From 331fc58c932d6d7055b202d0c6dc0d77212a89f8 Mon Sep 17 00:00:00 2001
From: Benjamin Auder <benjamin.auder@somewhere>
Date: Thu, 13 Dec 2018 15:39:26 +0100
Subject: [PATCH] Add true repetition detection

---
 TODO                                  |   1 -
 public/javascripts/base_rules.js      |  32 ++-
 public/javascripts/components/game.js |   4 +-
 public/javascripts/utils/md5.js       | 379 ++++++++++++++++++++++++++
 views/variant.pug                     |   1 +
 5 files changed, 400 insertions(+), 17 deletions(-)
 delete mode 100644 TODO
 create mode 100644 public/javascripts/utils/md5.js

diff --git a/TODO b/TODO
deleted file mode 100644
index bb4d6e16..00000000
--- a/TODO
+++ /dev/null
@@ -1 +0,0 @@
-Full detection of repeated positions (including turn)
diff --git a/public/javascripts/base_rules.js b/public/javascripts/base_rules.js
index 5020094c..a10a43ca 100644
--- a/public/javascripts/base_rules.js
+++ b/public/javascripts/base_rules.js
@@ -54,6 +54,7 @@ class ChessRules
 	constructor(fen, moves)
 	{
 		this.moves = moves;
+		this.hashStates = {}; //for repetitions detection
 		// Use fen string to initialize variables, flags and board
 		this.board = VariantRules.GetBoard(fen);
 		this.setFlags(fen);
@@ -727,6 +728,18 @@ class ChessRules
 			this.kingPos[c] = [move.start.x, move.start.y];
 	}
 
+	// Store a hash of the position + flags + turn after a move is played
+	// (for repetitions detection)
+	addHashState()
+	{
+		const strToHash = this.getFen() + " " + this.turn;
+		const hash = hex_md5(strToHash);
+		if (!this.hashStates[hash])
+			this.hashStates[hash] = 1;
+		else
+			this.hashStates[hash]++;
+	}
+
 	play(move, ingame)
 	{
 		// DEBUG:
@@ -741,6 +754,9 @@ class ChessRules
 		this.moves.push(move);
 		this.epSquares.push( this.getEpSquare(move) );
 		VariantRules.PlayOnBoard(this.board, move);
+
+		if (!!ingame)
+			this.addHashState();
 	}
 
 	undo(move)
@@ -760,22 +776,10 @@ class ChessRules
 	//////////////
 	// END OF GAME
 
-	// Basic check for 3 repetitions (in the last moves only)
-	// TODO: extend to usual 3-repetition recognition (storing FEN with move?)
+	// Check for 3 repetitions (position + flags + turn)
 	checkRepetition()
 	{
-		if (this.moves.length >= 8)
-		{
-			const L = this.moves.length;
-			if (_.isEqual(this.moves[L-1], this.moves[L-5]) &&
-				_.isEqual(this.moves[L-2], this.moves[L-6]) &&
-				_.isEqual(this.moves[L-3], this.moves[L-7]) &&
-				_.isEqual(this.moves[L-4], this.moves[L-8]))
-			{
-				return true;
-			}
-		}
-		return false;
+		return Object.values(this.hashStates).some(elt => { return (elt >= 3); });
 	}
 
 	// Is game over ? And if yes, what is the score ?
diff --git a/public/javascripts/components/game.js b/public/javascripts/components/game.js
index 6af331b3..208e0482 100644
--- a/public/javascripts/components/game.js
+++ b/public/javascripts/components/game.js
@@ -1008,7 +1008,7 @@ Vue.component('my-game', {
 			this.endGame(this.mycolor=="w"?"0-1":"1-0");
 		},
 		newGame: function(mode, fenInit, color, oppId, moves, continuation) {
-			const fen = "M7/8/8/3K1k2/8/8/8/8 0000";//fenInit || VariantRules.GenRandInitFen();
+			const fen = fenInit || VariantRules.GenRandInitFen();
 			console.log(fen); //DEBUG
 			if (mode=="human" && !oppId)
 			{
@@ -1066,7 +1066,7 @@ Vue.component('my-game', {
 			}
 			else if (mode == "computer")
 			{
-				this.mycolor = "w";//Math.random() < 0.5 ? 'w' : 'b';
+				this.mycolor = Math.random() < 0.5 ? 'w' : 'b';
 				if (this.mycolor == 'b')
 					setTimeout(this.playComputerMove, 500);
 			}
diff --git a/public/javascripts/utils/md5.js b/public/javascripts/utils/md5.js
new file mode 100644
index 00000000..24d190e4
--- /dev/null
+++ b/public/javascripts/utils/md5.js
@@ -0,0 +1,379 @@
+/*
+ * A JavaScript implementation of the RSA Data Security, Inc. MD5 Message
+ * Digest Algorithm, as defined in RFC 1321.
