fix(plugin): proper possibleMoves calculation

Author: xeruf

plugin/src/main/kotlin/sc/plugin2023/Board.kt

@@ -2,9 +2,6 @@ package sc.plugin2023
 
 import com.thoughtworks.xstream.annotations.XStreamAlias
 import sc.api.plugins.*
-import sc.shared.InvalidMoveException
-import sc.shared.MoveMistake
-import java.util.LinkedList
 import kotlin.random.Random
 import sc.plugin2023.util.PluginConstants as Constants
 
@@ -65,6 +62,13 @@ class Board(fields: TwoDBoard<Field> = generateFields()): RectangularBoard<Field
         return field.fish
     }
 
+    fun possibleMovesFrom(pos: Coordinates) =
+        Vector.DoubledHex.directions.flatMap { vector ->
+            (1 until Constants.BOARD_SIZE).map {
+                Move.run(pos, vector * it)
+            }.takeWhile { getOrEmpty(it.to).fish > 0 }
+        }
+    
     /** Returns a list of the non-null filter outputs */
     fun <T> filterFields(filter: (Field, Coordinates) -> T?): Collection<T> =
             gameField.flatMapIndexed { y, row ->

plugin/src/main/kotlin/sc/plugin2023/GameState.kt

@@ -40,7 +40,7 @@ data class GameState @JvmOverloads constructor(
             if(!move.to.minus(move.from).straight)
                 throw InvalidMoveException(MoveMistake.INVALID_MOVE, move)
             // TODO avoid this check
-            if(move !in getPossibleMoves())
+            if(move !in board.possibleMovesFrom(move.from))
                 throw InvalidMoveException(MoveMistake.INVALID_MOVE, move)
             board[move.from] = null
         } else {
@@ -62,14 +62,7 @@ data class GameState @JvmOverloads constructor(
         return if(pieces.size < PluginConstants.PENGUINS) {
             board.filterValues { it.fish == 1 }.map { Move(null, it.key) }
         } else {
-            pieces.flatMap { (pos, _) ->
-                // TODO incomplete
-                Vector.DoubledHex.directions.mapNotNull { vector ->
-                    Move.run(pos, vector).takeIf { move ->
-                        board.getOrEmpty(move.to).fish > 0
-                    }
-                }
-            }
+            pieces.flatMap { (pos, _) -> board.possibleMovesFrom(pos) }
         }
     }
 

plugin/src/test/kotlin/sc/plugin2023/BoardTest.kt

@@ -46,14 +46,15 @@ class BoardTest: FunSpec({
             clone shouldBe makeBoard(0 y 0 to 1)
         }
     }
-    context("Board performs Moves") {
-        context("refuses invalid moves") {
-            test("can't move off the fields") {
-                // TODO
-            }
-            test("can't move onto own piece") {
-                // TODO
-            }
+    context("Board generates Moves") {
+        val board = makeBoard(0 y 0 to 0)
+        test("many possible moves") {
+            // right, right down
+            board.possibleMovesFrom(0 y 0) shouldHaveSize 2 * (PluginConstants.BOARD_SIZE - 1)
+        }
+        test("restricted moves") {
+            board[1 y 1] = Team.ONE
+            board.possibleMovesFrom(0 y 0) shouldHaveSize PluginConstants.BOARD_SIZE - 1
         }
     }
     context("Board calculates diffs") {

plugin/src/test/kotlin/sc/plugin2023/GameStateTest.kt

@@ -1,5 +1,6 @@
 package sc.plugin2023
 
+import io.kotest.core.datatest.forAll
 import io.kotest.core.spec.style.FunSpec
 import io.kotest.matchers.*
 import io.kotest.matchers.booleans.*
@@ -54,15 +55,16 @@ class GameStateTest: FunSpec({
     }
     context("move calculation") {
         test("initial placement") {
-            val board = makeBoard()
-            GameState(board).getPossibleMoves() shouldHaveSize board.size
+            forAll(Board(), makeBoard()) { board ->
+                GameState(board).getPossibleMoves() shouldHaveSize board.size
+            }
         }
         test("first moves") {
             // Board with max penguins for one player
             GameState(makeBoard(*Array(PluginConstants.PENGUINS) { it y it to 0 })).getPossibleMoves() shouldHaveAtLeastSize PluginConstants.PENGUINS * 2
         }
         test("immovable") {
-            // Board with max penguins for one player
+            // Board with max penguins for both players
             val state = GameState(Board(listOf(
                     MutableList(PluginConstants.PENGUINS) { Field(penguin = Team.ONE) },
                     MutableList(PluginConstants.PENGUINS) { Field(penguin = Team.TWO) })))