From 8b84aca71093dfefd01622c5be2f96ac18326b79 Mon Sep 17 00:00:00 2001
From: calebboyd <caleb.boyd@gmail.com>
Date: Wed, 23 Sep 2015 13:28:56 -0500
Subject: [PATCH 1/2] expose next on context

---
 index.js     | 62 ++++++++++++++++++++++++++++++++++++----------------
 test/test.js | 13 +++++++++--
 2 files changed, 54 insertions(+), 21 deletions(-)

diff --git a/index.js b/index.js
index 0c5669b..befd013 100644
--- a/index.js
+++ b/index.js
@@ -6,6 +6,45 @@
 
 module.exports = compose;
 
+function noop () {
+  return Promise.resolve()
+}
+
+/**
+ * Try catch middlware invocation
+ * @api private
+ * @param fn
+ * @param ctx
+ * @param next
+ * @returns {Promise<any>}
+ */
+
+function tryCatch(fn, ctx, next) {
+  try {
+    return Promise.resolve(fn(ctx, next))
+  } catch (err) {
+    return Promise.reject(err)
+  }
+}
+
+
+/**
+ * Reducer for creating storing next reference
+ * @api private
+ * @param next
+ * @param mw
+ * @returns {Function}
+ */
+
+function middlewareReducer(next, mw) {
+  return function(ctx, nextFn) {
+    ctx.next = next && function () { return next(ctx) }
+      || nextFn
+      || noop
+    return tryCatch(mw, ctx, ctx.next)
+  }
+}
+
 /**
  * Compose `middleware` returning
  * a fully valid middleware comprised
@@ -21,25 +60,10 @@ function compose(middleware){
   for (const fn of middleware) {
     if (typeof fn !== 'function') throw new TypeError('Middleware must be composed of functions!')
   }
-
-  /**
-   * @param {Object} context
-   * @return {Promise}
-   * @api public
-   */
-
-  return function (context, next) {
-    return dispatch(0)
-    function dispatch(i) {
-      const fn = middleware[i] || next
-      if (!fn) return Promise.resolve()
-      try {
-        return Promise.resolve(fn(context, function next() {
-          return dispatch(i + 1)
-        }))
-      } catch(err) {
-        return Promise.reject(err);
-      }
+  if (!middleware.length) {
+    return function(ctx, next) {
+      return tryCatch(next || noop, ctx, noop)
     }
   }
+  return middleware.reduceRight(middlewareReducer, undefined)
 }
diff --git a/test/test.js b/test/test.js
index 814bcb1..959e1d5 100644
--- a/test/test.js
+++ b/test/test.js
@@ -174,9 +174,18 @@ describe('Koa Compose', function(){
 
     return compose(stack.map(co.wrap))({}).then(function () {
       throw 'promise was not rejected'
-    })
-    .catch(function (e) {
+    }).catch(function (e) {
       e.should.be.instanceof(Error)
     })
   })
+
+  it('should expose next on the context', function () {
+    var stack = [];
+
+    stack.push(function (context, next) {
+      context.next.should.equal(next)
+    })
+
+    return compose(stack.map(co.wrap))({})
+  })
 })

From 1c9c3d1a6de9410b496f04f354fb69915d0cd657 Mon Sep 17 00:00:00 2001
From: calebboyd <caleb.boyd@gmail.com>
Date: Thu, 24 Sep 2015 22:21:53 -0500
Subject: [PATCH 2/2] pass initial next function through

---
 index.js     |  2 +-
 test/test.js | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/index.js b/index.js
index befd013..38acae3 100644
--- a/index.js
+++ b/index.js
@@ -38,7 +38,7 @@ function tryCatch(fn, ctx, next) {
 
 function middlewareReducer(next, mw) {
   return function(ctx, nextFn) {
-    ctx.next = next && function () { return next(ctx) }
+    ctx.next = next && function () { return next(ctx, nextFn) }
       || nextFn
       || noop
     return tryCatch(mw, ctx, ctx.next)
diff --git a/test/test.js b/test/test.js
index 959e1d5..b20ed9d 100644
--- a/test/test.js
+++ b/test/test.js
@@ -179,6 +179,28 @@ describe('Koa Compose', function(){
     })
   })
 
+  it('should return a valid middleware', function () {
+    var val = 0
+    compose([
+      compose([
+        (ctx, next) => {
+          val++
+          return next()
+        },
+        (ctx, next) => {
+          val++
+          return next()
+        }
+      ]),
+      (ctx, next) => {
+        val++
+        return next()
+      }
+    ])({}).then(function () {
+      val.should.equal(3)
+    })
+  })
+
   it('should expose next on the context', function () {
     var stack = [];