Rough draft of a framework for simpler, more elegant Scalatron bot coding

Example Bot 2 - The Tag Team

// Example Bot #2: The Tag Team

/** This bot spawns a collection of companion mini-bots which strive to remain at a configurable
  * offset relative to their master bot. The master bot runs in large circles.
  *
  * The master bot uses the following state parameters:
  *  - heading          = direction it is currently traveling
  *  - lastRotationTime = simulation the time when the bot last rotated its heading
  *  - lastSpawnTime    = simulation time when the last mini-bot was spawned
  * The mini-bots use the following state parameters:
  *  - offset           = the desired offset from the master, as seen by the master
  */
object ControlFunction
{
    val RotationDelay = 16  // wait this many simulation steps before turning

    def forMaster(bot: Bot) {
        val heading = bot.inputAsXYOrElse("heading", XY(0,1))
        bot.move(heading)

        // rotate the heading by 45 degrees counter-clockwise every few steps
        val lastRotationTime = bot.inputAsIntOrElse("lastRotationTime", 0)
        if((bot.time-lastRotationTime) > RotationDelay) {
            val newHeading = heading.rotateCounterClockwise45
            bot.set("heading" -> newHeading, "lastRotationTime" -> bot.time)
        }

        // can we spawn a mini-bot? We don't do it more often than every 10 cycles.
        val lastSpawnTime = bot.inputAsIntOrElse("lastSpawnTime", 0)
        if((bot.time - lastSpawnTime) > RotationDelay ) {
            // yes, we can (try to) spawn a mini-bot
            if(bot.energy > 100) {
                bot
                .spawn(heading.rotateClockwise45, "offset" -> heading * 10)
                .set("lastSpawnTime" -> bot.time)
                .say("Off you go!")
                .status("Circling...")
            } else {
                bot.status("Low Energy")
            }
        } else {
            bot.status("Waiting...")
        }
    }

    def forSlave(bot: MiniBot) {
        val actualOffset = bot.offsetToMaster.negate                    // as seen from master
        val desiredOffset = bot.inputAsXYOrElse("offset", XY(10,10))    // as seen from master
        bot.move((desiredOffset - actualOffset).signum)
    }
}



// -------------------------------------------------------------------------------------------------
// Framework
// -------------------------------------------------------------------------------------------------

class ControlFunctionFactory {
    def create = (input: String) => {
        val (opcode, params) = CommandParser(input)
        opcode match {
            case "React" =>
                val bot = new BotImpl(params)
                if( bot.generation == 0 ) {
                    ControlFunction.forMaster(bot)
                } else {
                    ControlFunction.forSlave(bot)
                }
                bot.toString
            case _ => "" // OK
        }
    }
}


// -------------------------------------------------------------------------------------------------


trait Bot {
    // inputs
    def inputOrElse(key: String, fallback: String): String
    def inputAsIntOrElse(key: String, fallback: Int): Int
    def inputAsXYOrElse(keyPrefix: String, fallback: XY): XY
    def view: View
    def energy: Int
    def time: Int
    def generation: Int

    // outputs
    def move(delta: XY) : Bot
    def say(text: String) : Bot
    def status(text: String) : Bot
    def spawn(offset: XY, params: (String,Any)*) : Bot
    def set(params: (String,Any)*) : Bot
}

trait MiniBot extends Bot {
    // inputs
    def offsetToMaster: XY

    // outputs
    def explode(blastRadius: Int) : Bot
}


case class BotImpl(inputParams: Map[String, String]) extends MiniBot {
    // input
    def inputOrElse(key: String, fallback: String) = inputParams.getOrElse(key, fallback)
    def inputAsIntOrElse(key: String, fallback: Int) = inputParams.get(key).map(_.toInt).getOrElse(fallback)
    def inputAsXYOrElse(key: String, fallback: XY) = inputParams.get(key).map(s => XY(s)).getOrElse(fallback)

    val view = View(inputParams("view"))
    val energy = inputParams("energy").toInt
    val time = inputParams("time").toInt
    val generation = inputParams("generation").toInt
    def offsetToMaster = inputAsXYOrElse("master", XY.Zero)


    // output

    private var stateParams = Map.empty[String,Any]     // holds "Set()" commands
    private var commands = ""                           // holds all other commands

