'use strict';

var gun = Gun({
   peers: ['https://jessemcdonald.info/gun'],
   /* workaround for persistent errors accumulating which break synchronization */
   localStorage: false,
});

let initialBoard = (function (){
   var init = JSON.stringify({
      light: [
         'rnbqkbnr',
         'pppppppp',
         '        ',
         '        ',
         '        ',
         '        ',
         '        ',
         '        ',
      ],
      dark: [
         '        ',
         '        ',
         '        ',
         '        ',
         '        ',
         '        ',
         'pppppppp',
         'rnbqkbnr',
      ],
      player: 'light',
      timestamp: new Date().getTime(),
   });
   return function (){ return JSON.parse(init); }
})();

function cloneJSON(obj){
   return JSON.parse(JSON.stringify(obj));
}

function isLight(side){
   return side[0] === 'l';
}

function isDark(side){
   return side[0] === 'd';
}

function normalizeSide(side){
   return isDark(side) ? 'dark' : 'light';
}

function otherSide(side){
   return isDark(side) ? 'light' : 'dark';
}

function boardGet(board, where, side){
   side = normalizeSide(side);
   if (where === 'phantom') {
      if (!board.phantom || board.phantom.type[1] !== side[0]) {
         return ' ';
      } else {
         return board.phantom.type[0];
      }
   } else {
      var column = 'abcdefgh'.indexOf(where[0]);
      var row = Number(where[1]) - 1;
      return board[side][row][column];
   }
}

function boardPut(board, where, side, piece){
   side = normalizeSide(side);
   var column = 'abcdefgh'.indexOf(where[0]);
   var row = Number(where[1]) - 1;
   var data = board[side][row];
   var prefix = data.substring(0, column);
   var suffix = data.substring(column + 1, 8);
   board[side][row] = prefix + piece + suffix;
}

function countMoves(board) {
   var n = 0;
   while (board && board.prior) {
      if (board.prior.player !== board.player) {
         ++n;
      }
      board = board.prior;
   }
   return n;
}

function offsetSquare(from, columnsRight, rowsUp){
   var column = 'abcdefgh'.indexOf(from[0]);
   var row = Number(from[1]) - 1;

   if (column < 0 || column > 7 || row < 0 || row > 7) {
      return null;
   }

   column += columnsRight;
   row += rowsUp;

   if (column < 0 || column > 7 || row < 0 || row > 7) {
      return null;
   }

   return 'abcdefgh'[column] + String(row + 1);
}

function validDestination(board, side, where, canCapture){
   var ours = boardGet(board, where, side);
   var theirs = boardGet(board, where, otherSide(side));
   return ((theirs === ' ') ? (ours === ' ') : canCapture);
}

function scanPath(accum, board, side, from, canCapture, columnsLeft, rowsUp, remainder){
   while (true) {
      var there = offsetSquare(from, columnsLeft, rowsUp);
      if (!there || !validDestination(board, side, there, canCapture)) { return; }
      accum.push(there);
      if (boardGet(board, there, otherSide(side)) !== ' ' || remainder < 1) { return; }
      from = there;
      remainder -= 1;
   }
}

function hasMoved(board, side, where){
   side = normalizeSide(side);

   while (true) {
      if (!board) {
         return false;
      }

      const move = board.move;

      if (move && move.side === side && move.to === where) {
         return true;
      }

      board = board.prior;
   }
}

function legalMoves(board, side, type, from, canCapture){
   if (board.move && board.move.took === 'k') {
      return [];
   }

   const ortho = [[-1, 0], [1, 0], [0, -1], [0, 1]];
   const diag = [[-1, -1], [-1, 1], [1, -1], [1, 1]];
   var legals = [];

