split Destination enum into unit

Signed-off-by: Jason Volk <jason@zemos.net>

src/service/sending/dest.rs

@@ -0,0 +1,56 @@
+use std::fmt::Debug;
+
+use conduit::implement;
+use ruma::{OwnedServerName, OwnedUserId};
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum Destination {
+	Appservice(String),
+	Push(OwnedUserId, String), // user and pushkey
+	Normal(OwnedServerName),
+}
+
+#[implement(Destination)]
+#[must_use]
+pub fn get_prefix(&self) -> Vec<u8> {
+	match self {
+		Self::Normal(server) => {
+			let len = server.as_bytes().len().saturating_add(1);
+
+			let mut p = Vec::with_capacity(len);
+			p.extend_from_slice(server.as_bytes());
+			p.push(0xFF);
+			p
+		},
+		Self::Appservice(server) => {
+			let sigil = b"+";
+			let len = sigil
+				.len()
+				.saturating_add(server.as_bytes().len())
+				.saturating_add(1);
+
+			let mut p = Vec::with_capacity(len);
+			p.extend_from_slice(sigil);
+			p.extend_from_slice(server.as_bytes());
+			p.push(0xFF);
+			p
+		},
+		Self::Push(user, pushkey) => {
+			let sigil = b"$";
+			let len = sigil
+				.len()
+				.saturating_add(user.as_bytes().len())
+				.saturating_add(1)
+				.saturating_add(pushkey.as_bytes().len())
+				.saturating_add(1);
+
+			let mut p = Vec::with_capacity(len);
+			p.extend_from_slice(sigil);
+			p.extend_from_slice(user.as_bytes());
+			p.push(0xFF);
+			p.extend_from_slice(pushkey.as_bytes());
+			p.push(0xFF);
+			p
+		},
+	}
+}