add border-radius mixin example

examples/border-radius.css

@@ -0,0 +1,24 @@
+
+button {
+  border-radius: 5px
+}
+
+button {
+  border-radius: top 5px
+}
+
+button {
+  border-radius: 5px 10px
+}
+
+button {
+  border-radius: top 5px bottom 10px
+}
+
+button {
+  border-radius: left 5px
+}
+
+button {
+  border-radius: left 5px right 2px
+}

examples/border-radius.js

@@ -0,0 +1,51 @@
+
+var rework = require('..')
+  , read = require('fs').readFileSync;
+
+var css = rework(read('examples/border-radius.css', 'utf8'))
+  .use(rework.mixin({ 'border-radius': borderRadius }))
+  .toString()
+
+function borderRadius(str) {
+  var vals = str.split(/\s+/);
+  var pos;
+  var ret;
+
+  for (var i = 0; i < vals.length; ++i) {
+    var val = vals[i];
+    if (isPosition(val)) {
+      ret = ret || {};
+      pos = val;
+      val = vals[++i];
+      switch (pos) {
+        case 'top':
+        case 'bottom':
+          ret['border-' + pos + '-left-radius'] = val;
+          ret['border-' + pos + '-right-radius'] = val;
+          break;
+        case 'left':
+        case 'right':
+          ret['border-top-' + pos + '-radius'] = val;
+          ret['border-bottom-' + pos + '-radius'] = val;
+          break;
+      }
+    }
+  }
+
+  if (!ret) {
+    return {
+      'border-radius': str
+    }
+  }
+
+  return ret;
+}
+
+function isPosition(str) {
+  return 'top' == str
+    || 'bottom' == str
+    || 'left' == str
+    || 'right' == str;
+}
+
+console.log(css);