5 files changed, 110 insertions, 5 deletions

diff --git a/src/encoding/headermap.rs b/src/encoding/headermap.rs
index 5d1fa0a..01e1962 100644
--- a/src/encoding/headermap.rs
+++ b/src/encoding/headermap.rs
@@ -25,6 +25,9 @@ impl HeaderMap {
     pub fn get<H: Header>(&self) -> Option<Result<H>> {
         self.get_raw(H::NAME).map(H::from_str)
     }
+    pub fn get_res<H: Header>(&self) -> Result<H> {
+        self.get().ok_or(anyhow!("{} header missing", H::NAME))?
+    }
     pub fn insert_raw(&mut self, key: String, value: String) {
         self.0.push((key, value))
     }
diff --git a/src/encoding/headers.rs b/src/encoding/headers.rs
index 9e785f0..afcfef1 100644
--- a/src/encoding/headers.rs
+++ b/src/encoding/headers.rs
@@ -1,4 +1,4 @@
-use super::{headermap::HeaderMap, method::Method};
+use super::{headermap::HeaderMap, method::Method, uri::Uri};
 use anyhow::{anyhow, bail, Result};
 use std::{fmt::Display, str::FromStr};
 
@@ -31,7 +31,6 @@ header!("Content-Length", struct ContentLength(usize));
 header!("Content-Type", struct ContentType(String));
 header!("Call-ID", struct CallID(String));
 header!("Via", struct Via(String));
-header!("Contact", struct Contact(String));
 header!("Max-Forwards", struct MaxForwards(usize));
 header!("From", struct From(String));
 header!("To", struct To(String));
@@ -100,7 +99,7 @@ impl FromStr for WWWAuthenticate {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct Authorization {
     pub username: String,
     pub realm: String,
@@ -140,3 +139,34 @@ pub fn unquote(v: &str) -> Result<String> {
         .ok_or(anyhow!("end quote missing"))?
         .to_string())
 }
+
+#[derive(Debug)]
+pub struct Contact {
+    pub display_name: Option<String>,
+    pub uri: Uri,
+    pub params: String,
+}
+
+impl Header for Contact {
+    const NAME: &'static str = "Contact";
+}
+impl Display for Contact {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let Self {
+            display_name,
+            uri,
+            params,
+        } = self;
+        if let Some(display_name) = display_name {
+            write!(f, "{display_name} <{uri}>{params}")
+        } else {
+            write!(f, "<{uri}>{params}")
+        }
+    }
+}
+impl FromStr for Contact {
+    type Err = anyhow::Error;
+    fn from_str(_s: &str) -> Result<Self, Self::Err> {
+        todo!()
+    }
+}
diff --git a/src/transaction/auth.rs b/src/transaction/auth.rs
new file mode 100644
index 0000000..f64bb4b
--- /dev/null
+++ b/src/transaction/auth.rs
@@ -0,0 +1,51 @@
+use crate::encoding::{
+    headers::{Authorization, WWWAuthenticate},
+    method::Method,
+    request::Request,
+    response::Response,
+    uri::Uri,
+};
+use anyhow::Result;
+
+impl Authorization {
+    pub fn construct(
+        request: &Request,
+        failed_response: &Response,
+        username: &str,
+        password: &str,
+    ) -> Result<Authorization> {
+        let challenge = failed_response.headers.get::<WWWAuthenticate>().unwrap()?;
+
+        Ok(Authorization {
+            response: response_digest(
+                username.to_string(),
+                challenge.realm.clone(),
+                password.to_string(),
+                request.method,
+                challenge.nonce.clone(),
+                request.uri.clone(),
+            ),
+            nonce: challenge.nonce,
+            realm: challenge.realm,
+            uri: request.uri.content.clone(),
+            username: username.to_string(),
+        })
+    }
+}
+
+fn response_digest(
+    username: String,
+    realm: String,
+    password: String,
+    method: Method,
+    nonce: String,
+    uri: Uri,
+) -> String {
+    let h = |s: String| hex::encode(md5::compute(s.as_bytes()).0);
+    let kd = |secret, data| h(format!("{secret}:{data}"));
+
+    let a1 = format!("{username}:{realm}:{password}");
+    let a2 = format!("{method}:{uri}");
+    let response_digest = kd(h(a1), format!("{nonce}:{}", h(a2)));
+    return response_digest;
+}
diff --git a/src/transaction/mod.rs b/src/transaction/mod.rs
index 3be9544..601b134 100644
--- a/src/transaction/mod.rs
+++ b/src/transaction/mod.rs
@@ -1,5 +1,12 @@
+pub mod auth;
+
 use crate::{
-    encoding::{headers::CSeq, request::Request, response::Response, Message},
+    encoding::{
+        headers::{CSeq, CallID},
+        request::Request,
+        response::Response,
+        Message,
+    },
     transport::Transport,
 };
 use anyhow::{anyhow, Result};
@@ -48,6 +55,20 @@ impl<T: Transport> TransactionUser<T> {
             }
         }
     }
+    pub async fn respond(&self, req: &Request, mut resp: Response) -> Result<()> {
+        resp.headers.insert(
+            req.headers
+                .get::<CSeq>()
+                .ok_or(anyhow!("cseq is mandatory"))??,
+        );
+        resp.headers.insert(
+            req.headers
+                .get::<CallID>()
+                .ok_or(anyhow!("call-id is mandatory"))??,
+        );
+        self.transport.send(Message::Response(resp)).await?;
+        Ok(())
+    }
 
     pub async fn transact(&self, mut request: Request) -> Result<mpsc::Receiver<Response>> {
         let seq = self.sequence.fetch_add(1, Ordering::Relaxed);
diff --git a/src/transport/udp.rs b/src/transport/udp.rs
index 391e2b3..78ca4f2 100644
--- a/src/transport/udp.rs
+++ b/src/transport/udp.rs
@@ -19,7 +19,7 @@ impl Transport for UdpTransport {
         let mut buf = [0; 1024];
         let size = self.sock.recv(&mut buf).await?;
         let message = String::from_utf8(buf[..size].to_vec())?;
-        debug!("{message}");
+        debug!("<- {message}");
         Message::from_str(message.trim_end())
     }
     async fn send(&self, request: Message) -> Result<()> {