From 4e43d1b217f5b7dc020bb5ca8afc018e9917c58b Mon Sep 17 00:00:00 2001
From: Max Bernstein <max@bernsteinbear.com>
Date: Fri, 24 Nov 2023 12:12:08 -0500
Subject: [PATCH] Add list length function

---
 scrapscript.py | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/scrapscript.py b/scrapscript.py
index 8e12a787..4521fd1b 100755
--- a/scrapscript.py
+++ b/scrapscript.py
@@ -1833,6 +1833,17 @@ def test_stdlib_serialize_expr(self) -> None:
             Bytes(value=b"d4:leftd4:type3:Int5:valuei1ee2:op3:ADD5:rightd4:type3:Int5:valuei2ee4:type5:Binope"),
         )
 
+    def test_stdlib_listlength_empty_list_returns_zero(self) -> None:
+        self.assertEqual(self._run("$$listlength []", STDLIB), Int(0))
+
+    def test_stdlib_listlength_returns_length(self) -> None:
+        self.assertEqual(self._run("$$listlength [1,2,3]", STDLIB), Int(3))
+
+    def test_stdlib_listlength_with_non_list_raises_type_error(self) -> None:
+        with self.assertRaises(TypeError) as ctx:
+            self._run("$$listlength 1", STDLIB)
+        self.assertEqual(ctx.exception.args[0], "listlength Expected List, but got Int")
+
 
 class BencodeTests(unittest.TestCase):
     def test_bencode_int(self) -> None:
@@ -2006,11 +2017,18 @@ def jsondecode(obj: Object) -> Object:
     return make_object(data)
 
 
+def listlength(obj: Object) -> Object:
+    if not isinstance(obj, List):
+        raise TypeError(f"listlength Expected List, but got {type(obj).__name__}")
+    return Int(len(obj.items))
+
+
 STDLIB = {
     "$$add": NativeFunction(lambda x: NativeFunction(lambda y: Int(unpack_int(x) + unpack_int(y)))),
     "$$fetch": NativeFunction(fetch),
     "$$jsondecode": NativeFunction(jsondecode),
     "$$serialize": NativeFunction(lambda obj: Bytes(serialize(obj))),
+    "$$listlength": NativeFunction(listlength),
 }