+ * Version 2.2 Copyright (C) Paul Johnston 1999 - 2009
+ * Other contributors: Greg Holt, Andrew Kepert, Ydnar, Lostinet
+ * Distributed under the BSD License
+ * See http://pajhome.org.uk/crypt/md5 for more info.
+ */
+
+/*
+ * Configurable variables. You may need to tweak these to be compatible with
+ * the server-side, but the defaults work in most cases.
+ */
+var hexcase = 0;   /* hex output format. 0 - lowercase; 1 - uppercase        */
+var b64pad  = "";  /* base-64 pad character. "=" for strict RFC compliance   */
+
+/*
+ * These are the functions you'll usually want to call
+ * They take string arguments and return either hex or base-64 encoded strings
+ */
+function hex_md5(s)    { return rstr2hex(rstr_md5(str2rstr_utf8(s))); }
+function b64_md5(s)    { return rstr2b64(rstr_md5(str2rstr_utf8(s))); }
+function any_md5(s, e) { return rstr2any(rstr_md5(str2rstr_utf8(s)), e); }
+function hex_hmac_md5(k, d)
+  { return rstr2hex(rstr_hmac_md5(str2rstr_utf8(k), str2rstr_utf8(d))); }
+function b64_hmac_md5(k, d)
+  { return rstr2b64(rstr_hmac_md5(str2rstr_utf8(k), str2rstr_utf8(d))); }
+function any_hmac_md5(k, d, e)
+  { return rstr2any(rstr_hmac_md5(str2rstr_utf8(k), str2rstr_utf8(d)), e); }
+
+/*
+ * Perform a simple self-test to see if the VM is working
+ */
+function md5_vm_test()
+{
+  return hex_md5("abc").toLowerCase() == "900150983cd24fb0d6963f7d28e17f72";
+}
+
+/*
+ * Calculate the MD5 of a raw string
+ */
+function rstr_md5(s)
+{
+  return binl2rstr(binl_md5(rstr2binl(s), s.length * 8));
+}
+
+/*
+ * Calculate the HMAC-MD5, of a key and some data (raw strings)
+ */
+function rstr_hmac_md5(key, data)
+{
+  var bkey = rstr2binl(key);
+  if(bkey.length > 16) bkey = binl_md5(bkey, key.length * 8);
+
+  var ipad = Array(16), opad = Array(16);
+  for(var i = 0; i < 16; i++)
+  {
+    ipad[i] = bkey[i] ^ 0x36363636;
+    opad[i] = bkey[i] ^ 0x5C5C5C5C;
+  }
+
+  var hash = binl_md5(ipad.concat(rstr2binl(data)), 512 + data.length * 8);
+  return binl2rstr(binl_md5(opad.concat(hash), 512 + 128));
+}
+
+/*
+ * Convert a raw string to a hex string
+ */
+function rstr2hex(input)
+{
+  try { hexcase } catch(e) { hexcase=0; }
+  var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";
+  var output = "";
+  var x;
+  for(var i = 0; i < input.length; i++)
+  {
+    x = input.charCodeAt(i);
+    output += hex_tab.charAt((x >>> 4) & 0x0F)
+           +  hex_tab.charAt( x        & 0x0F);
+  }
+  return output;
+}
+
+/*
+ * Convert a raw string to a base-64 string
+ */
+function rstr2b64(input)
+{
+  try { b64pad } catch(e) { b64pad=''; }
+  var tab = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+  var output = "";
+  var len = input.length;
+  for(var i = 0; i < len; i += 3)
+  {
+    var triplet = (input.charCodeAt(i) << 16)
+                | (i + 1 < len ? input.charCodeAt(i+1) << 8 : 0)
+                | (i + 2 < len ? input.charCodeAt(i+2)      : 0);
+    for(var j = 0; j < 4; j++)
+    {
+      if(i * 8 + j * 6 > input.length * 8) output += b64pad;
+      else output += tab.charAt((triplet >>> 6*(3-j)) & 0x3F);
+    }
+  }
+  return output;
+}
+
+/*
+ * Convert a raw string to an arbitrary string encoding
+ */
+function rstr2any(input, encoding)
+{
+  var divisor = encoding.length;
+  var i, j, q, x, quotient;
+
+  /* Convert to an array of 16-bit big-endian values, forming the dividend */
+  var dividend = Array(Math.ceil(input.length / 2));
+  for(i = 0; i < dividend.length; i++)
+  {
+    dividend[i] = (input.charCodeAt(i * 2) << 8) | input.charCodeAt(i * 2 + 1);
+  }
+
+  /*
+   * Repeatedly perform a long division. The binary array forms the dividend,
+   * the length of the encoding is the divisor. Once computed, the quotient
+   * forms the dividend for the next step. All remainders are stored for later
+   * use.
