li/cil/oc/server/computer/Drivers.scala

package li.cil.oc.server.computer

import scala.collection.mutable.ArrayBuffer

import li.cil.oc.api.IBlockDriver
import li.cil.oc.api.IItemDriver
import net.minecraft.block.Block
import net.minecraft.item.ItemStack
import net.minecraft.world.World

/**
 * This class keeps track of registered drivers and provides installation logic
 * for each registered driver.
 *
 * Each component type must register its driver with this class to be used with
 * computers, since this class is used to determine whether an object is a
 * valid component or not.
 *
 * All drivers must be installed once the game starts - in the init phase - and
 * are then injected into all computers started up past that point. A driver is
 * a set of functions made available to the computer. These functions will
 * usually require a component of the type the driver wraps to be installed in
 * the computer, but may also provide context-free functions.
 */
private[oc] object Drivers {
  /** The list of registered block drivers. */
  private val blocks = ArrayBuffer.empty[BlockDriver]

  /** The list of registered item drivers. */
  private val items = ArrayBuffer.empty[ItemDriver]

  /** Used to keep track of whether we're past the init phase. */
  var locked = false

  /**
   * Registers a new driver for a block component.
   *
   * Whenever the neighboring blocks of a computer change, it checks if there
   * exists a driver for the changed block, and if so installs it.
   *
   * @param driver the driver for that block type.
   */
  def add(driver: IBlockDriver) {
    if (locked) throw new IllegalStateException("Please register all drivers in the init phase.")
    if (!blocks.exists(entry => entry.instance == driver))
      blocks += new BlockDriver(driver)
  }

  /**
   * Registers a new driver for an item component.
   *
   * Item components can inserted into a computers component slots. They have
   * to specify their type, to determine into which slots they can fit.
   *
   * @param driver the driver for that item type.
   */
  def add(driver: IItemDriver) {
    if (locked) throw new IllegalStateException("Please register all drivers in the init phase.")
    if (!blocks.exists(entry => entry.instance == driver))
      items += new ItemDriver(driver)
  }

  /**
   * Used when a new block is placed next to a computer to see if we have a
   * driver for it. If we have one, we'll return it.
   *
   * @param block the type of block to check for a driver for.
   * @return the driver for that block type if we have one.
   */
  def driverFor(world: World, block: Block) = blocks.find(_.instance.worksWith(world: World, block))

  /**
   * Used when an item component is added to a computer to see if we have a
   * driver for it. If we have one, we'll return it.
   *
   * @param item the type of item to check for a driver for.
   * @return the driver for that item type if we have one.
   */
  def driverFor(item: ItemStack) = items.find(_.instance.worksWith(item))

  /**
   * Used by the computer to initialize its Lua state, injecting the APIs of
   * all known drivers.
   */
  private[computer] def installOn(computer: Computer) =
    (blocks ++ items).foreach(_.installOn(computer))
}