diff --git a/assets/opencomputers/lua/boot.lua b/assets/opencomputers/lua/boot.lua
index fbab782d2..daa5236a3 100644
--- a/assets/opencomputers/lua/boot.lua
+++ b/assets/opencomputers/lua/boot.lua
@@ -58,7 +58,7 @@ do
       end
     end
   end
-  wrapRecursive(drivers)
+  wrapRecursive(driver)
 end
 
 --[[ Permanent value tables.
diff --git a/assets/opencomputers/lua/kernel.lua b/assets/opencomputers/lua/kernel.lua
index 2433400d1..e5881312a 100644
--- a/assets/opencomputers/lua/kernel.lua
+++ b/assets/opencomputers/lua/kernel.lua
@@ -72,6 +72,8 @@ local function buildSandbox()
       yield = coroutine.yield
     },
 
+    driver = driver,
+
     math = {
       abs = math.abs,
       acos = math.acos,
@@ -139,6 +141,8 @@ local function buildSandbox()
       unpack = table.unpack
     }
   }
+
+  -- Make the sandbox its own globals table.
   sandbox._G = sandbox
 
   -- Allow sandboxes to load code, but only in text form, and in the sandbox.
diff --git a/com/naef/jnlua/LuaState.java b/com/naef/jnlua/LuaState.java
index e4d1f3592..0207b0bf5 100644
--- a/com/naef/jnlua/LuaState.java
+++ b/com/naef/jnlua/LuaState.java
@@ -750,7 +750,7 @@ public class LuaState {
 	 */
 	public synchronized void pushJavaObject(Object object) {
 		check();
-		getConverter().convertJavaObject(this, object);
+		converter.convertJavaObject(this, object);
 	}
 
 	/**
@@ -1961,6 +1961,23 @@ public class LuaState {
 		throw getArgException(index, String.format("invalid option '%s'", s));
 	}
 
+  /**
+   * Checks if the value of the specified function argument is a boolean. If
+   * so, the argument value is returned as a boolean. Otherwise, the method
+   * throws a Lua runtime exception with a descriptive error message.
+   * 
+   * @param index
+   *            the argument index
+   * @return the integer value
+   */
+  public synchronized boolean checkBoolean(int index) {
+    check();
+    if (!isBoolean(index)) {
+      throw getArgTypeException(index, LuaType.BOOLEAN);
+    }
+    return toBoolean(index);
+  }
+
 	/**
 	 * Checks if the value of the specified function argument is a number or a
 	 * string convertible to a number. If so, the argument value is returned as
diff --git a/li/cil/oc/Config.scala b/li/cil/oc/Config.scala
index 13fe0da18..b5fdc2dcc 100644
--- a/li/cil/oc/Config.scala
+++ b/li/cil/oc/Config.scala
@@ -5,6 +5,7 @@ object Config {
   var blockMonitorId = 3651
 
   var itemHDDId = 4600
+  var itemGPUId = 4601
 
   var threads = 4
 }
\ No newline at end of file
diff --git a/li/cil/oc/OpenComputers.scala b/li/cil/oc/OpenComputers.scala
index b86c7f16c..bc3a0083e 100644
--- a/li/cil/oc/OpenComputers.scala
+++ b/li/cil/oc/OpenComputers.scala
@@ -1,5 +1,7 @@
 package li.cil.oc
 
+import java.util.logging.Logger
+
 import cpw.mods.fml.common.Mod
 import cpw.mods.fml.common.Mod.EventHandler
 import cpw.mods.fml.common.SidedProxy
@@ -12,6 +14,9 @@ import li.cil.oc.common.CommonProxy
 @Mod(modid = "OpenComputers", name = "OpenComputers", version = "0.0.0", dependencies = "required-after:Forge@[9.10.0.804,)", modLanguage = "scala")
 @NetworkMod(clientSideRequired = true, serverSideRequired = false)
 object OpenComputers {
+  /** Logger used all throughout this mod. */
+  val log = Logger.getLogger("OpenComputers")
+
   @SidedProxy(
     clientSide = "li.cil.oc.client.ClientProxy",
     serverSide = "li.cil.oc.common.CommonProxy")
diff --git a/li/cil/oc/api/Callback.java b/li/cil/oc/api/Callback.java
index e7d537e93..3d2224d20 100644
--- a/li/cil/oc/api/Callback.java
+++ b/li/cil/oc/api/Callback.java
@@ -6,29 +6,39 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 /**
- * This annotation is used by components to mark methods that are part of the
- * API they expose to computers.
+ * This annotation is used by {@see IDriver}s to mark methods that are part of
+ * the API they expose to computers.
  * 
- * If the component provides an API, each method annotated like this an entry in
- * the API table will be generated. The actual entry will be a wrapper that
+ * If the driver provides an API, for each method annotated like this an entry
+ * in the API table will be generated. The actual entry will be a wrapper that
  * takes care of parameter transformation and all the Lua protocol stuff. This
- * does limit the types you can use for parameters and return types, however.
+ * requires fixed parameters and return types, however, i.e. one parameter will
+ * always have to be one specific type (which is not necessary in Lua since it
+ * is a dynamic language).
  * 
- * Supported parameter types are: Boolean, Integer, Double and String. These map
- * to boolean, number, number, and string respectively. If a function parameter
- * is of an unsupported type its value will always be the type's default value.
+ * Any type is supported as long as it can be converted by JNLua's {@see
+ * com.naef.jnlua.DefaultConverter}. However, so as not to break persistence
+ * (i.e. saving a computer's state and seamlessly resume after reloading) only
+ * simple types such as booleans, numbers and strings and table types such as
+ * <tt>Map</tt>,<tt>List</tt> and arrays should be passed along.
  * 
- * Supported return types are: Boolean, Integer, Double, String and Array. These
- * map to the same types as parameter types, with the exception of arrays which
- * are interpreted as tuples, meaning they will be dissolved into multiple
- * return values. If a return value type is of an unsupported type it will be
- * ignored.
+ * If you wish more flexibility in how you handle parameters, define the
+ * callback with the following signature:
+ * 
+ * <pre>
+ * Object[] callback(IComputerContext, Object[])
+ * </pre>
+ * 
+ * In this case the first argument is the computer from which the function was
+ * called, the second is the array of objects passed along from Lua, which may
+ * be an arbitrary number of arbitrarily typed object (although still only basic
+ * types as described above are supported). The returned array must also contain
+ * only basic types as described above and represents the values returned as
+ * results to Lua as with automatically wrapped functions.
  */
 @Retention(RetentionPolicy.RUNTIME)
 @Target(ElementType.METHOD)
 public @interface Callback {
-  /**
-   * The name under which the method will be available in Lua.
-   */
+  /** The name under which the method will be available in Lua. */
   String name();
 }
\ No newline at end of file
diff --git a/li/cil/oc/api/ComponentType.scala b/li/cil/oc/api/ComponentType.scala
index fdcdb5211..4b8a38163 100644
--- a/li/cil/oc/api/ComponentType.scala
+++ b/li/cil/oc/api/ComponentType.scala
@@ -12,5 +12,4 @@ object ComponentType extends Enumeration {
   val RAM = Value("RAM")
   val HDD = Value("HDD")
   val PCI = Value("PCI")
-  val GPU = Value("GPU")
 }
\ No newline at end of file
diff --git a/li/cil/oc/api/IBlockDriver.scala b/li/cil/oc/api/IBlockDriver.scala
index e2efa0b60..6a4659fb2 100644
--- a/li/cil/oc/api/IBlockDriver.scala
+++ b/li/cil/oc/api/IBlockDriver.scala
@@ -9,22 +9,34 @@ import net.minecraft.block.Block
  * placed in the world, and particularly: next to computers. An example for
  * this are external drives, monitors and modems.
  *
- * When a block component is added next to a computer, the computer's OS will
- * be notified via a signal so that it may install the component's driver, for
- * example. After that the OS may start to interact with the component via the
- * API functions it provides.
+ * When a block component is placed next to a computer, the list of registered
+ * drivers is queried using the drivers' {@see #worksWith} functions. The first
+ * driver that replies positively will be used as the component's driver and
+ * the component will be installed. If no driver is found the item will be
+ * ignored.
+ *
+ * The computer will store a list of installed components, the values of which
+ * are based on what the driver returns from its {@see #component} function
+ * at the point of time the component is installed.
+ * If a driver's API function queries a component via the context using
+ * {@see IComputerContext#component()} the returned value will be exactly that.
+ *
+ * Note that it is possible to write one driver that supports as many different
+ * blocks as you wish. I'd recommend writing one per device (type), though, to
+ * keep things modular and the {@see IDriver#componentName} more meaningful.
  */
 trait IBlockDriver extends IDriver {
   /**
-   * The type of block this driver handles.
+   * Used to determine the block types this driver handles.
    *
-   * When a block is added next to a computer and has this type, this driver
-   * will be used for the block. The return value must not change over the
-   * lifetime of this driver.
+   * This is used to determine which driver to use for a block placed next to a
+   * computer. Note that the return value should not change over time; if it
+   * does, though, an already installed component will not be ejected, since
+   * this value is only checked when adding components.
    *
-   * @return the block type this driver is used for.
+   * param block the block type to check for.
    */
-  def blockType: Block
+  def worksWith(block: Block): Boolean
 
