local tArgs = { ... }
if #tArgs ~= 1 then
  print( "Usage: excavate <diameter>" )
  return
end

-- Mine in a quarry pattern until we hit something we can't dig
local size = tonumber( tArgs[1] )
if size < 1 then
  print( "Excavate diameter must be positive" )
  return
end

local depth = 0
local unloaded = 0
local collected = 0

local xPos,zPos = 0,0
local xDir,zDir = 0,1

local goTo -- Filled in further down
local refuel -- Filled in further down

local function unload( _bKeepOneFuelStack )
  _bKeepOneFuelStack = false
  print( "Unloading items..." )
  for n=1,16 do
    local nCount = turtle.getItemCount(n)
    if nCount > 0 then
      turtle.select(n)
      local bDrop = true
      if _bKeepOneFuelStack then
        bDrop = false
        _bKeepOneFuelStack = false
      end
      if bDrop then
        turtle.drop()
        unloaded = unloaded + nCount
      end
    end
  end
  collected = 0
  turtle.select(1)
end

local function returnSupplies()
  local x,y,z,xd,zd = xPos,depth,zPos,xDir,zDir
  print( "Returning to surface..." )
  goTo( 0,0,0,0,-1 )

  local fuelNeeded = 2*(x+y+z) + 1
  if not refuel( fuelNeeded ) then
    unload( true )
    print( "Waiting for fuel" )
    while not refuel( fuelNeeded ) do
      sleep(1)
    end
  else
    unload( true )
  end

  print( "Resuming mining..." )
  goTo( x,y,z,xd,zd )
end

local function collect()
  local bFull = true
  local nTotalItems = 0
  for n=1,16 do
    local nCount = turtle.getItemCount(n)
    if nCount == 0 then
      bFull = false
    end
    nTotalItems = nTotalItems + nCount
  end

  if nTotalItems > collected then
    collected = nTotalItems
    if math.fmod(collected + unloaded, 50) == 0 then
      print( "Mined "..(collected + unloaded).." items." )
    end
  end

  if bFull then
    print( "No empty slots left." )
    return false
  end
  return true
end

function refuel( ammount )
  return true
end

local function tryForwards()
  if not refuel() then
    print( "Not enough Fuel" )
    returnSupplies()
  end

  while not turtle.forward() do
    if turtle.detect() then
      if turtle.dig() then
        if not collect() then
          returnSupplies()
        end
      else
        return false
      end
    else
      sleep( 0.5 )
    end
  end

  xPos = xPos + xDir
  zPos = zPos + zDir
  return true
end

local function tryDown()
  if not refuel() then
    print( "Not enough Fuel" )
    returnSupplies()
  end

  while not turtle.down() do
    if turtle.detectDown() then
      if turtle.digDown() then
        if not collect() then
          returnSupplies()
        end
      else
        return false
      end
    else
      sleep( 0.5 )
    end
  end

  depth = depth + 1
  if math.fmod( depth, 10 ) == 0 then
    print( "Descended "..depth.." metres." )
  end

  return true
end

local function turnLeft()
  turtle.turnLeft()
  xDir, zDir = -zDir, xDir
end

local function turnRight()
  turtle.turnRight()
  xDir, zDir = zDir, -xDir
end

function goTo( x, y, z, xd, zd )
  while depth > y do
    if turtle.up() then
      depth = depth - 1
    elseif turtle.digUp() then
      collect()
    else
      sleep( 0.5 )
    end
  end

  if xPos > x then
    while xDir ~= -1 do
      turnLeft()
    end
    while xPos > x do
      if turtle.forward() then
        xPos = xPos - 1
      elseif turtle.dig() then
        collect()
      else
        sleep( 0.5 )
      end
    end
  elseif xPos < x then
    while xDir ~= 1 do
      turnLeft()
    end
    while xPos < x do
      if turtle.forward() then
        xPos = xPos + 1
      elseif turtle.dig() then
        collect()
      else
        sleep( 0.5 )
      end
    end
  end

  if zPos > z then
    while zDir ~= -1 do
      turnLeft()
    end
    while zPos > z do
      if turtle.forward() then
        zPos = zPos - 1
      elseif turtle.dig() then
        collect()
      else
        sleep( 0.5 )
      end
    end
  elseif zPos < z then
    while zDir ~= 1 do
      turnLeft()
    end
    while zPos < z do
      if turtle.forward() then
        zPos = zPos + 1
      elseif turtle.dig() then
        collect()
      else
        sleep( 0.5 )
      end
    end
  end

  while depth < y do
    if turtle.down() then
      depth = depth + 1
    elseif turtle.digDown() then
      collect()
    else
      sleep( 0.5 )
    end
  end

  while zDir ~= zd or xDir ~= xd do
    turnLeft()
  end
end

if not refuel() then
  print( "Out of Fuel" )
  return
end

print( "Excavating..." )

local reseal = false
turtle.select(1)
if turtle.digDown() then
  reseal = true
end

local alternate = 0
local done = false
while not done do
  for n=1,size do
    for m=1,size-1 do
      if not tryForwards() then
        done = true
        break
      end
    end
    if done then
      break
    end
    if n<size then
      if math.fmod(n + alternate,2) == 0 then
        turnLeft()
        if not tryForwards() then
          done = true
          break
        end
        turnLeft()
      else
        turnRight()
        if not tryForwards() then
          done = true
          break
        end
        turnRight()
      end
    end
  end
  if done then
    break
  end

  if size > 1 then
    if math.fmod(size,2) == 0 then
      turnRight()
    else
      if alternate == 0 then
        turnLeft()
      else
        turnRight()
      end
      alternate = 1 - alternate
    end
  end

  if not tryDown() then
    done = true
    break
  end
end

print( "Returning to surface..." )

-- Return to where we started
goTo( 0,0,0,0,-1 )
unload( false )
goTo( 0,0,0,0,1 )

-- Seal the hole
if reseal then
  turtle.placeDown()
end

print( "Mined "..(collected + unloaded).." items total." )