--[[
Digger: A simple program to dig a 1 x 2 shaft straight

Author: Brandon Weaver (keystonelemur / baweaver)

Notes: I guess you could use this as a bridge builder too,
       but I'll make a better program for that one later.

       Some of the more common functionality such as 180s and
       checking fuel levels really should be an API level concern
       so I'll get to that one later.
--]]

local tArgs = { ... }

if tArgs[1] == 'help' then
  print('Usage:')
  print('  miner [distance] [set safe blocks] [set torches]')
  print('')
  print('setSafeBlock - Whether to set blocks to prevent a fall')
  print('setTorches   - Whether to set torches')
  return
end

-- Distance to mine
local distance = tArgs[1] or 1

-- Whether or not to set blocks on an imminent fall
local safeBlock = tArgs[2]

-- Whether or not to set torches from slot 2
local torches = tArgs[3]

-- Shorten the turtle name
local t = turtle

-- Finds the shortage of fuel for the round trip
function checkFuelDeficit()
  return (2 * distance - t.getFuelLevel()) + 2
end

-- Confirm that we have adequate fuel for the trip
level = checkFuelDeficit()
if level > 0 then
  -- Attempt to correct the deficit
  print('Insufficient fuel of'..level..' units, attempting refuel...')
  t.refuel(level)

  -- See if that worked, or end the program
  newLevel = checkFuelDeficit()
  if newLevel > 0 then
    print('Cannot make trip, fuel is short by'..newLevel..' units. Goodbye')
    return
  end
end

-- Confirm that we have enough torches to cover the span
--   TODO - consider increasing the slots, while 320 is large it may
--          not be enough for some.
if torches then
  requiredTorches = math.floor(distance / 5)
  currentStock    = turtle.getItemCount(3)
  deficit         = requiredTorches - currentStock

  if deficit > 0 then
    print('Insufficient torches to cover the distance, '..deficit..' more torches required!')
    return
  end
end

print('Mining '..distance..' squares')
print('')

function turnAround()
  t.turnRight()
  t.turnRight()
end

-- Set a safety block to keep from a nasty fall
function setSafeBlock()
  if safeBlock then
    t.select(2)
    t.placeDown()
  end
end

-- Set a torch for visibility
function setTorch(currentLocation)
  if torches and currentLocation % 5 == 0 then
    t.select(3)
    turnAround()
    t.place()
    turnAround()
  end
end

-- Clear a forward path
function clearForward(currentLocation)
  setSafeBlock()

  -- Make sure to deal with sand and friends
  while t.detect() do t.dig() end

  t.forward()
  setTorch(currentLocation)
  t.digUp()
end

-- Make it come back to the origin
function returnHome()
  turnAround()
  t.up()

  for returnLocation = 0, distance do
     -- Make sure to deal with sand and friends
    while t.detect() do t.dig() end

    t.forward()
  end
end

-- Main program loop
for currentLocation = 0, distance do
  -- Do you REALLY want it every block notifications?
  if currentLocation % 5 == 0 then
    print('Mined '..currentLocation..' blocks')
  end

  clearForward(currentLocation)
end

returnHome()