package mtmc.emulator

import mtmc.emulator.MonTanaMiniComputer.ComputerStatus
import kotlin.math.max

/**
 *
 * @author jbanes
 */
class MTMCClock
  (private val computer: MonTanaMiniComputer) {
  fun run() {
    var instructions: Long = 0
    var ips: Long = 0
    var expected: Long = 0
    var virtual: Long = 0

    var startTime = System.currentTimeMillis()
    var deltaStart: Long
    var delta: Long

    var speed: Long = 0
    var pulse: Long
    var ms: Long = 10

    while (computer.getStatus() == ComputerStatus.EXECUTING) {
      speed = max(computer.speed, 0).toLong()
      pulse = (if (speed <= 0) 1000000 else max(speed / 100, 1))
      ms = (if (pulse < 10) 1000 / speed else 10)

      deltaStart = System.currentTimeMillis()
      delta = ms - (System.currentTimeMillis() - deltaStart)


      /* We've lost more than a second. Recalibrate. */
      if ((expected - virtual) > pulse * 100) {
        startTime = deltaStart
        virtual = 0
      }


      /* Throttles to every 10ms, but "catches up" if we're behind */
      if (delta > 0 && (expected - virtual) < pulse && speed != 0L) {
        try {
          Thread.sleep(delta)
        } catch (e: InterruptedException) {
        }
      }

      instructions += computer.pulse(pulse)

      virtual += pulse
      ips = (virtual * 1000) / max(1, System.currentTimeMillis() - startTime)
      expected = (System.currentTimeMillis() - startTime) * speed / 1000
    }

    System.err.println("Executed " + instructions + " instructions at a rate of " + ips + " ips (speed = " + speed + ")")
  }

  fun step() {
    computer.fetchAndExecute()
    computer.fetchCurrentInstruction()
    computer.notifyOfStepExecution()
  }

  fun back() {
    computer.rewind()
    computer.fetchCurrentInstruction()
    computer.notifyOfStepExecution()
  }
}