src/main/scala/li/cil/oc/util/Audio.scala

package li.cil.oc.util

import java.nio.ByteBuffer

import cpw.mods.fml.common.FMLCommonHandler
import cpw.mods.fml.common.eventhandler.SubscribeEvent
import cpw.mods.fml.common.gameevent.TickEvent.ClientTickEvent
import net.minecraft.client.Minecraft
import net.minecraft.client.audio.SoundCategory
import org.lwjgl.BufferUtils
import org.lwjgl.openal.{AL, AL10, Util}

import scala.collection.mutable

/**
 * This class contains the logic used by computers' internal "speakers".
 * It can generate square waves with a specific frequency and duration
 * and will play them through OpenAL, acquiring sources as necessary.
 * Tones that have finished playing are disposed automatically in the
 * tick handler.
 */
object Audio {
  private def sampleRate = 8000

  private val sources = mutable.Set.empty[Source]

  private def volume = Minecraft.getMinecraft.gameSettings.getSoundLevel(SoundCategory.BLOCKS)

  def play(x: Float, y: Float, z: Float, frequencyInHz: Int, durationInMilliseconds: Int) {
    val distanceBasedGain = math.max(0, 1 - Minecraft.getMinecraft.thePlayer.getDistance(x, y, z) / 12).toFloat
    val gain = distanceBasedGain * volume
    if (gain > 0 && AL.isCreated) {
      val sampleCount = durationInMilliseconds * sampleRate / 1000
      val data = BufferUtils.createByteBuffer(sampleCount)
      val step = frequencyInHz / sampleRate.toFloat
      var offset = 0f
      for (sample <- 0 until sampleCount) {
        val angle = 2 * math.Pi * offset
        // We could sort of fake the square wave with a little less
        // computational effort, but until somebody complains let's
        // go with the fourier series! We leave out the  4 / Pi because
        // it's just an approximation and we avoid clipping like this.
        val value = (0 to 6).map(k => math.sin((1 + k * 2) * angle) / (1 + k * 2)).sum * Byte.MaxValue
        // val tmp = math.sin(angle) * Byte.MaxValue
        // val value = math.signum(tmp) * 0.99 + tmp * 0.01
        offset += step
        if (offset > 1) offset -= 1
        data.put(value.toByte)
      }
      data.rewind()

      sources.synchronized(sources += new Source(x, y, z, data, gain))
    }
  }

  def update() {
    sources.synchronized(sources --= sources.filter(_.checkFinished))

    // Clear error stack.
    if (AL.isCreated) {
      AL10.alGetError()
    }
  }

  private class Source(val x: Float, y: Float, z: Float, val data: ByteBuffer, val gain: Float) {
    // Clear error stack.
    AL10.alGetError()

    val (source, buffer) = {
      val buffer = AL10.alGenBuffers()
      Util.checkALError()

      try {
        AL10.alBufferData(buffer, AL10.AL_FORMAT_MONO8, data, sampleRate)
        Util.checkALError()

        val source = AL10.alGenSources()
        Util.checkALError()

        try {
          AL10.alSourceQueueBuffers(source, buffer)
          Util.checkALError()

          AL10.alSource3f(source, AL10.AL_POSITION, x, y, z)
          AL10.alSourcef(source, AL10.AL_GAIN, gain * 0.3f)
          Util.checkALError()

          AL10.alSourcePlay(source)
          Util.checkALError()

          (source, buffer)
        }
        catch {
          case t: Throwable =>
            AL10.alDeleteSources(source)
            throw t
        }
      }
      catch {
        case t: Throwable =>
          AL10.alDeleteBuffers(buffer)
          throw t
      }
    }

    def checkFinished = AL10.alGetSourcei(source, AL10.AL_SOURCE_STATE) != AL10.AL_PLAYING && {
      AL10.alDeleteSources(source)
      AL10.alDeleteBuffers(buffer)
      true
    }
  }

  FMLCommonHandler.instance.bus.register(this)

  @SubscribeEvent
  def onTick(e: ClientTickEvent) {
    update()
  }
}