fix(relay): harden lifecycle and protocol handling

scripts/codegen.sh

@@ -8,16 +8,18 @@ if [[ "${1:-}" == "--check" ]]; then
   shift
 fi
 
+python3 scripts/generate_relay_protocol.py
 dart run slang
 dart run build_runner build --delete-conflicting-outputs "$@"
 
 if $check; then
   generated_changes="$({
-    git diff --name-only -- lib
+    git diff --name-only -- lib server/relay_protocol_gen.go
     git ls-files --others --exclude-standard -- \
       ':(glob)lib/**/*.g.dart' \
-      ':(glob)lib/**/*.freezed.dart'
-  } | grep -E '\.(g|freezed)\.dart$' || true)"
+      ':(glob)lib/**/*.freezed.dart' \
+      server/relay_protocol_gen.go
+  } | grep -E '(\.(g|freezed)\.dart|relay_protocol_gen\.go)$' || true)"
 
   if [[ -n "$generated_changes" ]]; then
     echo "Generated files are out of date:" >&2

scripts/generate_relay_protocol.py

@@ -0,0 +1,117 @@
+#!/usr/bin/env python3
+"""Generate Dart and Go relay protocol constants from relay_protocol.json."""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parent.parent
+SPEC_PATH = ROOT / "relay_protocol.json"
+DART_PATH = ROOT / "lib/watch_together/services/relay_protocol.g.dart"
+GO_PATH = ROOT / "server/relay_protocol_gen.go"
+
+
+def camel_to_pascal(value: str) -> str:
+    return value[:1].upper() + value[1:]
+
+
+def dart_source(spec: dict) -> str:
+    lines = [
+        "// Generated by scripts/generate_relay_protocol.py. Do not edit.",
+        "",
+        "abstract final class RelayProtocol {",
+    ]
+    for group in ("clientMessageTypes", "serverMessageTypes"):
+        for name, value in spec[group].items():
+            lines.append(f"  static const String {name} = {value!r};")
+    for name, value in spec["errorCodes"].items():
+        lines.append(f"  static const String {name}Code = {value!r};")
+    lines.append("")
+    for name, value in spec["limits"].items():
+        lines.append(f"  static const int {name} = {value};")
+    lines.extend(
+        [
+            "",
+            "  static final RegExp _idPattern = RegExp(r'^[A-Za-z0-9_-]+$');",
+            "",
+            "  static bool isValidSessionId(String value) =>",
+            "      value.isNotEmpty && value.length <= maxSessionIdLength && _idPattern.hasMatch(value);",
+            "",
+            "  static bool isValidPeerId(String value) =>",
+            "      value.isNotEmpty && value.length <= maxPeerIdLength && _idPattern.hasMatch(value);",
+            "}",
+            "",
+        ]
+    )
+    return "\n".join(lines)
+
+
+def go_source(spec: dict) -> str:
+    lines = [
+        "// Code generated by scripts/generate_relay_protocol.py. DO NOT EDIT.",
+        "",
+        "package main",
+        "",
+        "const (",
+    ]
+    protocol_constants = []
+    for group in ("clientMessageTypes", "serverMessageTypes"):
+        protocol_constants.extend(
+            (f"relayType{camel_to_pascal(name)}", f'"{value}"')
+            for name, value in spec[group].items()
+        )
+    protocol_constants.extend(
+        (f"relayError{camel_to_pascal(name)}", f'"{value}"')
+        for name, value in spec["errorCodes"].items()
+    )
+    protocol_name_width = max(len(name) for name, _ in protocol_constants)
+    lines.extend(
+        f"\t{name:<{protocol_name_width}} = {value}"
+        for name, value in protocol_constants
+    )
+    lines.append("")
+    go_limit_names = {
+        "maxRoomSize": "maxRoomSize",
+        "maxMessageSize": "maxMessageSize",
+        "maxSessionIdLength": "maxSessionIDLength",
+        "maxPeerIdLength": "maxPeerIDLength",
+    }
+    limit_constants = [
+        (go_limit_names[name], str(value)) for name, value in spec["limits"].items()
+    ]
+    limit_name_width = max(len(name) for name, _ in limit_constants)
+    lines.extend(
+        f"\t{name:<{limit_name_width}} = {value}"
+        for name, value in limit_constants
+    )
+    lines.extend(
+        [
+            ")",
+            "",
+            "func validRelayID(value string, maxLength int) bool {",
+            "\tif len(value) == 0 || len(value) > maxLength {",
+            "\t\treturn false",
+            "\t}",
+            "\tfor _, ch := range value {",
+            "\t\tif (ch < 'a' || ch > 'z') && (ch < 'A' || ch > 'Z') &&",
+            "\t\t\t(ch < '0' || ch > '9') && ch != '_' && ch != '-' {",
+            "\t\t\treturn false",
+            "\t\t}",
+            "\t}",
+            "\treturn true",
+            "}",
+            "",
+        ]
+    )
+    return "\n".join(lines)
+
+
+def main() -> None:
+    spec = json.loads(SPEC_PATH.read_text(encoding="utf-8"))
+    DART_PATH.write_text(dart_source(spec), encoding="utf-8")
+    GO_PATH.write_text(go_source(spec), encoding="utf-8")
+
+
+if __name__ == "__main__":
+    main()