local computer = require("computer")
local component = require("component")
local sides = require("sides")

local Black = 0x000000
local Blue = 0x0000FF
local Green = 0x008000
local Red = 0xFF0000
local White = 0xFFFFFF
local Yellow = 0xFFFF00

local gpu = component.gpu
local batBuffer = component.batterybuffer_16_tier_03
local w, h = gpu.getResolution()
local previousCharge = 0
local refreshRate = 5

local function round(num) return math.floor(num+.5) end

local function drawMainScreen()
    gpu.setBackground(Black)
    gpu.fill(1, 1, w, h, " ") -- clears the screen
    gpu.setForeground(Yellow)
        gpu.setResolution(17, 3)
end

local function getStoredCharge(c)
    local inv = c.getAllStacks()
    local storedCharge = 0
        local maxCharge = 0
        local differenceCharge = 0
    for i = 1, c.getInventorySize(), 1 do
                if inv[i] == nil then
                else
            storedCharge = storedCharge + inv[i].charge
                        maxCharge = maxCharge + inv[i].maxCharge
                        end
        end
        maxCharge = maxCharge + c.getEUCapacity()
    storedCharge = storedCharge + c.getStoredEU()
        if previousCharge > storedCharge then
                differenceCharge = 0
                previousCharge = storedCharge
        else
                differenceCharge = 1
                previousCharge = storedCharge
        end
    return maxCharge, storedCharge, differenceCharge
end

local function updateScreen()
        local maxCharge, storedCharge, differenceCharge = getStoredCharge(batBuffer)
        gpu.fill(1, 2, 17, 3, " ")
        gpu.fill(1, 3, 17, 3, " ")
        gpu.setForeground(Blue)
        gpu.set(1, 1, "Stored EU")
        gpu.setForeground(Yellow)
        gpu.set(1, 2, "Max: " .. maxCharge .. " EU")
        if differenceCharge == 0 then
                gpu.setForeground(Red)
        else
                gpu.setForeground(Green)
        end
        gpu.set(1, 3, tostring(storedCharge) .. " EU " .. tostring(round(((storedCharge/maxCharge)*100))) .. "%")
end

drawMainScreen()
 while true do
        updateScreen()
        os.sleep(refreshRate)
 end