From a99426e03f3151991f449991561f250d17efd4a4 Mon Sep 17 00:00:00 2001
From: Sorrel Bri <sorrel.bri.june@gmail.com>
Date: Sat, 2 May 2020 22:04:22 -0700
Subject: [PATCH] Game.returnToMove(x) where x >= 0 returns game state at move
 x

---
 packages/server/services/Game.v2.js  | 20 +++++++++-----
 packages/server/test/Game.v2.spec.js | 41 +++++++++++++++++++++++-----
 2 files changed, 47 insertions(+), 14 deletions(-)

diff --git a/packages/server/services/Game.v2.js b/packages/server/services/Game.v2.js
index 9232357..88d1f9d 100644
--- a/packages/server/services/Game.v2.js
+++ b/packages/server/services/Game.v2.js
@@ -238,14 +238,20 @@ const Game = ({gameData = {}, gameRecord = []} = {}) => {
       return { game: this, group };
     },
 
-    returnToMove: function(idx) {
-      if (idx < 0) {
-        const { komi, handicap, boardSize } = this;
-        return Game({ 
-          gameData: { komi, handicap, boardSize }, 
-          gameRecord: [...this.gameRecord.slice(0, this.gameRecord.length + idx)]
-        })
+    returnToMove: function(lastMove) {
+      const { komi, handicap, boardSize } = this;
+      if (lastMove === 0) {
+        return Game({
+          gameData: { komi, handicap, boardSize }
+        }).initGame();
       }
+      const length = this.gameRecord.length;
+      const index = lastMove < 0 ? length + lastMove : lastMove;
+      if (lastMove >= length && lastMove > 0) return this;
+      return Game({ 
+        gameData: { komi, handicap, boardSize }, 
+        gameRecord: [...this.gameRecord.slice(0, index)]
+      });
     }
   }
 };
diff --git a/packages/server/test/Game.v2.spec.js b/packages/server/test/Game.v2.spec.js
index c609a06..1f16d19 100644
--- a/packages/server/test/Game.v2.spec.js
+++ b/packages/server/test/Game.v2.spec.js
@@ -405,8 +405,14 @@ describe('capture logic: snapback, ko and playing in eyes', () => {
 });
 
 describe('Game history functionality', () => {
-  const firstMove = { player: 'black', pos: { x: 4, y: 4 }};
-  const secondMove = { player: 'white', pos: { x: 16, y: 16 }};
+  const firstMove =   { player: 'black', pos: { x: 4, y: 4 }};
+  const secondMove =  { player: 'white', pos: { x: 16, y: 16 }};
+  const thirdMove =   { player: 'black', pos: { x: 16, y: 4 } };
+  const fourthMove =  { player: 'white', pos: { x: 4, y: 16 }};
+  const fifthMove =   { player: 'black', pos: { x: 10, y: 4 } };
+  const sixthMove =   { player: 'white', pos: { x: 4, y: 10 }};
+  const seventhMove = { player: 'black', pos: { x: 10, y: 16 } };
+  const eighthMove =  { player: 'white', pos: { x: 16, y: 10 }};
 
   it('makeMove creates gameRecord item', done => {
     Game().initGame()
@@ -423,16 +429,16 @@ describe('Game history functionality', () => {
   });
 
   const rewoundGame = () => Game().initGame()
-  .makeMove(firstMove)
-  .makeMove(secondMove)
-  .makeMove({ player: 'black', pos: { x: 16, y: 4 } })
-  .returnToMove(-1);
+    .makeMove(firstMove)
+    .makeMove(secondMove)
+    .makeMove(thirdMove)
+    .returnToMove(-1);
 
   it('Game.returnToMove returns new Game with gameRecord', done => {
     rewoundGame()
       .gameRecord.should.eql([ firstMove, secondMove ])
     done();
-  })
+  });
   
   it('Game.returnToMove returns new Game with new board state', done => {
     rewoundGame()
@@ -442,6 +448,27 @@ describe('Game history functionality', () => {
     rewoundGame()
       .boardState['16-16'].stone.should.eql(-1);
     done();
+  });
+
+  const resetGame = () => [
+    firstMove, secondMove, thirdMove, fourthMove, fifthMove, sixthMove, seventhMove, eighthMove
+  ].reduce((game, move) => game.makeMove(move), Game().initGame());
+
+  it('Game.returnToMove(0) returns to init board state', done => {
+    const erasedGame = resetGame()
+      .returnToMove(0)
+    erasedGame.gameRecord.should.eql([])
+    erasedGame.boardState['4-4'].stone.should.eql(0)
+    done();
+  });
+
+  it('Game.returnToMove(5) returns to state after 5th move', done => {
+    const fifthMoveGame = resetGame()
+      .returnToMove(5);
+    fifthMoveGame.gameRecord.should.eql([firstMove, secondMove, thirdMove, fourthMove, fifthMove]);
+    fifthMoveGame.boardState['10-4'].stone.should.eql(1)
+    fifthMoveGame.boardState['4-10'].stone.should.eql(0)
+    done();
   })
 })