Add support for Topic header (#41)

src/clients/request_builder.rs

@@ -49,6 +49,10 @@ where
         builder = builder.header("Urgency", urgency.to_string());
     }
 
+    if let Some(topic) = message.topic {
+        builder = builder.header("Topic", topic);
+    }
+
     if let Some(payload) = message.payload {
         builder = builder
             .header(CONTENT_ENCODING, payload.content_encoding.to_str())
@@ -116,14 +120,17 @@ mod tests {
 
         builder.set_ttl(420);
         builder.set_urgency(Urgency::VeryLow);
+        builder.set_topic("some-topic".into());
 
         let request = build_request::<isahc::Body>(builder.build().unwrap());
         let ttl = request.headers().get("TTL").unwrap().to_str().unwrap();
         let urgency = request.headers().get("Urgency").unwrap().to_str().unwrap();
+        let topic = request.headers().get("Topic").unwrap().to_str().unwrap();
         let expected_uri: Uri = "fcm.googleapis.com".parse().unwrap();
 
         assert_eq!("420", ttl);
         assert_eq!("very-low", urgency);
+        assert_eq!("some-topic", topic);
         assert_eq!(expected_uri.host(), request.uri().host());
     }
 

src/error.rs

@@ -37,6 +37,8 @@ pub enum WebPushError {
     InvalidPackageName,
     /// The TTL value provided was not valid or was not provided
     InvalidTtl,
+    /// The Topic value provided was invalid
+    InvalidTopic,
     /// The request was missing required crypto keys
     MissingCryptoKeys,
     /// One or more of the crypto key elements are invalid.
@@ -109,6 +111,7 @@ impl WebPushError {
             WebPushError::TlsError => "tls_error",
             WebPushError::InvalidPackageName => "invalid_package_name",
             WebPushError::InvalidTtl => "invalid_ttl",
+            WebPushError::InvalidTopic => "invalid_topic",
             WebPushError::InvalidResponse => "invalid_response",
             WebPushError::MissingCryptoKeys => "missing_crypto_keys",
             WebPushError::InvalidCryptoKeys => "invalid_crypto_keys",
@@ -150,6 +153,7 @@ impl fmt::Display for WebPushError {
             WebPushError::InvalidPackageName =>
                 write!(f, "Make sure the message was addressed to a registration token whose package name matches the value passed in the request."),
             WebPushError::InvalidTtl => write!(f, "The TTL value provided was not valid or was not provided"),
+            WebPushError::InvalidTopic => write!(f, "The Topic value provided was invalid"),
             WebPushError::InvalidResponse => write!(f, "The response data couldn't be parses"),
             WebPushError::MissingCryptoKeys  => write!(f, "The request is missing cryptographic keys"),
             WebPushError::InvalidCryptoKeys  => write!(f, "The request is having invalid cryptographic keys"),

src/message.rs

@@ -87,6 +87,8 @@ pub struct WebPushMessage {
     pub ttl: u32,
     /// The urgency of the message (very-low | low | normal | high)
     pub urgency: Option<Urgency>,
+    /// The topic of the mssage
+    pub topic: Option<String>,
     /// The encrypted request payload, if sending any data.
     pub payload: Option<WebPushPayload>,
 }
@@ -102,6 +104,7 @@ pub struct WebPushMessageBuilder<'a> {
     payload: Option<WebPushPayloadBuilder<'a>>,
     ttl: u32,
     urgency: Option<Urgency>,
+    topic: Option<String>,
     vapid_signature: Option<VapidSignature>,
 }
 
@@ -115,6 +118,7 @@ impl<'a> WebPushMessageBuilder<'a> {
             subscription_info,
             ttl: 2_419_200,
             urgency: None,
+            topic: None,
             payload: None,
             vapid_signature: None,
         }
@@ -136,6 +140,18 @@ impl<'a> WebPushMessageBuilder<'a> {
         self.urgency = Some(urgency);
     }
 
+    /// Assign a topic to the push message. A message that has been stored
+    /// by the push service can be replaced with new content if the message
+    /// has been assigned a topic. If the user agent is offline during the
+    /// time that the push messages are sent, updating a push message avoid
+    /// the situation where outdated or redundant messages are sent to the
+    /// user agent. A message with a topic replaces any outstanding push
+    /// messages with an identical topic. It is an arbitrary string
+    /// consisting of at most 32 base64url characters.
+    pub fn set_topic(&mut self, topic: String) {
+        self.topic = Some(topic);
+    }
+
     /// Add a VAPID signature to the request. To be generated with the
     /// [VapidSignatureBuilder](struct.VapidSignatureBuilder.html).
     pub fn set_vapid_signature(&mut self, vapid_signature: VapidSignature) {
@@ -153,6 +169,18 @@ impl<'a> WebPushMessageBuilder<'a> {
     /// Builds and if set, encrypts the payload.
     pub fn build(self) -> Result<WebPushMessage, WebPushError> {
         let endpoint: Uri = self.subscription_info.endpoint.parse()?;
+        let topic: Option<String> = self
+            .topic
+            .map(|topic| {
+                if topic.len() > 32 {
+                    Err(WebPushError::InvalidTopic)
+                } else if topic.chars().all(is_base64url_char) {
+                    Ok(topic)
+                } else {
+                    Err(WebPushError::InvalidTopic)
+                }
+            })
+            .transpose()?;
 
         if let Some(payload) = self.payload {
             let p256dh = base64::decode_config(&self.subscription_info.keys.p256dh, base64::URL_SAFE)?;
@@ -164,15 +192,21 @@ impl<'a> WebPushMessageBuilder<'a> {
                 endpoint,
                 ttl: self.ttl,
                 urgency: self.urgency,
+                topic,
                 payload: Some(http_ece.encrypt(payload.content)?),
             })
         } else {
             Ok(WebPushMessage {
                 endpoint,
                 ttl: self.ttl,
                 urgency: self.urgency,
+                topic,
                 payload: None,
             })
         }
     }
 }
+
+fn is_base64url_char(c: char) -> bool {
+    return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') || (c == '-' || c == '_');
+}