// SPDX-License-Identifier: Apache-2.0

package firrtl.stage.phases

import firrtl.{AnnotationSeq, ChirrtlForm, CircuitState, Compiler => FirrtlCompiler, Transform, seqToAnnoSeq}
import firrtl.options.{Dependency, Phase, PhasePrerequisiteException, Translator}
import firrtl.stage.{CompilerAnnotation, FirrtlCircuitAnnotation, Forms, RunFirrtlTransformAnnotation}
import firrtl.stage.TransformManager.TransformDependency

import scala.collection.mutable

/** An encoding of the information necessary to run the FIRRTL compiler once */
private[stage] case class CompilerRun(
  stateIn:    CircuitState,
  stateOut:   Option[CircuitState],
  transforms: Seq[Transform],
  compiler:   Option[FirrtlCompiler])

/** An encoding of possible defaults for a [[CompilerRun]] */
private[stage] case class Defaults(
  annotations: AnnotationSeq = Seq.empty,
  transforms:  Seq[Transform] = Seq.empty,
  compiler:    Option[FirrtlCompiler] = None)

/** Runs the FIRRTL compilers on an [[AnnotationSeq]]. If the input [[AnnotationSeq]] contains more than one circuit
  * (i.e., more than one [[firrtl.stage.FirrtlCircuitAnnotation FirrtlCircuitAnnotation]]), then annotations will be
  * broken up and each run will be executed in parallel.
  *
  * The [[AnnotationSeq]] will be chunked up into compiler runs using the following algorithm. All annotations that
  * occur before the first [[firrtl.stage.FirrtlCircuitAnnotation FirrtlCircuitAnnotation]] are treated as global
  * annotations that apply to all circuits. Annotations after a circuit are only associated with their closest
  * preceeding circuit. E.g., for the following annotations (where A, B, and C are some annotations):
  *
  *    A(a), FirrtlCircuitAnnotation(x), B, FirrtlCircuitAnnotation(y), A(b), C, FirrtlCircuitAnnotation(z)
  *
  * Then this will result in three compiler runs:
  *   - FirrtlCircuitAnnotation(x): A(a), B
  *   - FirrtlCircuitAnnotation(y): A(a), A(b), C
  *   - FirrtlCircuitAnnotation(z): A(a)
  *
  * A(a) is a default, global annotation. B binds to FirrtlCircuitAnnotation(x). A(a), A(b), and C bind to
  * FirrtlCircuitAnnotation(y). Note: A(b) ''may'' overwrite A(a) if this is a CompilerAnnotation.
  * FirrtlCircuitAnnotation(z) has no annotations, so it only gets the default A(a).
  */
class Compiler extends Phase with Translator[AnnotationSeq, Seq[CompilerRun]] {

  override def prerequisites =
    Seq(
      Dependency[AddDefaults],
      Dependency[AddImplicitEmitter],
      Dependency[Checks],
      Dependency[AddCircuit],
      Dependency[AddImplicitOutputFile]
    )

  override def optionalPrerequisiteOf = Seq.empty

  override def invalidates(a: Phase) = false

  /** Convert an [[AnnotationSeq]] into a sequence of compiler runs. */
  protected def aToB(a: AnnotationSeq): Seq[CompilerRun] = {
    var foundFirstCircuit = false
    val c = mutable.ArrayBuffer.empty[CompilerRun]
    a.foldLeft(Defaults()) {
      case (d, FirrtlCircuitAnnotation(circuit)) =>
        foundFirstCircuit = true
        CompilerRun(CircuitState(circuit, ChirrtlForm, d.annotations, None), None, d.transforms, d.compiler) +=: c
        d
      case (d, a) if foundFirstCircuit =>
        a match {
          case RunFirrtlTransformAnnotation(transform) =>
            c(0) = c(0).copy(transforms = transform +: c(0).transforms)
            d
          case CompilerAnnotation(compiler) =>
            c(0) = c(0).copy(compiler = Some(compiler))
            d
          case annotation =>
            val state = c(0).stateIn
            c(0) = c(0).copy(stateIn = state.copy(annotations = annotation +: state.annotations))
            d
        }
      case (d, a) if !foundFirstCircuit =>
        a match {
          case RunFirrtlTransformAnnotation(transform) => d.copy(transforms = transform +: d.transforms)
          case CompilerAnnotation(compiler)            => d.copy(compiler = Some(compiler))
          case annotation                              => d.copy(annotations = annotation +: d.annotations)
        }
    }
    c.toSeq
  }

  /** Expand compiler output back into an [[AnnotationSeq]]. Annotations used in the construction of the compiler run are
    * removed ([[CompilerAnnotation]]s and [[RunFirrtlTransformAnnotation]]s).
    */
  protected def bToA(b: Seq[CompilerRun]): AnnotationSeq =
    b.flatMap(bb => FirrtlCircuitAnnotation(bb.stateOut.get.circuit) +: bb.stateOut.get.annotations)

  /** Run the FIRRTL compiler some number of times. If more than one run is specified, a parallel collection will be
    * used.
    */
  protected def internalTransform(b: Seq[CompilerRun]): Seq[CompilerRun] = {
    def f(c: CompilerRun): CompilerRun = {
      val targets = c.compiler match {
        case Some(d) => c.transforms.reverse.map(Dependency.fromTransform(_)) ++ compilerToTransforms(d)
        case None =>
          val hasEmitter = c.transforms.collectFirst { case _: firrtl.Emitter => true }.isDefined
          if (!hasEmitter) {
            throw new PhasePrerequisiteException("No compiler specified!")
          } else {
            c.transforms.reverse.map(Dependency.fromTransform)
          }
      }
      val tm = new firrtl.stage.transforms.Compiler(targets)
      /* Transform order is lazily evaluated. Force it here to remove its resolution time from actual compilation. */
      val (timeResolveDependencies, _) = firrtl.Utils.time { tm.flattenedTransformOrder }
      logger.info(f"Computed transform order in: $timeResolveDependencies%.1f ms")
      /* Show the determined transform order */
      logger.info("Determined Transform order that will be executed:\n" + tm.prettyPrint("  "))
      /* Run all determined transforms tracking how long everything takes to run */
      val (timeExecute, annotationsOut) = firrtl.Utils.time { tm.transform(c.stateIn) }
      logger.info(f"Total FIRRTL Compile Time: $timeExecute%.1f ms")
      c.copy(stateOut = Some(annotationsOut))
    }

    if (b.size <= 1) { b.map(f) }
    else {
      collection.parallel.immutable.ParVector(b: _*).par.map(f).seq
    }
  }

  private def compilerToTransforms(a: FirrtlCompiler): Seq[TransformDependency] = a match {
    case _: firrtl.NoneCompiler         => Forms.ChirrtlForm
    case _: firrtl.HighFirrtlCompiler   => Forms.MinimalHighForm
    case _: firrtl.MiddleFirrtlCompiler => Forms.MidForm
    case _: firrtl.LowFirrtlCompiler    => Forms.LowForm
    case _: firrtl.VerilogCompiler | _: firrtl.SystemVerilogCompiler => Forms.LowFormOptimized
    case _: firrtl.MinimumVerilogCompiler => Forms.LowFormMinimumOptimized
  }

}
