From d1806abe0cb8a46455ad4cd3f0d8bc4fb317ccb3 Mon Sep 17 00:00:00 2001
From: Ian Storm Taylor <ian@ianstormtaylor.com>
Date: Tue, 25 Mar 2014 14:15:52 -0700
Subject: [PATCH] add sort by function

---
 lib/index.js                               | 28 +++++++++++++---------
 test/fixtures/sort-function/build/one.md   |  1 +
 test/fixtures/sort-function/build/three.md |  1 +
 test/fixtures/sort-function/build/two.md   |  1 +
 test/fixtures/sort-function/src/one.md     |  6 +++++
 test/fixtures/sort-function/src/three.md   |  6 +++++
 test/fixtures/sort-function/src/two.md     |  6 +++++
 test/index.js                              | 20 ++++++++++++++++
 8 files changed, 58 insertions(+), 11 deletions(-)
 create mode 100644 test/fixtures/sort-function/build/one.md
 create mode 100644 test/fixtures/sort-function/build/three.md
 create mode 100644 test/fixtures/sort-function/build/two.md
 create mode 100644 test/fixtures/sort-function/src/one.md
 create mode 100644 test/fixtures/sort-function/src/three.md
 create mode 100644 test/fixtures/sort-function/src/two.md

diff --git a/lib/index.js b/lib/index.js
index d6391c2..ce43eeb 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -41,7 +41,7 @@ function plugin(opts){
     });
 
     /**
-     * Sort the collection.
+     * Sort the collections.
      */
 
     keys.forEach(function(key){
@@ -49,16 +49,22 @@ function plugin(opts){
       var settings = opts[key];
       var sort = settings.sortBy || 'date';
       var col = metadata[key];
-      col.sort(function(a, b){
-        a = a[sort];
-        b = b[sort];
-        if (!a && !b) return 0;
-        if (!a) return -1;
-        if (!b) return 1;
-        if (b > a) return -1;
-        if (a > b) return 1;
-        return 0;
-      });
+
+      if ('function' == typeof sort) {
+        col.sort(sort);
+      } else {
+        col.sort(function(a, b){
+          a = a[sort];
+          b = b[sort];
+          if (!a && !b) return 0;
+          if (!a) return -1;
+          if (!b) return 1;
+          if (b > a) return -1;
+          if (a > b) return 1;
+          return 0;
+        });
+      }
+
       if (settings.reverse) col.reverse();
     });
 
diff --git a/test/fixtures/sort-function/build/one.md b/test/fixtures/sort-function/build/one.md
new file mode 100644
index 0000000..43dd47e
--- /dev/null
+++ b/test/fixtures/sort-function/build/one.md
@@ -0,0 +1 @@
+one
\ No newline at end of file
diff --git a/test/fixtures/sort-function/build/three.md b/test/fixtures/sort-function/build/three.md
new file mode 100644
index 0000000..1d19714
--- /dev/null
+++ b/test/fixtures/sort-function/build/three.md
@@ -0,0 +1 @@
+three
\ No newline at end of file
diff --git a/test/fixtures/sort-function/build/two.md b/test/fixtures/sort-function/build/two.md
new file mode 100644
index 0000000..64c5e58
--- /dev/null
+++ b/test/fixtures/sort-function/build/two.md
@@ -0,0 +1 @@
+two
\ No newline at end of file
diff --git a/test/fixtures/sort-function/src/one.md b/test/fixtures/sort-function/src/one.md
new file mode 100644
index 0000000..d37b9bf
--- /dev/null
+++ b/test/fixtures/sort-function/src/one.md
@@ -0,0 +1,6 @@
+---
+collection: articles
+title: Alpha
+---
+
+one
\ No newline at end of file
diff --git a/test/fixtures/sort-function/src/three.md b/test/fixtures/sort-function/src/three.md
new file mode 100644
index 0000000..bf34f25
--- /dev/null
+++ b/test/fixtures/sort-function/src/three.md
@@ -0,0 +1,6 @@
+---
+collection: articles
+title: Gamma
+---
+
+three
\ No newline at end of file
diff --git a/test/fixtures/sort-function/src/two.md b/test/fixtures/sort-function/src/two.md
new file mode 100644
index 0000000..7a944e4
--- /dev/null
+++ b/test/fixtures/sort-function/src/two.md
@@ -0,0 +1,6 @@
+---
+collection: articles
+title: Beta
+---
+
+two
\ No newline at end of file
diff --git a/test/index.js b/test/index.js
index b8e2d6e..2d08eb0 100644
--- a/test/index.js
+++ b/test/index.js
@@ -72,6 +72,26 @@ describe('metalsmith-collections', function(){
       });
   });
 
+  it('should accept a "sortBy" function', function(done){
+    var metalsmith = Metalsmith('test/fixtures/sort');
+    metalsmith
+      .use(collections({ articles: { sortBy: sort }}))
+      .build(function(err){
+        if (err) return done(err);
+        var articles = metalsmith.metadata().articles;
+        assert.equal('Gamma', articles[0].title);
+        assert.equal('Beta', articles[1].title);
+        assert.equal('Alpha', articles[2].title);
+        done();
+      });
+
+    function sort(a, b){
+      a = a.title.slice(1);
+      b = b.title.slice(1);
+      return a > b ? 1 : -1;
+    }
+  });
+
   it('should accept a "reverse" option', function(done){
     var metalsmith = Metalsmith('test/fixtures/sort');
     metalsmith