1 files changed, 93 insertions, 0 deletions
diff --git a/node_modules/on-headers/index.js b/node_modules/on-headers/index.js
new file mode 100644
index 0000000..089f2b3
--- /dev/null
+++ b/node_modules/on-headers/index.js
@@ -0,0 +1,93 @@
+/*!
+ * on-headers
+ * Copyright(c) 2014 Douglas Christopher Wilson
+ * MIT Licensed
+ */
+
+'use strict'
+
+/**
+ * Reference to Array slice.
+ */
+
+var slice = Array.prototype.slice
+
+/**
+ * Execute a listener when a response is about to write headers.
+ *
+ * @param {Object} res
+ * @return {Function} listener
+ * @api public
+ */
+
+module.exports = function onHeaders(res, listener) {
+  if (!res) {
+    throw new TypeError('argument res is required')
+  }
+
+  if (typeof listener !== 'function') {
+    throw new TypeError('argument listener must be a function')
+  }
+
+  res.writeHead = createWriteHead(res.writeHead, listener)
+}
+
+function createWriteHead(prevWriteHead, listener) {
+  var fired = false;
+
+  // return function with core name and argument list
+  return function writeHead(statusCode) {
+    // set headers from arguments
+    var args = setWriteHeadHeaders.apply(this, arguments);
+
+    // fire listener
+    if (!fired) {
+      fired = true
+      listener.call(this)
+
+      // pass-along an updated status code
+      if (typeof args[0] === 'number' && this.statusCode !== args[0]) {
+        args[0] = this.statusCode
+        args.length = 1
+      }
+    }
+
+    prevWriteHead.apply(this, args);
+  }
+}
+
+function setWriteHeadHeaders(statusCode) {
+  var length = arguments.length
+  var headerIndex = length > 1 && typeof arguments[1] === 'string'
+    ? 2
+    : 1
+
+  var headers = length >= headerIndex + 1
+    ? arguments[headerIndex]
+    : undefined
+
+  this.statusCode = statusCode
+
+  // the following block is from node.js core
+  if (Array.isArray(headers)) {
+    // handle array case
+    for (var i = 0, len = headers.length; i < len; ++i) {
+      this.setHeader(headers[i][0], headers[i][1])
+    }
+  } else if (headers) {
+    // handle object case
+    var keys = Object.keys(headers)
+    for (var i = 0; i < keys.length; i++) {
+      var k = keys[i]
+      if (k) this.setHeader(k, headers[k])
+    }
+  }
+
+  // copy leading arguments
+  var args = new Array(Math.min(length, headerIndex))
+  for (var i = 0; i < args.length; i++) {
+    args[i] = arguments[i]
+  }
+
+  return args
+}