local me = peripheral.wrap("left")

function resetTerm()
    term.clear()
    term.setCursorPos(1,1)
end

function printHelp()
    resetTerm()
    print("[1] Add or update item")
    print("[2] Remove item")
    print("[3] List all items")
end

function loadConfig()
    local file = fs.open("./stock.config", "r")
    local data = file.readAll()
    file.close()
    return textutils.unserialize(data) or {}
end

function saveConfig(table)
    local file = fs.open("./stock.config", "w")
    file.write(textutils.serialize(table))
    file.close()
    resetTerm()
    print("Config saved successfully.")
    sleep(2)
end

function q(text)
    resetTerm()
    print(text)
    local t = read()
    return t
end

function tableLength(T)
    local count = 0
    for _ in pairs(T) do count = count + 1 end
    return count
end

function listTable(table)
    local toShow = 8
    local count = 1
    for key, val in pairs(table) do
        print("Key: ", key, " - Value: ", val)
        if count % toShow then
            print("Press any key to continue...")
            os.pullEvent("key")
        end
    end
end

while true do
    printHelp()
    local action = read()

    if action == "1" then

        resetTerm()
        local config = loadConfig()
        local item = q("ID of item to add or update:")
        local ok, meItem = pcall(me.findItem, item)
        if not ok then
            resetTerm()
            print("Item not found. Canceling...")
            sleep(2)
        else
            local name = meItem.getMetadata().name
            if config[name] then
                local yn = q("That item already exists. Would you like to update quantity? (y/n)\nCurrent quantity: " .. config[name].qty)
                if yn == "y" then
                    local qty = tonumber(q("Quantity to keep in stock:"))
                    config[name].qty = qty
                    saveConfig(config)
                else
                    resetTerm()
                    print("Canceling...")
                    sleep(2)
                end
            else
                local qty = tonumber(q("Quantity to keep in stock:"))
                local t = {}
                t["qty"] = qty
                t["name"] = name
                config[name] = t
                saveConfig(config)
            end
        end

    elseif action == "2" then

        local config = loadConfig()
        if tableLength(config) > 0 then
            local item = q("Enter the item you would like to remove.")
            local ok, meItem = pcall(me.findItem, item)
            if not ok then
                resetTerm()
                print("Item not found. Canceling...")
                sleep(2)
            else
                config[meItem.getMetadata().name] = nil
                saveConfig(config)
            end
        else
            resetTerm()
            print("No items to delete.")
            sleep(2)
        end

    elseif action == "3" then

        local config = loadConfig()
        resetTerm()
        print("Listing all saved items:")
        if tableLength(config) < 1 then
            print("No saved items... Continuing in 2 seconds.")
            sleep(2)
        else
            listTable(config)
        end

    end
end