ControllerObj = {}

require("lib")

function ControllerObj:new()
    local obj = obj or {}
    setmetatable(obj, {__index = self})

    obj.isEnabled = false

    obj.p = 1.0         -- proportional gain
    obj.tn = 1.0        -- integral reset time
    obj.d = 0.0         -- derivative
    obj.dFilter = 0     -- derivative filter time (in cylces)
    obj.dError = false  -- use error for derivative. if false, use value 

    obj.sp = 10.0       -- setpoint
    obj.pv = 0.0

    obj.intMax = 100.0  -- integral max
    obj.intMin = 0.0    -- integral min

    obj.outMax = 100.0  -- output max
    obj.outMin = 0.0    -- output min

    obj.error = 0.0     -- gain

    obj.errorLast = 0.0 -- last error
    obj.errorList = {}

    obj.dCalcLast = 0.0 -- last value used for derivative calculation
    obj.dCalcList = {}  -- smoothing buffer
    obj.dCalcSum = 0.0  --

    obj.int = 0.0       -- integral
    obj.deriv = 0       -- derivative
    obj.cv = 0          -- output

    obj.tLast = os.epoch("utc")
    obj.firstCall = true

    return obj
end

function ControllerObj:update(pv)
    -- time delta calc so the integral is more accurate and the controller doesnt fluctuate with bad server tickrates
    -- os.epoch("utc") is used because its far more accurate than os.time
    local tNow = os.epoch("utc")
    local tDelta = (tNow - self.tLast) / 1000
    if tDelta <= 0 or tDelta >= 10 then
        tDelta = 1
    end

    self.pv = pv

    -- immediately exit if the controller is disabled
    if not self.isEnabled then
        return 0.0
    end

    -- gain
    self.error = (self.sp - self.pv) * self.p

    -- integral
    if self.tn <= 0 then
        self.int = 0.0
    elseif self.cv < self.outMax and self.cv > self.outMin then -- anti windup
        if self.int + self.error + self.deriv >= self.outMax then
            self.int = self.outMax - (self.error + self.deriv)
        else
            self.int = ((self.error / self.tn) * tDelta) + self.int
        end
    end

    if self.int <= self.intMin then self.int = self.intMin end
    if self.int >= self.intMax then self.int = self.intMax end

    -- derivative

    local dVal = 0.0

    if self.dError then
        dVal = self.error   -- error derivative
    else
        dVal = -(self.pv*self.p) -- value RoC derivative
    end

    if self.d >= 0 then
        if self.dFilter > 0 then
            self.dCalcSum = smooth(self.dCalcList, dVal, self.dFilter)

            self.deriv = ((self.dCalcSum - self.dCalcLast) * self.d)*tDelta
            self.dCalcLast = self.dCalcSum
        else
            self.dCalcSum = 0.0
            self.deriv = ((dVal - self.dCalcLast) * self.d)*tDelta
            self.dCalcLast = dVal
        end
    else
        self.deriv = 0
    end

    self.tLast = os.epoch("utc")

    -- output
    self.cv = self.error + self.int + self.deriv
    if self.cv <= self.outMin then self.cv = self.outMin end
    if self.cv >= self.outMax then self.cv = self.outMax end

    if self.firstCall and self.cv >= self.outMax then self.int = 0 end

    self.firstCall = false
    return self.cv
end

function ControllerObj:setEnabled(bool)
    self.isEnabled = bool or false
    if not self.isEnabled then
        self:reset()
    end
end


function ControllerObj:setGain(gain)
    self.p = gain
end

function ControllerObj:setResetTime(time)
    self.tn = time
end

function ControllerObj:setDerivative(deriv)
    self.d = deriv
end

function ControllerObj:setDerivativeMode(bool)
    self.dError = bool
end 

function ControllerObj:setDerivativeFilter(cycles)
    self.dFilter = cycles
end

function ControllerObj:setSetpoint(sp)
    self.sp = sp
end

function ControllerObj:setIntegralMax(max)
    self.intMax = max
end

function ControllerObj:setIntegralMin(min)
    self.intMin = min
end

function ControllerObj:setOutputMax(max)
    self.outMax = max
end

function ControllerObj:setOutputMin(min)
    self.outMin = min
end

function ControllerObj:reset()  -- reset the controller values to 0
    self.error = 0.0
    self.int = 0.0
    self.deriv = 0.0
    self.cv = 0.0
    self.errorList = {}
    self.firstCall = false
end

function ControllerObj:getPV()
    return self.pv
end

function ControllerObj:getCV()
    return self.cv
end