--[[
 Build simple bridge
 Slot 1-15: Building block
 Slot 16: fuel
--]]

-- Parameters


-- Variables

local itemBlockSlot = 0
local fuelSlot = 16
local collected = 0

-- Process commandline

local tArgs = { ... }
if #tArgs < 0 then
    print( "Usage: SimpleBridge <length>" )
    print( "======================================" )
    print( "")
    print( "Expected content in inventory of turtle:" )
    print( "Slot 1 to 15: Block to us" )
    print( "Slot 16: Fuel")
    return
end

local length = tonumber( tArgs[1] )
if length < 1 then
    print( "length must be 1+" )
    return
end

local function checkSlot(slotNr,description)
   if turtle.getItemCount(slotNr)==0 then
      print("Expected item '"..description.."' in slot "..slotNr..".")
      return false
   end
   return true
end

-- Check slots

if not checkSlot(1,"BuildingBlocks") then return end
if not checkSlot(fuelSlot,"fuel") then return end

-- Main Code

local function collect()
    collected = collected + 1
    if math.fmod(collected, 100) == 0 then
        print( "Mined "..collected.." items." )
    end
end
local function refuel()
    local fuelLevel = turtle.getFuelLevel()
    if fuelLevel == "unlimited" or fuelLevel > 0 then
        return
    end

    local function tryRefuel()
        if turtle.getItemCount(fuelSlot) > 0 then
            turtle.select(fuelSlot)
            if turtle.refuel(1) then
                return true
            end
        end
        turtle.select(1)
        return false
    end
    if not tryRefuel() then
        print( "Add more fuel in slot "..fuelSlot.." to continue." )
        while not tryRefuel() do
            sleep(1)
        end
        print( "Resuming Tunnel." )
    end
end
local function tryDig()
    while turtle.detect() do
        if turtle.dig() then
            collect()
            sleep(0.5)
        else
            return false
        end
    end
    return true
end
local function tryDigUp()
    while turtle.detectUp() do
        if turtle.digUp() then
            collect()
            sleep(0.5)
        else
            return false
        end
    end
    return true
end
local function tryDigDown()
 while turtle.detectDown() do
  if turtle.digDown() then
    collect()
    sleep(0.5)
 else
   return false
  end
 end
 return true
end
local function tryUp()
    refuel()
    while not turtle.up() do
        if turtle.detectUp() then
            if not tryDigUp() then
                return false
            end
        elseif turtle.attackUp() then
            collect()
        else
            sleep( 0.5 )
        end
    end
    return true
end
local function tryDown()
    refuel()
    while not turtle.down() do
        if turtle.detectDown() then
            if not tryDigDown() then
                return false
            end
        elseif turtle.attackDown() then
            collect()
        else
            sleep( 0.5 )
        end
    end
    return true
end
local function tryForward()
    refuel()
    while not turtle.forward() do
        if turtle.detect() then
            if not tryDig() then
                return false
            end
        elseif turtle.attack() then
            collect()
        else
            sleep( 0.5 )
        end
    end
    return true
end
local function DumpStatistics()
    print( "Statistics:")
    print( string.rep("=",20))
    print( "Mined "..collected.." blocks total." )
    print( string.rep("=",20))
end

local function checkOrSwapItemBlockSlot()
    while (turtle.getItemCount(itemBlockSlot)==0) do
        itemBlockSlot=itemBlockSlot+1
        if itemBlockSlot==16 then return false end
    end
    turtle.select(itemBlockSlot)
    return true
end

local function buildBridgeSection()
    if not checkOrSwapItemBlockSlot() then return false end
    if not tryForward() then return false end
    turtle.digDown()
    turtle.digUp()
    turtle.placeDown()
    turtle.turnLeft()
    turtle.dig()
    turtle.place()
    turtle.turnRight()
    turtle.turnRight()
    turtle.dig()
    turtle.place()
    turtle.turnLeft()
    return true
end

local function mine()
    for n=1,length do
        if not buildBridgeSection() then return false end
    end
    return true
end

if mine() then
    print( "Job complete." )
else
    print( "Job aborted prematurely.")
end
DumpStatistics()