/* NSC -- new Scala compiler
 * Copyright 2005-2014 LAMP/EPFL
 * @author  Martin Odersky
 */

package scala.tools.nsc.backend.jvm

import scala.tools.asm.tree.{InsnList, AbstractInsnNode, ClassNode, MethodNode}
import java.io.{StringWriter, PrintWriter}
import scala.tools.asm.util.{CheckClassAdapter, TraceClassVisitor, TraceMethodVisitor, Textifier}
import scala.tools.asm.{ClassWriter, Attribute, ClassReader}
import scala.collection.convert.decorateAsScala._
import scala.tools.nsc.backend.jvm.opt.InlineInfoAttributePrototype

object AsmUtils {

  /**
   * Print the bytecode of methods generated by GenBCode to the standard output. Only methods
   * whose name contains `traceMethodPattern` are traced.
   */
  final val traceMethodEnabled = false
  final val traceMethodPattern = ""

  /**
   * Print the bytecode of classes generated by GenBCode to the standard output.
   */
  final val traceClassEnabled = false
  final val traceClassPattern = ""

  /**
   * Print the bytedcode of classes as they are serialized by the ASM library. The serialization
   * performed by `asm.ClassWriter` can change the code generated by GenBCode. For example, it
   * introduces stack map frames, it computes the maximal stack sizes, and it replaces dead
   * code by NOPs (see also https://github.com/scala/scala/pull/3726#issuecomment-42861780).
   */
  final val traceSerializedClassEnabled = false
  final val traceSerializedClassPattern = ""

  def traceMethod(mnode: MethodNode): Unit = {
    println(s"Bytecode for method ${mnode.name}")
    println(textify(mnode))
  }

  def traceClass(cnode: ClassNode): Unit = {
    println(s"Bytecode for class ${cnode.name}")
    println(textify(cnode))
  }

  def traceClass(bytes: Array[Byte]): Unit = traceClass(readClass(bytes))

  def readClass(bytes: Array[Byte]): ClassNode = {
    val node = new ClassNode()
    new ClassReader(bytes).accept(node, Array[Attribute](InlineInfoAttributePrototype), 0)
    node
  }

  /**
   * Returns a human-readable representation of the cnode ClassNode.
   */
  def textify(cnode: ClassNode): String = {
    val trace = new TraceClassVisitor(new PrintWriter(new StringWriter))
    cnode.accept(trace)
    val sw = new StringWriter
    val pw = new PrintWriter(sw)
    trace.p.print(pw)
    sw.toString
  }

  /**
   * Returns a human-readable representation of the code in the mnode MethodNode.
   */
  def textify(mnode: MethodNode): String = {
    val trace = new TraceClassVisitor(new PrintWriter(new StringWriter))
    mnode.accept(trace)
    val sw = new StringWriter
    val pw = new PrintWriter(sw)
    trace.p.print(pw)
    sw.toString
  }

  /**
   * Returns a human-readable representation of the given instruction.
   */
  def textify(insn: AbstractInsnNode): String = {
    val trace = new TraceMethodVisitor(new Textifier)
    insn.accept(trace)
    val sw = new StringWriter
    val pw = new PrintWriter(sw)
    trace.p.print(pw)
    sw.toString.trim
  }

  /**
   * Returns a human-readable representation of the given instruction sequence.
   */
  def textify(insns: Iterator[AbstractInsnNode]): String = {
    val trace = new TraceMethodVisitor(new Textifier)
    insns.foreach(_.accept(trace))
    val sw: StringWriter = new StringWriter
    val pw: PrintWriter = new PrintWriter(sw)
    trace.p.print(pw)
    sw.toString.trim
  }

  /**
   * Returns a human-readable representation of the given instruction sequence.
   */
  def textify(insns: InsnList): String = textify(insns.iterator().asScala)

  /**
   * Run ASM's CheckClassAdapter over a class. Returns None if no problem is found, otherwise
   * Some(msg) with the verifier's error message.
   */
  def checkClass(classNode: ClassNode): Option[String] = {
    val cw = new ClassWriter(ClassWriter.COMPUTE_MAXS)
    classNode.accept(cw)
    val sw = new StringWriter()
    val pw = new PrintWriter(sw)
    CheckClassAdapter.verify(new ClassReader(cw.toByteArray), false, pw)
    val res = sw.toString
    if (res.isEmpty) None else Some(res)
  }
}
