feat: removed fivefold repetition, condensed to twenty-five move rule

Author: dechristopher

game.go

@@ -40,18 +40,12 @@ const (
 DrawOffer
 // Stalemate indicates that the game was drawn by stalemate.
 Stalemate
-// ThreefoldRepetition indicates that the game was drawn when the game
-// state was repeated three times and a player requested a draw.
+// ThreefoldRepetition indicates that the game was automatically drawn
+// by the game state being repeated three times.
 ThreefoldRepetition
-// FivefoldRepetition indicates that the game was automatically drawn
-// by the game state being repeated five times.
-FivefoldRepetition
-// FiftyMoveRule indicates that the game was drawn by the half
-// move clock being one hundred or greater when a player requested a draw.
-FiftyMoveRule
-// SeventyFiveMoveRule indicates that the game was automatically drawn
-// when the half move clock was one hundred and fifty or greater.
-SeventyFiveMoveRule
+// TwentyFiveMoveRule indicates that the game was automatically drawn
+// when the half move clock was fifty or greater.
+TwentyFiveMoveRule
 // InsufficientMaterial indicates that the game was automatically drawn
 // because there was insufficient material for checkmate.
 InsufficientMaterial
@@ -267,10 +261,6 @@ func (g *Game) Draw(method Method) error {
 if g.numRepetitions() < 3 {
 return errors.New("octad: draw by ThreefoldRepetition requires at least three repetitions of the current board state")
 }
-case FiftyMoveRule:
-if g.pos.halfMoveClock < 100 {
-return fmt.Errorf("octad: draw by FiftyMoveRule requires the half move clock to be at 100 or greater but is %d", g.pos.halfMoveClock)
-}
 case DrawOffer:
 default:
 return fmt.Errorf("octad: unsupported draw method %s", method.String())
@@ -300,9 +290,6 @@ func (g *Game) EligibleDraws() []Method {
 if g.numRepetitions() >= 3 {
 draws = append(draws, ThreefoldRepetition)
 }
-if g.pos.halfMoveClock >= 100 {
-draws = append(draws, FiftyMoveRule)
-}
 return draws
 }
 
@@ -363,15 +350,15 @@ func (g *Game) updatePosition() {
 }
 
 // five fold rep creates automatic draw
-if !g.ignoreAutomaticDraws && g.numRepetitions() >= 5 {
+if !g.ignoreAutomaticDraws && g.numRepetitions() >= 3 {
 g.outcome = Draw
-g.method = FivefoldRepetition
+g.method = ThreefoldRepetition
 }
 
 // 75 move rule creates automatic draw
-if !g.ignoreAutomaticDraws && g.pos.halfMoveClock >= 150 && g.method != Checkmate {
+if !g.ignoreAutomaticDraws && g.pos.halfMoveClock >= 50 && g.method != Checkmate {
 g.outcome = Draw
-g.method = SeventyFiveMoveRule
+g.method = TwentyFiveMoveRule
 }
 
 // insufficient material creates automatic draw

game_test.go

@@ -158,55 +158,8 @@ func TestInvalidThreeFoldRepetition(t *testing.T) {
 }
 }
 
-func TestFiveFoldRepetition(t *testing.T) {
-g, err := NewGame()
-if err != nil {
-t.Fatalf(err.Error())
-return
-}
-moves := []string{
-"Nc2", "Nb3", "Na1", "Nd4",
-"Nc2", "Nb3", "Na1", "Nd4",
-"Nc2", "Nb3", "Na1", "Nd4",
-"Nc2", "Nb3", "Na1", "Nd4",
-"Nc2", "Nb3", "Na1", "Nd4",
-}
-for _, m := range moves {
-if err = g.MoveStr(m); err != nil {
-t.Fatal(err)
-}
-}
-if g.Outcome() != Draw || g.Method() != FivefoldRepetition {
-t.Fatal("game: should automatically draw after five repetitions")
-}
-}
-
-func TestFiftyMoveRule(t *testing.T) {
-ofen, _ := OFEN("n2k/4/3K/N3 b - - 100 60")
-g, err := NewGame(ofen)
-if err != nil {
-t.Fatalf(err.Error())
-return
-}
-if err := g.Draw(FiftyMoveRule); err != nil {
-t.Fatal(err)
-}
-}
-
-func TestInvalidFiftyMoveRule(t *testing.T) {
-ofen, _ := OFEN("n2k/4/3K/N3 b - - 99 60")
-g, err := NewGame(ofen)
-if err != nil {
-t.Fatalf(err.Error())
-return
-}
-if err = g.Draw(FiftyMoveRule); err == nil {
-t.Fatal("game: should require fifty moves")
-}
-}
-
-func TestSeventyFiveMoveRule(t *testing.T) {
-ofen, _ := OFEN("n2k/4/3K/N3 b - - 149 80")
+func TestTwentyFiveMoveRule(t *testing.T) {
+ofen, _ := OFEN("n2k/4/3K/N3 b - - 49 24")
 g, err := NewGame(ofen)
 if err != nil {
 t.Fatalf(err.Error())
@@ -215,8 +168,8 @@ func TestSeventyFiveMoveRule(t *testing.T) {
 if err = g.MoveStr("Kc4"); err != nil {
 t.Fatal(err)
 }
-if g.Outcome() != Draw || g.Method() != SeventyFiveMoveRule {
-t.Fatal("game: should automatically draw after seventy five moves w/ no pawn move or capture")
+if g.Outcome() != Draw || g.Method() != TwentyFiveMoveRule {
+t.Fatal("game: should automatically draw after twenty five moves w/ no pawn move or capture")
 }
 }