Finish Request struct trait impl's; TODO: write tests

src/request.rs

@@ -13,3 +13,59 @@ impl fmt::Display for Request {
         write!(f, "misfin://{}@{} {}\r\n", self.user, self.host, self.message)
     }
 }
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum ParseRequestError {
+    MissingSeparator,
+    EmptyUser,
+    EmptyHost,
+    EmptyMessage,
+    Malformed,
+    ParseHostError(ParseHostError),
+}
+
+impl fmt::Display for ParseRequestError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::ParseHostError(e) => write!(f, "{e}"),
+            _ => write!(f, "{self:?}")
+        }
+    }
+}
+
+impl std::error::Error for ParseRequestError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        match self {
+            Self::ParseHostError(e) => Some(e),
+            _ => None,
+        }
+    }
+}
+
+impl From<ParseHostError> for ParseRequestError {
+    fn from(value: ParseHostError) -> Self {
+        Self::ParseHostError(value)
+    }
+}
+
+impl FromStr for Request {
+    type Err = ParseRequestError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        if !s.ends_with("\r\n") {
+            return Err(ParseRequestError::Malformed);
+        }
+        if let Some((user, message)) = s.split_once(' ') {
+            let message = message.trim_end().to_string();
+            if let Some((user, host)) = user.rsplit_once('@') {
+                let host = host.parse()?;
+                let user = user.to_string();
+                Ok(Request { user, host, message })
+            } else {
+                Err(ParseRequestError::MissingSeparator)
+            }
+        } else {
+            Err(ParseRequestError::MissingSeparator)
+        }
+    }
+}