From d78481c1ceea86b39cdafad8cc718b3d9d611f48 Mon Sep 17 00:00:00 2001
From: David Greenspan <dgreenspan@alum.mit.edu>
Date: Sun, 16 Sep 2012 02:28:41 -0700
Subject: [PATCH] introduce Meteor.deps.ContextSet, use in Session

---
 packages/deps/deps-utils.js | 42 ++++++++++++++++++++++
 packages/deps/package.js    |  2 +-
 packages/session/session.js | 72 +++++++++++--------------------------
 3 files changed, 64 insertions(+), 52 deletions(-)
 create mode 100644 packages/deps/deps-utils.js

diff --git a/packages/deps/deps-utils.js b/packages/deps/deps-utils.js
new file mode 100644
index 0000000000..3010a0e087
--- /dev/null
+++ b/packages/deps/deps-utils.js
@@ -0,0 +1,42 @@
+(function () {
+
+  // Constructor for an empty ContextSet.
+  var ContextSet = function () {
+    this._contextsById = {};
+  };
+
+  // Adds the Context `ctx` to the set (if it is
+  // not already present).  The Context will only
+  // remain in the set as long as it has not been
+  // invalidated.
+  // Returns true if the context was newly added.
+  ContextSet.prototype.add = function (ctx) {
+    var self = this;
+    if (ctx && ! (ctx.id in self._contextsById)) {
+      self._contextsById[ctx.id] = ctx;
+      ctx.on_invalidate(function () {
+        delete self._contextsById[ctx.id];
+      });
+      return true;
+    }
+    return false;
+  };
+
+  // Invalidate all Contexts in the set and remove
+  // them from the set.
+  ContextSet.prototype.invalidateAll = function () {
+    var self = this;
+    for (var id in self._contextsById)
+      self._contextsById[id].invalidate();
+  };
+
+  // Returns true if there are no Contexts in this set.
+  ContextSet.prototype.isEmpty = function () {
+    var self = this;
+    for(var id in self._contextsById)
+      return false;
+    return true;
+  };
+
+  Meteor.deps.ContextSet = ContextSet;
+})();
\ No newline at end of file
diff --git a/packages/deps/package.js b/packages/deps/package.js
index 9949cfdd73..f21ff22073 100644
--- a/packages/deps/package.js
+++ b/packages/deps/package.js
@@ -9,5 +9,5 @@ Package.on_use(function (api, where) {
   where = where || ['client', 'server'];
 
   api.use('underscore', where);
-  api.add_files('deps.js', where);
+  api.add_files(['deps.js', 'deps-utils.js'], where);
 });
diff --git a/packages/session/session.js b/packages/session/session.js
index 11b39c580b..f2ca6683f5 100644
--- a/packages/session/session.js
+++ b/packages/session/session.js
@@ -1,31 +1,9 @@
 // XXX could use some tests
 
 Session = _.extend({}, {
-  keys: {},
-  key_deps: {}, // key -> context id -> context
-  key_value_deps: {}, // key -> value -> context id -> context
-
-  // XXX remove debugging method (or improve it, but anyway, don't
-  // ship it in production)
-  dump_state: function () {
-    var self = this;
-    console.log("=== Session state ===");
-    for (var key in self.key_deps) {
-      var ids = _.keys(self.key_deps[key]);
-      if (!ids.length)
-        continue;
-      console.log(key + ": " + _.reject(ids, function (x) {return x === "_once"}).join(' '));
-    }
-
-    for (var key in self.key_value_deps) {
-      for (var value in self.key_value_deps[key]) {
-        var ids = _.keys(self.key_value_deps[key][value]);
-        if (!ids.length)
-          continue;
-        console.log(key + "(" + value + "): " + _.reject(ids, function (x) {return x === "_once";}).join(' '));
-      }
-    }
-  },
+  keys: {}, // key -> value
+  key_deps: {}, // key -> ContextSet
+  key_value_deps: {}, // key -> value -> ContextSet
 
   set: function (key, value) {
     var self = this;
@@ -35,30 +13,24 @@ Session = _.extend({}, {
       return;
     self.keys[key] = value;
 
-    var invalidate = function (map) {
-      if (map)
-        for (var id in map)
-          map[id].invalidate();
+    var invalidateAll = function (set) {
+      set && set.invalidateAll();
     };
 
-    self._ensureKey(key);
-    invalidate(self.key_deps[key]);
-    invalidate(self.key_value_deps[key][old_value]);
-    invalidate(self.key_value_deps[key][value]);
+    invalidateAll(self.key_deps[key]);
+    if (self.key_value_deps[key]) {
+      invalidateAll(self.key_value_deps[key][old_value]);
+      invalidateAll(self.key_value_deps[key][value]);
+    }
   },
 
   get: function (key) {
     var self = this;
     var context = Meteor.deps.Context.current;
-    self._ensureKey(key);
-
-    if (context && !(context.id in self.key_deps[key])) {
-      self.key_deps[key][context.id] = context;
-      context.on_invalidate(function () {
-        delete self.key_deps[key][context.id];
-      });
+    if (context) {
+      self._ensureKey(key);
+      self.key_deps[key].add(context);
     }
-
     return self.keys[key];
   },
 
@@ -74,19 +46,17 @@ Session = _.extend({}, {
 
     if (context) {
       self._ensureKey(key);
+
       if (!(value in self.key_value_deps[key]))
-        self.key_value_deps[key][value] = {};
+        self.key_value_deps[key][value] = new Meteor.deps.ContextSet;
 
-      if (!(context.id in self.key_value_deps[key][value])) {
-        self.key_value_deps[key][value][context.id] = context;
+      var isNew = self.key_value_deps[key][value].add(context);
+      if (isNew) {
         context.on_invalidate(function () {
-          delete self.key_value_deps[key][value][context.id];
-
           // clean up [key][value] if it's now empty, so we don't use
           // O(n) memory for n = values seen ever
-          for (var x in self.key_value_deps[key][value])
-            return;
-          delete self.key_value_deps[key][value];
+          if (self.key_value_deps[key][value].isEmpty())
+            delete self.key_value_deps[key][value];
         });
       }
     }
@@ -97,8 +67,8 @@ Session = _.extend({}, {
   _ensureKey: function (key) {
     var self = this;
     if (!(key in self.key_deps)) {
-      self.key_deps[key] = {};
-      self.key_value_deps[key] = {};
+      self.key_deps[key] = new Meteor.deps.ContextSet;
+      self.key_value_deps[key] = new Meteor.deps.ContextSet;
     }
   }
 });