ccTrade.lua

--auxchar's ComputerCraft Trade Script--

--Edit These.
tradeName = "Example Trade"
supplyChestName = "diamond_chest_1" --name the upper chest gives you when you right click on its modem.
currencyChestName = "diamond_chest_0" --same, but for the lower chest
price = 1   --These need to be whole numbers.
payOut = 1

--You may or may not need to chaange these...
payOutStackSize = 64
currencyId = 21256
currencyDamage = 1
currencyStackSize = 64

--Don't change these unless you know what you're doing.
modemDirection = "right"
tradeChestDirection = "left"
currencyChestDirection = "down"
supplyChestDirection = "down"

--From here on down, it's just code. You shouldn't have to care what lies beyond this point.
function remoteWrap(side, name)
  local m = peripheral.wrap(side)
  local remotePeripheral = {
    wrapData = {
      modem = m,
      peripheralName = name
    }
  }
  local meta = {
    __index = function(t,k)
      return function(...)
        local wrapData = t.wrapData
        return wrapData.modem.callRemote(wrapData.peripheralName, k, ...)
      end
    end
  }
  setmetatable(remotePeripheral,meta)
  return remotePeripheral
end

function stackCheck(id,damage,stack)
  local idCheck
  local damageCheck
  if id then
    idCheck = (id == stack.id)
  else
    idCheck = true
  end
  if damage then
    damageCheck = (damage == stack.dmg)
  else
    damageCheck = true
  end
  return damageCheck and idCheck
end

function pushAmount(chest,amount,direction,...)
  local id = arg[1]
  local damgae = arg[2]
  local pushed = 0
  for i = 0,chest.getSizeInventory()-1 do
    stack = chest.getStackInSlot(i)
    if stack then
      if stackCheck(id,damage,stack) then
        if pushed < amount then
          pushed = pushed + chest.push(direction, i, amount-pushed)
        end
        if pushed == amount then
          break
        end
      end
    end
    sleep(.02)
  end
  return pushed
end

function getAmount(chest,...)
  local id = arg[1]
  local damage = arg[2]
  local found = 0
  for i = 0,chest.getSizeInventory()-1 do
    stack = chest.getStackInSlot(i)
    if stack then
      if stackCheck(id,damage,stack) then
        found = found + stack.qty
      end
    end
    sleep(.02)
  end
  return found
end

function getSpace(chest, stackSize,...)
  local id = arg[1]
  local damage = arg[2]
  local found = 0
  for i = 0,chest.getSizeInventory()-1 do
    stack = chest.getStackInSlot(i)
    if stack then
      if stack.id == id and stack.damage == damage then
        found = found + stackSize - stack.qty
      end
    else
      found = found + stackSize
    end
    sleep(.02)
  end
  return found
end

-- Main stuff
supplyChest = remoteWrap(modemDirection,supplyChestName)
currencyChest = remoteWrap(modemDirection,currencyChestName)
tradeChest = peripheral.wrap(tradeChestDirection)

function exchange(trades)
  pushAmount(tradeChest, price*trades, currencyChestDirection, currencyId, currencyDamage)
  pushAmount(supplyChest, payOut*trades, supplyChestDirection)
end

function trade()
  limits = {
    math.floor(getAmount(supplyChest)/payOut),
    math.floor(getSpace(currencyChest,currencyStackSize)/price),
    math.floor(getSpace(tradeChest, payOutStackSize)/payOut),
    math.floor(getAmount(tradeChest, currencyId, currencyDamage)/price)
  }
  table.sort(limits, function(a,b) return a<b end)
  exchange(limits[1])
end

while true do
  for i = 0,tradeChest.getSizeInventory()-1 do
    stack = tradeChest.getStackInSlot(i)
    if stack then
      if stack.name == tradeName then
        trade()
        sleep(1)
        break
      end
    end
    sleep(.02)
  end
  sleep(1)
end