Bridge legacy Flask APIs through Engine fallback

Data/Engine/bootstrapper.py

@@ -18,7 +18,7 @@ from .interfaces import (
 from .interfaces.eventlet_compat import apply_eventlet_patches
 from .repositories.sqlite import connection as sqlite_connection
 from .repositories.sqlite import migrations as sqlite_migrations
-from .server import create_app
+from .server import attach_legacy_bridge, create_app
 from .services.container import build_service_container
 from .services.crypto.certificates import ensure_certificate
 
@@ -71,12 +71,19 @@ def bootstrap() -> EngineRuntime:
     logger.info("default-admin-ensured")
 
     app = create_app(settings, db_factory=db_factory)
+    attach_legacy_bridge(app, settings, logger=logger)
     services = build_service_container(settings, db_factory=db_factory, logger=logger.getChild("services"))
     app.extensions["engine_services"] = services
     register_http_interfaces(app, services)
-    socketio = create_socket_server(app, settings.socketio)
-    register_ws_interfaces(socketio, services)
-    services.scheduler_service.start(socketio)
+
+    legacy_active = bool(app.config.get("ENGINE_LEGACY_BRIDGE_ACTIVE"))
+    if legacy_active:
+        socketio = None
+        logger.info("legacy-ws-deferred")
+    else:
+        socketio = create_socket_server(app, settings.socketio)
+        register_ws_interfaces(socketio, services)
+        services.scheduler_service.start(socketio)
     logger.info("bootstrap-complete")
     return EngineRuntime(
         app=app,

Data/Engine/interfaces/http/__init__.py

@@ -26,7 +26,11 @@ def register_http_interfaces(app: Flask, services: EngineServiceContainer) -> No
     The implementation is intentionally minimal for the initial scaffolding.
     """
 
-    for registrar in _REGISTRARS:
+    registrars = list(_REGISTRARS)
+    if app.config.get("ENGINE_LEGACY_BRIDGE_ACTIVE"):
+        registrars = [r for r in registrars if r is not job_management.register]
+
+    for registrar in registrars:
         registrar(app, services)
 
 

Data/Engine/server.py

@@ -2,8 +2,11 @@
 
 from __future__ import annotations
 
+import importlib
+import logging
+import os
 from pathlib import Path
-from typing import Optional
+from typing import Any, Iterable, Optional
 
 from flask import Flask, request, send_from_directory
 from flask_cors import CORS
@@ -100,4 +103,135 @@ def create_app(
     return app
 
