cryptpad/www/common/cursor.js

define([
    '/common/treesome.js',
    '/bower_components/rangy/rangy-core.min.js'
], function (Tree, Rangy, saveRestore) {
    window.Rangy = Rangy;
    window.Tree = Tree;
    // do some function for the start and end of the cursor

    var log = function (x) { console.log(x); };
    var error = function (x) { console.log(x); };
    var verbose = function (x) { if (window.verboseMode) { console.log(x); } };

    /* accepts the document used by the editor */
    return function (inner) {
        var cursor = {};

        // there ought to only be one cursor at a time, so let's just
        // keep it internally
        var Range = cursor.Range = {
            start: {
                el: null,
                offset: 0
            },
            end: {
                el: null,
                offset:0
            }
        };

        /* FIXME we shouldn't use this, as only one might have been lost */
        cursor.lost = function () {
            return !(Tree.contains(Range.start.el.$, inner) &&
                Tree.contains(Range.end.el.$, inner));
        };

        // assumes a negative index
        var seekLeft = cursor.seekLeft = function (el, delta, current) {
            var textLength;
            var previous;

            // normalize

            if (-delta >= current) {
                delta += current;
                current = 0;
            } else {
                current += delta;
                delta = 0;
            }

            while (delta) {
                previous = el;
                el = Tree.previousNode(el, inner);
                if (el) {
                    textLength = el.textContent.length;
                    if (-delta > textLength) {
                        delta -= textLength;
                    } else {
                        current = textLength + delta;
                        delta = 0;
                    }
                } else {
                    return {
                        el: previous,
                        offset: 0,
                        error: "out of bounds"
                    };
                }
            }
            return {
                el: el,
                offset: current
            };
        };

        // seekRight assumes a positive delta
        var seekRight = cursor.seekRight = function (el, delta, current) {
            var textLength;
            var previous;

            // normalize
            delta += current;
            current = 0;

            while (delta) {
                if (el) {
                    textLength = el.textContent.length;
                    if (delta >= textLength) {
                        delta -= textLength;
                        previous = el;
                        el = Tree.nextNode(el, inner);
                    } else {
                        current = delta;
                        delta = 0;
                    }
                } else {
                    // don't ever return a negative index
                    if (previous.textContent.length) {
                        textLength = previous.textContent.length - 1;
                    } else {
                        textLength = 0;
                    }
                    return {
                        el: previous,
                        offset: textLength,
                        error: "out of bounds"
                    };
                }
            }
            return {
                el: el,
                offset: current
            };
        };

        var seekToDelta = cursor.seekToDelta = function (el, delta, current) {
            var result = null;
            if (el) {
                if (delta < 0)  {
                    return seekLeft(el, delta, current);
                } else if (delta > 0) {
                    return seekRight(el, delta, current);
                } else {
                    result = {
                        el: el,
                        offset: current
                    };
                }
            } else {
                error("[cursor.seekToDelta] el is undefined");
            }
            return result;
        };

        var checkFromEnd = cursor.checkFromEnd = function (root, predicate) {
            var last = Tree.rightmostNode(root);
            var success = false;
            var i = 0;
            while (last && !success) {
                success = predicate(last, i++);
                last = Tree.previousNode(last, root);
            }
            return success;
        };

        /*  uses closure to capture the root node because I'm lazy

        */
        var getTrailingNodes = cursor.getTrailingNodes = function (el) {
            var trailing = [];
            var success = cursor.checkFromEnd(inner, function (cur) {
                if (cur === el) {
                    trailing.push(cur);
                    return true;
                } else { trailing.push(cur); }
            });
            return success && trailing;
        };

        var recoverNodeByTrailing = cursor.recoverNodeByTrailing = function (trailing) {
            // clone the array
            var T = trailing.slice(0);
            var L = T.length;
            var el = null;
            cursor.checkFromEnd(inner, function (cur, i) {
                if (i >= L) {
                    //console.log("[cursor.recoverNodeByTrailing] out of bounds");
                    return true;
                } else {
                    if (cur.nodeName !== T[i].nodeName) {
                        console.log("[cursor.recoverNodeByTrailing] false name");
                        console.log(cur);
                        return true;
                    } else if (cur.nodeName === T[i].nodeName && i === L - 1) {
                        el = cur;
                        return true;
                    } else {
                        return false;
                    }
                }
            });
            return el;
        };

        /* cursor.find uses information produced by side effects of 'update'
            to recover the cursor
        */
        cursor.find = function () {
            ['start', 'end'].forEach(function (pos) {
                // is this metric even reliable?
                var node;
                var trailing = Range[pos].trailing;
                if (Range[pos].lost) {
                    if (trailing.length) {
                        // use the trailing nodes to find the node..
                        node = recoverNodeByTrailing(trailing);
                    }
                    if (node) {
                        // if that worked....great!
                        Range[pos].el = node;

                    } else {
                        // if not, try falling back to the nearest parent?

