Initial fastapi structure.

pyproject.toml

@@ -26,6 +26,13 @@ dependencies = [
 [project.scripts]
 pqn = "pqnstack.cli:app"
 
+[project.optional-dependencies]
+webapp = [
+    "fastapi>=0.115.14",
+    "httpx>=0.28.1",
+    "pydantic>=2.11.7",
+]
+
 [dependency-groups]
 dev = ["mypy>=1.13.0", "pytest-cov>=6.0.0", "ruff>=0.8.0"]
 
@@ -34,6 +41,7 @@ dev = ["mypy>=1.13.0", "pytest-cov>=6.0.0", "ruff>=0.8.0"]
 files = ["src"]
 strict = true
 pretty = true
+plugins = ['pydantic.mypy']
 
 enable_error_code = ["ignore-without-code"]
 

src/pqnstack/app/main.py

@@ -0,0 +1,75 @@
+import logging
+from collections.abc import AsyncGenerator
+from typing import Annotated
+
+import httpx
+from fastapi import Depends
+from fastapi import FastAPI
+from fastapi import status
+from pydantic import BaseModel
+
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+app = FastAPI()
+
+
+async def get_http_client() -> AsyncGenerator[httpx.AsyncClient, None]:
+    async with httpx.AsyncClient() as client:
+        yield client
+
+
+ClientDep = Annotated[httpx.AsyncClient, Depends(get_http_client)]
+
+
+class NodeState(BaseModel):
+    waveplates_available: bool = False
+    chsh_basis: list[float] = [0.0, 45.0]
+
+
+state = NodeState()
+
+
+@app.get("/")
+async def root() -> dict[str, str]:
+    return {"message": "Hello World"}
+
+
+@app.post("/chsh")
+async def chsh(basis: tuple[float, float], other_node_address: str, http_client: ClientDep) -> dict[str, str] | int:
+    logger.debug("Starting CHSH")
+    expectations = []
+    for angle in basis:
+        # measure ab, a'b, ab', a'b' for one expectation value
+        counts = []
+        for a in [angle, angle + 90]:
+            # local_instruments.hwp.move_to(a)  # ruff: noqa: ERA001
+            logger.info("moving waveplate", extra={"angle": a})
+
+            for i in range(2):
+                for perp in [False, True]:
+                    r = await http_client.get(
+                        f"http://{other_node_address}/chsh/request-angle-by-basis?i={i}&perp={perp}"
+                    )
+
+                    # TODO: Handle other status codes
+                    if r.status_code != status.HTTP_200_OK:
+                        logger.error("Failed to request follower: %s", r.text)
+                        return {"error": "Failed to request follower"}
+                    # count = local_instruments.measure(measurement_config)  # ruff: noqa: ERA001
+                    count = 1
+                    logger.info("measuring counts, %s", count)
+                    counts.append(count)
+
+        # expectation = compute_expectation(counts)  # ruff: noqa: ERA001
+        expectation = sum(counts)
+        expectations.append(expectation)
+
+    # chsh_result = compute_chsh(expectations)  # ruff: noqa: ERA001
+    return sum(expectations)
+
+
+@app.post("/chsh/request-angle-by-basis")
+async def request_angle_by_basis(index: int, *, perp: bool = False) -> bool:
+    angle = state.chsh_basis[index] + 90 * perp
+    logger.info("moving waveplate", extra={"angle": angle})
+    return True