-- Usage (program name) <x> <y> <z>


local tArgs = {...}

xHome, yHome, zHome = gps.locate(3)

xStart = tonumber( tArgs[1] )
yStart = tonumber( tArgs[2] )
zStart = tonumber( tArgs[3] )

xCount = 0
yCount = 0
zCount = 0

function checkIfFuel()
    return turtle.refuel(0)
  end

function smartRefuel()
    local fuelLimit = turtle.getFuelLimit()
    if turtle.getFuelLevel() < fuelLimit / 4 then
        for i = 1, 16 do
            turtle.select(i)
            if checkIfFuel() then
                turtle.refuel()
            end
        end
    end
end

function inventoryDump()
    turtle.select(16)
    turtle.placeUp()
    for i = 15, 2, -1 do
       turtle.select(i)
       if turtle.getItemCount( turtle.getSelectedSlot() ) > 0 then
            turtle.dropUp()
        end
    end
    turtle.select(16)
    turtle.select(1)
    smartRefuel()
end

-- 4 for North, 1 for East, 2 for South, 3 for West
function getDirection()
    local stX, stY, stZ
    local nwX, nwY, nwZ
    local clcX, clcZ
    local facing

    stX, stY, stZ = gps.locate(3)
    turtle.forward()
    sleep(1)
    nwX, nwY, nwZ = gps.locate(3)

    clcX = stX - nwX
    clcZ = stZ - nwZ

    if tonumber(clcX) ~= 0 then
        if tonumber(clcX) < 0 then
            facing = 1
        end
        if tonumber(clcX) > 0 then
            facing = 3
        end
    end
    if tonumber(clcZ) ~= 0 then
        if tonumber(clcZ) < 0 then
            facing = 2
        end
        if tonumber(clcZ) > 0 then
            facing = 4
        end
    end
    turtle.back()
    return facing
end

function faceNorth()
    local direction = getDirection()
    if tonumber(direction) == 3 then
        turtle.turnLeft()
    elseif tonumber(direction) == 4 then
        turtle.turnLeft()
        turtle.turnLeft()
    elseif tonumber(direction) == 1 then
        turtle.turnRight()
    end
end

function safeBreakDown()
    if turtle.detectDown then
        turtle.digDown()
    end
end

function smartTurn(counter)
    if counter % 2 == 0 then
        turtle.turnRight()
    else
        turtle.turnLeft()
    end
end

function goToX()
    local homeCopy = xHome
    if homeCopy < xStart then
        turtle.turnLeft()
        while homeCopy ~= xStart do
            turtle.forward()
            homeCopy = homeCopy + 1
            xCount = xCount + 1
        end
        turtle.turnLeft()
    elseif homeCopy > xStart then
        turtle.turnRight()
        while homeCopy ~= xStart do
            turtle.forward()
            homeCopy = homeCopy - 1
            xCount = xCount - 1
        end
    end
end
function goToZ()
    local homeCopy = zHome
    if homeCopy < zStart then
        while homeCopy ~= zStart do
            turtle.forward()
            homeCopy = homeCopy + 1
            zCount = zCount + 1
        end
    elseif homeCopy > zStart then
        turtle.turnLeft()
        turtle.turnLeft()
        while homeCopy > zStart do
            turtle.forward()
            homeCopy = homeCopy - 1
            zCount = zCount - 1
        end
    end
end
function goToY()
    local homeCopy = yHome
    if homeCopy < yStart then
        while homeCopy ~= yStart do
            turtle.moveUp()
            homeCopy = homeCopy + 1
            yCount = yCount + 1
        end
    elseif homeCopy > yStart then
        while homeCopy > yStart do
            safeBreakDown()
            turtle.down()
            homeCopy = homeCopy - 1
            yCount = yCount - 1
        end
    end
end

function goToCoords()
    faceNorth()
    goToX()
    faceNorth()
    goToZ()
    goToY()
    smartRefuel()
end

function quarry()
    for i = 1, 3 do
        turtle.digDown()
        turtle.down()
        for j = 1, 20 do
            for k = 1, 19 do
                turtle.dig()
                turtle.forward()
            end
            smartRefuel()
            if j < 20 then
                smartTurn(j)
                turtle.dig()
                turtle.forward()
                smartTurn(j)
            end
        end
        turtle.turnLeft()
        for j = 1, 19 do
            turtle.forward()
        end
        turtle.turnLeft()
    end
end

function returnHome()
    for i = 1, 3 do
        turtle.up()
    end
    xMove = math.abs(xCount)
    yMove = math.abs(yCount)
    zMove = math.abs(zCount)

    for i = 1, math.abs(yMove) do
        turtle.up()
    end

    if xCount < 0 then
        turtle.turnLeft()
    else
        turtle.turnRight()
    end
    for i = 1, math.abs(xMove) do
        turtle.forward()
    end
    faceNorth()

    if zCount > 0 then
        turtle.turnLeft()
        turtle.turnLeft()
    end
    for i = 1, math.abs(zMove) do
        turtle.forward()
    end
end

function miner()
    goToCoords()
    faceNorth()
    quarry()
    returnHome()
    inventoryDump()
end

miner()