Push WIP

www/_socket/sharejs_textarea-transport-only.js

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