package dotty.tools
package dotc

import core._
import Contexts._
import Periods._
import Symbols._
import Scopes._
import typer.{FrontEnd, Typer, Mode, ImportInfo, RefChecks}
import reporting.ConsoleReporter
import dotty.tools.dotc.core.Phases.Phase
import dotty.tools.dotc.transform._
import dotty.tools.dotc.transform.TreeTransforms.{TreeTransform, TreeTransformer}
import dotty.tools.dotc.core.DenotTransformers.DenotTransformer
import dotty.tools.dotc.core.Denotations.SingleDenotation

class Compiler {

  /** Meta-ordering constraint:
   *
   *  DenotTransformers that change the signature of  their denotation's info must go
   *  after erasure. The reason is that denotations are permanently referred to by
   *  TermRefs which contain a signature. If the signature of a symbol would change,
   *  all refs to it would become outdated - they could not be dereferenced in the
   *  new phase.
   *
   *  As an example, addGetters would change a field
   *
   *     val x: T
   *
   *  to a method
   *
   *     def x: T
   *
   *  but this would affect the signature of `x` (goes from NotAMethod to a method
   *  signature). So we can't do this before erasure.
   *
   *  After erasure, signature changing denot-transformers are OK because erasure
   *  will make sure that only term refs with fixed SymDenotations survive beyond it. This
   *  is possible because:
   *
   *   - splitter has run, so every ident or select refers to a unique symbol
   *   - after erasure, asSeenFrom is the identity, so every reference has a
   *     plain SymDenotation, as opposed to a UniqueRefDenotation.
   */
  def phases: List[List[Phase]] =
    List(
      List(new FrontEnd),
      List(new FirstTransform,
           new SyntheticMethods),
      List(new SuperAccessors),
      // pickling goes here
      List(new RefChecks,
           new ElimRepeated,
           new ElimLocals),
      List(new ExtensionMethods),
      List(new TailRec),
      List(new PatternMatcher,
           new ExplicitOuter,
           // new LazyValTranformContext().transformer, // disabled, awaiting fixes
           new Splitter),
      List(new ElimByName,
           new TypeTestsCasts,
           new InterceptedMethods,
           new Literalize),
      List(new Erasure),
      List(new CapturedVars)
    )

  var runId = 1
  def nextRunId = {
    runId += 1; runId
  }

  /** Produces the following contexts, from outermost to innermost
   *
   *    bootStrap:   A context with next available runId and a scope consisting of
   *                 the RootPackage _root_
   *    start        A context with RootClass as owner and the necessary initializations
   *                 for type checking.
   *    imports      For each element of RootImports, an import context
   */
  def rootContext(implicit ctx: Context): Context = {
    ctx.definitions.init(ctx)
    ctx.usePhases(phases)
    val rootScope = new MutableScope
    val bootstrap = ctx.fresh
      .setPeriod(Period(nextRunId, FirstPhaseId))
      .setScope(rootScope)
    rootScope.enter(ctx.definitions.RootPackage)(bootstrap)
    val start = bootstrap.fresh
      .setOwner(defn.RootClass)
      .setTyper(new Typer)
      .setMode(Mode.ImplicitsEnabled)
      .setTyperState(new MutableTyperState(ctx.typerState, new ConsoleReporter()(ctx), isCommittable = true))
    ctx.definitions.init(start) // set context of definitions to start
    def addImport(ctx: Context, sym: Symbol) =
      ctx.fresh.setImportInfo(ImportInfo.rootImport(sym)(ctx))
    (start.setRunInfo(new RunInfo(start)) /: defn.RootImports)(addImport)
  }

  def newRun(implicit ctx: Context): Run = {
    try new Run(this)(rootContext)
    finally {
      ctx.base.reset()
      ctx.runInfo.clear()
    }
  }
}