-- 🐢 Smart Strip Miner: Mines 3-high, Snakes, Tracks Fuel + Inventory
-- Chest behind turtle. Coal in slot 16.

-- === Interactive Setup ===
print("📐 Set up your mining area:")
write("Enter width (X axis): ") width = tonumber(read())
write("Enter length (Z axis): ") length = tonumber(read())
write("Enter total depth to mine downward (in blocks): ") totalDepth = tonumber(read())

if not width or not length or not totalDepth then
  error("❌ Invalid input. Please enter numbers only.")
end

local layers = math.floor(totalDepth / 3)

-- === State ===
local x, y, z = 0, 0, 0
local dir = 0 -- 0=N, 1=E, 2=S, 3=W

-- === Fuel Logic ===
function fillFuelTank()
  local maxFuel = turtle.getFuelLimit()
  local currentFuel = turtle.getFuelLevel()
  local needed = maxFuel - currentFuel

  turtle.select(16)
  local coalCount = turtle.getItemCount(16)
  local perCoal = 80
  local coalToUse = math.min(math.ceil(needed / perCoal), coalCount)

  if coalToUse > 0 then
    print("⛽ Filling fuel with "..coalToUse.." coal...")
    turtle.refuel(coalToUse)
    print("✅ Fuel: "..turtle.getFuelLevel().."/"..maxFuel)
  else
    error("❌ No coal in slot 16.")
  end
end

function calculateFuelTo(xT, yT, zT)
  return math.abs(x - xT) + math.abs(y - yT) + math.abs(z - zT)
end

function ensureFuel(required)
  if turtle.getFuelLevel() < required then
    turtle.select(16)
    if not turtle.refuel(1) then
      print("⛽ Insert coal in slot 16 to continue...")
      while not turtle.refuel(1) do sleep(5) end
    end
    print("✅ Refueled to "..turtle.getFuelLevel())
  end
end

-- === Position & Direction ===
function updatePosition(move)
  if move == "forward" then
    if dir == 0 then z = z - 1 elseif dir == 1 then x = x + 1
    elseif dir == 2 then z = z + 1 elseif dir == 3 then x = x - 1 end
  elseif move == "back" then
    if dir == 0 then z = z + 1 elseif dir == 1 then x = x - 1
    elseif dir == 2 then z = z - 1 elseif dir == 3 then x = x + 1 end
  elseif move == "down" then y = y - 1
  elseif move == "up" then y = y + 1 end
end

function turnLeft() dir = (dir - 1) % 4; turtle.turnLeft() end
function turnRight() dir = (dir + 1) % 4; turtle.turnRight() end
function face(targetDir) while dir ~= targetDir do turnRight() end end

-- === Movement ===
function smartForward()
  ensureFuel(1)
  while not turtle.forward() do
    turtle.dig()
    sleep(0.3)
  end
  updatePosition("forward")
end

function smartDown()
  ensureFuel(1)
  while not turtle.down() do
    turtle.digDown()
    sleep(0.3)
  end
  updatePosition("down")
end

function smartUp()
  ensureFuel(1)
  while not turtle.up() do
    turtle.digUp()
    sleep(0.3)
  end
  updatePosition("up")
end

function descendThree()
  for i = 1, 3 do smartDown() end
end

-- === Dig Helper ===
function dig3Column()
  turtle.digUp()
  turtle.dig()
  turtle.digDown()
end

-- === Inventory ===
function isInventoryFull()
  for i = 1, 15 do if turtle.getItemCount(i) == 0 then return false end end
  return true
end

function dumpInventory()
  for i = 1, 15 do
    turtle.select(i)
    turtle.drop()
  end
end

-- === Navigation ===
function goTo(xT, yT, zT)
  while y > yT do smartDown() end
  while y < yT do smartUp() end
  if x > xT then face(3) elseif x < xT then face(1) end
  while x ~= xT do smartForward() end
  if z > zT then face(0) elseif z < zT then face(2) end
  while z ~= zT do smartForward() end
end

-- === MAIN ===
fillFuelTank()

for layer = 1, layers do
  print("⛏️ Mining layer "..layer.." at Y="..y)

  for row = 1, width do
    for col = 1, length - 1 do
      dig3Column()

      if turtle.getFuelLevel() < calculateFuelTo(0, 0, 0) + 10 then
        print("⚠️ Returning to refuel.")
        local sx, sy, sz, sd = x, y, z, dir
        goTo(0, 0, 0)
        face(2)
        dumpInventory()
        ensureFuel(calculateFuelTo(sx, sy, sz))
        goTo(sx, sy, sz)
        face(sd)
      end

      if isInventoryFull() then
        print("📦 Inventory full. Returning.")
        local sx, sy, sz, sd = x, y, z, dir
        goTo(0, 0, 0)
        face(2)
        dumpInventory()
        goTo(sx, sy, sz)
        face(sd)
      end

      smartForward()
    end

    -- Snake turn
    if row < width then
      local turnFunc = row % 2 == 1 and turnRight or turnLeft
      turnFunc(); smartForward(); dig3Column(); turnFunc()
    end
  end

  -- End-of-layer dump and descend
  goTo(0, 0, 0)
  local returnDir = dir
  face(2) -- face South to chest
  dumpInventory()
  face(returnDir)

  if layer < layers then descendThree() end
end

print("✅ Done mining all layers.")
goTo(0, 0, 0)
face(2)