   if (from === 'phantom') {
      from = board.phantom.from;
   }

   if (type === 'k') {
      for (const dir of ortho.concat(diag)) {
         scanPath(legals, board, side, from, false, dir[0], dir[1], 0);
      }
      if (from[0] === 'e' && from[1] === (isDark(side) ? '8' : '1')) {
         /* check for castling conditions */
         if (!hasMoved(board, side, from)) {
            if (boardGet(board, 'f' + from[1], side) === ' ' &&
                boardGet(board, 'g' + from[1], side) === ' ' &&
                boardGet(board, 'h' + from[1], side) === 'r') {
               if (!hasMoved(board, side, 'h' + from[1])) {
                  legals.push('g' + from[1]);
               }
            }
            if (boardGet(board, 'd' + from[1], side) === ' ' &&
                boardGet(board, 'c' + from[1], side) === ' ' &&
                boardGet(board, 'b' + from[1], side) === ' ' &&
                boardGet(board, 'a' + from[1], side) === 'r') {
               if (!hasMoved(board, side, 'a' + from[1])) {
                  legals.push('c' + from[1]);
               }
            }
         }
      }
   } else if (type === 'q') {
      for (const dir of ortho.concat(diag)) {
         scanPath(legals, board, side, from, canCapture, dir[0], dir[1], 8);
      }
   } else if (type === 'b') {
      for (const dir of diag) {
         scanPath(legals, board, side, from, canCapture, dir[0], dir[1], 8);
      }
   } else if (type === 'n') {
      for (const there of [offsetSquare(from, -1,  2), offsetSquare(from, 1,  2),
                           offsetSquare(from, -2,  1), offsetSquare(from, 2,  1),
                           offsetSquare(from, -2, -1), offsetSquare(from, 2, -1),
                           offsetSquare(from, -1, -2), offsetSquare(from, 1, -2)]) {
         if (there && validDestination(board, side, there, canCapture)) {
            legals.push(there);
         }
      }
   } else if (type === 'r') {
      for (const dir of ortho) {
         scanPath(legals, board, side, from, canCapture, dir[0], dir[1], 8);
      }
   } else if (type === 'p') {
      const dark = isDark(side);
      const forward = offsetSquare(from, 0, dark ? -1 : 1);
      const forward2 = offsetSquare(from, 0, dark ? -2 : 2);
      const diagL = offsetSquare(from, -1, dark ? -1 : 1);
      const diagR = offsetSquare(from,  1, dark ? -1 : 1);

      if (forward && validDestination(board, side, forward, false)) {
         legals.push(forward);
         if (dark ? (from[1] >= '7') : (from[1] <= '2')) {
            if (forward2 && validDestination(board, side, forward2, false)) {
               legals.push(forward2);
            }
         }
      }

      if (canCapture) {
         for (const there of [diagL, diagR]) {
            if (there) {
               if (boardGet(board, there, otherSide(side)) !== ' ') {
                  legals.push(there);
               } else {
                  var otherBoard = board;
                  while (otherBoard && otherBoard.move && otherBoard.move.side[0] === side[0]) {
                     otherBoard = otherBoard.prior;
                  }
                  if (otherBoard && otherBoard.move) {
                     const move = otherBoard.move;
                     if (move.side[0] !== side[0] && move.type === 'p') {
                        const from =
                           (move.from === 'phantom') ?
                              otherBoard.prior.phantom.from :
                              move.from;
                        if (from[0] === there[0] && from[1] === forward2[1]) {
                           /* en passant */
                           legals.push(there);
                        }
                     }
                  }
               }
            }
         }
      }
   }

   return legals;
}

function movePiece(priorBoard, side, from, to){
   var other = otherSide(side);
   var type = boardGet(priorBoard, from, side);
   var took = boardGet(priorBoard, to, other);
   var replacedFrom = to;
   var replaced = boardGet(priorBoard, replacedFrom, side);
   var alongside = boardGet(priorBoard, from, other);
   var actuallyFrom = (from === 'phantom') ? priorBoard.phantom.from : from;

   const legals = legalMoves(priorBoard, side, type, from, alongside === ' ');
   if (!legals.includes(to)) {
      return priorBoard;
   }

   var undoBoard = priorBoard;
   if (undoBoard.subsequent) {
      undoBoard = cloneJSON(undoBoard);
      delete undoBoard.subsequent;
   }

   var board = cloneJSON(undoBoard);
   board.prior = undoBoard;

   board.timestamp = new Date().getTime();

