besogo/js/saveSgf.js

Embeddable SGF player for the game of Go (aka Weiqi, Baduk)

// Convert game state tree into SGF string
besogo.composeSgf = function(editor) {
    'use strict';
    return '(' + composeNode(editor.getRoot()) + ')';

    // Recursively composes game node tree
    function composeNode(tree) {
        var string = ';', // Node starts with semi-colon
            children = tree.children,
            i; // Scratch iteration variable

        if (!tree.parent) { // Null parent means node is root
            // Compose root-specific properties
            string += composeRootProps(tree);
        }
        string += composeNodeProps(tree); // Compose general properties

        // Recurse composition on child nodes
        if (children.length === 1) { // Continue sequence if only one child
            string += '\n' + composeNode(children[0]);
        } else if (children.length > 1) {
            for (i = 0; i < children.length; i++) {
                string += '\n(' + composeNode(children[i]) + ')';
            }
        }

        return string;
    }

    // Composes root specific properties
    function composeRootProps(tree) {
        var string = 'FF[4]GM[1]CA[UTF-8]AP[besogo:' + besogo.VERSION + ']',
            x = tree.getSize().x,
            y = tree.getSize().y,
            gameInfo = editor.getGameInfo(), // Game info structure
            hasGameInfo = false, // Flag for existence of game info
            id; // Scratch iteration variable

        if (x === y) { // Square board size
            string += 'SZ[' + x + ']';
        } else { // Non-square board size
            string += 'SZ[' + x + ':' + y + ']';
        }
        string += 'ST[' + editor.getVariantStyle() + ']\n'; // Line break after header

        for ( id in gameInfo ) { // Compose game info properties
            if (gameInfo.hasOwnProperty(id) && gameInfo[id]) { // Skip empty strings
                string += id + '[' + escapeText(gameInfo[id]) + ']';
                hasGameInfo = true;
            }
        }
        string += (hasGameInfo ? '\n' : ''); // Line break if game info exists

        return string;
    }

    // Composes other properties
    function composeNodeProps(node) {
        var string = '',
            props, // Scratch variable for property structures
            stone, i, j; // Scratch iteration variables

        // Compose either move or setup properties depending on type of node
        if (node.getType() === 'move') { // Compose move properties
            stone = node.move;
            string += (stone.color === 1) ? 'W' : 'B';
            string += '[' + coordsToLetters(stone.x, stone.y) + ']';
        } else if (node.getType() === 'setup') { // Compose setup properties
            props = { AB: [], AW: [], AE: [] };
            for (i = 1; i <= node.getSize().x; i++) {
                for (j = 1; j <= node.getSize().y; j++) {
                    stone = node.getSetup(i, j);
                    if (stone) { // If setup stone placed, add to structure
                        props[ stone ].push({ x: i, y: j });
                    }
                }
            }
            string += composePointLists(props);
        }

        // Compose markup properties
        props = { CR: [], SQ: [], TR: [], MA: [], SL: [], LB: [] };
        for (i = 1; i <= node.getSize().x; i++) {
            for (j = 1; j <= node.getSize().y; j++) {
                stone = node.getMarkup(i, j);
                if (stone) { // If markup placed
                    if (typeof stone === 'string') { // String is label mark
                        props.LB.push({ x: i, y: j, label: stone });
                    } else { // Numerical code for markup
                        // Convert numerical code to property ID
                        stone = (['CR', 'SQ', 'TR', 'MA', 'SL'])[stone - 1];
                        props[stone].push({ x: i, y: j });
                    }
                }
            }
        }
        string += composePointLists(props);

        if (node.comment) { // Compose comment property
            string += (string ? '\n' : ''); // Add line break if other properties exist
            string += 'C[' + escapeText(node.comment) + ']';
        }

        return string;
    } // END function composeNodeProps

    // Composes properties from structure of point lists
    // Each member should be an array of points for property ID = key
    // Each point should specify point with (x, y) and may have optional label
    function composePointLists(lists) {
        var string = '',
            id, points, i; // Scratch iteration variables

        for (id in lists) { // Object own keys specifies property IDs
            if (lists.hasOwnProperty(id)) {
                points = lists[id]; // Corresponding members are point lists
                if (points.length > 0) { // Only add property if list non-empty
                    string += id;
                    for (i = 0; i < points.length; i++) {
                        string += '[' + coordsToLetters(points[i].x, points[i].y);
                        if (points[i].label) { // Add optional composed label
                            string += ':' + escapeText(points[i].label);
                        }
                        string += ']';
                    }
                }
            }
        }
        return string;
    }

    // Escapes backslash and close bracket for text output
    function escapeText(input) {
        input = input.replace(/\\/g, '\\\\'); // Escape backslash
        return input.replace(/\]/g, '\\]'); // Escape close bracket
    }

    // Converts numerical coordinates to letters
    function coordsToLetters(x, y) {
        if (x === 0 || y === 0) {
            return '';
        } else {
            return numToChar(x) + numToChar(y);
        }
    }

    function numToChar(num) { // Helper for coordsToLetters
        if (num > 26) { // Numbers 27-52 to A-Z
            return String.fromCharCode('A'.charCodeAt(0) + num - 27);
        } else { // Numbers 1-26 to a-z
            return String.fromCharCode('a'.charCodeAt(0) + num - 1);
        }
    }
};