From 34886ff2f5d0ed075196ceb067d9d0620688aacf Mon Sep 17 00:00:00 2001
From: Whitney Young <wbyoung@fadingred.com>
Date: Wed, 27 May 2015 14:59:56 -0700
Subject: [PATCH] Support for relationships.

---
 README.md     |  2 +-
 index.js      | 54 +++++++++++++++++++++++++++++++++++++++++++++++----
 package.json  |  4 ++--
 test/tests.js | 43 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 96 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index 0674196..e5bd91d 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,7 @@ using [Azul.js][azul] with Express. For more information, see the
 ```js
 app.post('/articles', at.route(function(req, res, next, Article, Author) {
   Author.objects.findOrCreate({ name: req.body.author }).then(function(author) {
-    return Article.create({ author: author, title: req.body.title }).save();
+    return author.createArticle({ title: req.body.title }).save();
   })
   .then(function(article) {
     res.send({ article: article.json });
diff --git a/index.js b/index.js
index 1d61f38..e39e4d1 100644
--- a/index.js
+++ b/index.js
@@ -3,8 +3,6 @@
 var _ = require('lodash');
 var BPromise = require('bluebird');
 
-// TODO: this does not currently work across relationships
-
 var setupRequest = function(db, req) {
   if (req.azul && req.azul.transaction) { return; } // already set up
 
@@ -120,6 +118,54 @@ var makeExpressErrorRoute = function(fn) {
   };
 };
 
+/**
+ * Create a model class binder function.
+ *
+ * The resulting function should be called with the name of a model to bind. A
+ * bound model will be created from that name. All relationships on that model
+ * will also be bound properly. The result is a model that you can safely use
+ * that has been bound to the query/transaction.
+ *
+ * @param {Database} db
+ * @param {Request} req
+ * @return {Function}
+ */
+var modelBinder = function(db, req) {
+  var query = req.azul.query;
+  var bound = {};
+  var bind = function(/*name*/) {
+    var name = arguments[0].toLowerCase();
+    if (!bound[name]) {
+      var subclass = bound[name] = db.model(name).extend();
+      var prototype = subclass.__class__.prototype;
+
+      // create an override of each relation defined on the model with the
+      // relation's model classes swapped out for bound models. note that no
+      // re-configuration will occur for the relation objects. they'll simply
+      // use a different model class when creating or accessing instances.
+      _.keysIn(prototype).filter(function(key) {
+        return key.match(/Relation$/);
+      })
+      .forEach(function(key) {
+        // TODO: we're accessing protected variables on the relation here. it
+        // would be a good idea to expose a tested method in the main azul
+        // project that we're sure will exist.
+        var relation = Object.create(prototype[key]); // copy relation
+        relation._modelClass = bind(relation._modelClass.__name__);
+        relation._relatedModel = bind(relation._relatedModel.__name__);
+        Object.defineProperty(prototype, key, { // redefine property
+          enumerable: true, get: function() { return relation; },
+        });
+      });
+
+      // redefine the query object on this model class
+      subclass.reopenClass({ query: query });
+    }
+    return bound[name];
+  };
+  return bind;
+};
+
 /**
  * A wrapper for Express routes that binds queries & model classes to the
  * transaction.
@@ -173,9 +219,9 @@ var route = function(db, fn) {
 
     // setup the azul argument, binding queries and model classes
     var query = req.azul.query;
+    var binder = modelBinder(db, req);
     var azulArgs = azulParams.map(function(arg) {
-      return arg === 'query' ? query :
-        db.model(arg).extend({}, { query: query });
+      return arg === 'query' ? query : binder(arg);
     });
 
     // combine args & bind function we're wrapping
diff --git a/package.json b/package.json
index 64f27c3..161204c 100644
--- a/package.json
+++ b/package.json
@@ -36,10 +36,10 @@
     "lodash": "^3.6.0"
   },
   "peerDependencies": {
-    "azul": "^0.0.1-alpha.13"
+    "azul": "^0.0.1-alpha.14"
   },
   "devDependencies": {
-    "azul": "^0.0.1-alpha.13",
+    "azul": "^0.0.1-alpha.14",
     "chai": "^2.3.0",
     "coveralls": "^2.11.2",
     "istanbul": "^0.3.13",
diff --git a/test/tests.js b/test/tests.js
index 52fd89f..e0499fc 100644
--- a/test/tests.js
+++ b/test/tests.js
@@ -479,6 +479,49 @@ describe('azul-transaction', function() {
 
     });
 
+    it('works with relationships', function(done) {
+      db.model('article').reopen({
+        author: db.belongsTo(),
+        comments: db.hasMany(),
+      });
+      db.model('author', { articles: db.hasMany(), });
+      db.model('comment', { article: db.belongsTo() });
+      adapter.respond(/select \* from "authors"/i, [{ id: 5 }]);
+      adapter.respond(/select \* from "articles"/i,
+        [{ id: 1, 'author_id': 5 }]);
+
+      BPromise.bind().then(function() {
+        var route = at.route(function(req, res, query, Article) {
+          Article.objects.find(1).tap(function(article) {
+            return article.fetchAuthor();
+          })
+          .tap(function(article) {
+            return article.commentObjects.fetch();
+          })
+          .then(function() {
+            res.end();
+          })
+          .catch(done);
+        });
+        return route(req, res, next); // invoke route
+      })
+      .then(function() {
+        expect(adapter.executed).to.eql(['BEGIN']);
+        return res._end.wait;
+      })
+      .then(function() {
+        expect(adapter.clients.length).to.eql(1);
+        expect(adapter.executed).to.eql([
+          'BEGIN',
+          ['SELECT * FROM "articles" WHERE "id" = ? LIMIT 1', [1]],
+          ['SELECT * FROM "authors" WHERE "id" = ? LIMIT 1', [5]],
+          ['SELECT * FROM "comments" WHERE "article_id" = ?', [1]],
+          'COMMIT'
+        ]);
+      })
+      .then(done, done);
+    });
+
   });
 
   describe('test setup', function() {