goto (computercraft turtle program)

rednet.open("right")

tArgs = { ... }

local goTo =  {}
local facing
local blocksv
local blocks

goTo.x = tonumber(tArgs[1])
goTo.y = tonumber(tArgs[2]) or 64
goTo.z = tonumber(tArgs[3])

local function turn(_side,_n)  --- function to turn
    if _side == "left" then
        for i=1, _n do
            turtle.turnLeft()
        end
    elseif _side == "right" then
        for i=1, _n do
            turtle.turnRight()
        end
    end
end

local function ensureWalking()  --- make sure that the turtle walked
    if turtle.forward() then  --- ensure that the turtle walked
        blocks = blocks - 1
        return true
    else
        turtle.attack()
        ensureWalking()
    end
end

local function ensureVertical(_a) --- call like ensureVertical{direction = "up"}
    if _a == "up" then
        if turtle.up() then  --- ensure that the turtle walked
            blocksv = blocksv - 1
            return true
        else
            turtle.attackUp()
            ensureVertical(_a)
        end
    elseif _a == "down" then
        if turtle.down() then  --- ensure that the turtle walked
            blocksv = blocksv - 1
            return true
        else
            turtle.attackDown()
            ensureVertical(_a)
        end
    end
end

local function digAndWalk(_a) --- function to dig, walk and replace blocks, call like digAndWalk{times = 1}
    if _a == nil then _a = 1 end
    blocks = _a or 1
    turtle.select(4)
    turtle.dropUp()
    while blocks > 0 do
        while turtle.detect() do
            turtle.dig()
            if turtle.getItemCount(4) < 1 then  --  making sure it is not lava
                break
            end
        end
        ensureWalking()
    end
end

local function getFacing()
    local cx, cy, cz = gps.locate() -- get the current position
    digAndWalk()
    local nx, ny, nz = gps.locate() -- get the new position
    if nx > cx then
        facing = "east"
    elseif nx < cx then
        facing = "west"
    elseif nz > cz then
        facing = "south"
    elseif nz < cz then
        facing = "north"
    end
    print(facing)
end

local function facingNorth()
    if facing == "north" then
        return true
    elseif facing == "east" then
        facing = "north"
        turn("left",1)
        return true
    elseif facing == "south" then
        facing = "north"
        turn("right",2)
        return true
    elseif facing == "west" then
        facing = "north"
        turn("right",1)
        return true
    else
        return false
    end
end

local function pickItem(_from,_to,_number)  -- function to use enderchest of illing cabinet as storage for fuel, and also pick it
    turtle.select(7)
    turtle.digDown()
    turtle.select(_from)
    turtle.placeDown()
    turtle.select(_to)
    turtle.suckDown(_number)
    turtle.select(_from)
    turtle.digDown()
    turtle.select(7)
    turtle.placeDown()
end

local function checkFuel()
    local cx, cy, cz = gps.locate() --- yes again!
    local fuelNeeded = math.ceil(math.abs(cx - goTo.x) + math.abs(cz - goTo.z) + math.abs(cy - goTo.y))
    local coalNeeded = math.ceil(fuelNeeded/80 - turtle.getFuelLevel())
    if coalNeeded > 64 then
        print("Put "..tostring(coalNeeded).." coal in the first slot")
        return false
    elseif coalNeeded <= 0 then
        return true
    elseif coalNeeded > 0 and turtle.getItemCount(1) == coalNeeded then
        turtle.select(1)
        turtle.refuel(coalNeeded)
        return true
    elseif coalNeeded > 0 and turtle.getItemCount(16) == 1 then
        pickItem(16,1,coalNeeded)
        turtle.select(1)
        turtle.refuel(coalNeeded)
        return true
    else
        print("Put "..tostring(coalNeeded).." coal in the first slot")
        return false
    end
end

local function digVertical()
    local arg = {}
    local cx, cy, cz = gps.locate()
    turtle.select(4)
    turtle.dropUp()
    if cy > goTo.y then
        blocksv = cy - goTo.y
        while blocksv > 0 do
            while turtle.detectDown() do
                turtle.digDown()
                if turtle.getItemCount(4) < 1 then  --  making sure it is not lava
                    break
                end
            end
            ensureVertical("down")
        end
    elseif cy < goTo.y then
        blocksv = goTo.y - cy
        while blocksv > 0 do
            while turtle.detectUp() do
                turtle.digUp()
                if turtle.getItemCount(4) < 1 then  --  making sure it is not lava
                    break
                end
            end
            ensureVertical("up")
        end
    end
end

local function walk()
    local cx, cy, cz = gps.locate()
    if facingNorth() then
        digVertical()
        if goTo.z > cz then
            turn("right", 2)
            digAndWalk(math.abs(goTo.z - cz))
            if goTo.x > cx then
                turn("left",1)
                digAndWalk(math.abs(goTo.x - cx))
            elseif goTo.x < cx then
                turn("right", 1)
                digAndWalk(math.abs(goTo.x - cx))
            end
        elseif goTo.z < cz then
            digAndWalk(math.abs(goTo.z - cz))
            if goTo.x > cx then
                turn("right",1)
                digAndWalk(math.abs(goTo.x - cx))
            elseif goTo.x < cx then
                turn("left",1)
                digAndWalk(math.abs(goTo.x - cx))
            end
        elseif goTo.z == cz then  --- the z coordinates are the same!
            if goTo.x > cx then
                turn("right",1)
                digAndWalk(math.abs(goTo.x - cx))
            elseif goTo.x < cx then
                turn("left",1)
                digAndWalk(math.abs(goTo.x - cx))
            end
        end
    end
end

local function writeStr(arg) -- writeStr{color = colors.white, bgColor = colors.black, str = "Hi"}
    local color = arg.color or colors.white
    local str = arg.str
    local bgColor = arg.bgColor or colors.black
    term.setTextColor(color)
    term.setBackgroundColor(bgColor)
    print(str)
    term.setTextColor(colors.white)
    term.setBackgroundColor(colors.black)
end

local function checkArgs()
    if #tArgs < 3 or #tArgs > 3 then
        writeStr{color = colors.green, str = "Goto usages:"}
        writeStr{color = colors.green, str = "goto <x> <y> <z>"}
        return false
    elseif tonumber(tArgs[1]) and tonumber(tArgs[2]) and tonumber(tArgs[3]) then
        return true
    else
        writeStr{color = colors.green, str = "Goto usages:"}
        writeStr{color = colors.green, str = "goto <x> <y> <z>"}
        return false
    end
end

--- MAIN ACTION ---

if checkArgs() and checkFuel() then
    getFacing()
    facingNorth()
    walk()
end