detect terminal and include in request headers (#2437)

This adds the terminal version to the UA header.

codex-rs/core/src/terminal.rs

@@ -0,0 +1,72 @@
+use std::sync::OnceLock;
+
+static TERMINAL: OnceLock<String> = OnceLock::new();
+
+pub fn user_agent() -> String {
+    TERMINAL.get_or_init(detect_terminal).to_string()
+}
+
+/// Sanitize a header value to be used in a User-Agent string.
+///
+/// This function replaces any characters that are not allowed in a User-Agent string with an underscore.
+///
+/// # Arguments
+///
+/// * `value` - The value to sanitize.
+fn is_valid_header_value_char(c: char) -> bool {
+    c.is_ascii_alphanumeric() || c == '-' || c == '_' || c == '.' || c == '/'
+}
+
+fn sanitize_header_value(value: String) -> String {
+    value.replace(|c| !is_valid_header_value_char(c), "_")
+}
+
+fn detect_terminal() -> String {
+    sanitize_header_value(
+        if let Ok(tp) = std::env::var("TERM_PROGRAM")
+            && !tp.trim().is_empty()
+        {
+            let ver = std::env::var("TERM_PROGRAM_VERSION").ok();
+            match ver {
+                Some(v) if !v.trim().is_empty() => format!("{tp}/{v}"),
+                _ => tp,
+            }
+        } else if let Ok(v) = std::env::var("WEZTERM_VERSION") {
+            if !v.trim().is_empty() {
+                format!("WezTerm/{v}")
+            } else {
+                "WezTerm".to_string()
+            }
+        } else if std::env::var("KITTY_WINDOW_ID").is_ok()
+            || std::env::var("TERM")
+                .map(|t| t.contains("kitty"))
+                .unwrap_or(false)
+        {
+            "kitty".to_string()
+        } else if std::env::var("ALACRITTY_SOCKET").is_ok()
+            || std::env::var("TERM")
+                .map(|t| t == "alacritty")
+                .unwrap_or(false)
+        {
+            "Alacritty".to_string()
+        } else if let Ok(v) = std::env::var("KONSOLE_VERSION") {
+            if !v.trim().is_empty() {
+                format!("Konsole/{v}")
+            } else {
+                "Konsole".to_string()
+            }
+        } else if std::env::var("GNOME_TERMINAL_SCREEN").is_ok() {
+            return "gnome-terminal".to_string();
+        } else if let Ok(v) = std::env::var("VTE_VERSION") {
+            if !v.trim().is_empty() {
+                format!("VTE/{v}")
+            } else {
+                "VTE".to_string()
+            }
+        } else if std::env::var("WT_SESSION").is_ok() {
+            return "WindowsTerminal".to_string();
+        } else {
+            std::env::var("TERM").unwrap_or_else(|_| "unknown".to_string())
+        },
+    )
+}