libluna: Add String::join()

libluna/include/luna/String.h

@@ -32,6 +32,8 @@ class String
         return view().split_once(delim);
     }
 
+    static Result<String> join(const Vector<String>& vec, StringView delim);
+
     void trim(StringView delim);
 
     static Result<String> format(const String& fmt, ...);

libluna/src/String.cpp

@@ -2,6 +2,7 @@
 #include <luna/CString.h>
 #include <luna/Format.h>
 #include <luna/String.h>
+#include <luna/StringBuilder.h>
 #include <luna/Vector.h>
 
 String::String()
@@ -163,3 +164,20 @@ Result<String> String::from_cstring(const char* str)
     if (!dup) return err(ENOMEM);
     return String { dup };
 }
+
+Result<String> String::join(const Vector<String>& vec, StringView delim)
+{
+    if (vec.size() == 0) return String {};
+    if (vec.size() == 1) return vec[0].clone();
+
+    StringBuilder sb;
+    TRY(sb.add(vec[0].view()));
+
+    for (usize i = 1; i < vec.size(); i++)
+    {
+        TRY(sb.add(delim));
+        TRY(sb.add(vec[i].view()));
+    }
+
+    return sb.string();
+}