   /**
    * Get a reference to the actual component.
@@ -38,5 +50,5 @@ trait IBlockDriver extends IDriver {
    * @param z the Z coordinate of the block to get the component for.
    * @return the block component at that location, controlled by this driver.
    */
-  def getComponent(x: Int, y: Int, z: Int): Object
+  def component(x: Int, y: Int, z: Int): Object
 }
\ No newline at end of file
diff --git a/li/cil/oc/api/IDriver.scala b/li/cil/oc/api/IDriver.scala
index 7d4104112..885bb6941 100644
--- a/li/cil/oc/api/IDriver.scala
+++ b/li/cil/oc/api/IDriver.scala
@@ -1,5 +1,7 @@
 package li.cil.oc.api
 
+import java.io.InputStream
+
 /**
  * This interface specifies the structure of a driver for a component.
  *
@@ -7,6 +9,16 @@ package li.cil.oc.api
  * used as computer components. They specify an API that is injected into the
  * Lua state when the driver is installed, and provide general information used
  * by the computer.
+ *
+ * Note that drivers themselves are singletons. They can define a parameter of
+ * type {@see IComputerContext} in their API functions which will hold the
+ * context in which they are called - essentially a representation of the
+ * computer they were called form. This context can be used to get a component
+ * in the computer (e.g. passed as another parameter) and to send signals to
+ * the computer.
+ *
+ * Do not implement this interface directly; use the {@see IItemDriver} and
+ * {@see IBlockDriver} interfaces for the respective component types.
  */
 trait IDriver {
   /**
@@ -15,49 +27,100 @@ trait IDriver {
    * This is used to allow computer programs to check the type of a component.
    * Components attached to a computer are identified by a number. This value
    * is returned when the type for such an ID is requested, so it should be
-   * unique for each driver.
+   * unique for each driver. For example, when a component is installed and the
+   * install signal was sent, the Lua code may check the type of the installed
+   * component using <code>drivers.component</code>. The returned string will
+   * be this one.
    */
   def componentName: String
 
   /**
-   * The name of the API this component exposes to computers.
+   * The name of the API this component exposes to computers, if any.
    *
    * The component may return null or an empty string if it does not wish to
    * define an API. If this is the case, we will not look for methods marked
    * with the {@link Callback} annotation.
    *
+   * This is the name of the table made available in the global drivers table,
+   * for example if this were to return 'disk', then the API will be available
+   * in Lua via <code>drivers.disk</code>.
+   *
    * This should be unique for individual component types. If not, functions
    * in that API table may block another component's API from being installed
    * properly: existing entries are not overwritten.
    *
+   * Note that this <em>must not</em> be 'component', since that is reserved
+   * for a function that returns the type of an installed component given its
+   * ID.
+   *
    * @return the name of the API made available to Lua.
    */
-  def apiName: String
+  def apiName: String = null
 
   /**
    * Some initialization code that is run when the driver is installed.
    *
    * This is run after the driver's API table has been installed. It is loaded
-   * into the Lua state in a temporary environment that has access to the
-   * globals table and is discarded after the script has run.
+   * into the Lua state and run in the global, un-sandboxed environment. This
+   * means your scripts can mess things up bad, so make sure you know what
+   * you're doing and exposing.
    *
-   * This can be null or an empty string to do nothing. Otherwise this is
-   * expected to be valid Lua code.
+   * This can be null to do nothing. Otherwise this is expected to be valid Lua
+   * code (it is simply loaded via <code>load()</code> and then executed).
+   *
+   * The stream has to be recreated each time this is called. Normally you will
+   * return something along the lines of
+   *   <code>Mod.class.getResourceAsStream("/assets/mod/lua/ocapi.lua")</code>
+   * from this method. If you wish to hard-code the returned script, you can
+   * use <code>new ByteArrayInputStream(yourScript.getBytes())</code> instead.
+   * Note that the stream will automatically closed.
    *
    * @return the Lua code to run after installing the API table.
    */
-  def apiCode: String
+  def apiCode: InputStream = null
+
+  /**
+   * This is called when a component is added to a computer.
+   *
+   * This happens if either of the following takes place:
+   * - The component is an item component and added in the computer.
+   * - The component is a block component and placed next to the computer.
+   * - The component is already in / next to the computer and the computer was
+   *   off and is now starting up again. In this case this is called before the
+   *   computer thread is started.
+   *
+   * You can use this to initialize some internal state or send some signal(s)
+   * to the computer. For example, graphics cards will scan for unbound
+   * monitors and automatically bind to the first free one.
+   *
+   * This is called before the install signal is sent to the computer.
+   *
+   * @param computer the computer to which the component is being added.
+   * @param component a handle to the component, as it was provided by the
+   * driver in its {@link IBlockDriver#component}/{@link IItemDriver#component}
+   * function.
+   */
+  def onInstall(computer: IComputerContext, component: Any) = {}
 