+   */
+  var full_length = Math.ceil(input.length * 8 /
+                                    (Math.log(encoding.length) / Math.log(2)));
+  var remainders = Array(full_length);
+  for(j = 0; j < full_length; j++)
+  {
+    quotient = Array();
+    x = 0;
+    for(i = 0; i < dividend.length; i++)
+    {
+      x = (x << 16) + dividend[i];
+      q = Math.floor(x / divisor);
+      x -= q * divisor;
+      if(quotient.length > 0 || q > 0)
+        quotient[quotient.length] = q;
+    }
+    remainders[j] = x;
+    dividend = quotient;
+  }
+
+  /* Convert the remainders to the output string */
+  var output = "";
+  for(i = remainders.length - 1; i >= 0; i--)
+    output += encoding.charAt(remainders[i]);
+
+  return output;
+}
+
+/*
+ * Encode a string as utf-8.
+ * For efficiency, this assumes the input is valid utf-16.
+ */
+function str2rstr_utf8(input)
+{
+  var output = "";
+  var i = -1;
+  var x, y;
+
+  while(++i < input.length)
+  {
+    /* Decode utf-16 surrogate pairs */
+    x = input.charCodeAt(i);
+    y = i + 1 < input.length ? input.charCodeAt(i + 1) : 0;
+    if(0xD800 <= x && x <= 0xDBFF && 0xDC00 <= y && y <= 0xDFFF)
+    {
+      x = 0x10000 + ((x & 0x03FF) << 10) + (y & 0x03FF);
+      i++;
+    }
+
+    /* Encode output as utf-8 */
+    if(x <= 0x7F)
+      output += String.fromCharCode(x);
+    else if(x <= 0x7FF)
+      output += String.fromCharCode(0xC0 | ((x >>> 6 ) & 0x1F),
+                                    0x80 | ( x         & 0x3F));
+    else if(x <= 0xFFFF)
+      output += String.fromCharCode(0xE0 | ((x >>> 12) & 0x0F),
+                                    0x80 | ((x >>> 6 ) & 0x3F),
+                                    0x80 | ( x         & 0x3F));
+    else if(x <= 0x1FFFFF)
+      output += String.fromCharCode(0xF0 | ((x >>> 18) & 0x07),
+                                    0x80 | ((x >>> 12) & 0x3F),
+                                    0x80 | ((x >>> 6 ) & 0x3F),
+                                    0x80 | ( x         & 0x3F));
+  }
+  return output;
+}
+
+/*
+ * Encode a string as utf-16
+ */
+function str2rstr_utf16le(input)
+{
+  var output = "";
+  for(var i = 0; i < input.length; i++)
+    output += String.fromCharCode( input.charCodeAt(i)        & 0xFF,
+                                  (input.charCodeAt(i) >>> 8) & 0xFF);
+  return output;
+}
+
+function str2rstr_utf16be(input)
+{
+  var output = "";
+  for(var i = 0; i < input.length; i++)
+    output += String.fromCharCode((input.charCodeAt(i) >>> 8) & 0xFF,
+                                   input.charCodeAt(i)        & 0xFF);
+  return output;
+}
+
+/*
+ * Convert a raw string to an array of little-endian words
+ * Characters >255 have their high-byte silently ignored.
+ */
+function rstr2binl(input)
+{
+  var output = Array(input.length >> 2);
+  for(var i = 0; i < output.length; i++)
+    output[i] = 0;
+  for(var i = 0; i < input.length * 8; i += 8)
+    output[i>>5] |= (input.charCodeAt(i / 8) & 0xFF) << (i%32);
+  return output;
+}
+
+/*
+ * Convert an array of little-endian words to a string
+ */
+function binl2rstr(input)
+{
+  var output = "";
+  for(var i = 0; i < input.length * 32; i += 8)
+    output += String.fromCharCode((input[i>>5] >>> (i % 32)) & 0xFF);
+  return output;
+}
+
+/*
+ * Calculate the MD5 of an array of little-endian words, and a bit length.
