feat: support default terminal editor (#1082)

Cargo.toml

@@ -65,6 +65,7 @@ html_to_markdown = "0.1.0"
 rust-embed = "8.5.0"
 os_info = { version = "3.8.2", default-features = false }
 bm25 = { version = "2.0.1", features = ["parallelism"] }
+which = "7.0.1"
 
 [dependencies.reqwest]
 version = "0.12.0"

src/config/mod.rs

@@ -35,7 +35,7 @@ use std::{
     io::Write,
     path::{Path, PathBuf},
     process,
-    sync::Arc,
+    sync::{Arc, OnceLock},
 };
 use syntect::highlighting::ThemeSet;
 
@@ -88,6 +88,8 @@ __INPUT__
 const LEFT_PROMPT: &str = "{color.green}{?session {?agent {agent}>}{session}{?role /}}{!session {?agent {agent}>}}{role}{?rag @{rag}}{color.cyan}{?session )}{!session >}{color.reset} ";
 const RIGHT_PROMPT: &str = "{color.purple}{?session {?consume_tokens {consume_tokens}({consume_percent}%)}{!consume_tokens {consume_tokens}}}{color.reset}";
 
+static EDITOR: OnceLock<Option<String>> = OnceLock::new();
+
 #[derive(Debug, Clone, Deserialize)]
 #[serde(default)]
 pub struct Config {
@@ -1640,10 +1642,20 @@ impl Config {
     }
 
     pub fn editor(&self) -> Result<String> {
-        self.editor
-            .clone()
-            .or_else(|| env::var("VISUAL").ok().or_else(|| env::var("EDITOR").ok()))
-            .ok_or_else(|| anyhow!("No editor, please configure `editor` or set $EDITOR/$VISUAL environment variable."))
+        EDITOR.get_or_init(move || {
+            let editor = self.editor.clone()
+                .or_else(|| env::var("VISUAL").ok().or_else(|| env::var("EDITOR").ok()))
+                .unwrap_or_else(|| {
+                    if cfg!(windows) {
+                        "notepad".to_string()
+                    } else {
+                        "nano".to_string()
+                    }
+                });
+            which::which(&editor).ok().map(|_| editor)
+        })
+        .clone()
+        .ok_or_else(|| anyhow!("Editor not found. Please add the `editor` configuration or set the $EDITOR or $VISUAL environment variable."))
     }
 
     pub fn repl_complete(