   board.move = {
      side: normalizeSide(side),
      type: type,
      from: from,
      to: to
   };
   if (took !== ' ') {
      board.move.took = took;
   }
   if (replaced !== ' ') {
      board.move.replaced = replaced;
   }
   if (alongside !== ' ') {
      board.move.alongside = alongside;
   }
   if (type === 'k' && actuallyFrom[0] === 'e' && to[0] === 'g') {
      board.move.castle = true;
      boardPut(board, 'h' + actuallyFrom[1], side, ' ');
      boardPut(board, 'f' + actuallyFrom[1], side, 'r');
   }
   if (type === 'k' && actuallyFrom[0] === 'e' && to[0] === 'c') {
      board.move.queen_castle = true;
      boardPut(board, 'a' + actuallyFrom[1], side, ' ');
      boardPut(board, 'd' + actuallyFrom[1], side, 'r');
   }
   if (type === 'p' && (isDark(side) ? (to[1] === '1') : (to[1] === '8'))) {
      board.move.promotion = 'q';  /* TODO: allow other choices */
      type = 'q';
   }
   if (alongside === 'p' && (isDark(other) ? (to[1] === '1') : (to[1] === '8'))) {
      board.move.promotion = 'q';  /* TODO: allow other choices */
      alongside = 'q';
   }
   if (type === 'p' && alongside === ' ' && replaced === ' ' && to[0] !== actuallyFrom[0]) {
      var otherBoard = priorBoard;
      while (otherBoard && otherBoard.move && otherBoard.move.side[0] === side[0]) {
         otherBoard = otherBoard.prior;
      }
      if (otherBoard && otherBoard.move) {
         const move = otherBoard.move;
         if (move.type === 'p' && move.to[0] === to[0] && move.to[1] === actuallyFrom[1]) {
            const moveFrom = (move.from === 'phantom') ? otherBoard.prior.phantom.from : move.from;
            if (move.side[0] === other[0] && moveFrom[1] != to[1]) {
               board.move.en_passant = true;
               alongside = 'p';
               boardPut(board, move.to, other, ' ');
               replacedFrom = move.to;
               replaced = boardGet(board, replacedFrom, side);
               boardPut(board, replacedFrom, side, ' ');
            }
         }
      }
   }

   if (from === 'phantom') {
      delete board.phantom;
   } else {
      boardPut(board, from, side, ' ');
      boardPut(board, from, other, ' ');
   }

   boardPut(board, to, side, type);

   if (alongside !== ' ') {
      boardPut(board, to, other, alongside);
   }

   if (replaced === ' ') {
      board.player = otherSide(board.player);
   } else {
      board.phantom = { from: replacedFrom, type: replaced + side[0] };
   }

   return board;
}

function renderHistory(board) {
   var list = [];

   while (board && board.move) {
      list.push(board.move);
      board = board.prior;
   }

   const NBSP = '\u00a0';  /* non-breaking space */
   const SHY = '\u00ad'  /* soft hyphen */
   const ZWSP = '\u200b';  /* zero-width space */

   var result = '';
   var n = 0;

   while (list.length > 0) {
      const move = list.pop();
      if (move.from === 'phantom') {
         const piece = move.type === 'p' ? '' : move.type.toUpperCase();
         const took = move.took ? 'x' : '';
         result += SHY + '*' + piece + took + move.to;
      } else {
         if (n > 0 || isDark(move.side)) {
            result += ' ';
         }

         if (isLight(move.side)) {
            ++n;
            result += String(n) + '.' + NBSP;
         }

         if (move.pass) {
            result += '...';
         } else if (move.alongside) {
            if (isLight(move.side)) {
               result += move.type.toUpperCase() + move.alongside.toUpperCase() + move.from + move.to;
            } else {
               result += move.alongside.toUpperCase() + move.type.toUpperCase() + move.from + move.to;
            }
         } else if (move.castle) {
            result += 'O-O';
         } else if (move.queen_castle) {
            result += 'O-O-O';
         } else {
            const piece = move.type === 'p' ? '' : move.type.toUpperCase();
            const took = move.took ? 'x' : '';
            result += piece + move.from + took + move.to;
         }
      }

      if (move.en_passant) {
         result += 'e.p.';
      }

      if (move.promotion) {
         result += '(' + move.promotion[0].toUpperCase() + ')';
      }