+ */
+function binl_md5(x, len)
+{
+  /* append padding */
+  x[len >> 5] |= 0x80 << ((len) % 32);
+  x[(((len + 64) >>> 9) << 4) + 14] = len;
+
+  var a =  1732584193;
+  var b = -271733879;
+  var c = -1732584194;
+  var d =  271733878;
+
+  for(var i = 0; i < x.length; i += 16)
+  {
+    var olda = a;
+    var oldb = b;
+    var oldc = c;
+    var oldd = d;
+
+    a = md5_ff(a, b, c, d, x[i+ 0], 7 , -680876936);
+    d = md5_ff(d, a, b, c, x[i+ 1], 12, -389564586);
+    c = md5_ff(c, d, a, b, x[i+ 2], 17,  606105819);
+    b = md5_ff(b, c, d, a, x[i+ 3], 22, -1044525330);
+    a = md5_ff(a, b, c, d, x[i+ 4], 7 , -176418897);
+    d = md5_ff(d, a, b, c, x[i+ 5], 12,  1200080426);
+    c = md5_ff(c, d, a, b, x[i+ 6], 17, -1473231341);
+    b = md5_ff(b, c, d, a, x[i+ 7], 22, -45705983);
+    a = md5_ff(a, b, c, d, x[i+ 8], 7 ,  1770035416);
+    d = md5_ff(d, a, b, c, x[i+ 9], 12, -1958414417);
+    c = md5_ff(c, d, a, b, x[i+10], 17, -42063);
+    b = md5_ff(b, c, d, a, x[i+11], 22, -1990404162);
+    a = md5_ff(a, b, c, d, x[i+12], 7 ,  1804603682);
+    d = md5_ff(d, a, b, c, x[i+13], 12, -40341101);
+    c = md5_ff(c, d, a, b, x[i+14], 17, -1502002290);
+    b = md5_ff(b, c, d, a, x[i+15], 22,  1236535329);
+
+    a = md5_gg(a, b, c, d, x[i+ 1], 5 , -165796510);
+    d = md5_gg(d, a, b, c, x[i+ 6], 9 , -1069501632);
+    c = md5_gg(c, d, a, b, x[i+11], 14,  643717713);
+    b = md5_gg(b, c, d, a, x[i+ 0], 20, -373897302);
+    a = md5_gg(a, b, c, d, x[i+ 5], 5 , -701558691);
+    d = md5_gg(d, a, b, c, x[i+10], 9 ,  38016083);
+    c = md5_gg(c, d, a, b, x[i+15], 14, -660478335);
+    b = md5_gg(b, c, d, a, x[i+ 4], 20, -405537848);
+    a = md5_gg(a, b, c, d, x[i+ 9], 5 ,  568446438);
+    d = md5_gg(d, a, b, c, x[i+14], 9 , -1019803690);
+    c = md5_gg(c, d, a, b, x[i+ 3], 14, -187363961);
+    b = md5_gg(b, c, d, a, x[i+ 8], 20,  1163531501);
+    a = md5_gg(a, b, c, d, x[i+13], 5 , -1444681467);
+    d = md5_gg(d, a, b, c, x[i+ 2], 9 , -51403784);
+    c = md5_gg(c, d, a, b, x[i+ 7], 14,  1735328473);
+    b = md5_gg(b, c, d, a, x[i+12], 20, -1926607734);
+
+    a = md5_hh(a, b, c, d, x[i+ 5], 4 , -378558);
+    d = md5_hh(d, a, b, c, x[i+ 8], 11, -2022574463);
+    c = md5_hh(c, d, a, b, x[i+11], 16,  1839030562);
+    b = md5_hh(b, c, d, a, x[i+14], 23, -35309556);
+    a = md5_hh(a, b, c, d, x[i+ 1], 4 , -1530992060);
+    d = md5_hh(d, a, b, c, x[i+ 4], 11,  1272893353);
+    c = md5_hh(c, d, a, b, x[i+ 7], 16, -155497632);
+    b = md5_hh(b, c, d, a, x[i+10], 23, -1094730640);
+    a = md5_hh(a, b, c, d, x[i+13], 4 ,  681279174);
+    d = md5_hh(d, a, b, c, x[i+ 0], 11, -358537222);
+    c = md5_hh(c, d, a, b, x[i+ 3], 16, -722521979);
+    b = md5_hh(b, c, d, a, x[i+ 6], 23,  76029189);
