Add support for overwriting handlers

Closes GH-26.

Author: sethvincent

index.js

@@ -5,11 +5,14 @@ module.exports = toMDAST;
 var minify = require('rehype-minify-whitespace')();
 var xtend = require('xtend');
 var one = require('./one');
+var handlers = require('./handlers');
 
 h.augment = augment;
 
-function toMDAST(tree) {
-  return one(h, minify(tree));
+function toMDAST(tree, options) {
+  options = options || {};
+  h.handlers = xtend(handlers, options.handlers || {});
+  return one(h, minify(tree), null);
 }
 
 function h(node, type, props, children) {

one.js

@@ -4,15 +4,14 @@ module.exports = one;
 
 var has = require('has');
 var all = require('./all');
-var handlers = require('./handlers');
 
 function one(h, node, parent) {
   var fn = null;
 
-  if (node.type === 'element' && has(handlers, node.tagName)) {
-    fn = handlers[node.tagName];
-  } else if (has(handlers, node.type)) {
-    fn = handlers[node.type];
+  if (node.type === 'element' && has(h.handlers, node.tagName)) {
+    fn = h.handlers[node.tagName];
+  } else if (has(h.handlers, node.type)) {
+    fn = h.handlers[node.type];
   }
 
   return (typeof fn === 'function' ? fn : unknown)(h, node, parent);

tests/index.js

@@ -149,3 +149,43 @@ test('fixtures', function (t) {
     });
   }
 });
+
+test('handlers option', function (t) {
+  var options = {
+    handlers: {
+      div: function (h, node) {
+        node.children[0].value = 'Beta';
+        node.type = 'paragraph';
+        return h(node, 'paragraph', node.children);
+      }
+    }
+  };
+
+  t.deepEqual(
+    toMDAST({
+      type: 'root',
+      children: [{
+        type: 'element',
+        tagName: 'div',
+        properties: {},
+        children: [{
+          type: 'text',
+          value: 'Alpha'
+        }]
+      }]
+    }, options),
+    {
+      type: 'root',
+      children: [{
+        type: 'paragraph',
+        children: [{
+          type: 'text',
+          value: 'Beta'
+        }]
+      }]
+    },
+    'use handlers passed as option'
+  );
+
+  t.end();
+});