Improved user message for rate-limit errors (#2695)

This PR improves the error message presented to the user when logged in
with ChatGPT and a rate-limit error occurs. In particular, it provides
the user with information about when the rate limit will be reset. It
removes older code that attempted to do the same but relied on parsing
of error messages that are not generated by the ChatGPT endpoint. The
new code uses newly-added error fields.

codex-rs/core/src/error.rs

@@ -128,27 +128,70 @@ pub enum CodexErr {
 #[derive(Debug)]
 pub struct UsageLimitReachedError {
     pub plan_type: Option<String>,
+    pub resets_in_seconds: Option<u64>,
 }
 
 impl std::fmt::Display for UsageLimitReachedError {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        // Base message differs slightly for legacy ChatGPT Plus plan users.
         if let Some(plan_type) = &self.plan_type
             && plan_type == "plus"
         {
             write!(
                 f,
-                "You've hit your usage limit. Upgrade to Pro (https://openai.com/chatgpt/pricing), or wait for limits to reset (every 5h and every week.)."
+                "You've hit your usage limit. Upgrade to Pro (https://openai.com/chatgpt/pricing) or try again"
             )?;
+            if let Some(secs) = self.resets_in_seconds {
+                let reset_duration = format_reset_duration(secs);
+                write!(f, " in {reset_duration}.")?;
+            } else {
+                write!(f, " later.")?;
+            }
         } else {
-            write!(
-                f,
-                "You've hit your usage limit. Limits reset every 5h and every week."
-            )?;
+            write!(f, "You've hit your usage limit.")?;
+
+            if let Some(secs) = self.resets_in_seconds {
+                let reset_duration = format_reset_duration(secs);
+                write!(f, " Try again in {reset_duration}.")?;
+            } else {
+                write!(f, " Try again later.")?;
+            }
         }
+
         Ok(())
     }
 }
 
+fn format_reset_duration(total_secs: u64) -> String {
+    let days = total_secs / 86_400;
+    let hours = (total_secs % 86_400) / 3_600;
+    let minutes = (total_secs % 3_600) / 60;
+
+    let mut parts: Vec<String> = Vec::new();
+    if days > 0 {
+        let unit = if days == 1 { "day" } else { "days" };
+        parts.push(format!("{} {}", days, unit));
+    }
+    if hours > 0 {
+        let unit = if hours == 1 { "hour" } else { "hours" };
+        parts.push(format!("{} {}", hours, unit));
+    }
+    if minutes > 0 {
+        let unit = if minutes == 1 { "minute" } else { "minutes" };
+        parts.push(format!("{} {}", minutes, unit));
+    }
+
+    if parts.is_empty() {
+        return "less than a minute".to_string();
+    }
+
+    match parts.len() {
+        1 => parts[0].clone(),
+        2 => format!("{} {}", parts[0], parts[1]),
+        _ => format!("{} {} {}", parts[0], parts[1], parts[2]),
+    }
+}
+
 #[derive(Debug)]
 pub struct EnvVarError {
     /// Name of the environment variable that is missing.
@@ -195,19 +238,23 @@ mod tests {
     fn usage_limit_reached_error_formats_plus_plan() {
         let err = UsageLimitReachedError {
             plan_type: Some("plus".to_string()),
+            resets_in_seconds: None,
         };
         assert_eq!(
             err.to_string(),
-            "You've hit your usage limit. Upgrade to Pro (https://openai.com/chatgpt/pricing), or wait for limits to reset (every 5h and every week.)."
+            "You've hit your usage limit. Upgrade to Pro (https://openai.com/chatgpt/pricing) or try again later."
         );
     }
 
     #[test]
     fn usage_limit_reached_error_formats_default_when_none() {
-        let err = UsageLimitReachedError { plan_type: None };
+        let err = UsageLimitReachedError {
+            plan_type: None,
+            resets_in_seconds: None,
+        };
         assert_eq!(
             err.to_string(),
-            "You've hit your usage limit. Limits reset every 5h and every week."
+            "You've hit your usage limit. Try again later."
         );
     }
 
@@ -215,10 +262,59 @@ mod tests {
     fn usage_limit_reached_error_formats_default_for_other_plans() {
         let err = UsageLimitReachedError {
             plan_type: Some("pro".to_string()),
+            resets_in_seconds: None,
         };
         assert_eq!(
             err.to_string(),
-            "You've hit your usage limit. Limits reset every 5h and every week."
+            "You've hit your usage limit. Try again later."
+        );
+    }
+
+    #[test]
+    fn usage_limit_reached_includes_minutes_when_available() {
+        let err = UsageLimitReachedError {
+            plan_type: None,
+            resets_in_seconds: Some(5 * 60),
+        };
+        assert_eq!(
+            err.to_string(),
+            "You've hit your usage limit. Try again in 5 minutes."
+        );
+    }
+
+    #[test]
+    fn usage_limit_reached_includes_hours_and_minutes() {
+        let err = UsageLimitReachedError {
+            plan_type: Some("plus".to_string()),
+            resets_in_seconds: Some(3 * 3600 + 32 * 60),
+        };
+        assert_eq!(
+            err.to_string(),
+            "You've hit your usage limit. Upgrade to Pro (https://openai.com/chatgpt/pricing) or try again in 3 hours 32 minutes."
+        );
+    }
+
+    #[test]
+    fn usage_limit_reached_includes_days_hours_minutes() {
+        let err = UsageLimitReachedError {
+            plan_type: None,
+            resets_in_seconds: Some(2 * 86_400 + 3 * 3600 + 5 * 60),
+        };
+        assert_eq!(
+            err.to_string(),
+            "You've hit your usage limit. Try again in 2 days 3 hours 5 minutes."
+        );
+    }
+
+    #[test]
+    fn usage_limit_reached_less_than_minute() {
+        let err = UsageLimitReachedError {
+            plan_type: None,
+            resets_in_seconds: Some(30),
+        };
+        assert_eq!(
+            err.to_string(),
+            "You've hit your usage limit. Try again in less than a minute."
         );
     }
 }