local tArgs={...}
local turtleId
local isWirelessTurtle
local messageOutputFileName


local function printUsage()
  write([[
Usage:
farm <length> <width> [timer]
  <length> is the length of each row
of the field
  <width> is the number of rows
  [timer] is an optional number of
seconds to wait before repeating.
-- Press any key to continue --]])
  os.pullEvent("key")
  print([[

Placement
The turtle should begin above a chest facing towards the first row, and will move right for each subsequent row. The chest should contain the item to be planted. If the plant has seeds different from the harvested items, like wheat, place a 2nd chest above the turtle for the output.
Note: If area is not already plowed or
planted it must be a farming turtle.]])
end


if #tArgs<2 then
  printUsage()
  return
end

local length=tonumber(tArgs[1])
local width=tonumber(tArgs[2])
local repeatTime=tonumber(tArgs[3]) or 0


isWirelessTurtle = peripheral.isPresent("right")
if (isWirelessTurtle == true) then
  turtleId = os.getComputerLabel()
  rednet.open("right")
end

function writeMessage(message)
    print(message)

    -- If this turtle has a modem, then write the message to red net
    if (isWirelessTurtle == true) then
      if (turtleId == nil) then
        rednet.broadcast(message)
      else
        -- Broadcast the message (prefixed with the turtle's id)
        rednet.broadcast("[".. turtleId.."] "..message)
      end
    end

    if (messageOutputFileName ~= nil) then
      -- Open file, write message and close file (flush doesn't seem to work!)
      local outputFile = io.open(messageOutputFileName, "a")
      outputFile:write(message)
      outputFile:write("\n")
      outputFile:close()
    end
end


local function repeatUntil(func)
  while not func() do sleep(.5) end
end

local function step()
    if turtle.detect()
    then turtle.dig()
     end
  turtle.forward()
  --dry soil occassionally untils between dig and plant,
  --so repeat until successful on planting (or out of things to plant)
  local tryCount=0
  repeat
    turtle.digDown()
    tryCount=tryCount+1
  until turtle.placeDown() or turtle.getItemCount(1)==0 or tryCount==3
end



local function waitForKey(prompt)
    writeMessage(prompt)
  os.pullEvent("key")
end


local function harvest()
  --do I have enough fuel?
  local cost=(length+1)*width
  --if odd rows, add return trip
  if width%2==1 then
    cost=cost+length
  end
  while type(turtle.getFuelLevel())=="number" and cost>turtle.getFuelLevel() do
    waitForKey("Insufficient fuel. Place fuel in any slot and press a key to continue...")

    for i=2,16 do
      turtle.select(i)
      if turtle.refuel() then
        break
      end
    end
    turtle.select(1)
    term.clear()
  end
  writeMessage("Harvesting...")

  step()
  local turnNext=turtle.turnRight
  local turnOther=turtle.turnLeft
  for row=1,width do
    for pos=1,length-1 do
      step()
    end
    if row<width then
      turnNext()
      step()
      turnNext()
    end
    local temp=turnNext
    turnNext=turnOther
    turnOther=temp
  end

  --return to start position
  --if odd number of rows, we're at far end of rows, return
  if width%2==1 then
    for i=1,length do
      --if we hit something, just wait a bit and retry;
      repeatUntil(turtle.back)
    end
    turtle.turnLeft()
  else
    --was even rows, so at right end of rows facing opposite way
    repeatUntil(turtle.forward)
    turtle.turnRight()
  end
  --head back to first row
  for i=1,width-1 do
    repeatUntil(turtle.forward)
  end
  --turn to face starting direction
  turtle.turnRight()

  --unload!
  writeMessage("Unloading...")
  --anythign matching what's in slot 1 goes down, rest goes up
  for i=2,16 do
    turtle.select(i)
    if turtle.getItemCount(i)>0 then
      if turtle.compareTo(1) then
        while not turtle.dropDown() do
          waitForKey("input chest full, empty it and press any key to continue...")
    writeMessage("input chest full, empty it and press any key to continue...")
        end
      else
        while not turtle.dropUp() do
          waitForKey("output chest full, empty it and press any key to continue...")
    writeMessage("output chest full, empty it and press any key to continue...")
        end
      end
    end
  end
  turtle.select(1)
end

--load up with stuffs
turtle.select(1)
turtle.suckDown()

if repeatTime>0 then
  while true do
    harvest()
    term.clear()
    local i=repeatTime
    while i>0 do
      local tick,interval=1,"second"
      if i>3600 then
        tick,interval=3600,"hour"
      elseif i>60 then
        tick,interval=60,"minute"
      end
      local count=math.floor(i/tick)
      if count==1 and tick>1 then
        tick=i-tick
      else
        interval=interval.."s"
      end
      term.setCursorPos(1,1)
      term.clearLine()
      write("Harvesting again in "..count.." "..interval)
      sleep(tick)
      i=i-tick
    end
  end
else
  harvest()
  --drop seeds back
  turtle.select(1)
  turtle.dropDown()
end