 1, 4 do
        turtle.forward()
    end
    for x = 1, 2 do
        turtle.turnLeft()
    end
    turtle.down()
end

function build_wither(wither_slot, ss_slot)
    turtle.down() --move from the middle of the wither to the bottom

    --select soul sand slot
    turtle.select(ss_slot)

    turtle.place() --soul sand bottom
    turtle.up()
    turtle.place() --soul sand middle
    turtle.turnLeft()
    turtle.forward()
    turtle.turnRight()
    turtle.place() --soul sand left
    turtle.select(wither_slot)
    turtle.up()
    turtle.place() --wither skull left
    turtle.down()

    turtle.turnRight()

    --move forward 2
    move_direction("forward", 2)

    turtle.turnLeft()
    turtle.select(ss_slot)
    turtle.place() --soul sand right
    turtle.up()
    turtle.select(wither_slot)
    turtle.place() --wither skull right
    turtle.turnLeft()
    turtle.forward()
    turtle.turnRight()
    turtle.place() --wither skull middle
end

function drop_direction(direction, slot, amount)
    local current = turtle.getSelectedSlot()
    turtle.select(slot)
    direction = string.lower(direction)
    local success = false
    if direction == "right" then
        turtle.turnRight()
        success = turtle.drop(amount)
        turtle.turnLeft()
    elseif direction == "left" then
        turtle.turnLeft()
        success = turtle.drop(amount)
        turtle.turnRight()
    elseif direction == "up" then
        success = turtle.dropUp(amount)
    elseif direction == "down" then
        success = turtle.dropDown(amount)
    elseif direction == "back" then
        for x = 1, 2 do
            turtle.turnLeft()
        end
        success = turtle.drop(amount)
        for x = 1, 2 do
            turtle.turnRight()
        end
    elseif direction == "front" then
        success = turtle.drop(amount)
    else
        print("An undefined direction string was entered!")
    end
    turtle.select(current)
    return success
end

function valid_fuel(item_name, item_damage)
    if item_name == "minecraft:coal" and (item_damage == 0 or item_damage == 1) then  --vanilla
        return true
    elseif item_name == "Railcraft:fuel.coke" then  --railcraft
        return true
    elseif item_name == "ImmersiveEngineering:material" and item_damage == 6 then  --immersive engineering
        return true
    end
    return false
end

function table_length(T)
    local count = 0
    for _ in pairs(T) do count = count + 1 end
    return count
end

function determine_slots()
    local soul_sand_found = false
    local soul_sand_slot = 0
    local wither_skulls_found = false
    local wither_skull_slot = 0
    local fuel_slot = 0
    for x = 4, 16 do  --loop through all slots
        local item_info = turtle.getItemDetail(x)
        if item_info ~= nil then  --valid item
            local item_name = item_info.name
            local item_damage = item_info.damage
            if item_name == "minecraft:skull" and item_damage == 1 then  --wither skulls
                wither_skulls_found = true
                wither_skull_slot = x
            elseif item_name == "minecraft:soul_sand" then  --soul sand
                soul_sand_found = true
                soul_sand_slot = x
            elseif valid_fuel(item_name, item_damage) then
                fuel_slot = x
            end
        end
    end
    if soul_sand_found and wither_skulls_found then
        local response = {wither_skull_slot, soul_sand_slot}
        if fuel_slot > 0 then
            response[3] = fuel_slot
        end
        return response
    end
    return false
end

function refuel_turtle(count)
    local current = turtle.getSelectedSlot()
    turtle.select(slot)
    turtle.refuel(count)
    turtle.select(current)
end

--arguments
local command = ...
if command then
    command = string.lower(command)
else
    show_usage()
    return
end

--variables
--slot variables
local wither_skull_slot = 0
local soul_sand_slot = 0
local fuel_slot = 0

