74 lines
2.2 KiB
JavaScript
74 lines
2.2 KiB
JavaScript
define(function () {
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/* applyChange takes:
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ctx: the context (aka the realtime)
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oldval: the old value
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newval: the new value
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it performs a diff on the two values, and generates patches
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which are then passed into `ctx.remove` and `ctx.insert`
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*/
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var applyChange = function(ctx, oldval, newval) {
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// Strings are immutable and have reference equality. I think this test is O(1), so its worth doing.
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if (oldval === newval) {
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return;
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}
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var commonStart = 0;
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while (oldval.charAt(commonStart) === newval.charAt(commonStart)) {
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commonStart++;
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}
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var commonEnd = 0;
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while (oldval.charAt(oldval.length - 1 - commonEnd) === newval.charAt(newval.length - 1 - commonEnd) &&
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commonEnd + commonStart < oldval.length && commonEnd + commonStart < newval.length) {
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commonEnd++;
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}
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if (oldval.length !== commonStart + commonEnd) {
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if (ctx.localChange) { ctx.localChange(true); }
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ctx.remove(commonStart, oldval.length - commonStart - commonEnd);
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}
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if (newval.length !== commonStart + commonEnd) {
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if (ctx.localChange) { ctx.localChange(true); }
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ctx.insert(commonStart, newval.slice(commonStart, newval.length - commonEnd));
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console.log("insert: " + newval.slice(commonStart, newval.length - commonEnd));
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}
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};
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var attachTextarea = function(config) {
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var ctx = config.realtime;
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// initial state will always fail the !== check in genop.
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// because nothing will equal this object
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var content = {};
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// FIXME this is only necessary because we need to be able to update the
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// textarea. This is being deprecated, however. Instead
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var replaceText = function(newText) {
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content = newText;
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};
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// *** remote -> local changes
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ctx.onPatch(function(pos, length) {
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replaceText(ctx.getUserDoc());
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});
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// propogate()
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return function (newContent) {
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if (newContent !== content) {
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applyChange(ctx, ctx.getUserDoc(), newContent);
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if (ctx.getUserDoc() !== newContent) {
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console.log("Expected that: `ctx.getUserDoc() === newContent`!");
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}
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return true;
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}
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return false;
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};
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};
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return { attach: attachTextarea };
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});
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