 
-__all__ = ["create_app"]
+def attach_legacy_bridge(
+    app: Flask,
+    settings: EngineSettings,
+    *,
+    logger: Optional[logging.Logger] = None,
+) -> None:
+    """Attach the legacy Flask application as a fallback dispatcher.
+
+    Borealis ships a mature API surface inside ``Data/Server/server.py``.  The
+    Engine will eventually supersede it, but during the migration the React
+    frontend still expects the historical endpoints to exist.  This helper
+    attempts to load the legacy application and wires it as a fallback WSGI
+    dispatcher so any route the Engine does not yet implement transparently
+    defers to the proven implementation.
+    """
+
+    log = logger or logging.getLogger("borealis.engine.legacy")
+
+    if not _legacy_bridge_enabled():
+        log.info("legacy-bridge-disabled")
+        return
+
+    legacy = _load_legacy_app(settings, app, log)
+    if legacy is None:
+        log.warning("legacy-bridge-unavailable")
+        return
+
+    app.config["ENGINE_LEGACY_BRIDGE_ACTIVE"] = True
+    app.wsgi_app = _FallbackDispatcher(app.wsgi_app, legacy.wsgi_app)  # type: ignore[assignment]
+    app.extensions["legacy_flask_app"] = legacy
+    log.info("legacy-bridge-active")
+
+
+def _legacy_bridge_enabled() -> bool:
+    raw = os.getenv("BOREALIS_ENGINE_ENABLE_LEGACY_BRIDGE", "1")
+    return raw.strip().lower() in {"1", "true", "yes", "on"}
+
+
+def _load_legacy_app(
+    settings: EngineSettings,
+    engine_app: Flask,
+    logger: logging.Logger,
+) -> Optional[Flask]:
+    try:
+        legacy_module = importlib.import_module("Data.Server.server")
+    except Exception as exc:  # pragma: no cover - defensive
+        logger.exception("legacy-import-failed", exc_info=exc)
+        return None
+
+    legacy_app = getattr(legacy_module, "app", None)
+    if not isinstance(legacy_app, Flask):
+        logger.error("legacy-app-missing")
+        return None
+
+    # Align runtime configuration so both applications share database and
+    # session state.
+    try:
+        setattr(legacy_module, "DB_PATH", str(settings.database_path))
+    except Exception:  # pragma: no cover - defensive
+        logger.warning("legacy-db-path-sync-failed", extra={"path": str(settings.database_path)})
+
+    _synchronise_session_config(engine_app, legacy_app)
+
+    return legacy_app
+
+
+def _synchronise_session_config(engine_app: Flask, legacy_app: Flask) -> None:
+    legacy_app.secret_key = engine_app.config.get("SECRET_KEY", legacy_app.secret_key)
+    for key in (
+        "SESSION_COOKIE_HTTPONLY",
+        "SESSION_COOKIE_SECURE",
+        "SESSION_COOKIE_SAMESITE",
+        "SESSION_COOKIE_DOMAIN",
+    ):
+        value = engine_app.config.get(key)
+        if value is not None:
+            legacy_app.config[key] = value
+
+
+class _FallbackDispatcher:
+    """WSGI dispatcher that retries a secondary app when the primary 404s."""
+
+    __slots__ = ("_primary", "_fallback", "_retry_statuses")
+
+    def __init__(
+        self,
+        primary: Any,
+        fallback: Any,
+        *,
+        retry_statuses: Iterable[int] = (404,),
+    ) -> None:
+        self._primary = primary
+        self._fallback = fallback
+        self._retry_statuses = {int(status) for status in retry_statuses}
+
+    def __call__(self, environ: dict[str, Any], start_response: Any) -> Iterable[bytes]:
+        captured_body: list[bytes] = []
+        captured_status: dict[str, Any] = {}
+
+        def _capture_start_response(status: str, headers: list[tuple[str, str]], exc_info: Any = None):
+            captured_status["status"] = status
+            captured_status["headers"] = headers
+            captured_status["exc_info"] = exc_info
+
+            def _write(data: bytes) -> None:
+                captured_body.append(data)
+
+            return _write
+
+        primary_iterable = self._primary(environ, _capture_start_response)
+        try:
+            for chunk in primary_iterable:
+                captured_body.append(chunk)
+        finally:
+            close = getattr(primary_iterable, "close", None)
+            if callable(close):
+                close()
+
+        status_line = str(captured_status.get("status") or "500 Internal Server Error")
+        try:
+            status_code = int(status_line.split()[0])
+        except Exception:  # pragma: no cover - defensive
+            status_code = 500
+
+        if status_code not in self._retry_statuses:
+            start_response(status_line, captured_status.get("headers", []), captured_status.get("exc_info"))
+            return captured_body
+
+        return self._fallback(environ, start_response)
+
+
+__all__ = ["attach_legacy_bridge", "create_app"]

Data/Engine/tests/test_server_legacy_bridge.py

@@ -0,0 +1,60 @@
+from __future__ import annotations
+
+from typing import Callable, Iterable
+
+import pytest
+
+pytest.importorskip("flask")
+
+from Data.Engine.server import _FallbackDispatcher
+
+
+def _wsgi_app(status: str, body: bytes) -> Callable:
+    def _app(environ, start_response):  # type: ignore[override]
+        start_response(status, [("Content-Type", "text/plain"), ("Content-Length", str(len(body)))])
+        return [body]
+
+    return _app
+
+
+def _invoke(app: Callable, path: str = "/") -> tuple[str, bytes]:
+    status_holder: dict[str, str] = {}
+    body_parts: list[bytes] = []
+
+    def _start_response(status: str, headers: Iterable[tuple[str, str]], exc_info=None):  # type: ignore[override]
+        status_holder["status"] = status
+        return body_parts.append
+
+    environ = {"PATH_INFO": path, "REQUEST_METHOD": "GET", "wsgi.input": None}
+    result = app(environ, _start_response)
+    try:
+        for chunk in result:
+            body_parts.append(chunk)
+    finally:
+        close = getattr(result, "close", None)
+        if callable(close):
+            close()
+
+    return status_holder.get("status", ""), b"".join(body_parts)
+
+
+def test_fallback_dispatcher_primary_wins() -> None:
+    primary = _wsgi_app("200 OK", b"engine")
+    fallback = _wsgi_app("200 OK", b"legacy")
+    dispatcher = _FallbackDispatcher(primary, fallback)
+
+    status, body = _invoke(dispatcher)
+
+    assert status == "200 OK"
+    assert body == b"engine"
+
+
+def test_fallback_dispatcher_uses_fallback_on_404() -> None:
+    primary = _wsgi_app("404 Not Found", b"missing")
+    fallback = _wsgi_app("200 OK", b"legacy")
+    dispatcher = _FallbackDispatcher(primary, fallback)
+
+    status, body = _invoke(dispatcher)
+
+    assert status == "200 OK"
+    assert body == b"legacy"