--handle commands
if command == "test" then  --tests for debugging
    determine_slots()
elseif command == "build" then  --build casing
    if not is_case_constructed() then
        if compare_casing_slots() then
            local casing_count_one = turtle.getItemCount(casing_slot_one)
            local casing_count_two = turtle.getItemCount(casing_slot_two)
            local total_casing_count = casing_count_one + casing_count_two
            local spike_count = turtle.getItemCount(spike_slot)
            if total_casing_count >= casing_needed then
                if spike_count >= spikes_needed then
                    print("Building witherboss farm casing (this may take a while)...")
                    build_casing()
                    print("Done!")
                else
                    print(tostring(spike_count) .. "/" .. tostring(spikes_needed) .. " Spike Blocks")
                end
            else
                print(tostring(total_casing_count) .. "/" .. tostring(casing_needed) .. " Casing Blocks")
            end
        else
            print("Casing materials aren't the same!")
        end
    else
        print("Casing is already constructed!")
    end
elseif command == "run" then  --run the actual wither builder
    --1.5 second loop to wait on a redstone signal
    local announced = false
    while true do
        --determine slots every 1.5 seconds
        local fuel_found = false
        local slot_response = determine_slots()
        if type(slot_response) == "table" then
            wither_skull_slot = slot_response[1]
            soul_sand_slot = slot_response[2]
            if table_length(slot_response) == 3 then
                fuel_slot = slot_response[3]
                fuel_found = true
            end
        else
            print("Soul sand and/or wither skulls not found!")
            return
        end

        --variables
        local soul_sand_count = turtle.getItemCount(soul_sand_slot)
        local wither_skull_count = turtle.getItemCount(wither_skull_slot)

        local wither_skull_remainder = wither_skull_count % wither_skulls_needed
        local soul_sand_remainder = soul_sand_count % soul_sand_needed

        --refuel if low fuel level
        if fuel_found then
            local fuel_count = turtle.getItemCount(fuel_slot)
            if turtle.getFuelLevel() ~= "unlimited" and turtle.getFuelLevel() < 1 and fuel_count > 0 then
                print("Refueling turtle...")
                refuel_turtle(fuel_count)
                print("Done!")
            end
        end

        --errors with divisibility in wither skulls correction
        if wither_skull_remainder > 0 and wither_skull_count > wither_skulls_needed then
            print("Wither skulls count not divisible by " .. tostring(wither_skulls_needed) .. "! Fixing...")
            drop_direction(chest_direction, wither_skull_slot, wither_skull_remainder)
            wither_skull_count = wither_skull_count - wither_skull_remainder
            wither_skull_remainder = 0
            print("Wither skull divisibility error fixed!")
        end

        --error with divisibility in soul sand correction
        if soul_sand_remainder > 0 and soul_sand_count > soul_sand_needed then
            print("Soul sand count not divisible by " .. tostring(soul_sand_needed) .. "! Fixing...")
            drop_direction(chest_direction, soul_sand_slot, soul_sand_remainder)
            soul_sand_count = soul_sand_count - soul_sand_remainder
            soul_sand_remainder = 0
            print("Soul sand divisibility error fixed!")
        end

        --wait on a redstone signal on the back
        if redstone.getInput(redstone_direction) == true then
            if wither_skull_count > 0 and soul_sand_count > 0 and wither_skull_remainder == 0 and soul_sand_remainder == 0 then
                --reset announced
                announced = false

                --find out how many wither bosses it can generate
                total_with_skulls = wither_skull_count / wither_skulls_needed
                total_with_ss = soul_sand_count / soul_sand_needed
                if total_with_skulls == total_with_ss then
                    --print the amount the turtle is able to spawn
                    print(tostring(total_with_skulls) .. " Wither Bosses Left!")

                    --run pre-boss build tasks
                    pre_boss_builder()

                    --begin building the wither from the bottom up and ending with the central wither skull
                    build_wither(wither_skull_slot, soul_sand_slot)

                    --run post-boss build tasks
                    post_boss_builder()

                    print("Wither Boss Spawned, Prepare Yourself!")
                else
                    if total_with_skulls > total_with_ss then
                        local deficit = (total_with_skulls - total_with_ss) * wither_skulls_needed
                        drop_direction("right", wither_skull_slot, deficit)
                        print("The soul sand deficit has been corrected!")
                    elseif total_with_ss > total_with_skulls then
                        local deficit = (total_with_ss - total_with_skulls) * soul_sand_needed
                        drop_direction("right", soul_sand_slot, deficit)
                        print("The wither skull deficit has been corrected!")
                    end
                end
            else
                if not announced then
                    print("Slot 1 = wither skulls (minimum of 3)!")
                    print("Slot 2 = soul sand (minimum of 4)!")
                    announced = true
                end
            end
        end
        sleep(1.5) --sleep because why not?
    end
else
    show_usage()
end