/* NSC -- new Scala compiler
 * Copyright 2005-2012 LAMP/EPFL
 * @author  Martin Odersky
 */


package scala
package tools.nsc
package backend
package jvm

import scala.collection.{ mutable, immutable }
import scala.annotation.switch

import scala.tools.asm

/*
 *  Prepare in-memory representations of classfiles using the ASM Tree API, and serialize them to disk.
 *
 *  Three pipelines are at work, each taking work items from a queue dedicated to that pipeline:
 *
 *  (There's another pipeline so to speak, the one that populates queue-1 by traversing a CompilationUnit until ClassDefs are found,
 *   but the "interesting" pipelines are the ones described below)
 *
 *    (1) In the first queue, an item consists of a ClassDef along with its arrival position.
 *        This position is needed at the time classfiles are serialized to disk,
 *        so as to emit classfiles in the same order CleanUp handed them over.
 *        As a result, two runs of the compiler on the same files produce jars that are identical on a byte basis.
 *        See `ant test.stability`
 *
 *    (2) The second queue contains items where a ClassDef has been lowered into:
 *          (a) an optional mirror class,
 *          (b) a plain class, and
 *          (c) an optional bean class.
 *
 *    (3) The third queue contains items ready for serialization.
 *        It's a priority queue that follows the original arrival order,
 *        so as to emit identical jars on repeated compilation of the same sources.
 *
 *  Plain, mirror, and bean classes are built respectively by PlainClassBuilder, JMirrorBuilder, and JBeanInfoBuilder.
 *
 *  @author  Miguel Garcia, http://lamp.epfl.ch/~magarcia/ScalaCompilerCornerReloaded/
 *  @version 1.0
 *
 */
abstract class GenBCode extends BCodeSyncAndTry {
  import global._

  val phaseName = "jvm"

  override def newPhase(prev: Phase) = new BCodePhase(prev)

  final class PlainClassBuilder(cunit: CompilationUnit) extends SyncAndTryBuilder(cunit)

  class BCodePhase(prev: Phase) extends StdPhase(prev) {

    override def name = phaseName
    override def description = "Generate bytecode from ASTs using the ASM library"
    override def erasedTypes = true

    private var bytecodeWriter  : BytecodeWriter   = null
    private var mirrorCodeGen   : JMirrorBuilder   = null
    private var beanInfoCodeGen : JBeanInfoBuilder = null

    /* ---------------- q1 ---------------- */

    case class Item1(arrivalPos: Int, cd: ClassDef, cunit: CompilationUnit) {
      def isPoison = { arrivalPos == Int.MaxValue }
    }
    private val poison1 = Item1(Int.MaxValue, null, null)
    private val q1 = new java.util.LinkedList[Item1]

    /* ---------------- q2 ---------------- */

    case class Item2(arrivalPos:   Int,
                     mirror:       asm.tree.ClassNode,
                     plain:        asm.tree.ClassNode,
                     bean:         asm.tree.ClassNode,
                     outFolder:    scala.tools.nsc.io.AbstractFile) {
      def isPoison = { arrivalPos == Int.MaxValue }
    }

    private val poison2 = Item2(Int.MaxValue, null, null, null, null)
    private val q2 = new _root_.java.util.LinkedList[Item2]

    /* ---------------- q3 ---------------- */

    /*
     *  An item of queue-3 (the last queue before serializing to disk) contains three of these
     *  (one for each of mirror, plain, and bean classes).
     *
     *  @param jclassName  internal name of the class
     *  @param jclassBytes bytecode emitted for the class SubItem3 represents
     */
    case class SubItem3(
      jclassName:  String,
      jclassBytes: Array[Byte]
    )

    case class Item3(arrivalPos: Int,
                     mirror:     SubItem3,
                     plain:      SubItem3,
                     bean:       SubItem3,
                     outFolder:  scala.tools.nsc.io.AbstractFile) {

      def isPoison  = { arrivalPos == Int.MaxValue }
    }
    private val i3comparator = new java.util.Comparator[Item3] {
      override def compare(a: Item3, b: Item3) = {
        if (a.arrivalPos < b.arrivalPos) -1
        else if (a.arrivalPos == b.arrivalPos) 0
        else 1
      }
    }
    private val poison3 = Item3(Int.MaxValue, null, null, null, null)
    private val q3 = new java.util.PriorityQueue[Item3](1000, i3comparator)

