CEX v1.03

-- Check that some fuel exists (consumes one if it does exist; there is no other way to verify)
function CheckInitialFuel()
    for i = 1, 16 do
        turtle.select(i)
        if turtle.refuel(1) then -- If fuel was successfully used, swap the stack to the first slot (faster refueling next time, probably unnecessary)
            --turtle.transferTo(i, 1)
            return true
        end
    end

    return false
end

function DigThenMove(dir)
    local movedSuccessfully = false

    while movedSuccessfully == false do
        if dir == "forward" then
            while turtle.detect() do
                turtle.dig()
            end
        elseif dir == "up" then
            while turtle.detectUp() do
                turtle.digUp()
            end
        elseif dir == "down" then
            while turtle.detectDown() do
                turtle.digDown()
            end
        end

        if dir == "forward" then
            movedSuccessfully = turtle.forward()
        elseif dir == "up" then
            movedSuccessfully = turtle.up()
        else
            movedSuccessfully = turtle.down()
        end
    end
end

-- Mines all blocks directly in front of the turtle (one square), then moves one square forward (blocks like gravel or sand can fall and result in a block being directly in front of the turtle multiple times)
function RefuelIfNeeded()
    if turtle.getFuelLevel() <= 5 then -- If the turtle is empty or nearly empty on fuel, search for a fuel source and refuel (prioritize left to right, top to bottom)
        for i = 1, 16 do
            turtle.select(i)
            if turtle.refuel(1) then -- If fuel was successfully used, swap the stack to the first slot (faster refueling next time, probably unnecessary)
                return
            end
        end
        WaitForFuel()
    end
end

function WaitForFuel()
    print("Please add fuel.")

    while true do
        for i = 1, 16 do
            turtle.select(i)
            if turtle.refuel(1) then
                return
            end
        end
        sleep(5)
    end
end

function TurnTurtle(reverseDirection)
    -- The reverse direction flag is used for turning back to the initial facing direction (i.e. forward) after a row of clearing
    if (reverseDirection) then
        if rightOrLeft == "right" then
            turtle.turnLeft()
        else
            turtle.turnRight()
        end
    else
        if (rightOrLeft == "right") then
            turtle.turnRight()
        else
            turtle.turnLeft()
        end
    end
end

function MoveVertically()
    if upOrDown == "up" then
        DigThenMove("up")
        --turtle.up()
    else -- direction == "down"
        DigThenMove("down")
        --turtle.down()
    end
end

-- Return the turtle to whence he came
function ReturnToStart()
    -- Return to the starting plane (height)
    if length%2 == 0 then
        for i = 1,height-1 do
            if initialVertical == "up" then
                turtle.down()
            else
                turtle.up()
            end
        end
    end

    -- Return to the side of the cuboid the turtle started on (left or right edge)
    if (height*length)%2 ~= 0 then
        if initialHorizontal == "right" then
            turtle.turnLeft()
        else
            turtle.turnRight()
        end

        for i = 1,width-1 do
            turtle.forward()
        end

        -- Adjust facing to be the same as when the turtle started
        if initialHorizontal == "right" then
            turtle.turnRight()
        else
            turtle.turnLeft()
        end
    end

    -- Return to the side of the cuboid the turtle started (rear edge).  Turtle should now be at the starting coordinates
    for i =1,length-1 do
            turtle.back()
    end
end

function DumpItems()
    turtle.turnLeft()
    if turtle.detect() then
            for i = 1,16 do
                turtle.select(i)
                turtle.drop()
            end
    end

    turtle.turnRight()
    --turtle.turnRight()
    -- Add code to check multiple sides for a chest (detect gets any block, though)
        -- Could attempt a refuel and if successful move fuel to slot 1 then dump the rest of the items (useful for dump and continue logic)
end

-- Consider adding default values for fields left blank
function PerformExcavation()
    for k = 1,length do
    DigThenMove("forward")

    for j = 1,height do
            if width > 1 then -- Only need to do turning if the width is greater than 1
                TurnTurtle(false)
            end

            for i = 1,width-1 do
                if RefuelIfNeeded() == false then
                    return false
                end
                DigThenMove("forward")
            end

            if width > 1 then
                TurnTurtle(true)
            end

            if (rightOrLeft == "right") then
                rightOrLeft = "left"
            else
                rightOrLeft = "right"
            end

            if j < height then
                MoveVertically()
            end
    end

    -- Change vertical direction the turtle will move to clear the next 2D piece (width x height)
    if upOrDown == "up" then
        upOrDown = "down"
    else
        upOrDown = "up"
    end
    end

    return true
end


-- Gather mining parameters from input (Should it go from current square down or up?  Should it go from current square left or right?  How wide / tall / long?  That is, determine which corner to start at and how big of a cuboid to mine.)
print("Clear left or right?")
print("[VALID: left | right]: ")
while true do
    rightOrLeft = string.lower(read())
    if (rightOrLeft == "right" or rightOrLeft == "left") then
            break
        else
            print("Bad entry. Clear left or right?")
            print("[VALID: left | right]: ")
    end
end


print("Clear up or down?")
print("[VALID: up | down]: ")
while true do
    upOrDown = string.lower(read())
    if (upOrDown == "up" or upOrDown == "down") then
        break
    else
        print("Bad entry. Clear up or down?")
        print("[VALID: up | down]: ")
    end
end


print("Enter width (left/right)")
print("[VALID: Any integer]: ")
while true do
    if pcall(function () width = tonumber(read()) end) then
        break
    else
        print("Bad entry. Enter width (left/right)?")
        print("[VALID: Any integer]: ")
    end
end


print("Enter height (above/below)")
print("[VALID: Any integer]: ")
while true do
    if pcall(function () height = tonumber(read()) end) then
        break;
    else
        write ("Bad entry. Enter height (above/below)?")
        print("[VALID: Any integer]: ")
    end
end


print("Enter length (forward)")
print("[VALID: Any integer]: ")
while true do
    if pcall(function () length = tonumber(read()) end) then
        break;
    else
        write ("Bad entry. Enter length (forward)?")
        print("[VALID: Any integer]: ")
    end
end

initialVertical = upOrDown
initialHorizontal = leftOrRight

RefuelIfNeeded()

if PerformExcavation() then
    ReturnToStart()
    --DumpItems()
end