derby/dist/textDiff.js

MVC framework making it easy to write realtime, collaborative applications that run in both Node.js and browsers.

exports.onStringInsert = onStringInsert;
exports.onStringRemove = onStringRemove;
exports.onTextInput = onTextInput;
function onStringInsert(el, previous, index, text) {
    function transformCursor(cursor) {
        return (index < cursor) ? cursor + text.length : cursor;
    }
    if (!previous) {
        previous = '';
    }
    var newText = previous.slice(0, index) + text + previous.slice(index);
    replaceText(el, newText, transformCursor);
}
function onStringRemove(el, previous, index, howMany) {
    function transformCursor(cursor) {
        return (index < cursor) ? cursor - Math.min(howMany, cursor - index) : cursor;
    }
    if (!previous) {
        previous = '';
    }
    var newText = previous.slice(0, index) + previous.slice(index + howMany);
    replaceText(el, newText, transformCursor);
}
function replaceText(el, newText, transformCursor) {
    var selectionStart = transformCursor(el.selectionStart);
    var selectionEnd = transformCursor(el.selectionEnd);
    var scrollTop = el.scrollTop;
    el.value = newText;
    if (el.scrollTop !== scrollTop) {
        el.scrollTop = scrollTop;
    }
    if (document.activeElement === el) {
        el.selectionStart = selectionStart;
        el.selectionEnd = selectionEnd;
    }
}
function onTextInput(model, segments, value) {
    var previous = model._get(segments) || '';
    if (previous === value)
        return;
    var start = 0;
    while (previous.charAt(start) === value.charAt(start)) {
        start++;
    }
    var end = 0;
    while (previous.charAt(previous.length - 1 - end) === value.charAt(value.length - 1 - end) &&
        end + start < previous.length &&
        end + start < value.length) {
        end++;
    }
    if (previous.length !== start + end) {
        var howMany = previous.length - start - end;
        model._stringRemove(segments, start, howMany);
    }
    if (value.length !== start + end) {
        var inserted = value.slice(start, value.length - end);
        model._stringInsert(segments, start, inserted);
    }
}