From 7b305b4920c5f988b8a33518521d0cbe1f826650 Mon Sep 17 00:00:00 2001
From: Diogo Doreto <diogo.doreto@gmail.com>
Date: Sun, 22 Nov 2015 21:44:14 -0200
Subject: [PATCH] Add support to n:m relations

---
 lib/sql.js       | 54 ++++++++++++++++++++++++++++++++----------------
 test/sql.test.js | 30 ++++++++++++++++++++++++++-
 2 files changed, 65 insertions(+), 19 deletions(-)

diff --git a/lib/sql.js b/lib/sql.js
index d3492f9..e7c1c06 100644
--- a/lib/sql.js
+++ b/lib/sql.js
@@ -1073,33 +1073,51 @@ SQLConnector.prototype.buildJoins = function(model, where) {
   var relations = modelDef.model.relations;
   var stmt = new ParameterizedSQL('', []);
 
+  var buildOneToMany = function buildOneToMany(modelFrom, keyFrom, modelTo, keyTo, filter) {
+    var modelToEscaped = this.tableEscaped(modelTo);
+    var innerFilter = assign({}, filter);
+    var innerIdField = {};
+    innerIdField[keyTo] = true;
+    innerFilter.fields = assign({}, innerFilter.fields, innerIdField);
+
+    var condition = this.columnEscaped(modelFrom, keyFrom) + '=' +
+      this.columnEscaped(modelTo, keyTo);
+
+    var innerSelect = this.buildSelect(modelTo, innerFilter, {
+      skipParameterize: true
+    });
+
+    return new ParameterizedSQL('INNER JOIN (', [])
+      .merge(innerSelect)
+      .merge(') AS ' + modelToEscaped)
+      .merge('ON ' + condition);
+  }.bind(this);
+
   for (var key in where) {
     if (!(key in relations)) continue;
 
     var rel = relations[key];
     var keyFrom = rel.keyFrom;
     var modelTo = rel.modelTo.definition.name;
-    var modelToEscaped = this.tableEscaped(modelTo);
     var keyTo = rel.keyTo;
 
-    var innerWhere = assign({}, where[key]);
-    var innerIdField = {};
-    innerIdField[keyTo] = true;
-    innerWhere.fields = assign({}, innerWhere.fields, innerIdField);
-
-    var condition = this.columnEscaped(model, keyFrom) + '=' +
-      this.columnEscaped(modelTo, keyTo);
-
-    var innerSelect = this.buildSelect(modelTo, innerWhere, {
-      skipParameterize: true
-    });
-
-    stmt
-      .merge('INNER JOIN (')
-      .merge(innerSelect)
-      .merge(') AS ' + modelToEscaped)
-      .merge('ON ' + condition);
+    var join;
+    if (!rel.modelThrough) {
+      // 1:n relation
+      join = buildOneToMany(model, keyFrom, modelTo, keyTo, where[key]);
+    } else {
+      // n:m relation
+      var modelThrough = rel.modelThrough.definition.name;
+      var keyThrough = rel.keyThrough;
+      var modelToKey = rel.modelTo.definition._ids[0].name;
+      var innerFilter = {fields: {}};
+      innerFilter.fields[keyThrough] = true;
 
+      var joinInner = buildOneToMany(model, keyFrom, modelThrough, keyTo, innerFilter);
+      join = buildOneToMany(modelThrough, keyThrough, modelTo, modelToKey, where[key]);
+      join = joinInner.merge(join);
+    }
+    stmt.merge(join);
   }
 
   return stmt;
diff --git a/test/sql.test.js b/test/sql.test.js
index e6859d4..a7268b2 100644
--- a/test/sql.test.js
+++ b/test/sql.test.js
@@ -57,6 +57,12 @@ describe('sql connector', function() {
     Order.belongsTo(Customer, {as: 'customer', foreignKey: 'customer_name'});
     Order.belongsTo(Store, {as: 'store', foreignKey: 'store_id'});
     Store.hasMany(Order, {as: 'orders', foreignKey: 'store_id'});
+    Store.hasMany(Customer, {
+      as: 'customers',
+      through: Order,
+      foreignKey: 'store_id',
+      keyThrough: 'customer_name'
+    });
     Customer.belongsTo(Store, {as: 'favorite_store', foreignKey: 'favorite_store'});
     Store.hasMany(Customer, {as: 'customers_fav', foreignKey: 'favorite_store'});
   });
@@ -343,7 +349,7 @@ describe('sql connector', function() {
     });
   });
 
-  it('builds SELECT with INNER JOIN', function () {
+  it('builds SELECT with INNER JOIN (1:n relation)', function () {
     var sql = connector.buildSelect('customer', {
       where: {
         orders: {
@@ -364,6 +370,28 @@ describe('sql connector', function() {
     });
   });
 
+  it('builds SELECT with INNER JOIN (n:n relation)', function () {
+    var sql = connector.buildSelect('store', {
+      where: {
+        customers: {
+          where: {
+            vip: true
+          }
+        }
+      }
+    });
+
+    expect(sql.toJSON()).to.eql({
+      sql: 'SELECT DISTINCT `STORE`.`ID`,`STORE`.`STATE` FROM `STORE` INNER JOIN' +
+      ' ( SELECT `ORDER`.`CUSTOMER_NAME`,`ORDER`.`STORE_ID` FROM `ORDER` ' +
+      'ORDER BY `ORDER`.`ID` ) AS `ORDER` ON `STORE`.`ID`=`ORDER`.`STORE_ID` ' +
+      'INNER JOIN ( SELECT `CUSTOMER`.`NAME` FROM `CUSTOMER` WHERE ' +
+      '`CUSTOMER`.`VIP`=$1 ORDER BY `CUSTOMER`.`NAME` ) AS `CUSTOMER` ON ' +
+      '`ORDER`.`CUSTOMER_NAME`=`CUSTOMER`.`NAME`  ORDER BY `STORE`.`ID`',
+      params: [true]
+    });
+  });
+
   it('builds SELECT with INNER JOIN and order by relation columns', function () {
     var sql = connector.buildSelect('order', {
       where: {