   /**
    * This is called when a component is removed from a computer.
    *
+   * This happens if either of the following takes place:
+   * - The component is an item component and removed from the computer.
+   * - The component is a block component and broken or the computer is broken.
+   * - The component is already in / next to the computer and the computer was
+   *   on and is now shutting down.
+   *
    * The component should remove all handles it currently provides to the
    * computer. For example, it should close any open files if it provides some
    * form of file system.
    *
+   * This is called before the uninstall signal is sent to the computer.
+   *
+   * @param computer the computer from which the component is being removed.
    * @param component a handle to the component, as it was provided by the
-   * driver in its {@link IBlockDriver#getComponent} or
-   * {@link IItemDriver#getComponent} function.
+   * driver in its {@link IBlockDriver#component}/{@link IItemDriver#component}
+   * function.
    */
-  def close(component: Object)
+  def onUninstall(computer: IComputerContext, component: Any) = {}
 }
\ No newline at end of file
diff --git a/li/cil/oc/api/IItemDriver.scala b/li/cil/oc/api/IItemDriver.scala
index c5582b0c3..2df47cc42 100644
--- a/li/cil/oc/api/IItemDriver.scala
+++ b/li/cil/oc/api/IItemDriver.scala
@@ -9,42 +9,65 @@ import net.minecraft.item.ItemStack
  * inserted into computers. An example for this are internal drives, memory
  * and power supply units.
  *
- * When an item component is added to a computer, the computer's OS will be
- * notified via a signal so that it may install the component's driver, for
- * example. After that the OS may start to interact with the component via the
- * API functions it provides.
+ * When trying to add an item to a computer the list of registered drivers is
+ * queried using the drivers' {@see #worksWith} functions. The first driver
+ * that replies positively and whose check against the slot type is successful,
+ * i.e. for which the {@see #componentType} matches the slot, will be used as
+ * the component's driver and the component will be installed. If no driver is
+ * found the item will be rejected and cannot be installed.
+ *
+ * The computer will store a list of installed components, the values of which
+ * are based on what the driver returns from its {@see #component} function
+ * at the point of time the component is installed.
+ * If a driver's API function queries a component via the context using
+ * {@see IComputerContext#component()} the returned value will be exactly that.
+ * 
+ * Note that it is possible to write one driver that supports as many different
+ * items as you wish. I'd recommend writing one per device (type), though, to
+ * keep things modular and the {@see IDriver#componentName} more meaningful.
  */
 trait IItemDriver extends IDriver {
   /**
-   * The component type of this item component.
+   * Used to determine the item types this driver handles.
    *
-   * This is used to determine into which slot of a computer this component may
-   * go.
+   * This is used to determine which driver to use for an item when installed
+   * in a computer. Note that the return value should not change over time; if
+   * it does, though, an already installed component will not be ejected, since
+   * this value is only checked when adding components.
    *
-   * @return the component type.
+   * @param item the item to check.
+   * @return true if the item is supported; false otherwise.
    */
-  def componentType: ComponentType.Value
+  def worksWith(item: ItemStack): Boolean
 
   /**
-   * The type of item this driver handles.
+   * The component type of the specified item this driver supports.
    *
-   * When an item is added into a computer and has this type, this driver will
-   * be used for the block. The return value must not change over the lifetime
-   * of this driver.
+   * This is used to determine into which slot of a computer the components
+   * this driver supports may go. This will only be called if a previous call
+   * to {@see #worksWith} with the same item type returned true.
    *
-   * @return the item type this driver is used for.
+   * @return the component type of the specified item.
    */
-  def itemType: ItemStack
+  def componentType(item: ItemStack): ComponentType.Value
 
   /**
-   * Get a reference to the actual component.
+   * Gets a reference to the actual component.
    *
-   * This is used to provide context to the driver's methods, for example
-   * when an API method is called this will always be passed as the first
-   * parameter. It is also passed to the {@link IDriver#close} method.
+   * It is called once when a component is installed in a computer. At that
+   * time, the component will be assigned a unique ID by which it is referred
+   * to by from the Lua side. The computer keeps track of the mapping from ID
+   * to the actual component, which will be the value returned from this.
+   *
+   * This is used to provide context to the driver's API methods. The driver
+   * may get a reference to a component via the ID passed from a Lua program,
+   * and act accordingly (for that it must also have a context parameter, see
+   * the general interface documentation).
+   *
+   * This value also passed to the driver's {@link IDriver#close} method.
    *
    * @param item the item instance for which to get the component.
    * @return the item component for that item, controlled by this driver.
    */
-  def getComponent(item: ItemStack): Object
+  def component(item: ItemStack): Any
 }
\ No newline at end of file
diff --git a/li/cil/oc/api/OpenComputersAPI.scala b/li/cil/oc/api/OpenComputersAPI.scala
index 610324a0d..80e371349 100644
--- a/li/cil/oc/api/OpenComputersAPI.scala
+++ b/li/cil/oc/api/OpenComputersAPI.scala
@@ -5,11 +5,11 @@ import li.cil.oc.server.computer.Drivers
 object OpenComputersAPI {
   def addDriver(driver: IBlockDriver) {
     // TODO Use reflection to allow distributing the API.
-    Drivers.addDriver(driver)
+    Drivers.add(driver)
   }
 
   def addDriver(driver: IItemDriver) {
     // TODO Use reflection to allow distributing the API.
-    Drivers.addDriver(driver)
+    Drivers.add(driver)
   }
 }
\ No newline at end of file
diff --git a/li/cil/oc/client/computer/Computer.scala b/li/cil/oc/client/computer/Computer.scala
index 25bd271a8..a7b6237b3 100644
--- a/li/cil/oc/client/computer/Computer.scala
+++ b/li/cil/oc/client/computer/Computer.scala
@@ -1,19 +1,44 @@
 package li.cil.oc.client.computer
 
-import li.cil.oc.common.computer.IInternalComputerContext
+import scala.reflect.runtime.universe._
+
+import li.cil.oc.api.IComputerContext
+import li.cil.oc.common.computer.IComputer
+import net.minecraft.block.Block
+import net.minecraft.item.ItemStack
 import net.minecraft.nbt.NBTTagCompound
 
