From 9e0b7be9a9c80b5df52854ab426bc60b794931ed Mon Sep 17 00:00:00 2001
From: unspeaker <hora.nqma@protonmail.com>
Date: Thu, 31 Jul 2025 21:00:13 +0300
Subject: [PATCH] fix(dsl): tail condition

---
 dsl/src/dsl.rs | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/dsl/src/dsl.rs b/dsl/src/dsl.rs
index 979585d..d8de0f5 100644
--- a/dsl/src/dsl.rs
+++ b/dsl/src/dsl.rs
@@ -6,19 +6,13 @@
 extern crate const_panic;
 use const_panic::PanicFmt;
 use std::fmt::Debug;
-
 pub(crate) use std::error::Error;
 pub(crate) use std::sync::Arc;
-
 pub(crate) use konst::string::{str_range, char_indices};
 pub(crate) use thiserror::Error;
 pub(crate) use ::tengri_core::*;
-
 pub(crate) use self::DslError::*;
-
-mod dsl_conv;
-pub use self::dsl_conv::*;
-
+mod dsl_conv; pub use self::dsl_conv::*;
 mod dsl_parse;
 pub(crate) use self::dsl_parse::*;
 pub mod parse { pub use crate::dsl_parse::*; }
@@ -47,11 +41,20 @@ pub trait DslExp: Dsl {
         Ok(exp_peek(self.src())?)
     }
     fn head (&self) -> DslPerhaps<&str> {
-        Ok(peek(&self.src()[1..])?)
+        let start = 1;
+        let src   = self.src();
+        let src   = &src[start.min(src.len().saturating_sub(1))..];
+        peek(src)
     }
     fn tail (&self) -> DslPerhaps<&str> {
-        Ok(if let Some((head_start, head_len)) = seek(&self.src()[1..])? {
-            peek(&self.src()[(1+head_start+head_len)..])?
+        let start = 1;
+        let src   = self.src();
+        let src   = &src[start.min(src.len().saturating_sub(1))..];
+        Ok(if let Some((head_start, head_len)) = seek(src)? {
+            let start = 1 + head_start + head_len;
+            let src   = self.src();
+            let src   = &src[start.min(src.len().saturating_sub(1))..];
+            peek(src)?
         } else {
             None
         })