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

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")
  }
 }