-class Computer(val owner: AnyRef) extends IInternalComputerContext {
-  def luaState = null
+/**
+ * This is a dummy class for the client side. It does nothing, really, just
+ * saves us a couple of side checks.
+ */
+class Computer(val owner: AnyRef) extends IComputerContext with IComputer {
+  // ----------------------------------------------------------------------- //
+  // IComputerContext
+  // ----------------------------------------------------------------------- //
+
+  def world = throw new NotImplementedError
+
+  def signal(name: String, args: Any*) = throw new NotImplementedError
+
+  def component[T: TypeTag](id: Int) = throw new NotImplementedError
+
+  // ----------------------------------------------------------------------- //
+  // IComputer
+  // ----------------------------------------------------------------------- //
+
+  def add(item: ItemStack, id: Int) = None
+
+  def add(block: Block, x: Int, y: Int, z: Int, id: Int) = None
+
+  def remove(id: Int) = false
 
   def start() = false
-  
+
   def stop() {}
 
   def update() {}
 
-  def signal(name: String, args: Any*) {}
-
   def readFromNBT(nbt: NBTTagCompound) {}
 
   def writeToNBT(nbt: NBTTagCompound) {}
diff --git a/li/cil/oc/common/CommonProxy.scala b/li/cil/oc/common/CommonProxy.scala
index ba8af09f0..965d7969d 100644
--- a/li/cil/oc/common/CommonProxy.scala
+++ b/li/cil/oc/common/CommonProxy.scala
@@ -8,6 +8,7 @@ import li.cil.oc.Blocks
 import li.cil.oc.Config
 import li.cil.oc.Items
 import li.cil.oc.server.computer.Computer
+import li.cil.oc.server.computer.Drivers
 
 class CommonProxy {
   def preInit(e: FMLPreInitializationEvent): Unit = {
@@ -30,5 +31,10 @@ class CommonProxy {
     new Computer(null)
   }
 
-  def postInit(e: FMLPostInitializationEvent): Unit = {}
+  def postInit(e: FMLPostInitializationEvent): Unit = {
+    // Lock the driver registry to avoid drivers being added after computers
+    // may have already started up. This makes sure the driver API won't change
+    // over the course of a game, since that could lead to weird effects.
+    Drivers.locked = true
+  }
 }
\ No newline at end of file
diff --git a/li/cil/oc/common/computer/IInternalComputerContext.scala b/li/cil/oc/common/computer/IInternalComputerContext.scala
deleted file mode 100644
index 717acf556..000000000
--- a/li/cil/oc/common/computer/IInternalComputerContext.scala
+++ /dev/null
@@ -1,20 +0,0 @@
-package li.cil.oc.common.computer
-
-import scala.collection.Seq
-import net.minecraft.nbt.NBTTagCompound
-import li.cil.oc.server.computer.IComputerContext
-import com.naef.jnlua.LuaState
-
-trait IInternalComputerContext extends IComputerContext {
-  def luaState: LuaState
-
-  def start(): Boolean
-
-  def stop(): Unit
-
-  def update()
-
-  def readFromNBT(nbt: NBTTagCompound)
-
-  def writeToNBT(nbt: NBTTagCompound)
-}
\ No newline at end of file
diff --git a/li/cil/oc/common/tileentity/TileEntityComputer.scala b/li/cil/oc/common/tileentity/TileEntityComputer.scala
index 87db03d52..8eafe8f86 100644
--- a/li/cil/oc/common/tileentity/TileEntityComputer.scala
+++ b/li/cil/oc/common/tileentity/TileEntityComputer.scala
@@ -34,7 +34,6 @@ class TileEntityComputer(isClient: Boolean) extends TileEntity with IComputerEnv
   }
 
   override def writeToNBT(nbt: NBTTagCompound) = {
-    println("SAVING")
     super.writeToNBT(nbt)
     computer.writeToNBT(nbt)
   }
@@ -52,14 +51,12 @@ class TileEntityComputer(isClient: Boolean) extends TileEntity with IComputerEnv
 
   @ForgeSubscribe
   def onChunkUnload(e: ChunkEvent.Unload) = {
-    println("CHUNK UNLOADING")
     MinecraftForge.EVENT_BUS.unregister(this)
     computer.stop()
   }
 
   @ForgeSubscribe
   def onWorldUnload(e: WorldEvent.Unload) = {
-    println("WORLD UNLOADING")
     MinecraftForge.EVENT_BUS.unregister(this)
     computer.stop()
   }
diff --git a/li/cil/oc/server/computer/Computer.scala b/li/cil/oc/server/computer/Computer.scala
index ec2f1e589..7db270699 100644
--- a/li/cil/oc/server/computer/Computer.scala
+++ b/li/cil/oc/server/computer/Computer.scala
@@ -2,22 +2,58 @@ package li.cil.oc.server.computer
 
 import java.util.concurrent._
 import java.util.concurrent.atomic.AtomicInteger
-
 import scala.Array.canBuildFrom
 import scala.collection.JavaConversions._
+import scala.collection.mutable._
+import scala.reflect.runtime.universe._
 import scala.util.Random
-
 import com.naef.jnlua._
-
 import li.cil.oc.Config
-import li.cil.oc.common.computer.IInternalComputerContext
+import li.cil.oc.api.IComputerContext
+import li.cil.oc.common.computer.IComputer
+import net.minecraft.block.Block
+import net.minecraft.item.ItemStack
 import net.minecraft.nbt._
+import java.util.Date
+import java.util.Calendar
+import java.util.Locale
 
-class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext with Runnable {
+/**
+ * Wrapper class for Lua states set up to behave like a pseudo-OS.
+ *
+ * This class takes care of the following:
+ * - Creating a new Lua state when started from a previously stopped state.
+ * - Updating the Lua state in a parallel thread so as not to block the game.
+ * - Managing a list of installed components and their drivers.
+ * - Synchronizing calls from the computer thread to drivers.
+ * - Saving the internal state of the computer across chunk saves/loads.
+ * - Closing the Lua state when stopping a previously running computer.
+ *
+ * See {@see Driver} to read more about component drivers and how they interact
+ * with computers - and through them the components they interface.
+ */
+class Computer(val owner: IComputerEnvironment) extends IComputerContext with IComputer with Runnable {
   // ----------------------------------------------------------------------- //
   // General
   // ----------------------------------------------------------------------- //
 
+  /**
+   * This is the list of components currently attached to the computer. It is
+   * updated whenever a component is placed into the computer or removed from
+   * it, as well as when a block component is placed next to it or removed.
+   *
+   * On the Lua side we only refer to components by an ID, which is the array
+   * index for the component array. Drivers may fetch the underlying component
+   * object via the IComputerContext.
+   *
+   * Since the Lua program may query a component's type from its own thread we
+   * have to synchronize access to the component map. Note that there's a
+   * chance the Lua programs may see a component before its install signal has
+   * been processed, but I can't think of a scenario where this could become
+   * a real problem.
+   */
+  private val components = new HashMap[Int, (Any, Driver)] with SynchronizedMap[Int, (Any, Driver)]
+
   /**
    * The current execution state of the computer. This is used to track how to
    * resume the computers main thread, if at all, and whether to accept new
@@ -26,7 +62,7 @@ class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext
   private var state = State.Stopped
 
