From 97158d8b6470954224098c12ad38d3ccfa04c03e Mon Sep 17 00:00:00 2001
From: Adam Hopkins <adam@amhopkins.com>
Date: Thu, 17 Feb 2022 12:11:47 +0200
Subject: [PATCH] Add altsvs

---
 sanic/touchup/schemes/altsvc.py | 56 +++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 sanic/touchup/schemes/altsvc.py

diff --git a/sanic/touchup/schemes/altsvc.py b/sanic/touchup/schemes/altsvc.py
new file mode 100644
index 00000000..05e7269b
--- /dev/null
+++ b/sanic/touchup/schemes/altsvc.py
@@ -0,0 +1,56 @@
+from __future__ import annotations
+
+from ast import Assign, Constant, NodeTransformer, Subscript
+from typing import TYPE_CHECKING, Any, List
+
+from sanic.http.constants import HTTP
+
+from .base import BaseScheme
+
+
+if TYPE_CHECKING:
+    from sanic import Sanic
+
+
+class AltSvcCheck(BaseScheme):
+    ident = "ALTSVC"
+
+    def visitors(self) -> List[NodeTransformer]:
+        return [RemoveAltSvc(self.app, self.app.state.verbosity)]
+
+
+class RemoveAltSvc(NodeTransformer):
+    def __init__(self, app: Sanic, verbosity: int = 0) -> None:
+        self._app = app
+        self._verbosity = verbosity
+        self._versions = {
+            info.settings["version"] for info in app.state.server_info
+        }
+
+    def visit_Assign(self, node: Assign) -> Any:
+        if any(self._matches(target) for target in node.targets):
+            if self._should_remove():
+                return None
+            assert isinstance(node.value, Constant)
+            node.value.value = self.value()
+        return node
+
+    def _should_remove(self) -> bool:
+        return len(self._versions) == 1
+
+    @staticmethod
+    def _matches(node) -> bool:
+        return (
+            isinstance(node, Subscript)
+            and isinstance(node.slice, Constant)
+            and node.slice.value == "alt-svc"
+        )
+
+    def value(self):
+        values = []
+        for info in self._app.state.server_info:
+            port = info.settings["port"]
+            version = info.settings["version"]
+            if version is HTTP.VERSION_3:
+                values.append(f'h3=":{port}"')
+        return ", ".join(values)