      if (move.took === 'k') {
         result += '#';
      }
   }

   return result;
}

function pieceStartDrag(ev, ui){
   const board = $('#cb_board').data('board');
   const dragged = $(this);
   const type = dragged.data('type');
   const from = dragged.data('location');
   const where = (from === 'phantom') ? board.phantom.from : from;
   const canCapture = boardGet(board, from, otherSide(type[1])) === ' ';
   const legals = legalMoves(board, type[1], type[0], where, canCapture);
   for (const there of legals) {
      $('#cb_' + there).addClass('cb-legal').droppable('enable');
   }
}

function pieceStopDrag(ev, ui){
   $('#cb_board .cb-legal').removeClass('cb-legal').droppable('disable');
}

function placePiece(where, type, count){
   var piece_id = 'cb_piece_' + type + '_' + count;
   var piece = $($('#' + piece_id)[0] || $('#cb_piece_' + type + ' img').clone());
   piece.attr('style', '');
   piece.attr('id', piece_id);
   piece.data({ type: type, location: where });
   piece.appendTo('#cb_' + where);
   piece.draggable({
      disabled: true,
      containment: '#cb_inner',
      revert: 'invalid',
      zIndex: 100,
      start: pieceStartDrag,
      stop: pieceStopDrag,
   });
   return piece;
}

function renderBoard(board){
   $('#cb_board .cb-piece .ui-draggable').draggable('destroy');
   $('#cb_board .cb-piece').attr('style', '').appendTo('#cb_hidden');
   $('#cb_board .cb-start').removeClass('cb-start');
   $('#cb_board .cb-end').removeClass('cb-end');
   $('#cb_phantom').appendTo('#cb_hidden');

   for (const side of ['light', 'dark']) {
      var counters = {};
      for (var row = 0; row < 8; ++row) {
         for (var column = 0; column < 8; ++column) {
            var here = 'abcdefgh'[column] + String(row+1);
            var type = board[side][row][column];
            if (type !== ' ') {
               if (!counters[type]) {
                  counters[type] = 0;
               }
               var count = ++counters[type];
               placePiece(here, type + side[0], count);
            }
         }
      }
   }

   var clss = isLight(board.player) ? '.cb-lt-piece' : '.cb-dk-piece';

   if (board.phantom) {
      var where = board.phantom.from;
      placePiece('phantom', board.phantom.type, 'ph');
      $('#cb_phantom').appendTo('#cb_' + where);
      $('#cb_board .ui-draggable').draggable('disable');
      $('#cb_phantom .ui-draggable-disabled').filter(clss).draggable('enable');
   } else {
      $('#cb_board .ui-draggable').draggable('disable');
      if (!board.move || board.move.took !== 'k') {
         $('#cb_board .ui-draggable-disabled').filter(clss).draggable('enable');
      }
   }

   if (board.move) {
      if (board.move.from === 'phantom') {
         $('#cb_' + board.prior.move.to).addClass('cb-start');
      } else {
         $('#cb_' + board.move.from).addClass('cb-start');
      }
      $('#cb_' + board.move.to).addClass('cb-end');
   }

   var msg = '';
   if (board.move && board.move.took === 'k') {
      msg = (isDark(board.move.side) ? 'Dark' : 'Light') + ' player won!';
   } else {
      msg = (isDark(board.player) ? 'Dark' : 'Light') + " player's move";
   }
   $('#cb_message').text(msg);

   $('#cb_history').text(renderHistory(board));
}

function setVisibleBoard(board, live){
   $('#cb_board').data('visible_board', board);
   renderBoard(board);

   $('#cb_nav_first').attr('disabled', board.prior ? false : true);
   $('#cb_nav_prev_turn').attr('disabled', board.prior ? false : true);
   $('#cb_nav_prev_state').attr('disabled', board.prior ? false : true);
   $('#cb_nav_next_state').attr('disabled', board.subsequent ? false : true);
   $('#cb_nav_next_turn').attr('disabled', board.subsequent ? false : true);

   if (live) {
      const liveBoard = $('#cb_board').data('board');
      $('#cb_undo').attr('disabled', liveBoard.prior ? false : true);
      $('#cb_redo').attr('disabled', liveBoard.subsequent ? false : true);
      $('#cb_pass').attr('disabled', liveBoard.phantom ? true : false);
      $('#cb_nav_last').attr('disabled', true);
      $('#cb_board').addClass('cb-live');
      $('#cb_board').removeClass('cb-archive');
   } else {
      $('#cb_undo').attr('disabled', true);
      $('#cb_redo').attr('disabled', true);
      $('#cb_pass').attr('disabled', true);
      $('#cb_board .ui-draggable').draggable('disable');
      $('#cb_nav_last').attr('disabled', false);
      $('#cb_board').removeClass('cb-live');
      $('#cb_board').addClass('cb-archive');
   }
}

function setCurrentBoard(board){
   $('#cb_board').data('board', board);

