local robotApi = require('robot')
local turtleUtils = require('turtle-utils')

local config = {
  startY = 109,
  targetY = 109,
  height = 4,
  size = 16
}

local LOWER_SIZE_LIMIT = 2;
local HIGHER_SIZE_LIMIT = 128;
local ADDITIONAL_FUEL_NEEDED = 256

local INITIAL_TARGET_Y = config.targetY - config.startY
local TARGET_Z = config.size - 1
local TARGET_X = config.size - 1

local MAX_X = TARGET_X
local MAX_Y = INITIAL_TARGET_Y + (config.height - 1)
local MAX_Z = TARGET_Z


local robot = robotApi.create()

local MAX_INVENTORY_BLOCKS = 16 * 64
local MIN_FUEL_NEEDED = 2 * ((config.size * 2) + INITIAL_TARGET_Y) + MAX_INVENTORY_BLOCKS + ADDITIONAL_FUEL_NEEDED

local miner = {
  robot = robot,
  mission = 'unload', -- "unload" | "refuel" | "mine" | "return-home" | "return-mine" | nil
  finished = false,
  lastPositionState = nil, -- { x, y, z, dir }
  targetY = INITIAL_TARGET_Y
}

local function isOdd(x)
  return (x % 2) == 1
end

local function checkConfig()
  if config.targetY >= config.startY then
    error('targetY should be lower than startY')
  end

  if config.height < 1 then
    error('height cannot be lower than 1')
  end

  if config.size < LOWER_SIZE_LIMIT then
    error('size cannot be lower than ' .. LOWER_SIZE_LIMIT)
  end

  if config.size > HIGHER_SIZE_LIMIT then
    error('size is too large (higher limit is ' .. HIGHER_SIZE_LIMIT .. ')')
  end

  if isOdd(config.size) then
    error('configured size should be even')
  end
end

local function prepareTurtle()
  turtle.select(1)
end

local function isProgramFinished()
  if miner.mission ~= nil then
    return false
  end

  local robotState = miner.robot.getState()

  return robotState.x == 0 and robotState.y == 0 and robotState.z == 0
end


local function unloadProcedure()
  print('> Starting unload procedure...')
  turtleUtils.waitForInventory('front')

  for i=1, 16, 1 do
    turtle.select(i)
    turtle.refuel()
    turtleUtils.tryDrop()
  end

  miner.mission = 'refuel'
end

local function refuelProcedure()
  print('> Starting refuel procedure (' .. turtleUtils.getFuelPercentage() .. '%)')
  turtleUtils.waitForInventory('top')

  turtle.select(1)

  while turtle.getFuelLevel() < MIN_FUEL_NEEDED do
    turtleUtils.trySuckUp()

    local ok = turtle.refuel()
    if not ok then
      turtleUtils.tryDrop()
    end
  end

  print('> Refuel done.')
  miner.mission = 'return-mine'
end

local function returnMineProcedure()
  if miner.finished then
    miner.mission = nil -- it will stop the loop
    return
  end

  if robot.lastPositionState then
    local robotState = miner.robot.getState()

    if robotState.y > miner.lastPositionState.y then
      miner.robot.down()
    elseif robotState.z < miner.lastPositionState.z then
      miner.robot.forward()
    else
      miner.robot.turnRight()

      for i=1, miner.lastPositionState.x, 1 do
        miner.robot.forward()
      end

      while miner.robot.getState().dir ~= miner.lastPositionState.dir do
        miner.robot.turnRight()
      end

      miner.mission = 'mine'
      print('> Starting mining procedure...')
    end
  else
    miner.mission = 'mine'
    print('> Starting mining procedure...')
  end
end

local function mineProcedure()
  local robotState = miner.robot.getState()
  local targetY = miner.targetY
  local targetZ = TARGET_Z

  -- 1. Move
  if robotState.y > targetY then
    turtle.digDown()
    miner.robot.down()
  elseif robotState.dir == 'FORWARD' and robotState.z < targetZ then
    turtleUtils.digAll()
    miner.robot.forward()
  elseif robotState.dir == 'FORWARD' and robotState.z == targetZ then
    miner.robot.turnRight()
    turtleUtils.digAll()
    miner.robot.forward()
    miner.robot.turnRight()
  elseif robotState.dir == 'BACKWARD' and robotState.z > 0 then
    turtleUtils.digAll()
    miner.robot.forward()
  elseif robotState.dir == 'BACKWARD' and robotState.z == 0 then
    miner.robot.turnLeft()
    turtleUtils.digAll()
    miner.robot.forward()
    miner.robot.turnLeft()
  end

  -- 2. Check
  if robotState.x == MAX_X and robotState.y == MAX_Y and robotState.z == 0 then
    miner.finished = true
    miner.mission = 'return-home'
    miner.lastPositionState = miner.robot.getState()
    print('> Starting return home procedure because mining session is finished...')
  elseif robotState.x == MAX_X and robotState.z == 0 then
    -- this part assume that the size of the mine is even
    miner.robot.turnRight()

    for i=1, config.size - 1, 1 do
      miner.robot.forward()
    end

    miner.robot.turnRight()
    -- mine the next stage
    miner.robot.up()
    miner.targetY = miner.targetY + 1
  end

  if turtleUtils.countFreeSlots() < 1 then
    print('> Starting return home procedure because inventory is almost full...')
    miner.mission = 'return-home'
    miner.lastPositionState = miner.robot.getState()
  end
end

local function returnHomeProcedure()
  local robotState = miner.robot.getState()

  if robotState.x == 0 and robotState.y == 0 and robotState.z == 0 then
    miner.mission = 'unload'
  elseif robotState.x == 0 and robotState.z == 0 then
    while miner.robot.getState().dir ~= 'FORWARD' do
      miner.robot.turnRight()
    end

    miner.robot.up()
  elseif robotState.x > 0 then
    if robotState.dir == 'FORWARD' then
      miner.robot.turnLeft()
    elseif robotState.dir == 'BACKWARD' then
      miner.robot.turnRight()
    end

    for i=1, robotState.x, 1 do
      miner.robot.forward()
    end

    miner.robot.turnLeft()
  elseif robotState.z > 0 then
    for i=1, robotState.z, 1 do
      miner.robot.forward()
    end

    miner.robot.turnLeft()
    miner.robot.turnLeft()
  end
end


checkConfig()
prepareTurtle()

print("> Miner program started, minimum fuel needed: " .. MIN_FUEL_NEEDED)

while not isProgramFinished() do
  if miner.mission == 'unload' then
    unloadProcedure()
  elseif miner.mission == 'refuel' then
    refuelProcedure()
  elseif miner.mission == 'mine' then
    mineProcedure()
  elseif miner.mission == 'return-home' then
    returnHomeProcedure()
  elseif miner.mission == 'return-mine' then
    returnMineProcedure()
  end
end

print("> Miner program finished!")