-- @include ../libs/constants.txt
require('../libs/constants.txt')

Engine = class('Engine')

function Engine:initialize(options)
    options = options or {}

    self.idleRPM = options.IdleRPM or 800
    self.maxRPM = options.MaxRPM or 8000

    self.flywheelMass = options.FlywheelMass or 4
    self.flywheelRadius = options.FlywheelRadius or 0.3

    self.startFriction = options.StartFriction or -30
    self.frictionCoeff = options.FrictionCoeff or 0.02

    self.limiterDuration = options.LimiterDuration or 0.05

    self.torqueMap = options.TorqueMap or {}

    self.throttle = 0

    self.torque = 0
    self.rpmFrac = 0
    self.rpm = self.idleRPM
    self.friction = 0

    self._fwInertia = self.flywheelMass * self.flywheelRadius ^ 2 / 2
    self._limiterTime = 0

    self._clutch = nil
end

function Engine:setThrottle(throttle)
    self.throttle = throttle
end

function Engine:linkClutch(clutch)
    self._clutch = clutch
    clutch:linkEngine(self)
end

function Engine:update()
    self.rpmFrac = math.clamp((self.rpm - self.idleRPM) / (self.maxRPM - self.idleRPM), 0, 1)
    self.friction = self.startFriction - self.rpm * self.frictionCoeff

    local tqIdx = math.clamp(math.floor(self.rpmFrac * #self.torqueMap), 1, #self.torqueMap)
    local maxInitialTorque = self.torqueMap[tqIdx] - self.friction

    local idleFadeStart = math.clamp(math.remap(self.rpm, self.idleRPM - 300, self.idleRPM, 1, 0), 0, 1)
    local idleFadeEnd = math.clamp(math.remap(self.rpm, self.idleRPM, self.idleRPM + 600, 1, 0), 0, 1)

    local additionalEnergySupply = idleFadeEnd * (-self.friction / maxInitialTorque) + idleFadeStart

    if self.rpm > self.maxRPM then
        self.throttle = 0
        self._limiterTime = timer.systime()
    else
        self.throttle = timer.systime() >= self._limiterTime + self.limiterDuration and self.throttle or 0
    end

    local masterThrottle = math.clamp(additionalEnergySupply + self.throttle, 0, 1)

    local realInitialTorque = maxInitialTorque * masterThrottle

    local loadTorque = self._clutch and self._clutch.torque or 0

    self.torque = realInitialTorque + self.friction

    self.rpm = self.rpm + (self.torque - loadTorque) / self._fwInertia * RAD_TO_RPM * TICK_INTERVAL
    self.rpm = math.max(self.rpm, 0)
end