   /* navigation should not include the redo stack */
   const visible = cloneJSON(board);
   delete visible.subsequent;
   setVisibleBoard(visible, true);
}

function randomId(){
   var res = '';
   for (var i = 0; i < 4; ++i) {
      var part = Math.floor(Math.random() * 65536).toString(16);
      res = res + ('0000'.substring(part.length, 4) + part);
   }
   return res;
}

var PacoSakoUUID = '7c38edd4-c931-49c8-9f1a-84de560815db';

function putState(board){
   var boardElem = $('#cb_board');
   var gameId = boardElem.data('gameId');
   var game = gun.get(PacoSakoUUID).get('games').get(gameId);
   var state = JSON.stringify(board);
   $('#cb_board').data('skip_notify', state);
   game.put({ board: state });
   putMeta();
}

function putMeta(){
   var board = $('#cb_board').data('board');
   var gameId = $('#cb_board').data('gameId');
   var lightName = $('#cb_light_name').val();
   var darkName = $('#cb_dark_name').val();
   var meta = gun.get(PacoSakoUUID).get('meta').get(gameId);
   var stat = (board.move && board.move.took === 'k') ? 'mate' : null;
   meta.put({
      gameId: gameId,
      lightName: lightName,
      darkName: darkName,
      moves: countMoves(board),
      timestamp: board.timestamp || new Date().getTime(),
      status: stat,
   });
}

function switchGameId(newId){
   var boardElem = $('#cb_board');
   var gameId = boardElem.data('gameId');

   if (newId === gameId) {
      return;
   }

   if (gameId) {
      //gun.get(PacoSakoUUID).get('games').get(gameId).off();
      //gun.get(PacoSakoUUID).get('meta').get(gameId).off();
   }

   boardElem.data('gameId', newId);
   location.hash = '#/' + newId;

   /* this will be the starting state if no data is received from peers */
   var newBoard = initialBoard();
   setCurrentBoard(newBoard);

   $('#cb_notify')[0].checked = false;
   $('#cb_light_name').val('');
   $('#cb_dark_name').val('');
   $('#cb_board').removeData('skip_notify');

   gun.get(PacoSakoUUID).get('games').get(newId).on(function(d){
      if (d && d.board && $('#cb_board').data('gameId') === newId) {
         const board = JSON.parse(d.board);
         const cb_board = $('#cb_board').first();
         if ($('#cb_notify')[0].checked && cb_board.data('skip_notify') !== d.board) {
            /* ignore partial moves and undo/redo */
            if (!board.phantom && !board.subsequent) {
               if (board.move && board.move.took === 'k') {
                  notify((isDark(board.move.side) ? 'Dark' : 'Light') + ' player won!');
               } else {
                  notify((isDark(board.player) ? 'Dark' : 'Light') + ' player\'s turn');
               }
               $('#cb_board').data('skip_notify', d.board);
            }
         }
         setCurrentBoard(board);
      }
   });

   gun.get(PacoSakoUUID).get('meta').get(newId).on(function(d){
      if (d && $('#cb_board').data('gameId') === newId) {
         $('#cb_light_name').val(d.lightName || '');
         $('#cb_dark_name').val(d.darkName || '');
      }
   });

   var selOpt = $('#cb_game_' + newId);
   if (selOpt.length === 1) {
      $('#cb_select_game')[0].selectedIndex = selOpt.index();
   } else {
      $('#cb_select_game')[0].selectedIndex = -1;
   }
}

function disableNotify(){
   $('#cb_notify')[0].checked = false;
   $('#cb_notify').attr('disabled', true);
}

function requestNotify(){
   try {
      Notification.requestPermission(function (permission){
         if (permission === 'denied') {
            disableNotify();
         }
      });
   } catch (err) {
      disableNotify();
   }
}

function notify(body) {
   try {
      Notification.requestPermission(function(permission){
         if (permission === 'granted') {
            navigator.serviceWorker.ready.then(function(registration){
               registration.showNotification('Paco Ŝako', {
                  badge: 'svg/Chess_klt45.svg',
                  icon: 'svg/Chess_klt45.svg',
                  body: body,
                  tag: 'notice',
               });
            });
         } else if (permission === 'denied') {
            disableNotify();
         }
      });
   } catch (err) {
      disableNotify();
   }
}