    /** Appends a new command to the command string; returns 'this' for fluent API. */
    private def append(s: String) : Bot = { commands += (if(commands.isEmpty) s else "|" + s); this }

    /** Renders commands and stateParams into a control function return string. */
    override def toString =
        commands +
            (if(stateParams.isEmpty) ""
            else ("|" + stateParams.map(e => e._1 + "=" + e._2).mkString("Set(",",",")")))

    def move(direction: XY) = append("Move(direction=" + direction + ")")
    def say(text: String) = append("Say(text=" + text + ")")
    def status(text: String) = append("Status(text=" + text + ")")
    def explode(blastRadius: Int) = append("Explode(size=" + blastRadius + ")")
    def spawn(offset: XY, params: (String,Any)*) =
        append("Spawn(direction=" + offset +
            (if(params.isEmpty) "" else "," + params.map(e => e._1 + "=" + e._2).mkString(",")) +
            ")")
    def set(params: (String,Any)*) = { stateParams ++= params; this }
    def set(keyPrefix: String, xy: XY) = { stateParams ++= List(keyPrefix+"x" -> xy.x, keyPrefix+"y" -> xy.y); this }
}


// -------------------------------------------------------------------------------------------------


/** Utility methods for parsing strings containing a single command of the format
  * "Command(key=value,key=value,...)"
  */
object CommandParser {
    /** "Command(..)" => ("Command", Map( ("key" -> "value"), ("key" -> "value"), ..}) */
    def apply(command: String): (String, Map[String, String]) = {
        /** "key=value" => ("key","value") */
        def splitParameterIntoKeyValue(param: String): (String, String) = {
            val segments = param.split('=')
            (segments(0), if(segments.length>=2) segments(1) else "")
        }

        val segments = command.split('(')
        if( segments.length != 2 )
            throw new IllegalStateException("invalid command: " + command)
        val opcode = segments(0)
        val params = segments(1).dropRight(1).split(',')
        val keyValuePairs = params.map(splitParameterIntoKeyValue).toMap
        (opcode, keyValuePairs)
    }
}


// -------------------------------------------------------------------------------------------------


/** Utility class for managing 2D cell coordinates.
  * The coordinate (0,0) corresponds to the top-left corner of the arena on screen.
  * The direction (1,-1) points right and up.
  */
case class XY(x: Int, y: Int) {
    override def toString = x + ":" + y

    def isNonZero = x != 0 || y != 0
    def isZero = x == 0 && y == 0
    def isNonNegative = x >= 0 && y >= 0

    def updateX(newX: Int) = XY(newX, y)
    def updateY(newY: Int) = XY(x, newY)

    def addToX(dx: Int) = XY(x + dx, y)
    def addToY(dy: Int) = XY(x, y + dy)

    def +(pos: XY) = XY(x + pos.x, y + pos.y)
    def -(pos: XY) = XY(x - pos.x, y - pos.y)
    def *(factor: Double) = XY((x * factor).intValue, (y * factor).intValue)

    def distanceTo(pos: XY): Double = (this - pos).length // Phythagorean
    def length: Double = math.sqrt(x * x + y * y) // Phythagorean

    def stepsTo(pos: XY): Int = (this - pos).stepCount // steps to reach pos: max delta X or Y
    def stepCount: Int = x.abs.max(y.abs) // steps from (0,0) to get here: max X or Y

    def signum = XY(x.signum, y.signum)

    def negate = XY(-x, -y)
    def negateX = XY(-x, y)
    def negateY = XY(x, -y)

    /** Returns the direction index with 'Right' being index 0, then clockwise in 45 degree steps. */
    def toDirection45: Int = {
        val unit = signum
        unit.x match {
            case -1 =>
                unit.y match {
                    case -1 =>
                        if(x < y * 3) Direction45.Left
                        else if(y < x * 3) Direction45.Up
                        else Direction45.UpLeft
                    case 0 =>
                        Direction45.Left
                    case 1 =>
                        if(-x > y * 3) Direction45.Left
                        else if(y > -x * 3) Direction45.Down
                        else Direction45.LeftDown
                }
            case 0 =>
                unit.y match {
                    case 1 => Direction45.Down
                    case 0 => throw new IllegalArgumentException("cannot compute direction index for (0,0)")
                    case -1 => Direction45.Up
                }
            case 1 =>
                unit.y match {
                    case -1 =>
                        if(x > -y * 3) Direction45.Right
                        else if(-y > x * 3) Direction45.Up
                        else Direction45.RightUp
                    case 0 =>
                        Direction45.Right
                    case 1 =>
                        if(x > y * 3) Direction45.Right
                        else if(y > x * 3) Direction45.Down
                        else Direction45.DownRight
                }
        }
    }