                    }
                } else {
                    // it wasn't lost, you don't need to do anything.
                }

            });
        };

        /*  cursor.update takes notes about wherever the cursor was last seen
            in the event of a cursor loss, the information produced by side
            effects of this function should be used to recover the cursor

            returns an error string if no range is found
        */
        cursor.update = function (sel, root) {
            verbose("cursor.update");
            root = root || inner;
            sel = sel || Rangy.getSelection(root);
            // FIXME under what circumstances are no ranges found?
            if (!sel.rangeCount) {
                error('[cursor.update] no ranges found');
                //return 'no ranges found';
            }
            var range = sel.getRangeAt(0);
  
            // Big R Range is caught in closure, and maintains persistent state

            ['start', 'end'].forEach(function (pos) {
                Range[pos].el = range[pos+'Container'];
                Range[pos].offset = range[pos+'Offset'];
                Range[pos].parents = Tree.parentsOf(Range[pos].el, root);

                // trailing is either an array or false
                var trailing = getTrailingNodes(Range[pos].el);

                // if it's false, then the cursor has been lost
                // TODO do a more careful check to see if the cursor has been destroyed.
                Range[pos].lost = !trailing;

                if (Range[pos].lost) {
                    // don't overwrite the previous trailing nodes
                    // that array will be used to recover the cursor

                } else {
                    // if you haven't lost the cursor, update the node list
                    Range[pos].trailing = trailing;
                }
            });
        };

        /*  0 -> neither is lost
            1 -> start is lost
            2 -> end is lost
            3 -> both are lost */
        var isLost = cursor.isLost = function () {
            var state = ['start', 'end'].map(function (pos, i) {
                return Tree.contains(Range[pos].el, inner)? 0 : i + 1;
            });
            return state[0] | state[1];
        };

        var recover = cursor.recover = function (lost) {
            var sel = Rangy.getSelection(inner);

            // create a range to modify
            var range = Rangy.createRange();

            /*  if range is backwards, cursor.delta fails
                so check if they're in the expected order
                before setting the new range */

            if (lost & 1) {
                Range.start.el = recoverNodeByTrailing(Range.start.trailing);
            }
            if (lost & 2) {
                Range.end.el = recoverNodeByTrailing(Range.end.trailing);
            }

            // el.parentNode is null
            var order = Tree.orderOfNodes(Range.start.el, Range.end.el, inner);
            var backward;

            // this could all be one line but nobody would be able to read it
            if (order === -1) {
                // definitely backward
                backward = true;
            } else if (order === 0) {
                // might be backward, check offsets to know for sure
                backward = (Range.start.offset > Range.end.offset);
            } else {
                // definitely not backward
                backward = false;
            }

            if (backward) {
                range.setStart(Range.end.el, Range.end.offset);
                range.setEnd(Range.start.el, Range.start.offset);
            } else {
                range.setStart(Range.start.el, Range.start.offset);
                range.setEnd(Range.end.el, Range.end.offset);
            }

            // actually set the cursor to the new range
            sel.setSingleRange(range);
        };

        cursor.delta = function (delta1, delta2) {
            var sel = Rangy.getSelection(inner);
            delta2 = (typeof delta2 !== 'undefined') ? delta2 : delta1;

            // update returns errors if there are problems
            // and updates the persistent Range object
            var err = cursor.update(sel, inner);
            if (err) { return err; }

            // create a range to modify
            var range = Rangy.createRange();

            /*
                The assumption below is that Range.(start|end).el
                actually exists. This might not be the case.
                TODO check if start and end elements are defined
            */

            // using infromation about wherever you were last...
            // move both parts by some delta
            var start = seekToDelta(Range.start.el, delta1, Range.start.offset);
            var end = seekToDelta(Range.end.el, delta2, Range.end.offset);

            /*  if range is backwards, cursor.delta fails
                so check if they're in the expected order
                before setting the new range */

            var order = Tree.orderOfNodes(start.el, end.el, inner);
            var backward;

            // this could all be one line but nobody would be able to read it
            if (order === -1) {
                // definitely backward
                backward = true;
            } else if (order === 0) {
                // might be backward, check offsets to know for sure
                backward = (start.offset > end.offset);
            } else {
                // definitely not backward
                backward = false;
            }

            if (backward) {
                range.setStart(end.el, end.offset);
                range.setEnd(start.el, start.offset);
            } else {
                range.setStart(start.el, start.offset);
                range.setEnd(end.el, end.offset);
            }

            // actually set the cursor to the new range
            sel.setSingleRange(range);
            return {
                startError: start.error,
                endError: end.error
            };
        };

        return cursor;
    };
});