Allow user to overwrite the |host| header while generating the request

As we discussed in #255, it's possible for us to provide
some way to sepcifiy the generated request's |host| header.

Now when the incoming request stuct contains a |host| header,
we will use it's value as outgoing |host| header's value.

If there's no |host| header specified, we still use the authority
part of uri as |host| header.

This behavior is complied with RFC 6455 and close issue #255

src/handshake/client.rs

@@ -96,17 +96,22 @@ impl<S: Read + Write> HandshakeRole for ClientHandshake<S> {
 fn generate_request(request: Request, key: &str) -> Result<Vec<u8>> {
     let mut req = Vec::new();
     let uri = request.uri();
+    let headers = request.headers();
 
-    let authority = uri.authority().ok_or(Error::Url(UrlError::NoHostName))?.as_str();
-    let host = if let Some(idx) = authority.find('@') {
-        // handle possible name:password@
-        authority.split_at(idx + 1).1
+    let host = if headers.contains_key(header::HOST) {
+        headers.get(header::HOST).unwrap().to_str()?
     } else {
-        authority
+        let authority = uri.authority().ok_or(Error::Url(UrlError::NoHostName))?.as_str();
+        if authority.is_empty() {
+            return Err(Error::Url(UrlError::EmptyHostName));
+        }
+        if let Some(idx) = authority.find('@') {
+            // handle possible name:password@
+            authority.split_at(idx + 1).1
+        } else {
+            authority
+        }
     };
-    if authority.is_empty() {
-        return Err(Error::Url(UrlError::EmptyHostName));
-    }
 
     write!(
         req,
@@ -124,12 +129,14 @@ fn generate_request(request: Request, key: &str) -> Result<Vec<u8>> {
     )
     .unwrap();
 
-    for (k, v) in request.headers() {
+    for (k, v) in headers {
+        if k == header::HOST {
+            continue;
+        }
         if k == header::CONNECTION
             || k == header::UPGRADE
             || k == header::SEC_WEBSOCKET_VERSION
             || k == header::SEC_WEBSOCKET_KEY
-            || k == header::HOST
         {
             return Err(Error::Protocol(ProtocolError::InvalidHeader(k.clone())));
         }
@@ -320,6 +327,27 @@ mod tests {
         assert_eq!(&request[..], &correct[..]);
     }
 
+    #[test]
+    fn request_formatting_with_host_header() {
+        let mut request = "wss://user:pass@localhost:9001/getCaseCount".into_client_request().unwrap();
+        request.headers_mut().insert(
+            http::header::HOST,
+            "foo.com:8080".parse().unwrap(),
+        );
+        let key = "A70tsIbeMZUbJHh5BWFw6Q==";
+        let correct = b"\
+        GET /getCaseCount HTTP/1.1\r\n\
+        Host: foo.com:8080\r\n\
+        Connection: Upgrade\r\n\
+        Upgrade: websocket\r\n\
+        Sec-WebSocket-Version: 13\r\n\
+        Sec-WebSocket-Key: A70tsIbeMZUbJHh5BWFw6Q==\r\n\
+        \r\n";
+        let request = generate_request(request, key).unwrap();
+        println!("Request: {}", String::from_utf8_lossy(&request));
+        assert_eq!(&request[..], &correct[..]);
+    }
+
     #[test]
     fn response_parsing() {
         const DATA: &[u8] = b"HTTP/1.1 200 OK\r\nContent-Type: text/html\r\n\r\n";