   /** The internal Lua state. Only set while the computer is running. */
-  private var lua: LuaState = null
+  private[computer] var lua: LuaState = null
 
   /**
    * The base memory consumption of the kernel. Used to permit a fixed base
@@ -42,7 +78,7 @@ class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext
    * means to communicate actively with the computer (passively only drivers
    * can interact with the computer by providing API functions).
    */
-  private val signals = new LinkedBlockingQueue[Signal](256)
+  private val signals = new LinkedBlockingQueue[Signal](100)
 
   // ----------------------------------------------------------------------- //
 
@@ -82,22 +118,61 @@ class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext
   private val saveMonitor = new Object()
 
   // ----------------------------------------------------------------------- //
-  // State
+  // IComputerContext
   // ----------------------------------------------------------------------- //
 
-  /** Starts asynchronous execution of this computer if it isn't running. */
-  def start(): Boolean = stateMonitor.synchronized(
+  def world = owner.world
+
+  def signal(name: String, args: Any*) = {
+    args.foreach {
+      case null | _: Byte | _: Char | _: Short | _: Int | _: Long | _: Float | _: Double | _: String => Unit
+      case _ => throw new IllegalArgumentException()
+    }
+    stateMonitor.synchronized(state match {
+      // We don't push new signals when stopped or shutting down.
+      case State.Stopped | State.Stopping => false
+      // Currently sleeping. Cancel that and start immediately.
+      case State.Sleeping =>
+        future.cancel(true)
+        state = State.Suspended
+        signals.offer(new Signal(name, args.toArray))
+        future = Executor.pool.submit(this)
+        true
+      // Running or in driver call or only a short yield, just push the signal.
+      case _ =>
+        signals.offer(new Signal(name, args.toArray))
+        true
+    })
+  }
+
+  def component[T: TypeTag](id: Int) = components.get(id) match {
+    case None => throw new IllegalArgumentException("no such component")
+    case Some(component) =>
+      if (component.getClass() == typeOf[T]) component.asInstanceOf[T]
+      else throw new IllegalArgumentException("bad component type")
+  }
+
+  // ----------------------------------------------------------------------- //
+  // IComputer
+  // ----------------------------------------------------------------------- //
+
+  def start() = stateMonitor.synchronized(
     state == State.Stopped && init() && {
       state = State.Suspended
       // Inject a dummy signal so that real one don't get swallowed. This way
-      // we can just ignore the parameters the first time the kernel is run.
+      // we can just ignore the parameters the first time the kernel is run
+      // and all actual signals will be read using coroutine.yield().
       signal("dummy")
+
+      // Initialize any installed components.
+      for ((component, driver) <- components.values)
+        driver.instance.onInstall(this, component)
+
       future = Executor.pool.submit(this)
       true
     })
 
-  /** Stops a computer, possibly asynchronously. */
-  def stop(): Unit = saveMonitor.synchronized(stateMonitor.synchronized {
+  def stop() = saveMonitor.synchronized(stateMonitor.synchronized {
     if (state != State.Stopped) {
       if (state != State.Running) {
         // If the computer is not currently running we can simply close it,
@@ -118,12 +193,6 @@ class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext
     }
   })
 
-  // ----------------------------------------------------------------------- //
-  // IComputerContext
-  // ----------------------------------------------------------------------- //
-
-  def luaState = lua
-
   def update() {
     stateMonitor.synchronized(state match {
       case State.Stopped | State.Stopping => return
@@ -152,34 +221,47 @@ class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext
     // Update world time for computer threads.
     worldTime = owner.world.getWorldInfo().getWorldTotalTime()
 
-    if (worldTime % 47 == 0) {
-      signal("test", "ha!")
-    }
-
     // Update last time run to let our executor thread know it doesn't have to
-    // pause, and wake it up if it did pause (because the game was paused).
+    // pause.
     lastUpdate = System.currentTimeMillis
   }
 
-  def signal(name: String, args: Any*) = {
-    args.foreach {
-      case _: Byte | _: Short | _: Int | _: Long | _: Float | _: Double | _: String => Unit
-      case _ => throw new IllegalArgumentException()
+  // ----------------------------------------------------------------------- //
+  // Note: driver interaction is synchronized, so we don't have to lock here.
+
+  def add(item: ItemStack, id: Int) =
+    Drivers.driverFor(item) match {
+      case None => None
+      case Some(driver) if !components.contains(id) =>
+        val component = driver.instance.component(item)
+        components += id -> (component, driver)
+        driver.instance.onInstall(this, component)
+        signal("component_install", id)
+        Some(driver.instance)
     }
-    stateMonitor.synchronized(state match {
-      // We don't push new signals when stopped or shutting down.
-      case State.Stopped | State.Stopping => /* Nothing. */
-      // Currently sleeping. Cancel that and start immediately.
-      case State.Sleeping =>
-        future.cancel(true)
-        state = State.Suspended
-        signals.offer(new Signal(name, args.toArray))
-        future = Executor.pool.submit(this)
-      // Running or in driver call or only a short yield, just push the signal.
-      case _ =>
-        signals.offer(new Signal(name, args.toArray))
-    })
-  }
+
+  def add(block: Block, x: Int, y: Int, z: Int, id: Int) =
+    Drivers.driverFor(block) match {
+      case None => None
+      case Some(driver) if !components.contains(id) =>
+        val component = driver.instance.component(x, y, z)
+        components += id -> (component, driver)
+        driver.instance.onInstall(this, component)
+        signal("component_install", id)
+        Some(driver.instance)
+    }
+
+  def remove(id: Int) =
+    if (components.contains(id)) {
+      val (component, driver) = components(id)
+      components.remove(id)
+      driver.instance.onUninstall(this, component)
+      signal("component_uninstall", id)
+      true
+    }
+    else false
+
+  // ----------------------------------------------------------------------- //
 
   def readFromNBT(nbt: NBTTagCompound): Unit =
     saveMonitor.synchronized(this.synchronized {
@@ -347,7 +429,11 @@ class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext
     return false
   }
 
-  def init(): Boolean = {
+  // ----------------------------------------------------------------------- //
+  // Internals
+  // ----------------------------------------------------------------------- //
+
+  private def init(): Boolean = {
     // Creates a new state with all base libraries and the persistence library
     // loaded into it. This means the state has much more power than it
     // rightfully should have, so we sandbox it a bit in the following.
@@ -359,18 +445,38 @@ class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext
 
     try {
       // Push a couple of functions that override original Lua API functions or
-      // that add new functionality to it.1)
-      lua.getGlobal("os")
+      // that add new functionality to it.
+      lua.newTable()
 
