README.md

Fluxgraph Backend — Pipeline Parse API

A small FastAPI service that validates serialised ReactFlow pipelines.

Endpoint

POST /pipelines/parse

Request — standard ReactFlow serialisation:

{ "nodes": [ { "id": "..." } ], "edges": [ { "id": "...", "source": "...", "target": "..." } ] }

Extra ReactFlow fields (position, data, sourceHandle, animated, …) are accepted and ignored.

Response:

{ "num_nodes": 3, "num_edges": 2, "is_dag": true }

There is also a GET / health check returning { "status": "ok" }.

DAG detection

is_dag is computed with Kahn's topological sort (check_is_dag in main.py) — O(V + E), no external graph library. Edges that reference a node id not present in nodes are ignored, so a partially-loaded frontend state can't crash the endpoint.

Run locally

Using uv (a uv.lock is committed):

cd backend
uv sync                       # install from pyproject.toml / uv.lock
uv run uvicorn main:app --reload   # http://localhost:8000

Or with a plain virtualenv + pip:

cd backend
python -m venv .venv && source .venv/bin/activate
pip install -r requirements.txt
uvicorn main:app --reload     # http://localhost:8000

Interactive API docs are available at http://localhost:8000/docs.

Tests

uv run pytest test_main.py -v   # 14 tests

Coverage includes empty/single-node graphs, linear chains, a diamond DAG, self-loops, 2- and 3-node cycles, disconnected components, and dangling edges.

Requirements

Python ≥ 3.12. Dependencies are declared in pyproject.toml (and mirrored in requirements.txt for the pip workflow): fastapi, uvicorn[standard], pydantic v2, plus httpx and pytest for tests.