crates/nuncio-cli/src/main.rs

@@ -1,9 +1,12 @@
 //! Nuncio CLI main application entry point.
 
 mod args;
+mod output;
 
 use args::{Cli, Commands};
 use clap::Parser;
+use output::format_json;
+use serde_json::json;
 
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
@@ -12,35 +15,35 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     match cli.command {
         Commands::Sync => {
             if cli.json {
-                println!(r#"{{"status":"ok","action":"sync"}}"#);
+                println!("{}", format_json(&json!({"action": "sync"})));
             } else {
                 println!("Triggering account synchronization...");
             }
         }
         Commands::List { folder } => {
             if cli.json {
-                println!(r#"{{"status":"ok","action":"list","folder":"{}"}}"#, folder);
+                println!("{}", format_json(&json!({"action": "list", "folder": folder})));
             } else {
                 println!("Listing messages in folder '{}'", folder);
             }
         }
         Commands::Send { to, subject, body: _ } => {
             if cli.json {
-                println!(r#"{{"status":"ok","action":"send","to":"{}"}}"#, to);
+                println!("{}", format_json(&json!({"action": "send", "to": to, "subject": subject})));
             } else {
                 println!("Sending message to {} ('{}')", to, subject);
             }
         }
         Commands::Search { query } => {
             if cli.json {
-                println!(r#"{{"status":"ok","action":"search","query":"{}"}}"#, query);
+                println!("{}", format_json(&json!({"action": "search", "query": query})));
             } else {
                 println!("Searching for '{}'", query);
             }
         }
         Commands::Config => {
             if cli.json {
-                println!(r#"{{"status":"ok","action":"config"}}"#);
+                println!("{}", format_json(&json!({"action": "config"})));
             } else {
                 println!("Nuncio CLI Configuration Operational");
             }

crates/nuncio-cli/src/output.rs

@@ -0,0 +1,71 @@
+//! Standardized JSON machine-readable output formatters for Unix scripting.
+
+use serde::Serialize;
+
+/// Standardized JSON response envelope for CLI machine output.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
+pub struct JsonResponse<T: Serialize> {
+    /// Result status string ("ok" or "error").
+    pub status: &'static str,
+    /// Result payload data (present if status is "ok").
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub data: Option<T>,
+    /// Error message string (present if status is "error").
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub error: Option<String>,
+}
+
+impl<T: Serialize> JsonResponse<T> {
+    /// Construct a successful JSON response wrapping payload data.
+    pub fn success(data: T) -> Self {
+        Self {
+            status: "ok",
+            data: Some(data),
+            error: None,
+        }
+    }
+}
+
+impl JsonResponse<()> {
+    /// Construct an error JSON response wrapping an error string.
+    pub fn error(message: &str) -> Self {
+        Self {
+            status: "error",
+            data: None,
+            error: Some(message.to_string()),
+        }
+    }
+}
+
+/// Serialize payload to a formatted JSON string.
+pub fn format_json<T: Serialize>(data: &T) -> String {
+    let response = JsonResponse::success(data);
+    serde_json::to_string(&response).unwrap_or_else(|_| r#"{"status":"error","error":"JSON serialization failed"}"#.to_string())
+}
+
+/// Serialize error message to a formatted JSON string.
+pub fn format_json_error(message: &str) -> String {
+    let response = JsonResponse::error(message);
+    serde_json::to_string(&response).unwrap_or_else(|_| r#"{"status":"error","error":"JSON serialization failed"}"#.to_string())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use serde_json::json;
+
+    #[test]
+    fn format_json_success_payload() {
+        let payload = json!({"count": 42, "user": "alice"});
+        let json_str = format_json(&payload);
+        assert!(json_str.contains(r#""status":"ok""#));
+        assert!(json_str.contains(r#""count":42"#));
+    }
+
+    #[test]
+    fn format_json_error_payload() {
+        let err_str = format_json_error("account not found");
+        assert!(err_str.contains(r#""status":"error""#));
+        assert!(err_str.contains(r#""error":"account not found""#));
+    }
+}