-      // Return ingame time for os.time().
+      // Set up driver information callbacks, i.e. to query for the presence of
+      // components with a given ID, and their type.
       lua.pushJavaFunction(new JavaFunction() {
         def invoke(lua: LuaState): Int = {
-          // Minecraft starts days at 6 o'clock, so we add those six hours.
-          lua.pushNumber(worldTime + 6000)
+          lua.pushBoolean(components.contains(lua.checkInteger(1)))
           return 1
         }
       })
-      lua.setField(-2, "time")
+      lua.setField(-2, "exists")
+
+      lua.pushJavaFunction(new JavaFunction() {
+        def invoke(lua: LuaState): Int = {
+          val id = lua.checkInteger(1)
+          components.get(id) match {
+            case None => lua.pushNil()
+            case Some((component, driver)) =>
+              lua.pushString(driver.instance.componentName)
+          }
+          return 1
+        }
+      })
+      lua.setField(-2, "type")
+
+      // "Pop" the components table.
+      lua.setGlobal("component")
+
+      // Push a couple of functions that override original Lua API functions or
+      // that add new functionality to it.
+      lua.getGlobal("os")
 
       // Custom os.clock() implementation returning the time the computer has
       // been running, instead of the native library...
@@ -385,6 +491,29 @@ class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext
       })
       lua.setField(-2, "clock")
 
+      // Return ingame time for os.time().
+      lua.pushJavaFunction(new JavaFunction() {
+        def invoke(lua: LuaState): Int = {
+          // Game time is in ticks, so that each day has 24000 ticks, meaning
+          // one hour is game time divided by one thousand. Also, Minecraft
+          // starts days at 6 o'clock, so we add those six hours. Thus:
+          // timestamp = (time + 6000) / 1000[h] * 60[m] * 60[s] * 1000[ms]
+          lua.pushNumber((worldTime + 6000) * 60 * 60)
+          return 1
+        }
+      })
+      lua.setField(-2, "time")
+
+      // Date-time formatting using Java's formatting capabilities.
+      lua.pushJavaFunction(new JavaFunction() {
+        def invoke(lua: LuaState): Int = {
+          val calendar = Calendar.getInstance(Locale.ENGLISH);
+          calendar.setTimeInMillis(lua.checkInteger(1))
+          return 1
+        }
+      })
+      lua.setField(-2, "date")
+
       // Custom os.difftime(). For most Lua implementations this would be the
       // same anyway, but just to be on the safe side.
       lua.pushJavaFunction(new JavaFunction() {
@@ -494,8 +623,8 @@ class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext
       // building a table of permanent values used when persisting/unpersisting
       // the state.
       lua.newTable()
-      lua.setGlobal("drivers")
-      Drivers.injectInto(this)
+      lua.setGlobal("driver")
+      Drivers.installOn(this)
 
       // Run the boot script. This creates the global sandbox variable that is
       // used as the environment for any processes the kernel spawns, adds a
@@ -538,9 +667,14 @@ class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext
     return false
   }
 
-  def close(): Unit = stateMonitor.synchronized(
+  private def close(): Unit = stateMonitor.synchronized(
     if (state != State.Stopped) {
       state = State.Stopped
+
+      // Shutdown any installed components.
+      for ((component, driver) <- components.values)
+        driver.instance.onUninstall(this, component)
+
       lua.setTotalMemory(Integer.MAX_VALUE);
       lua.close()
       lua = null
@@ -595,15 +729,7 @@ class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext
         // Got a signal, inject it and call any handlers (if any).
         case signal => {
           lua.pushString(signal.name)
-          signal.args.foreach {
-            case arg: Byte => lua.pushInteger(arg)
-            case arg: Short => lua.pushInteger(arg)
-            case arg: Int => lua.pushInteger(arg)
-            case arg: Long => lua.pushNumber(arg)
-            case arg: Float => lua.pushNumber(arg)
-            case arg: Double => lua.pushNumber(arg)
-            case arg: String => lua.pushString(arg)
-          }
+          signal.args.foreach(lua.pushJavaObject)
           lua.resume(1, 1 + signal.args.length)
         }
       }
@@ -700,27 +826,27 @@ class Computer(val owner: IComputerEnvironment) extends IInternalComputerContext
     /** The computer is paused and waiting for the game to resume. */
     val DriverReturnPaused = Value("DriverReturnPaused")
   }
-
-  /** Singleton for requesting executors that run our Lua states. */
-  private object Executor {
-    val pool = Executors.newScheduledThreadPool(Config.threads,
-      new ThreadFactory() {
-        private val threadNumber = new AtomicInteger(1)
-
-        private val group = System.getSecurityManager() match {
-          case null => Thread.currentThread().getThreadGroup()
-          case s => s.getThreadGroup()
-        }
-
-        def newThread(r: Runnable): Thread = {
-          val name = "OpenComputers-" + threadNumber.getAndIncrement()
-          val thread = new Thread(group, r, name)
-          if (!thread.isDaemon())
-            thread.setDaemon(true)
-          if (thread.getPriority() != Thread.MIN_PRIORITY)
-            thread.setPriority(Thread.MIN_PRIORITY)
-          return thread
-        }
-      })
-  }
 }
+
+/** Singleton for requesting executors that run our Lua states. */
+private[computer] object Executor {
+  val pool = Executors.newScheduledThreadPool(Config.threads,
+    new ThreadFactory() {
+      private val threadNumber = new AtomicInteger(1)
+
+      private val group = System.getSecurityManager() match {
+        case null => Thread.currentThread().getThreadGroup()
+        case s => s.getThreadGroup()
+      }
+
+      def newThread(r: Runnable): Thread = {
+        val name = "OpenComputers-" + threadNumber.getAndIncrement()
+        val thread = new Thread(group, r, name)
+        if (!thread.isDaemon())
+          thread.setDaemon(true)
+        if (thread.getPriority() != Thread.MIN_PRIORITY)
+          thread.setPriority(Thread.MIN_PRIORITY)
+        return thread
+      }
+    })
+}
\ No newline at end of file
diff --git a/li/cil/oc/server/computer/Driver.scala b/li/cil/oc/server/computer/Driver.scala
index 1c94fa814..2d814431f 100644
--- a/li/cil/oc/server/computer/Driver.scala
+++ b/li/cil/oc/server/computer/Driver.scala
@@ -1,23 +1,43 @@
 package li.cil.oc.server.computer
 
 import java.lang.reflect.Method
-
+import scala.compat.Platform.EOL
+import scala.reflect.runtime.universe._
 import com.naef.jnlua.JavaFunction
+import com.naef.jnlua.LuaRuntimeException
 import com.naef.jnlua.LuaState
+import li.cil.oc.OpenComputers
+import li.cil.oc.api._
 
-import li.cil.oc.api.Callback
-import li.cil.oc.api.IDriver
-import li.cil.oc.common.computer.IInternalComputerContext
+class ItemDriver(val instance: IItemDriver) extends Driver
+class BlockDriver(val instance: IBlockDriver) extends Driver
 
