ComputerCraft Controlled Villager Trading

--Variables to be changed:
local Trade_Post_Side = "right"
local Monitor_Side = "left"
--Don't change below here:
local TradePost = peripheral.wrap(Trade_Post_Side)
local Monitor = peripheral.wrap(Monitor_Side)

local Main_Exit = false
local Trades_Available = {}
local Page_Number = 0
Monitor.setTextScale(0.5)
local Monitor_Width,Monitor_Height = Monitor.getSize()
local Adjusted_Monitor = Monitor_Height - 3

function Get_List()
  Trades_Available = {}
  local Villager_Info = TradePost.getVillagerIds()
  if Villager_Info ~= nil then
    for i,v in pairs(Villager_Info) do
      local Num_Of_Trades = TradePost.getNumTrades(v)
      for x=1, Num_Of_Trades do
        local Construct = {}
        Construct["VillagerID"] = v
        Construct["TradeNumber"] = x-1
        Construct["FirstBought"] = TradePost.getItemBought(v,x-1)["name"]
        Construct["FirstQTY"] = TradePost.getItemBought(v,x-1)["qty"]
        if TradePost.getSecondItemBought(v,x-1) ~= nil then
          Construct["SecondBought"] = TradePost.getSecondItemBought(v,x-1)["name"]
          Construct["SecondQTY"] = TradePost.getSecondItemBought(v,x-1)["qty"]
        end
        Construct["SoldItem"] = TradePost.getItemSold(v,x-1)["name"]
        Construct["SoldQTY"] = TradePost.getItemSold(v,x-1)["qty"]
        table.insert(Trades_Available,Construct)
      end
    end
  end
end

function List_Trades(page)
  Monitor_Width, Monitor_Height = Monitor.getSize()
  Adjusted_Monitor = Monitor_Height - 3
  Monitor.clear()
  Get_List()
  if Trades_Available ~= nil then
    if page < 0 then
      page = math.floor(#Trades_Available / Adjusted_Monitor)
    end
    if (page * Adjusted_Monitor) >= #Trades_Available then
      page = 0
    end
    local Display_Counter
    if #Trades_Available - (page * Adjusted_Monitor) > Adjusted_Monitor then
      Display_Counter = (page * Adjusted_Monitor) + Adjusted_Monitor
    else
      Display_Counter = #Trades_Available
    end
    for i= 1+(page * Adjusted_Monitor), Display_Counter do
      local Info = Trades_Available[i]
      Monitor.setCursorPos(1,i-(page*Adjusted_Monitor)+1)
      Monitor.write(Info["FirstQTY"].." "..Info["FirstBought"])
      if Info["SecondBought"] ~= nil then
        Monitor.write(" + "..Info["SecondQTY"].." "..Info["SecondBought"])
      end
      Monitor.setCursorPos(math.floor(Monitor_Width/2),i-(page*Adjusted_Monitor)+1)
      Monitor.write("| ->"..Info["SoldQTY"].." "..Info["SoldItem"])
    end
  end
  Monitor.setCursorPos(math.floor(Monitor_Width/4),1)
  Monitor.write("BUYING")
  Monitor.setCursorPos(Monitor_Width-math.floor(Monitor_Width/4),1)
  Monitor.write("SELLING")
  Monitor.setCursorPos(1,Monitor_Height)
  Monitor.write("Check PgUp PgDn Page:"..page)
  Monitor.setCursorPos(Monitor_Width-4,Monitor_Height)
  Monitor.write("Quit")
  return page
end

List_Trades(0)

while Main_Exit == false do
  local event, side, x_pos, y_pos = os.pullEvent("monitor_touch")
  if y_pos == Monitor_Height then
    if x_pos <= 5 then
      Page_Number = List_Trades(Page_Number)
    elseif x_pos >= 7 and x_pos <= 10 then
      Page_Number = List_Trades(Page_Number+1)
    elseif x_pos >= 12 and x_pos <= 15 then
      Page_Number = List_Trades(Page_Number-1)
    elseif x_pos >= (Monitor_Width - 4) then
      Monitor.clear()
      Main_Exit = true
    end
  elseif y_pos >= 2 then
    local List_Pos = (y_pos - 1)+(Page_Number * Adjusted_Monitor)
    if Trades_Available[List_Pos] ~= nil then
      local Trade_Info = Trades_Available[List_Pos]
      TradePost.performTrade(Trade_Info["VillagerID"],Trade_Info["TradeNumber"])
    end
  end
end