    /*
     *  Pipeline that takes ClassDefs from queue-1, lowers them into an intermediate form, placing them on queue-2
     */
    class Worker1(needsOutFolder: Boolean) {

      val caseInsensitively = mutable.Map.empty[String, Symbol]

      def run() {
        while (true) {
          val item = q1.poll
          if (item.isPoison) {
            q2 add poison2
            return
          }
          else {
            try   { visit(item) }
            catch {
              case ex: Throwable =>
                ex.printStackTrace()
                error(s"Error while emitting ${item.cunit.source}\n${ex.getMessage}")
            }
          }
        }
      }

      /*
       *  Checks for duplicate internal names case-insensitively,
       *  builds ASM ClassNodes for mirror, plain, and bean classes;
       *  enqueues them in queue-2.
       *
       */
      def visit(item: Item1) {
        val Item1(arrivalPos, cd, cunit) = item
        val claszSymbol = cd.symbol

        // GenASM checks this before classfiles are emitted, https://github.com/scala/scala/commit/e4d1d930693ac75d8eb64c2c3c69f2fc22bec739
        val lowercaseJavaClassName = claszSymbol.javaClassName.toLowerCase
        caseInsensitively.get(lowercaseJavaClassName) match {
          case None =>
            caseInsensitively.put(lowercaseJavaClassName, claszSymbol)
          case Some(dupClassSym) =>
            item.cunit.warning(
              claszSymbol.pos,
              s"Class ${claszSymbol.javaClassName} differs only in case from ${dupClassSym.javaClassName}. " +
              "Such classes will overwrite one another on case-insensitive filesystems."
            )
        }

        // -------------- mirror class, if needed --------------
        val mirrorC =
          if (isStaticModule(claszSymbol) && isTopLevelModule(claszSymbol)) {
            if (claszSymbol.companionClass == NoSymbol) {
              mirrorCodeGen.genMirrorClass(claszSymbol, cunit)
            } else {
              log(s"No mirror class for module with linked class: ${claszSymbol.fullName}")
              null
            }
          } else null

        // -------------- "plain" class --------------
        val pcb = new PlainClassBuilder(cunit)
        pcb.genPlainClass(cd)
        val outF = if (needsOutFolder) getOutFolder(claszSymbol, pcb.thisName, cunit) else null;
        val plainC = pcb.cnode

        // -------------- bean info class, if needed --------------
        val beanC =
          if (claszSymbol hasAnnotation BeanInfoAttr) {
            beanInfoCodeGen.genBeanInfoClass(
              claszSymbol, cunit,
              fieldSymbols(claszSymbol),
              methodSymbols(cd)
            )
          } else null

          // ----------- hand over to pipeline-2

        val item2 =
          Item2(arrivalPos,
                mirrorC, plainC, beanC,
                outF)

        q2 add item2 // at the very end of this method so that no Worker2 thread starts mutating before we're done.

      } // end of method visit(Item1)

    } // end of class BCodePhase.Worker1

    /*
     *  Pipeline that takes ClassNodes from queue-2. The unit of work depends on the optimization level:
     *
     *    (a) no optimization involves:
     *          - converting the plain ClassNode to byte array and placing it on queue-3
     */
    class Worker2 {

      def run() {
        while (true) {
          val item = q2.poll
          if (item.isPoison) {
            q3 add poison3
            return
          }
          else {
            try   { addToQ3(item) }
            catch {
              case ex: Throwable =>
                ex.printStackTrace()
                error(s"Error while emitting ${item.plain.name}\n${ex.getMessage}")
            }
          }
        }
      }

      private def addToQ3(item: Item2) {

        def getByteArray(cn: asm.tree.ClassNode): Array[Byte] = {
          val cw = new CClassWriter(extraProc)
          cn.accept(cw)
          cw.toByteArray
        }

        val Item2(arrivalPos, mirror, plain, bean, outFolder) = item

        val mirrorC = if (mirror == null) null else SubItem3(mirror.name, getByteArray(mirror))
        val plainC  = SubItem3(plain.name, getByteArray(plain))
        val beanC   = if (bean == null)   null else SubItem3(bean.name, getByteArray(bean))

        q3 add Item3(arrivalPos, mirrorC, plainC, beanC, outFolder)

