IC2 Energy Monitor

-- User Settings --

local CONFIG = {
    title = "ENERGY MONITOR",
    refreshRate = 1,

    -- Colours --
    bgColor = colours.black,
    textColor = colours.white,
    barBg = colours.grey,
    barFillLow = colours.red,
    barFillMid = colours.yellow,
    barFillHigh = colours.green,

    -- Bar Settings --
    barWidthPercent = 0.8
}

-- Setup --
local mon = peripheral.find("monitor")
local psd = nil
for _,name in pairs(peripheral.getNames()) do
    if peripheral.getType(name) == "ic2:mfe"
    or peripheral.getType(name) == "ic2:mfsu"
    then
        psd = peripheral.wrap(name)
    end
end

if not mon then
    error("Monitor not found")
end

if not psd then
    error("Power storage device not found")
end

mon.setBackgroundColor(CONFIG.bgColor)
mon.clear()
mon.setTextScale(1)

-- Helper Functions --

local function centerText(y, text, color)
    local w, _ = mon.getSize()
    local x = math.floor((w - #text) / 2) + 1
    mon.setCursorPos(x, y)
    if color then mon.setTextColor(color) end
    mon.write(text)
end

local function getBarColor(percent)
    if percent >= 0.75 then
        return CONFIG.barFillHigh
    elseif percent >= 0.30 then
        return CONFIG.barFillMid
    else
        return CONFIG.barFillLow
    end
end

local function drawProgressBar(y, percent)
    local w, _ = mon.getSize()
    local barWidth = math.floor(w * CONFIG.barWidthPercent)
    local startX = math.floor((w - barWidth) / 2) + 1
    local filled = math.floor(barWidth * percent)

    -- background --
    mon.setBackgroundColor(CONFIG.barBg)
    mon.setCursorPos(startX, y)
    mon.write(string.rep(" ", barWidth))

    -- fill --
    mon.setBackgroundColor(getBarColor(percent))
    mon.setCursorPos(startX, y)
    mon.write(string.rep(" ", filled))

    mon.setBackgroundColor(CONFIG.bgColor)
end

-- Main Loop --
local lastStored = -1
local lastMax = -1
while true do
    mon.setBackgroundColor(CONFIG.bgColor)

    local stored
    local max

    if psd.getEUStored then
        stored = psd:getEUStored()
        max = psd:getEUCapacity()
    elseif psd.getEnergyStored then
        stored = psd:getEnergyStored()
        max = psd:getMaxEnergyStored()
    else
        stored = nil
        max = nil
    end

    if not stored or not max then
        centerText(2, "PSD METHOD ERROR", colours.red)
        sleep(2)
    else
        local percent = stored / max
        local _, h = mon.getSize()

        centerText(4, CONFIG.title, CONFIG.textColor)
        centerText(8, string.format("%d / %d EU", stored, max), CONFIG.textColor)
        centerText(9, string.format("%.2f%%", percent * 100), CONFIG.textColor)

        drawProgressBar(math.floor(h / 2), percent)
    end
    sleep(CONFIG.refreshRate)
end