    def rotateCounterClockwise45 = XY.fromDirection45((signum.toDirection45 + 1) % 8)
    def rotateCounterClockwise90 = XY.fromDirection45((signum.toDirection45 + 2) % 8)
    def rotateClockwise45 = XY.fromDirection45((signum.toDirection45 + 7) % 8)
    def rotateClockwise90 = XY.fromDirection45((signum.toDirection45 + 6) % 8)


    def wrap(boardSize: XY) = {
        val fixedX = if(x < 0) boardSize.x + x else if(x >= boardSize.x) x - boardSize.x else x
        val fixedY = if(y < 0) boardSize.y + y else if(y >= boardSize.y) y - boardSize.y else y
        if(fixedX != x || fixedY != y) XY(fixedX, fixedY) else this
    }
}


object XY {
    /** Parse an XY value from XY.toString format, e.g. "2:3". */
    def apply(s: String) : XY = { val a = s.split(':'); XY(a(0).toInt,a(1).toInt) }

    val Zero = XY(0, 0)
    val One = XY(1, 1)

    val Right     = XY( 1,  0)
    val RightUp   = XY( 1, -1)
    val Up        = XY( 0, -1)
    val UpLeft    = XY(-1, -1)
    val Left      = XY(-1,  0)
    val LeftDown  = XY(-1,  1)
    val Down      = XY( 0,  1)
    val DownRight = XY( 1,  1)

    def fromDirection45(index: Int): XY = index match {
        case Direction45.Right => Right
        case Direction45.RightUp => RightUp
        case Direction45.Up => Up
        case Direction45.UpLeft => UpLeft
        case Direction45.Left => Left
        case Direction45.LeftDown => LeftDown
        case Direction45.Down => Down
        case Direction45.DownRight => DownRight
    }

    def fromDirection90(index: Int): XY = index match {
        case Direction90.Right => Right
        case Direction90.Up => Up
        case Direction90.Left => Left
        case Direction90.Down => Down
    }

    def apply(array: Array[Int]): XY = XY(array(0), array(1))
}


object Direction45 {
    val Right = 0
    val RightUp = 1
    val Up = 2
    val UpLeft = 3
    val Left = 4
    val LeftDown = 5
    val Down = 6
    val DownRight = 7
}


object Direction90 {
    val Right = 0
    val Up = 1
    val Left = 2
    val Down = 3
}


// -------------------------------------------------------------------------------------------------


case class View(cells: String) {
    val size = math.sqrt(cells.length).toInt
    val center = XY(size / 2, size / 2)

    def apply(relPos: XY) = cellAtRelPos(relPos)

    def indexFromAbsPos(absPos: XY) = absPos.x + absPos.y * size
    def absPosFromIndex(index: Int) = XY(index % size, index / size)
    def absPosFromRelPos(relPos: XY) = relPos + center
    def cellAtAbsPos(absPos: XY) = cells.charAt(indexFromAbsPos(absPos))

    def indexFromRelPos(relPos: XY) = indexFromAbsPos(absPosFromRelPos(relPos))
    def relPosFromAbsPos(absPos: XY) = absPos - center
    def relPosFromIndex(index: Int) = relPosFromAbsPos(absPosFromIndex(index))
    def cellAtRelPos(relPos: XY) = cells.charAt(indexFromRelPos(relPos))

    def offsetToNearest(c: Char) = {
        val matchingXY = cells.view.zipWithIndex.filter(_._1 == c)
        if( matchingXY.isEmpty )
            None
        else {
            val nearest = matchingXY.map(p => relPosFromIndex(p._2)).minBy(_.length)
            Some(nearest)
        }
    }
}