feat(use_case): add gRPC transport for UseCaseService

demo/use_case/grpc_demo.py

@@ -0,0 +1,103 @@
+"""gRPC demo — UseCaseService exposed as gRPC server.
+
+Run:
+    uv run --with grpcio python -m demo.use_case.grpc_demo
+"""
+
+import asyncio
+import json
+
+from pydantic import BaseModel
+
+from nexusx import UseCaseAppConfig, UseCaseService, create_use_case_grpc_server, query
+
+# ── DTOs ──────────────────────────────────────────
+
+
+class ItemDTO(BaseModel):
+    id: int
+    name: str
+    price: float
+
+
+# ── Service ───────────────────────────────────────
+
+
+class CatalogService(UseCaseService):
+    """Product catalog service."""
+
+    @query
+    async def list_items(cls) -> list[ItemDTO]:
+        return [
+            ItemDTO(id=1, name="Widget", price=9.99),
+            ItemDTO(id=2, name="Gadget", price=19.99),
+            ItemDTO(id=3, name="Doohickey", price=4.99),
+        ]
+
+    @query
+    async def get_item(cls, item_id: int) -> ItemDTO | None:
+        items = {
+            1: ItemDTO(id=1, name="Widget", price=9.99),
+            2: ItemDTO(id=2, name="Gadget", price=19.99),
+            3: ItemDTO(id=3, name="Doohickey", price=4.99),
+        }
+        return items.get(item_id)
+
+
+# ── Main ──────────────────────────────────────────
+
+PORT = 50051
+
+
+async def server():
+    config = UseCaseAppConfig(
+        name="catalog",
+        services=[CatalogService],
+    )
+    server = create_use_case_grpc_server(config, port=PORT)
+    await server.start()
+    print(f"gRPC server listening on port {PORT}")
+    await server.wait_for_termination()
+
+
+async def client():
+    from grpc import aio as grpc_aio
+
+    await asyncio.sleep(0.5)  # wait for server
+
+    async with grpc_aio.insecure_channel(f"localhost:{PORT}") as channel:
+        call = channel.unary_unary(
+            "/CatalogService/list_items",
+            request_serializer=lambda d: json.dumps(d).encode(),
+            response_deserializer=lambda b: b,
+        )
+        response = await call({})
+        data = json.loads(response)
+        print("\n── list_items ──")
+        for item in data["result"]:
+            print(f"  {item['id']}: {item['name']} — ${item['price']}")
+
+        # Get single item
+        call = channel.unary_unary(
+            "/CatalogService/get_item",
+            request_serializer=lambda d: json.dumps(d).encode(),
+            response_deserializer=lambda b: b,
+        )
+        response = await call({"item_id": 2})
+        data = json.loads(response)
+        print("\n── get_item(2) ──")
+        print(f"  {data['result']}")
+
+
+async def main():
+    server_task = asyncio.create_task(server())
+    await client()
+    server_task.cancel()
+    try:
+        await server_task
+    except asyncio.CancelledError:
+        pass
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

pyproject.toml

@@ -46,6 +46,9 @@ fastmcp = [
 cli = [
     "typer>=0.12.0",
 ]
+grpc = [
+    "grpcio>=1.60.0",
+]
 
 [project.urls]
 Homepage = "https://github.com/allmonday/nexusx"

src/nexusx/__init__.py

@@ -71,6 +71,7 @@ def resolve_author(self, loader=Loader('author')):
     create_jsonrpc_router,
     create_use_case_cli,
     create_use_case_flat_server,
+    create_use_case_grpc_server,
     create_use_case_mcp_server,
 )
 from nexusx.use_case import (
@@ -109,6 +110,7 @@ def resolve_author(self, loader=Loader('author')):
     "SelectionError",
     "create_use_case_mcp_server",
     "create_use_case_flat_server",
+    "create_use_case_grpc_server",
     "create_use_case_cli",
     "create_jsonrpc_router",
     "create_use_case_router",

src/nexusx/use_case/__init__.py

@@ -8,6 +8,7 @@
 from nexusx.use_case.cli import create_use_case_cli
 from nexusx.use_case.context import FromContext
 from nexusx.use_case.flat_server import create_use_case_flat_server
+from nexusx.use_case.grpc_server import create_use_case_grpc_server
 from nexusx.use_case.jsonrpc import create_jsonrpc_router
 from nexusx.use_case.router import create_router
 from nexusx.use_case.selection import SelectionError
@@ -17,6 +18,7 @@
 __all__ = [
     "create_use_case_cli",
     "create_use_case_flat_server",
+    "create_use_case_grpc_server",
     "create_jsonrpc_router",
     "create_router",
     "create_use_case_mcp_server",