From 6e7fbfa66fe3c7de0441cbde14f78685fed69dce Mon Sep 17 00:00:00 2001
From: Stephen Chung <schungx@live.com>
Date: Mon, 20 Sep 2021 16:25:23 +0800
Subject: [PATCH] Add pop to string.

---
 CHANGELOG.md                |  1 +
 src/packages/string_more.rs | 30 +++++++++++++++++++++++++++++-
 tests/string.rs             |  5 +++++
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index daa864c5..5b4c3e67 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -40,6 +40,7 @@ Enhancements
 ### String Values
 
 * `SmartString` now uses `LazyCompact` instead of `Compact` to minimize allocations.
+* Added `pop` for strings.
 
 ### `Scope` API
 
diff --git a/src/packages/string_more.rs b/src/packages/string_more.rs
index 65980026..4947b620 100644
--- a/src/packages/string_more.rs
+++ b/src/packages/string_more.rs
@@ -14,7 +14,7 @@ def_package!(crate:MoreStringPackage:"Additional string utilities, including str
 
 #[export_module]
 mod string_functions {
-    use crate::ImmutableString;
+    use crate::{ImmutableString, SmartString};
 
     #[rhai_fn(name = "+", name = "append")]
     pub fn add_append(
@@ -99,6 +99,34 @@ mod string_functions {
             *string = trimmed.to_string().into();
         }
     }
+    #[rhai_fn(return_raw)]
+    pub fn pop(string: &mut ImmutableString) -> Result<char, Box<EvalAltResult>> {
+        match string.make_mut().pop() {
+            Some(c) => Ok(c.into()),
+            None => EvalAltResult::ErrorStringBounds(0, 0, Position::NONE).into(),
+        }
+    }
+    #[rhai_fn(name = "pop")]
+    pub fn pop_string(
+        ctx: NativeCallContext,
+        string: &mut ImmutableString,
+        len: INT,
+    ) -> ImmutableString {
+        if len <= 0 {
+            return ctx.engine().empty_string.clone();
+        }
+
+        let mut chars = StaticVec::<char>::with_capacity(len as usize);
+
+        for _ in 0..len {
+            match string.make_mut().pop() {
+                Some(c) => chars.push(c),
+                None => break,
+            }
+        }
+
+        chars.into_iter().rev().collect::<SmartString>().into()
+    }
 
     pub fn to_upper(string: &str) -> ImmutableString {
         string.to_uppercase().into()
diff --git a/tests/string.rs b/tests/string.rs
index d60be0dc..62f00b86 100644
--- a/tests/string.rs
+++ b/tests/string.rs
@@ -100,6 +100,11 @@ fn test_string_mut() -> Result<(), Box<EvalAltResult>> {
     engine.register_fn("bar", |s: String| s.len() as INT);
     engine.register_fn("baz", |s: &mut String| s.len());
 
+    assert_eq!(engine.eval::<char>(r#"pop("hello")"#)?, 'o');
+    assert_eq!(engine.eval::<String>(r#"pop("hello", 3)"#)?, "llo");
+    assert_eq!(engine.eval::<String>(r#"pop("hello", 10)"#)?, "hello");
+    assert_eq!(engine.eval::<String>(r#"pop("hello", -42)"#)?, "");
+
     assert_eq!(engine.eval::<INT>(r#"foo("hello")"#)?, 5);
     assert_eq!(engine.eval::<INT>(r#"bar("hello")"#)?, 5);
     assert!(