+    a = md5_hh(a, b, c, d, x[i+ 9], 4 , -640364487);
+    d = md5_hh(d, a, b, c, x[i+12], 11, -421815835);
+    c = md5_hh(c, d, a, b, x[i+15], 16,  530742520);
+    b = md5_hh(b, c, d, a, x[i+ 2], 23, -995338651);
+
+    a = md5_ii(a, b, c, d, x[i+ 0], 6 , -198630844);
+    d = md5_ii(d, a, b, c, x[i+ 7], 10,  1126891415);
+    c = md5_ii(c, d, a, b, x[i+14], 15, -1416354905);
+    b = md5_ii(b, c, d, a, x[i+ 5], 21, -57434055);
+    a = md5_ii(a, b, c, d, x[i+12], 6 ,  1700485571);
+    d = md5_ii(d, a, b, c, x[i+ 3], 10, -1894986606);
+    c = md5_ii(c, d, a, b, x[i+10], 15, -1051523);
+    b = md5_ii(b, c, d, a, x[i+ 1], 21, -2054922799);
+    a = md5_ii(a, b, c, d, x[i+ 8], 6 ,  1873313359);
+    d = md5_ii(d, a, b, c, x[i+15], 10, -30611744);
+    c = md5_ii(c, d, a, b, x[i+ 6], 15, -1560198380);
+    b = md5_ii(b, c, d, a, x[i+13], 21,  1309151649);
+    a = md5_ii(a, b, c, d, x[i+ 4], 6 , -145523070);
+    d = md5_ii(d, a, b, c, x[i+11], 10, -1120210379);
+    c = md5_ii(c, d, a, b, x[i+ 2], 15,  718787259);
+    b = md5_ii(b, c, d, a, x[i+ 9], 21, -343485551);
+
+    a = safe_add(a, olda);
+    b = safe_add(b, oldb);
+    c = safe_add(c, oldc);
+    d = safe_add(d, oldd);
+  }
+  return Array(a, b, c, d);
+}
+
+/*
+ * These functions implement the four basic operations the algorithm uses.
+ */
+function md5_cmn(q, a, b, x, s, t)
+{
+  return safe_add(bit_rol(safe_add(safe_add(a, q), safe_add(x, t)), s),b);
+}
+function md5_ff(a, b, c, d, x, s, t)
+{
+  return md5_cmn((b & c) | ((~b) & d), a, b, x, s, t);
+}
+function md5_gg(a, b, c, d, x, s, t)
+{
+  return md5_cmn((b & d) | (c & (~d)), a, b, x, s, t);
+}
+function md5_hh(a, b, c, d, x, s, t)
+{
+  return md5_cmn(b ^ c ^ d, a, b, x, s, t);
+}
+function md5_ii(a, b, c, d, x, s, t)
+{
+  return md5_cmn(c ^ (b | (~d)), a, b, x, s, t);
+}
+
+/*
+ * Add integers, wrapping at 2^32. This uses 16-bit operations internally
+ * to work around bugs in some JS interpreters.
+ */
+function safe_add(x, y)
+{
+  var lsw = (x & 0xFFFF) + (y & 0xFFFF);
+  var msw = (x >> 16) + (y >> 16) + (lsw >> 16);
+  return (msw << 16) | (lsw & 0xFFFF);
+}
+
+/*
+ * Bitwise rotate a 32-bit number to the left.
+ */
+function bit_rol(num, cnt)
+{
+  return (num << cnt) | (num >>> (32 - cnt));
+}
diff --git a/views/variant.pug b/views/variant.pug
index 561663c7..7de86ca3 100644
--- a/views/variant.pug
+++ b/views/variant.pug
@@ -18,6 +18,7 @@ block javascripts
 	script(src="/javascripts/utils/misc.js")
 	script(src="/javascripts/utils/socket_url.js")
 	script(src="/javascripts/utils/array.js")
+	script(src="/javascripts/utils/md5.js")
 	script(src="/javascripts/base_rules.js")
 	script(src="/javascripts/variants/" + variant + ".js")
 	script.
-- 
2.44.0