$(function (){
   try {
      if (Notification.permission === 'denied') {
         disableNotify();
      } else {
         navigator.serviceWorker.register('sw.js').catch(disableNotify);
      }
   } catch (err) {
      disableNotify();
   }

   $('.cb-square').droppable({
      accept: '.cb-piece',
      disabled: true,
      deactivate: function(ev, ui){
         $(this).droppable('disable');
      },
      drop: function(ev, ui) {
         var dragged = ui.draggable;
         var type = dragged.data('type');
         var from = dragged.data('location');
         var to = this.id.replace(/^cb_/, '');
         dragged.appendTo('#cb_hidden');

         var newBoard = movePiece($('#cb_board').data('board'), type[1], from, to);
         putState(newBoard);
      },
   });

   function stepBack(board){
      if (!board.prior) {
         return cloneJSON(board);
      }

      const redoBoard = cloneJSON(board);
      delete redoBoard.prior;

      const newBoard = cloneJSON(board.prior);
      newBoard.subsequent = redoBoard;

      return newBoard;
   }

   function stepForward(board){
      if (!board.subsequent) {
         return cloneJSON(board);
      }

      const undoBoard = cloneJSON(board);
      delete undoBoard.subsequent;

      const newBoard = cloneJSON(board.subsequent);
      newBoard.prior = undoBoard;

      return newBoard;
   }

   $('#cb_undo').on('click', function(){
      putState(stepBack($('#cb_board').data('board')));
   });

   $('#cb_redo').on('click', function(){
      const board = stepForward($('#cb_board').data('board'));
      board.timestamp = new Date().getTime();
      putState(board);
   });

   $('#cb_nav_first').on('click', function(){
      var board = $('#cb_board').data('visible_board');
      if (board) {
         while (board.prior) {
            board = stepBack(board);
         }
         setVisibleBoard(board);
      }
   });

   $('#cb_nav_prev_turn').on('click', function(){
      var board = $('#cb_board').data('visible_board');
      board = stepBack(board);
      const player = board.player;
      while (board.prior && board.prior.player === player) {
         board = stepBack(board);
      }
      setVisibleBoard(board);
   });

   $('#cb_nav_prev_state').on('click', function(){
      setVisibleBoard(stepBack($('#cb_board').data('visible_board')));
   });

   $('#cb_nav_next_state').on('click', function(){
      setVisibleBoard(stepForward($('#cb_board').data('visible_board')));
   });

   $('#cb_nav_next_turn').on('click', function(){
      var board = $('#cb_board').data('visible_board');
      const player = board.player;
      board = stepForward(board);
      while (board.subsequent && board.player === player) {
         board = stepForward(board);
      }
      setVisibleBoard(board);
   });

   $('#cb_nav_last').on('click', function(){
      const visible = cloneJSON($('#cb_board').data('board'));
      delete visible.subsequent;
      setVisibleBoard(visible, true);
   });

   $('#cb_reset').on('click', function(){
      putState(initialBoard());
   });

   $('#cb_pass').on('click', function(){
      var board = $('#cb_board').data('board');
      if (!board.phantom) {
         var newBoard = cloneJSON(board);
         newBoard.prior = board;
         newBoard.move = { side: board.player, pass: true };
         newBoard.player = otherSide(board.player);
         newBoard.timestamp = new Date().getTime();
         putState(newBoard);
      }
   });

   $('#cb_select_game').on('change', function(){
      var optIndex = $('#cb_select_game')[0].selectedIndex;
      if (optIndex === 0) {
         switchGameId(randomId());
      } else if (optIndex >= 1) {
         var opt = $('#cb_select_game option')[optIndex];
         if (opt) {
            switchGameId(opt.id.replace(/^cb_game_/, ''));
         }
      }
   });

