Knob OO-API

local defaultColor = colors.white
local defaultBgColor = colors.black
local textSize = 2
local titleText = ""

local monitor = nil
local knobs = {}

local function getText(k)
    if( k.isOff and k.offText ) then
        return k.offText
    else
        return k.onText
    end
end

local function getTextColor(k)
    return k.isOn and k.onColor or k.offColor
end

local function getBgColor(k)
    return k.isOn and k.onBgColor or k.offBgColor
end

local Knob = {
    toggleState = function(self)
        self.isOn = not self.isOn
    end,

    setState = function(self, state)
        self.isOn = state and true or false
    end,

    -- Draws the knob on the set monitor
    draw = function(self)
        local bgColor = getBgColor(self)
        local textColor = getTextColor(self)
        local buttonText = getText(self)

        monitor.setBackgroundColor(bgColor)

        -- Finds the middle in the Y-Axis
        local ypos = math.floor(( self.yMin + self.yMax) / 2);
        -- Finds the middle in the X-Axis
        local xpos = math.floor(
            (self.xMax-self.xMin-string.len(buttonText))/2)+1

        for ytraverse = self.yMin, self.yMax do
            monitor.setCursorPos(self.xMin, ytraverse)
            -- If you are in the middle of your knob Y-Axis check for the
            -- middle of the X-Axis
            -- Whitespaces(spaces) are being filled around your knob name
            if ytraverse == ypos then
                for xtraverse = 0, (self.xMax-self.xMin-string.len(buttonText)+1) do
                    if( xtraverse == xpos ) then
                        monitor.setTextColor(textColor)
                        monitor.write(buttonText)
                        monitor.setTextColor(bgColor)
                    else
                        monitor.write(" ")
                    end
                end
            else
                for i = self.xMin, self.xMax do
                    monitor.write(" ")
                end
            end
        end
        monitor.setBackgroundColor(defaultBgColor)
    end
}

local knobmetatable = {
    __index = Knob
}

function new(name, xMin, xMax, yMin, yMax, text, textColor, bgColor)
    local k = {
        name = name,
        isOn = false,
        xMin = xMin,
        xMax = xMax,
        yMin = yMin,
        yMax = yMax,

        onBgColor = bgColor,
        offBgColor = textColor,
        onText = text,
        offText = nil,
        onColor = textColor,
        offColor = bgColor,

        onClick = nil,
        onActivate = nil,
        onDeactivate = nil,
    }

    setmetatable(k, knobmetatable)

    knobs[name] = k
    return k
end

function remove(name)
    knobs[name] = nil
    refreshDisplay()
end

function setMonitor(m)
    monitor = m
    monitor.setTextScale(textSize)
    monitor.setTextColor(defaultColor)
    monitor.setBackgroundColor(defaultBgColor)
end

function setTextSize(size)
    textSize = size
    if( monitor ) then
        monitor.setTextScale(textSize)
    end
end

function setTextColor(c)
    defaultColor = c
    if( monitor ) then
        monitor.setTextColor(c)
    end
end

function setBackgroundColor(c)
    defaultBgColor = c
    if( monitor ) then
        monitor.setBgColor(c)
    end
end

function setTitle(text)
    titleText = text
end

function refreshDisplay()
    monitor.clear()

    x, y = monitor.getSize()
    monitor.setCursorPos( (x - string.len(titleText))/2+1, 1)
    monitor.write(titleText)

    for name, knob in pairs(knobs) do
        knob:draw()
    end
end

function getKnob(name)
    return knobs[name]
end

-- Refreshes the Monitor and waits for touch events.
-- On a touch event, the state of the button is toggled,
-- and it's onClick and on(De)Activate handlers are called, in that order.
--
-- @param forever Set to any truthy value to run this method forever.
function run(forever)
    refreshDisplay()

    repeat
        local event, side, x, y = os.pullEvent("monitor_touch")
        for name, knob in pairs(knobs) do
            if (y>=knob.yMin and y<=knob.yMax and x>=knob.xMin and x<=knob.xMax) then
                knob.isOn = not knob.isOn
                if( knob.onClick ) then
                    knob:onClick()
                end
                if( knob.isOn and knob.onActivate ) then
                    knob:onActivate()
                end
                if( not knob.isOn and knob.onDeactivate ) then
                    knob:onDeactivate()
                end

                knob:draw()
            end
        end
        sleep(.1)
    until not forever
end

-- Convenience function for initializing variables needed to display knobs.
-- All of these can be set individually via set* methods
--
-- @param side String The side your monitor is on
-- @param textSize Integer The size of button text
-- @param textColor Color The default textColor for non-button text
-- @param bgColor Color The default background color for the monitor
function init(side, textSize, textColor, bgColor)
    monitor = peripheral.wrap(side)
    monitor.setTextScale(textSize)
    monitor.setTextColor(textColor)
    monitor.setBackgroundColor(bgColor)
    defaultBgColor = bgColor
    defaultColor = textColor
end