package snake

import java.nio.file.{Files, Paths}

/** Loads shared fixtures from ../fixtures/<name>.json and decodes them into the course's types. */
object Fixtures:
  private val dir = Paths.get(sys.props.getOrElse("user.dir", ".")).resolve("..").resolve("fixtures").normalize

  def load(name: String): ujson.Value =
    ujson.read(Files.readString(dir.resolve(s"$name.json")))

  /** The cases array of a fixture. */
  def cases(name: String): Seq[ujson.Value] = load(name)("cases").arr.toSeq

  /** Decode a nullable JSON value into an Option. */
  def opt[A](v: ujson.Value)(f: ujson.Value => A): Option[A] =
    if v.isNull then None else Some(f(v))

  def point(v: ujson.Value): Point = Point(v("x").num.toInt, v("y").num.toInt)

  def direction(v: ujson.Value): Direction = Direction.valueOf(v.str)

  def status(v: ujson.Value): Status = Status.valueOf(v.str)

  def action(v: ujson.Value): Action = v("tag").str match
    case "Tick"        => Action.Tick
    case "Turn"        => Action.Turn(direction(v("dir")))
    case "TogglePause" => Action.TogglePause
    case "Restart"     => Action.Restart
    case "Frame"       => Action.Frame
    case other         => throw new IllegalArgumentException(s"unknown action tag: $other")

  def gameState(v: ujson.Value): GameState = GameState(
    width = v("width").num.toInt,
    height = v("height").num.toInt,
    snake = v("snake").arr.toList.map(point),
    dir = direction(v("dir")),
    nextDir = direction(v("nextDir")),
    apple = opt(v("apple"))(point),
    seed = v("seed").num.toLong,
    score = v("score").num.toInt,
    status = status(v("status")),
    frame = v("frame").num.toInt
  )

  def shape(v: ujson.Value): Shape = v("tag").str match
    case "Rect" => Shape.Rect(v("x").num.toInt, v("y").num.toInt, v("w").num.toInt, v("h").num.toInt, v("color").str)
    case "Text" =>
      Shape.Text(v("x").num.toInt, v("y").num.toInt, v("text").str, v("color").str, v("size").num.toInt, v("align").str)
    case other => throw new IllegalArgumentException(s"unknown shape tag: $other")

  def list[A](v: ujson.Value)(f: ujson.Value => A): List[A] = v.arr.toList.map(f)