-private[oc] class Driver(val driver: IDriver) {
-  def injectInto(context: IInternalComputerContext) {
+/**
+ * Wrapper for external drivers.
+ *
+ * We create one instance per registered driver of this. It is used to inject
+ * the API the driver offers into the computer, and, in particular, for
+ * generating the wrappers for the API functions, which are closures with the
+ * computer the API was installed into to provide context should a function
+ * require it.
+ */
+abstract private[oc] class Driver {
+  /** The actual driver as registered via the Drivers registry. */
+  def instance: IDriver
+
+  /** Installs this driver's API on the specified computer. */
+  def installOn(computer: Computer) {
     // Check if the component actually provides an API.
-    val api = driver.apiName
+    val api = instance.apiName
     if (api == null || api.isEmpty()) return
-    val lua = context.luaState
+    if (api.equals("component")) {
+      OpenComputers.log.warning("Trying to register API with reserved name 'component'.")
+      return
+    }
+    val lua = computer.lua
 
     // Get or create table holding API tables.
-    lua.getGlobal("drivers") // ... drivers?
+    lua.getGlobal("driver") // ... drivers?
     assert(!lua.isNil(-1)) // ... drivers
 
     // Get or create API table.
@@ -29,95 +49,125 @@ private[oc] class Driver(val driver: IDriver) {
       lua.setField(-3, api) // ... drivers api
     } // ... drivers api
 
-    for (method <- driver.getClass().getMethods())
-      method.getAnnotation(classOf[Callback]) match {
-        case null => Unit // No annotation.
-        case annotation => {
+    val mirror = runtimeMirror(instance.getClass.getClassLoader)
+    val instanceMirror = mirror.reflect(instance)
+    val instanceType = instanceMirror.symbol.typeSignature
+    for (method <- instanceType.members collect { case m if m.isMethod => m.asMethod })
+      method.annotations collect {
+        case annotation: Callback => {
           val name = annotation.name
           lua.getField(-1, name) // ... drivers api func?
           if (lua.isNil(-1)) { // ... drivers api nil
             // No such entry yet.
             lua.pop(1) // ... drivers api
-            lua.pushJavaFunction(new MethodWrapper(context, method)) // ... drivers api func
+            lua.pushJavaFunction(new APIClosure(mirror, instanceMirror.reflectMethod(method), computer)) // ... drivers api func
             lua.setField(-2, name) // ... drivers api
           }
           else { // ... drivers api func
             // Entry already exists, skip it.
             lua.pop(1) // ... drivers api
-            // TODO Log warning properly via a logger.
-            println("WARNING: Duplicate API entry, ignoring: " + api + "." + name)
+            // Note that we can be sure it's an issue with two drivers
+            // colliding, because this is guaranteed to run before any user
+            // code had a chance to mess with the table.
+            OpenComputers.log.warning(String.format(
+              "Duplicate API entry, ignoring %s.%s of driver %s.",
+              api, name, instance.componentName))
           }
         }
       } // ... drivers api
     lua.pop(2) // ...
-  }
 
-  private class MethodWrapper(val context: IInternalComputerContext, val method: Method) extends JavaFunction {
-    def invoke(state: LuaState): Int = {
-      return 0
+    // Run custom init script.
+    val apiCode = instance.apiCode
+    if (apiCode != null) {
+      try {
+        lua.load(apiCode, instance.apiName, "t") // ... func
+        apiCode.close()
+        lua.call(0, 0) // ...
+      }
+      catch {
+        case e: LuaRuntimeException =>
+          OpenComputers.log.warning(String.format(
+            "Initialization code of driver %s threw an error: %s",
+            instance.componentName, e.getLuaStackTrace.mkString("", EOL, EOL)))
+        case e: Throwable =>
+          OpenComputers.log.warning(String.format(
+            "Initialization code of driver %s threw an error: %s",
+            instance.componentName, e.getStackTraceString))
+      }
     }
   }
 
-  /*
-  private class MethodWrapper(val context: IInternalComputerContext, val method: Method) extends JavaFunction {
-    private val classOfBoolean = classOf[Boolean]
-    private val classOfByte = classOf[Byte]
-    private val classOfShort = classOf[Short]
-    private val classOfInteger = classOf[Int]
-    private val classOfLong = classOf[Long]
-    private val classOfFloat = classOf[Float]
-    private val classOfDouble = classOf[Double]
-    private val classOfString = classOf[String]
-    private val parameterTypes = method.getParameterTypes.zipWithIndex
-    private val parameterCount = parameterTypes.size
-    private val returnType = method.getReturnType
-    private val returnsTuple = returnType.isInstanceOf[Array[Object]]
-    private val returnsNothing = returnType.equals(Void.TYPE)
+  /**
+   * This class is used to represent closures for driver API callbacks.
+   *
+   * It stores the computer it is used by, to allow passing it along as the
+   * {@see IComputerContext} for callbacks if they specify it as a parameter,
+   * and for interacting with the Lua state to pull parameters and push results
+   * returned from the callback.
+   */
+  private class APIClosure(mirror: Mirror, val method: MethodMirror, val computer: Computer) extends JavaFunction {
+    /**
+     * Based on the method's parameters we build a list of transformations
+     * that convert Lua input to the expected parameter type.
+     */
+    val parameterTransformations = buildParameterTransformations(mirror, method.symbol)
 
-    // TODO Rework all of this, most likely won't work because of type erasure.
-    def invoke(state: LuaState): Int = {
-      // Parse the parameters, convert them to Java types.
-      val parameters = Array(context) ++ parameterTypes.map {
-        //case (classOfBoolean, i) => boolean2Boolean(state.checkBoolean(i + 1))
-        case (classOfByte, i) => java.lang.Byte.valueOf(state.checkInteger(i + 1).toByte)
-        case (classOfShort, i) => java.lang.Short.valueOf(state.checkInteger(i + 1).toShort)
-        case (classOfInteger, i) => java.lang.Integer.valueOf(state.checkInteger(i + 1))
-        case (classOfLong, i) => java.lang.Long.valueOf(state.checkInteger(i + 1).toLong)
-        case (classOfFloat, i) => java.lang.Float.valueOf(state.checkNumber(i + 1).toFloat)
-        case (classOfDouble, i) => java.lang.Double.valueOf(state.checkNumber(i + 1))
-        case (classOfString, i) => state.checkString(i + 1)
-        case _ => null
-      }
+    /**
+     * Based on the method's return value we build a callback that will push
+     * that result to the stack, if any, and return the number of pushed values.
+     */
+    val returnTransformation = buildReturnTransformation(method.symbol)
 
