--[[Function Module program by Al Sweigart
Provides useful utility functions.]]

-- selectItem() selects the inventory
-- slot with the named item, returns
-- true if found and false if not
function select_item(name)
-- check all inventory slots
 local item
   for slot = 1, 16 do
     item = turtle.getItemDetail(slot)
     if item ~= nil and item['name'] == name then
       turtle.select(slot)
       return true
     end
  end

  return false  -- couldn't find item
end


-- selectEmptySlot() selects inventory
-- slot that is empty, returns true if
-- found, false if no empty spaces
function select_emptySlot()

  -- loop through all slots
  for slot = 1, 16 do  
    if turtle.getItemCount(slot) == 0 then
      turtle.select(slot)
      return true
    end
  end
  return false -- couldn't find empty space
end

-- countInventory() returns the total
-- numer of a given minecraft id item in the inventory
function count_inventory(minecraft_id)
  local total = 0

  for slot = 1, 16 do
    if turtle.getItemDetail(slot) == 'minecraft:' .. minecraft_id  then
      total = total + turtle.getItem(slot)
    end
  end
  return total
end

-- selectAndPlaceDown() selects a slot with given
-- minecraft id and places a block from it under the turtle
function select_and_place_down(minecraft_id)
  for slot = 1, 16 do
    if turtle.getItemDetail(slot) == 'minecraft:' .. minecraft_id  then
      turtle.select(slot)
      turtle.placeDown()
      return
    end
  end
end


-- build_wall() creates a wall stretching
-- in front of the turtle
function build_wall(length, height)
  if modules.count_inventory() > length * height then
    return false --not enough block
  end

  turtle.up()

  local movingForward = true

  for currentHeight = 1, height do
    for currentLength = 1, length do
      select_and_place_down() -- Place the block
      if movingForward and currentLength ~= length then
        turtle.forward()
      elseif not movingForward and currentLength ~= length then
        turtle.back()
      end
    end
    if currentHeight ~= height then
      turtle.up()
    end
    movingForward = not movingForward
  end

  -- done building wall; move to end position
  if movingForward then
    -- turtle is near the start position
    for currentLength = 1, length do
      turtle.forward()
    end
  else
    -- turtle is near the end position
    turtle.forward()
  end

  -- move down to the ground
  for currentHeight = 1, height do
    turtle.down()
  end

  return true
end

-- build_room() constructs four walls
-- and a ceiling
function build_room(length, width, height)
  if modules.count_inventory() < (((length -1) * height * 2) +
    ((width -1) * height * 2)) then
    return false -- not enough blocks
  end

  -- build the four walls
  build_wall(length -1, height)
  turtle.turnRight()

  build_wall(width - 1, height)
  turtle.turnRight()

  build_wall(length - 1, height)
  turtle.turnRight()

  build_wall(width - 1, height)
  turtle.turnRight()

  return true
end