Rewrote ot.coffee -> javascript

Author: josephg

lib/ot.coffee

@@ -0,0 +1,135 @@
+// This contains the master OT functions for the database. They look like
+// ot-types style operational transform functions, but they're a bit different.
+// These functions understand versions and can deal with out of bound create &
+// delete operations.
+
+var otTypes = require('ottypes');
+
+// Default validation function
+var defaultValidate = function() {};
+
+// Returns an error string on failure. Rockin' it C style.
+exports.checkOpData = function(opData) {
+  if (typeof opData !== 'object') return 'Missing opData';
+  if (typeof (opData.op || opData.create) !== 'object' && opData.del !== true) return 'Missing op1';
+  if (opData.create && typeof opData.create.type !== 'string') return 'Missing create type';
+
+  if ((opData.src != null) && typeof opData.src !== 'string') return 'Invalid src';
+  if ((opData.seq != null) && typeof opData.seq !== 'number') return 'Invalid seq';
+  if (!!opData.seq !== !!opData.src) return 'seq but not src';
+};
+
+exports.normalize = function(opData) {
+  // I'd love to also normalize opData.op if it exists, but I don't know the
+  // type of the operation. And I can't find that out until after transforming
+  // the operation anyway.
+  if (opData.create) {
+    // Store the full URI of the type, not just its short name
+    return opData.create.type = otTypes[opData.create.type].uri;
+  }
+};
+
+// This is the super apply function that takes in snapshot data (including the
+// type) and edits it in-place.  Returns an error string or null for success.
+exports.apply = function(data, opData) {
+  var err;
+
+  if (typeof opData !== 'object')
+    return 'Missing data';
+  if (!(typeof (opData.op || opData.create) === 'object' || opData.del === true))
+    return 'Missing op';
+
+  if ((data.v != null) && (opData.v != null) && data.v !== opData.v)
+    return 'Version mismatch';
+
+  var validate = opData.validate || defaultValidate;
+  var preValidate = opData.preValidate || defaultValidate;
+
+  if (opData.create) { // Create operations
+    if (data.type) return 'Document already exists';
+
+    // The document doesn't exist, although it might have once existed.
+    var create = opData.create;
+    var type = otTypes[create.type];
+    if (!type) return "Type not found";
+
+    if ((err = preValidate(opData, data))) return err;
+
+    var snapshot = type.create(create.data);
+    data.data = snapshot;
+    data.type = type.uri;
+    data.v++;
+
+    if ((err = validate(opData, data))) return err;
+
+  } else if (opData.del) { // Delete operations
+    if ((err = preValidate(opData, data))) return err;
+
+    opData.prev = {data:data.data, type:data.type};
+    delete data.data;
+    delete data.type;
+    data.v++;
+    if ((err = validate(opData, data))) return err;
+
+  } else { // Edit operations
+    if (!data.type) return 'Document does not exist';
+
+    var op = opData.op;
+    if (typeof op !== 'object') return 'Missing op';
+    var type = otTypes[data.type];
+    if (!type) return 'Type not found';
+
+    try {
+      // This shattering stuff is a little bit dodgy. Its important because it
+      // lets the OT type apply the operation incrementally, which means the
+      // operation can be validated piecemeal. (Even though the entire
+      // operation is accepted or rejected wholesale). Racer uses this, but I'm
+      // still not entirely sure its the right API.
+      var atomicOps = type.shatter ? type.shatter(op) : [op];
+      for (var i = 0; i < atomicOps.length; i++) {
+        var atom = atomicOps[i];
+        opData.op = atom;
+        if ((err = preValidate(opData, data))) return err;
+
+        // !! The money line.
+        data.data = type.apply(data.data, atom);
+
+        if ((err = validate(opData, data))) return err;
+      }
+      // Make sure to restore the operation before returning.
+      opData.op = op;
+
+    } catch (err) {
+      console.log(err.stack);
+      return err.message;
+    }
+    data.v++;
+  }
+};
+
+exports.transform = function(type, opData, appliedOpData) {
+  if (appliedOpData.del) {
+    if (!opData.del) return 'Document was deleted';
+
+    if (opData.v != null) {
+      opData.v++;
+    }
+    return;
+  }
+
+  if (appliedOpData.create) return 'Document created remotely';
+
+  if (!type) return 'Document does not exist';
+
+  if ((opData.v != null) && opData.v !== appliedOpData.v)
+    return 'Version mismatch';
+
+  if (typeof type === 'string') {
+    type = otTypes[type];
+    if (!type) return "Type not found";
+  }
+
+  opData.op = type.transform(opData.op, appliedOpData.op, 'left');
+  if (opData.v != null) opData.v++;
+};
+

lib/ot.js

@@ -28,6 +28,10 @@ describe 'ot', ->
       assert.ok ot.checkOpData {del:true, v:5, seq:123}
       assert.ok ot.checkOpData {del:true, v:5, src:'hi', seq:'there'}
 
+    it 'fails if a create operation is missing its type', ->
+      assert.ok ot.checkOpData {create:{}}
+      assert.ok ot.checkOpData {create:123}
+
     it 'accepts valid create operations', ->
       assert.equal null, ot.checkOpData {create:{type:simple.uri}}
       assert.equal null, ot.checkOpData {create:{type:simple.uri, data:'hi there'}}