From 50b4d7aa3573f3da9b59cddf2f59075d804fbfef Mon Sep 17 00:00:00 2001
From: DragonFriend <211247049+ADragonFriend@users.noreply.github.com>
Date: Wed, 14 May 2025 04:00:20 -0500
Subject: [PATCH] Add replace and treplace to String (#2127)

* Add replace and treplace functions to String
---
 lib/std/core/builtin.c3         |  1 -
 lib/std/core/string.c3          | 33 +++++++++++++++++++++++++++++++++
 releasenotes.md                 |  1 +
 test/unit/stdlib/core/string.c3 | 24 +++++++++++++++++++++++-
 4 files changed, 57 insertions(+), 2 deletions(-)

diff --git a/lib/std/core/builtin.c3 b/lib/std/core/builtin.c3
index e7171dc59..d677becf1 100644
--- a/lib/std/core/builtin.c3
+++ b/lib/std/core/builtin.c3
@@ -278,7 +278,6 @@ macro enum_by_name($Type, String enum_name) @builtin
 *>
 macro @enum_from_value($Type, #value, value) @builtin
 {
-	usz elements = $Type.elements;
 	foreach (e : $Type.values)
 	{
 		if (e.#value == value) return e;
diff --git a/lib/std/core/string.c3 b/lib/std/core/string.c3
index 8adaa10d5..58e20bc00 100644
--- a/lib/std/core/string.c3
+++ b/lib/std/core/string.c3
@@ -154,6 +154,39 @@ fn String join(Allocator allocator, String[] s, String joiner)
 	};
 }
 
+<*
+ Replace all instances of one substring with a different string.
+
+ @param [in] self
+ @param [in] needle : `The string to be replaced`
+ @param [in] new_str : `The replacement string`
+ @param [&inout] allocator : `The allocator to use for the String`
+ @return "The new string with the elements replaced"
+*>
+fn String String.replace(self, Allocator allocator, String needle, String new_str) @nodiscard
+{
+	@pool()
+	{
+		String[] split = self.tsplit(needle);
+		return dstring::join(tmem, split, new_str).copy_str(mem);
+	};
+}
+
+<*
+ Replace all instances of one substring with a different string, allocating the new string on the temp allocator.
+
+ @param [in] self
+ @param [in] needle : `The string to be replaced`
+ @param [in] new_str : `The replacement string`
+ @return "The new string with the elements replaced"
+*>
+fn String String.treplace(self, String needle, String new_str)
+{
+	String[] split = self.tsplit(needle);
+	return dstring::join(tmem, split, new_str).str_view();
+}
+
+
 <*
  Remove characters from the front and end of a string.
 
diff --git a/releasenotes.md b/releasenotes.md
index 403b0b128..5adc6b83f 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -21,6 +21,7 @@
 - std::ascii moved into std::core::ascii. Old _m variants are deprecated, as is uint methods.
 - Add `String.tokenize_all` to replace the now deprecated `String.splitter`
 - Add `String.count` to count the number of instances of a string.
+- Add `String.replace` and `String.treplace` to replace substrings within a string.
 - Add `Duration * Int` and `Clock - Clock` overload. 
 - Add `DateTime + Duration` overloads.
 
diff --git a/test/unit/stdlib/core/string.c3 b/test/unit/stdlib/core/string.c3
index 9a6bee9ed..245489917 100644
--- a/test/unit/stdlib/core/string.c3
+++ b/test/unit/stdlib/core/string.c3
@@ -195,6 +195,28 @@ fn void test_split_to_buffer()
 	free(strings);
 }
 
+fn void test_treplace()
+{
+	String test = "Befriend some dragons?";
+	assert(test.treplace("some", "all") == "Befriend all dragons?");
+	assert(test.treplace("?", "!") == "Befriend some dragons!");
+	assert(test.treplace("Never", "Always") == "Befriend some dragons?");
+}
+
+fn void test_replace()
+{
+	String test = "Befriend some dragons?";
+	String val = test.replace(mem, "some", "all");
+	test::eq(val, "Befriend all dragons?");
+	free(val);
+	val = test.replace(mem, "?", "!");
+	test::eq(val, "Befriend some dragons!");
+    free(val);
+    val = test.replace(mem, "Never", "Always");
+    test::eq(val, "Befriend some dragons?");
+    free(val);
+}
+
 fn void test_index_of()
 {
 	String test = "hello world hello";
@@ -283,4 +305,4 @@ fn void tokenize_all_skip_last()
         str.append("-");
 	}
 	test::eq(str.str_view(), "foo--bar-baz-");
-}
\ No newline at end of file
+}