      }

    } // end of class BCodePhase.Worker2

    var arrivalPos = 0

    /*
     *  A run of the BCodePhase phase comprises:
     *
     *    (a) set-up steps (most notably supporting maps in `BCodeTypes`,
     *        but also "the" writer where class files in byte-array form go)
     *
     *    (b) building of ASM ClassNodes, their optimization and serialization.
     *
     *    (c) tear down (closing the classfile-writer and clearing maps)
     *
     */
    override def run() {

      arrivalPos = 0 // just in case
      scalaPrimitives.init
      initBCodeTypes()

      // initBytecodeWriter invokes fullName, thus we have to run it before the typer-dependent thread is activated.
      bytecodeWriter  = initBytecodeWriter(cleanup.getEntryPoints)
      mirrorCodeGen   = new JMirrorBuilder
      beanInfoCodeGen = new JBeanInfoBuilder

      val needsOutfileForSymbol = bytecodeWriter.isInstanceOf[ClassBytecodeWriter]
      buildAndSendToDisk(needsOutfileForSymbol)

      // closing output files.
      bytecodeWriter.close()

      /* TODO Bytecode can be verified (now that all classfiles have been written to disk)
       *
       * (1) asm.util.CheckAdapter.verify()
       *       public static void verify(ClassReader cr, ClassLoader loader, boolean dump, PrintWriter pw)
       *     passing a custom ClassLoader to verify inter-dependent classes.
       *     Alternatively,
       *       - an offline-bytecode verifier could be used (e.g. Maxine brings one as separate tool).
       *       - -Xverify:all
       *
       * (2) if requested, check-java-signatures, over and beyond the syntactic checks in `getGenericSignature()`
       *
       */

      // clearing maps
      clearBCodeTypes()
    }

    /*
     *  Sequentially:
     *    (a) place all ClassDefs in queue-1
     *    (b) dequeue one at a time from queue-1, convert it to ASM ClassNode, place in queue-2
     *    (c) dequeue one at a time from queue-2, convert it to byte-array,    place in queue-3
     *    (d) serialize to disk by draining queue-3.
     */
    private def buildAndSendToDisk(needsOutFolder: Boolean) {

      feedPipeline1()
      (new Worker1(needsOutFolder)).run()
      (new Worker2).run()
      drainQ3()

    }

    /* Feed pipeline-1: place all ClassDefs on q1, recording their arrival position. */
    private def feedPipeline1() {
      super.run()
      q1 add poison1
    }

    /* Pipeline that writes classfile representations to disk. */
    private def drainQ3() {

      def sendToDisk(cfr: SubItem3, outFolder: scala.tools.nsc.io.AbstractFile) {
        if (cfr != null){
          val SubItem3(jclassName, jclassBytes) = cfr
          try {
            val outFile =
              if (outFolder == null) null
              else getFileForClassfile(outFolder, jclassName, ".class")
            bytecodeWriter.writeClass(jclassName, jclassName, jclassBytes, outFile)
          }
          catch {
            case e: FileConflictException =>
              error(s"error writing $jclassName: ${e.getMessage}")
          }
        }
      }

      var moreComing = true
      // `expected` denotes the arrivalPos whose Item3 should be serialized next
      var expected = 0

      while (moreComing) {
        val incoming = q3.poll
        moreComing   = !incoming.isPoison
        if (moreComing) {
          val item = incoming
          val outFolder = item.outFolder
          sendToDisk(item.mirror, outFolder)
          sendToDisk(item.plain,  outFolder)
          sendToDisk(item.bean,   outFolder)
          expected += 1
        }
      }

      // we're done
      assert(q1.isEmpty, s"Some ClassDefs remained in the first queue: $q1")
      assert(q2.isEmpty, s"Some classfiles remained in the second queue: $q2")
      assert(q3.isEmpty, s"Some classfiles weren't written to disk: $q3")

    }

    override def apply(cunit: CompilationUnit): Unit = {

      def gen(tree: Tree) {
        tree match {
          case EmptyTree            => ()
          case PackageDef(_, stats) => stats foreach gen
          case cd: ClassDef         =>
            q1 add Item1(arrivalPos, cd, cunit)
            arrivalPos += 1
        }
      }

      gen(cunit.body)
    }

  } // end of class BCodePhase

} // end of class GenBCode