   $('#cb_notify').on('change', function(){
      if (this.checked) {
         requestNotify();
      }
   });

   let updateMeta = function() { putMeta(); }
   $('#cb_light_name').on('input', updateMeta);
   $('#cb_dark_name').on('input', updateMeta);

   var gameId = location.hash.replace(/^#\//, '');
   if (gameId.length !== 16) {
      gameId = randomId();
   }

   switchGameId(gameId);

   function updateTitle(opt){
      opt = $(opt);

      const then = opt.data('then');
      const now = new Date().getTime();
      var age_str = '';
      if (then > now) {
         age_str = ' (future)';
      } else if ((now - then) < 60*60*1000) {
         age_str = ' (' + Math.floor((now - then) / (60*1000)) + 'm)';
      } else if ((now - then) < 24*60*60*1000) {
         age_str = ' (' + Math.floor((now - then) / (60*60*1000)) + 'h)';
      } else if ((now - then) < 14*24*60*60*1000) {
         age_str = ' (' + Math.floor((now - then) / (24*60*60*1000)) + 'd)';
      } else if (opt.data('gameId') !== $('#cb_board').data('gameId')) {
         opt.remove();
         return;
      }
      opt.text(opt.data('title') + age_str);
   }

   gun.get(PacoSakoUUID).get('meta').map().on(function(d){
      if (d && d.gameId) {
         const lightName = d.lightName ? d.lightName : 'Light';
         const darkName = d.darkName ? d.darkName : 'Dark';
         const moves = !d.moves ? '' :
            (', ' + d.moves + (d.moves === 1 ? ' move' : ' moves'));

         var opt = $('#cb_game_' + d.gameId);

         if (!(d.lightName || d.darkName) && !d.moves && d.gameId !== $('#cb_board').data('gameId')) {
            if (opt.length >= 1) {
               opt.remove();
            }
         } else {
            if (opt.length === 0) {
               opt = $('<option></option>');
               opt.attr('id', 'cb_game_' + d.gameId);
            }

            var stat = '';
            if (d.status) {
               stat = ', ' + d.status;
            }

            opt.data('gameId', d.gameId);
            opt.data('title', lightName + ' vs. ' + darkName + moves + stat);
            opt.data('then', d.timestamp || new Date().getTime());
            opt.addClass('cb-game-option');
            opt.appendTo('#cb_select_game');
            updateTitle(opt);

            var select = $('#cb_select_game');
            var list = select.children('.cb-game-option').get();
            list.sort(function(a,b) {
               const then_a = $(a).data('then');
               const then_b = $(b).data('then');
               return (then_a < then_b) ? 1 : (then_a === then_b) ? 0 : -1;
            });

            for (const e of list) {
               $(e).appendTo(select);
            }
         }

         var selOpt = $('#cb_game_' + $('#cb_board').data('gameId'));
         if (selOpt.length === 1) {
            $('#cb_select_game')[0].selectedIndex = selOpt.index();
         } else {
            $('#cb_select_game')[0].selectedIndex = -1;
         }
      }
   });

   window.setInterval(function(){
      $('#cb_select_game').first().children('.cb-game-option').each(function(idx,opt){
         updateTitle(opt);
      });
   }, 15000);

   window.setInterval(function(){
      const peers = gun._.opt.peers;
      var n_open = 0;
      var n_total = 0;
      for (const peerId in peers) {
         ++n_total;
         try {
            const peer = peers[peerId];
            if (peer.constructor === RTCPeerConnection) {
               if (peer.connectionState === 'connected') {
                  ++n_open;
               }
            } else if (peer.wire && peer.wire.constructor === WebSocket) {
               if (peer.wire.readyState === peer.wire.OPEN) {
                  ++n_open;
               }
            }
         } catch (err) {}
      }
      $('#cb_peers').text('Synchronizing with ' + n_open + (n_open === 1 ? ' peer' : ' peers') + ' (' + n_total + ' total).');
   }, 1000);

   window.onpopstate = function(event){
      var gameId = location.hash.replace(/^#\//, '');
      if (gameId.length === 16) {
         switchGameId(gameId);
      }
   };

   /* force page reload after four hours to keep client code up to date */
   window.setTimeout(function(){ location.reload(); }, 4*3600*1000);
});

/* vim:set expandtab sw=3 ts=8: */