Add FromStr impl for UserAgent (#5236)

* Add FromStr impl for UserAgent

* Convert error type to struct

common/http-api-client/src/user_agent.rs

@@ -1,7 +1,7 @@
 // Copyright 2024 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0
 
-use std::fmt;
+use std::{fmt, str::FromStr};
 
 use http::HeaderValue;
 use nym_bin_common::build_information::{BinaryBuildInformation, BinaryBuildInformationOwned};
@@ -15,6 +15,36 @@ pub struct UserAgent {
     pub git_commit: String,
 }
 
+#[derive(Clone, Debug, thiserror::Error)]
+#[error("invalid user agent string: {0}")]
+pub struct UserAgentError(String);
+
+impl FromStr for UserAgent {
+    type Err = UserAgentError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let parts: Vec<&str> = s.split('/').collect();
+        if parts.len() != 4 {
+            return Err(UserAgentError(s.to_string()));
+        }
+
+        Ok(UserAgent {
+            application: parts[0].to_string(),
+            version: parts[1].to_string(),
+            platform: parts[2].to_string(),
+            git_commit: parts[3].to_string(),
+        })
+    }
+}
+
+impl TryFrom<&str> for UserAgent {
+    type Error = UserAgentError;
+
+    fn try_from(s: &str) -> Result<Self, Self::Error> {
+        UserAgent::from_str(s)
+    }
+}
+
 impl fmt::Display for UserAgent {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let abbreviated_commit = self.git_commit.chars().take(7).collect::<String>();
@@ -55,3 +85,85 @@ impl From<BinaryBuildInformationOwned> for UserAgent {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parsing_valid_user_agent() {
+        let user_agent = "nym-mixnode/0.11.0/x86_64-unknown-linux-gnu/abcdefg";
+        let parsed = UserAgent::from_str(user_agent).unwrap();
+        assert_eq!(
+            parsed,
+            UserAgent {
+                application: "nym-mixnode".to_string(),
+                version: "0.11.0".to_string(),
+                platform: "x86_64-unknown-linux-gnu".to_string(),
+                git_commit: "abcdefg".to_string()
+            }
+        );
+    }
+
+    #[test]
+    fn parsing_invalid_user_agent() {
+        let user_agent = "nym-mixnode/0.11.0/x86_64-unknown-linux-gnu";
+        assert!(UserAgent::from_str(user_agent).is_err());
+    }
+
+    #[test]
+    fn converting_user_agent_to_string() {
+        let user_agent = UserAgent {
+            application: "nym-mixnode".to_string(),
+            version: "0.11.0".to_string(),
+            platform: "x86_64-unknown-linux-gnu".to_string(),
+            git_commit: "abcdefg".to_string(),
+        };
+
+        assert_eq!(
+            user_agent.to_string(),
+            "nym-mixnode/0.11.0/x86_64-unknown-linux-gnu/abcdefg"
+        );
+    }
+
+    #[test]
+    fn converting_user_agent_to_display() {
+        let user_agent = UserAgent {
+            application: "nym-mixnode".to_string(),
+            version: "0.11.0".to_string(),
+            platform: "x86_64-unknown-linux-gnu".to_string(),
+            git_commit: "abcdefg".to_string(),
+        };
+
+        assert_eq!(
+            format!("{}", user_agent),
+            "nym-mixnode/0.11.0/x86_64-unknown-linux-gnu/abcdefg"
+        );
+    }
+
+    #[test]
+    fn converting_user_agent_to_header_value_fails() {
+        let user_agent = UserAgent {
+            application: "nym-mixnode".to_string(),
+            version: "0.11.0".to_string(),
+            platform: "x86_64-unknown-linux-gnu".to_string(),
+            git_commit: "abcdefg".to_string(),
+        };
+
+        let header_value: Result<HeaderValue, _> = user_agent.clone().try_into();
+        assert!(header_value.is_ok());
+    }
+
+    #[test]
+    fn converting_user_agent_to_header_value_has_same_string_representation() {
+        let user_agent = UserAgent {
+            application: "nym-mixnode".to_string(),
+            version: "0.11.0".to_string(),
+            platform: "x86_64-unknown-linux-gnu".to_string(),
+            git_commit: "abcdefg".to_string(),
+        };
+
+        let header_value: HeaderValue = user_agent.clone().try_into().unwrap();
+        assert_eq!(header_value.to_str().unwrap(), user_agent.to_string());
+    }
+}