-      // Call the actual function, grab the result, if any.
-      val result = call(parameters: _*)
-
-      // Check the result, convert it to Lua.
-      if (returnsTuple) {
-        val array = result.asInstanceOf[Array[Object]]
-        array.foreach(v => push(state, v, v.getClass()))
-        return array.length
-      }
-      else if (returnsNothing) {
-        return 0
-      }
-      else {
-        push(state, result, returnType)
-        return 1
-      }
-    }
-
-    private def push(state: LuaState, value: Object, clazz: Class[_]) = clazz match {
-      case classOfBoolean => state.pushBoolean(value.asInstanceOf[Boolean])
-      case classOfInteger => state.pushNumber(value.asInstanceOf[Int])
-      case classOfDouble => state.pushNumber(value.asInstanceOf[Double])
-      case classOfString => state.pushString(value.asInstanceOf[String])
-      case _ => state.pushNil()
-    }
-
-    protected def call(args: AnyRef*) = {
-      method.invoke(driver, args)
+    /** This is the function actually called from the Lua state. */
+    def invoke(lua: LuaState): Int = {
+      return returnTransformation(computer,
+        method(parameterTransformations.map(_(computer)): _*))
     }
   }
-*/
+
+  /**
+   * This generates the transformation functions that are used to convert the
+   * Lua parameters to Java types to be passed on to the API function.
+   */
+  private def buildParameterTransformations(mirror: Mirror, method: MethodSymbol): Array[Computer => Any] = {
+    // No parameters?
+    if (method.paramss.length == 0 || method.paramss(0).length == 0) {
+      return Array()
+    }
+
+    val params = method.paramss(0)
+
+    // Do we have a callback function that wants to handle its arguments
+    // manually? If so, convert all arguments and pack them into an array.
+    // TODO test if this really works.
+    if (params.length == 2 &&
+      params(0) == typeOf[IComputerContext].typeSymbol &&
+      params(1) == typeOf[Array[Any]].typeSymbol) {
+      Array(
+        (c: Computer) => c,
+        (c: Computer) => (1 to c.lua.getTop()).map(
+          c.lua.toJavaObject(_, classOf[Object])))
+    }
+    // Otherwise build converters based on the method's signature.
+    else params.zipWithIndex.map {
+      case (t, i) if t == typeOf[IComputerContext].typeSymbol => (c: Computer) => c
+      case (t, i) => {
+        val clazz = mirror.runtimeClass(t.asClass)
+        (c: Computer) => c.lua.toJavaObject(i, clazz)
+      }
+    }.toArray
+  }
+
+  /**
+   * This generates the transformation function that is used to convert the
+   * return value of an API function to a Lua type and push it onto the stack,
+   * returning the number of values pushed. We need that number in case we
+   * return a tuple (i.e. the function returned an array).
+   */
+  private def buildReturnTransformation(method: MethodSymbol): (Computer, Any) => Int =
+    method.returnType match {
+      case t if t == Unit => (c, v) => 0
+      case t => (c, v) => c.lua.pushJavaObject(v); 1
+    }
 }
\ No newline at end of file
diff --git a/li/cil/oc/server/computer/Drivers.scala b/li/cil/oc/server/computer/Drivers.scala
index 8927c3dc9..4bbe30198 100644
--- a/li/cil/oc/server/computer/Drivers.scala
+++ b/li/cil/oc/server/computer/Drivers.scala
@@ -1,37 +1,48 @@
 package li.cil.oc.server.computer
 
-import scala.collection.mutable.Map
+import scala.collection.mutable.ArrayBuffer
 
 import li.cil.oc.api.IBlockDriver
 import li.cil.oc.api.IItemDriver
-import li.cil.oc.common.computer.IInternalComputerContext
 import net.minecraft.block.Block
 import net.minecraft.item.ItemStack
 
 /**
  * This class keeps track of registered drivers and provides installation logic
- * for each registered component type.
+ * 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 {
-  private val blocks = Map.empty[Int, Driver]
-  private val items = Map.empty[Int, Driver]
+  /** 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 adds it to the list of
-   * available components.
+   * exists a driver for the changed block, and if so installs it.
    *
    * @param driver the driver for that block type.
    */
-  def addDriver(driver: IBlockDriver) {
-    if (blocks.contains(driver.blockType.blockID)) return
-    blocks += driver.blockType.blockID -> new Driver(driver)
+  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)
   }
 
   /**
@@ -42,15 +53,34 @@ private[oc] object Drivers {
    *
    * @param driver the driver for that item type.
    */
-  def addDriver(driver: IItemDriver) {
-    if (items.contains(driver.itemType.itemID)) return
-    items += driver.itemType.itemID -> new Driver(driver)
+  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)
   }
 
-  def getDriver(block: Block) = blocks(block.blockID)
+  /**
+   * 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(block: Block) = blocks.find(_.instance.worksWith(block))
 
-  def getDriver(item: ItemStack) = blocks(item.itemID)
+  /**
+   * 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))
 
-  def injectInto(context: IInternalComputerContext) =
-    (blocks.values ++ items.values).foreach(_.injectInto(context))
+  /**
+   * 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))
 }
diff --git a/li/cil/oc/server/computer/IComputerContext.scala b/li/cil/oc/server/computer/IComputerContext.scala
deleted file mode 100644
index 1db5cea9d..000000000
--- a/li/cil/oc/server/computer/IComputerContext.scala
+++ /dev/null
@@ -1,9 +0,0 @@
-package li.cil.oc.server.computer
-
-import com.naef.jnlua.LuaState
-
-import net.minecraft.nbt.NBTTagCompound
-
-trait IComputerContext {
-  def signal(name: String, args: Any*)
-}
\ No newline at end of file
diff --git a/li/cil/oc/server/drivers/HDD.scala b/li/cil/oc/server/drivers/HDD.scala
index 1382d6e12..455137cbd 100644
--- a/li/cil/oc/server/drivers/HDD.scala
+++ b/li/cil/oc/server/drivers/HDD.scala
@@ -1,37 +1,35 @@
 package li.cil.oc.server.drivers
 
-import li.cil.oc.Items
+import li.cil.oc.Config
+import li.cil.oc.api.Callback
 import li.cil.oc.api.ComponentType
 import li.cil.oc.api.IItemDriver
 import li.cil.oc.server.components.Disk
 import net.minecraft.item.ItemStack
-import li.cil.oc.api.Callback
 
 object HDDDriver extends IItemDriver {
   def componentName = "disk"
 
-  def apiName = "disk"
-
-  def apiCode = null
+  override def apiName = "disk"
 
   @Callback(name = "mount")
-  def mount(component: Object, path: String) {
+  def mount(component: Any, path: String) {
 
   }
 
-  def componentType = ComponentType.HDD
+  def worksWith(item: ItemStack) = item.itemID == Config.itemHDDId
 
-  def itemType = new ItemStack(Items.hdd)
+  def componentType(item: ItemStack) = ComponentType.HDD
 
-  def getComponent(item: ItemStack) = new HDDComponent(item)
+  def component(item: ItemStack) = new HDDComponent(item)
 
-  def close(component: Object) {
+  def close(component: Any) {
     component.asInstanceOf[HDDComponent].close()
   }
 }
 
 class HDDComponent(val item: ItemStack) {
   val disk = new Disk()
-  
+
   def close() = disk.close()
 }
\ No newline at end of file