-- Stairwell program by Josh Swan
-- Version 1.3
-- Instructions: Copy file into 'ComputerCraft/lua/rom/programs/turtle' and rename to 'stairs' (no file suffix).

local tArgs = { ... }

if #tArgs ~= 5 then
  print( "Usage: stairs <width> <height> <depth> <railingWidth> <centerColumnWidth>" )
  print( "Start turtle on the right side of the stairs on the floor. Railings of width 'railingWidth' will be added to both sides of the stairs. The stairs will wrap clockwise around a center column of width 'centerColumnWidth'. Turtle will not stop if its inventory is full." )
  return
end

-- Mine a stairway to the specified depth and width
local width = tonumber( tArgs[1] )
local height = tonumber( tArgs[2] )
local depth = tonumber( tArgs[3] )
local railingWidth = tonumber(tArgs[4])
local columnWidth = tonumber(tArgs[5])
if columnWidth < 0 then
  columnWidth = 0
end

if width < 1 then
  print( "Stair width must be at least 1" )
  return
end
if height < 2 then
  print( "Stair height must be at least 2" )
  return
end
if depth < 1 then
  print( "Stair depth must be at least 1" )
  return
end
if railingWidth < 0 then
  print( "Railing width must be a positive number or zero for no railings" )
  return
end
if columnWidth > 0 then
  if columnWidth < 3 and railingWidth > 0 then
    print( "Center column width must be zero for a straight flight of stairs or at least 3 for a stairwell with railings" )
    return
  elseif columnWidth < 2 and railingWidth == 0 then
    print( "Center column width must be zero for a straight flight of stairs or at least 2 for a stairwell without railings" )
    return
  end
end

-- Digs stairs/stairwell
function createStairs(width, height, depth, railingWidth, columnWidth)
  local originalDepth = depth
  local totalDepth = 0

  while totalDepth < originalDepth do
    if columnWidth > 0  then
      depth = columnWidth-1
    end

    local atDepth = false
    for d=1, depth+1, 1 do
      for h=1, height-1, 1 do turtle.up() end
      digForward()

      if d == 1 then
        digStair(width, height - 1, railingWidth)
      elseif d == depth+1 and railingWidth > 0 then
	   digStair(width, height - 1, railingWidth)
      else
        digStair(width, height, railingWidth)
        totalDepth = totalDepth + 1
      end

      if totalDepth == originalDepth then
        atDepth = true
        break
      end
    end

    -- Position at top
    for h=1, height-1, 1 do turtle.up() end
    digForward()
    railingOffset(railingWidth)

    if atDepth then
      -- Make space at bottom
      digStair(width+(railingWidth*2), height-1, 0)
    else
      -- Dig landing
      digSquare(width+(railingWidth*2), height)

      -- Reposition for next flight
      for w=1, width-1+(railingWidth), 1 do
        turtle.back()
      end
      turtle.turnRight()
    end
  end
  return true
end

-- Helper function for digging a stair
function digStair(width, height, railingWidth)
  railingOffset(railingWidth)

  -- Dig stair too if there is no railing
 local digHeight = height + 1
  if railingWidth > 0 then
    digHeight = digHeight - 1
  end

  for h=1, digHeight, 1 do
    -- Mine width
    turtle.turnLeft()
    digLine(width-1+(railingWidth*2))
    turtle.turnRight()

    -- Dig down if we haven't reach the stair or railing level yet
    if h <= digHeight-1 then
      turtle.digDown()
      turtle.down()
    end
  end
  -- Cut stair out separately if there is a railing
  if railingWidth > 0 then

    -- Reposition turtle
    turtle.turnLeft()
    for r=1, railingWidth, 1 do
      turtle.forward()
    end
    turtle.digDown()
    turtle.down()

    -- Mine width
    for w=1, width-1, 1 do
      digForward()
    end
    -- Backup
    for w=1, width-1, 1 do
      turtle.back()
    end
    turtle.turnRight()
  end
end

-- Handles digging into falling blocks
function digForward()
  while not turtle.forward() do
    turtle.dig()
    sleep(0.3)
  end
end

-- Dig the specified number of blocks in the direction the turtle is facing
function digLine(length)
  for l=1, length, 1 do
    digForward()
  end
  -- Backup
  for l=1, length, 1 do
    turtle.back()
  end
end

-- Offset for right railing
function railingOffset(railingWidth)
  if railingWidth > 0 then
    turtle.turnRight()
    for r=1, railingWidth, 1 do
      digForward()
    end
    turtle.turnLeft()
  end
end

-- Digs square with specified width and height
function digSquare(width, height)
  for l=1, width, 1 do
    for h=1, height, 1 do
      -- Mine width
      turtle.turnLeft()
      digLine(width-1)
      turtle.turnRight()

      -- Dig down if we haven't reach the floor level
      if h < height then
        turtle.digDown()
        turtle.down()
      end
    end
    if l < width then
      for h=1, height-1, 1 do turtle.up() end
      digForward()
    end
  end
end

-- Execute stair creation --
----------------------------
print ("Digging stairs...")
createStairs(width, height, depth, railingWidth, columnWidth)