catalogue_backend/README.md

# Backend - Brand Product Search Engine (RAG API)

FastAPI service exposing the product catalog through:

- **Browse** - plain listing endpoints (`/api/brands`, `/api/brands/{brand}/products`)
- **Search** - pgvector semantic similarity search, no LLM (`/api/search`)
- **Chat** - full RAG: retrieval + local Ollama generation (`/api/chat`)
- **Admin** - trigger brand ingestion in the background (`/api/catalog/generate`)

Full setup, architecture, and troubleshooting steps are in the project
documentation (`docs/`). This file is just a fast local reference.

## Quick start

### One command (from the project root)

```bash
python run_project.py --backend-only
```

Picks up `backend/venv` if present (else the current interpreter) and starts
uvicorn with autoreload on port 8000. Drop `--backend-only` to run the React
frontend alongside it; `--help` lists the port and reload flags.

It does **not** start Postgres or Ollama for you - it reports them via
`/api/health` and warns if either is unreachable. Bring those up first
(see Manual below, and "Pulling the local LLM").

### Manual

```bash
cd backend
python3 -m venv .venv
source .venv/bin/activate          # Windows: .venv\Scripts\activate
pip install -r requirements.txt

cp .env.example .env               # then edit DB_PASSWORD etc.

# Auth is required: the app will not start without AUTH_SECRET_KEY and the two
# password hashes. This prints them, plus the sign-in passwords (shown once).
python scripts/make_auth_secrets.py

# Option A: already have a Postgres+pgvector catalog from the old project?
#   Just point .env at it (DB_HOST/DB_PORT/DB_NAME/DB_USER/DB_PASSWORD) - done.
# Option B: starting fresh locally?
docker compose -f docker-compose.yml up -d
python scripts/seed_sample_data.py     # loads bundled sample catalogs instantly

uvicorn app.main:app --reload --port 8000
```

Then open http://localhost:8000/docs for interactive API docs, or run the
frontend (`../frontend/README.md`) to use the React UI.

## Authentication

Reads are public; the 18 write/compute endpoints require a credential, enforced
by a dependency on each route (`app/api/deps.py`). Sign in for a bearer token:

```bash
curl -X POST localhost:8000/api/auth/login \
  -H 'Content-Type: application/json' \
  -d '{"username":"admin","password":"<from make_auth_secrets.py>"}'
```

Send it as `Authorization: Bearer <token>`, or use an `X-API-Key` from the
`API_KEYS` setting for server-to-server callers. `admin` passes every
permission check; `user` holds the product/store/inventory permissions.
`AUTH_ENABLED=false` disables all of it for local work — never in a deployment.
See the Authentication section of `../DEPLOYMENT.md` for the full endpoint map.

## MCP server

The catalog is exposed to AI clients over the Model Context Protocol at `/mcp`,
mounted onto this same FastAPI app (`app/mcp_server.py`) - no separate process
or container, so it deploys with the API and answers on the same host.

**15 tools, all read-only.** Catalog search and browse, nutrition facts and
health scores, healthier alternatives, per-store inventory and pricing,
discounts, trending and sales analytics. None of the write or compute endpoints
are reachable through MCP: a tool list is chosen from by a model rather than by
a person, and "retrain the models" is not something to leave one tool call away.

**Auth is the app's own access token** - there is no separate MCP credential.
Clients send `Authorization: Bearer <token>` from `POST /api/auth/login`, and
the same `Principal` and expiry apply as on the REST side. Note the practical
consequence: tokens expire after `AUTH_TOKEN_TTL_MINUTES` (12h by default), so a
long-running client has to refresh. Raise the TTL if that is a problem.

```jsonc
{
  "mcpServers": {
    "nearle-catalogue": {
      "type": "http",
      "url": "https://mcp.nearle.ai.in/mcp",
      "headers": { "Authorization": "Bearer <token>" }
    }
  }
}
```

The admin UI has an inspector at `/mcp` (React route, admin-only) listing every
tool with its arguments and a console to run one against live data. It is backed
by `GET /api/mcp/info` and `POST /api/mcp/tools/{name}` rather than by the MCP
endpoint itself - the browser would otherwise need a full MCP client to render a
tool list.

`fastmcp` requires Python 3.10+. The image is 3.11; on an older interpreter the
import fails, `app/main.py` logs a warning, and the REST API starts without the
MCP endpoint rather than failing outright.

## Ports

The container answers on **3000 and 8000 at the same time**, the same way the
frontend image answers on 80 and 3000. 3000 is what Dokploy routes a domain to;
8000 is what this README, the vite dev proxy and `docker-compose.yml` use. Both
being live means the deployment works whichever one it is pointed at, instead of
returning 502 from a healthy container.

`serve.py` is what makes that possible - uvicorn's CLI binds a single `--port`,
but `Server.run()` accepts a list of pre-bound sockets, so it is still one
process. If one port is unavailable it logs and carries on with the other; it
exits non-zero only when nothing is listening.

```bash
python serve.py               # 3000 and 8000
PORT=8080 python serve.py     # only 8080 (PORT pins a single port)
PORTS=80,3000 python serve.py # a different pair
```

For local development `uvicorn app.main:app --reload --port 8000` is still the
normal thing to run - one port is all you need, and it gives you autoreload.

## Persistence: the two volumes a deployment needs

Most state lives in Postgres, but three things are written to the filesystem,
and in a container those live inside the image - so a redeploy rebuilds the
image and silently discards them:

| Path | Written by |
|---|---|
| `/app/data/seed_catalogs` | `POST /api/user/products/add`, `/upload-file` - every product added through the UI is appended to the brand's JSON |
| `/app/app/intelligence/artifacts` | the training endpoints - every retrained `*.joblib` model |
| `/app/data` | catalogs saved by the ingestion pipeline |

Mount a volume on each (the first is inside the third, so two mounts cover all
three):

```
/app/data
/app/app/intelligence/artifacts
```

In Dokploy, add both under the service's **Volumes**. Named volume or bind
mount, either is fine - `docker compose --profile full up -d` shows the same
two mounts as named volumes.

Bind mounts normally break this pattern, because they start empty and hide the
seed catalogs and pre-trained models the image ships with. They are safe here:
the image keeps read-only copies at `/app/.bundled`, and on startup
`app/infrastructure/persistence.py` copies in whatever the mounted directory is
missing. It never overwrites an existing file, so a user-added product always
survives the next redeploy rather than being reverted to the bundled catalog.

If you leave the volumes off, the API still runs and logs a warning naming the
directories that will be lost.

Override the locations with `DATA_DIR`, `SEED_CATALOG_DIR` and
`MODEL_ARTIFACTS_DIR` if the writable data belongs somewhere else.

## Pulling the local LLM (one-time)

```bash
ollama pull qwen2.5:1.5b
ollama serve   # if not already running as a service
```

## Project layout

```
backend/
├── app/
│   ├── main.py                  # FastAPI app + router wiring
│   ├── infrastructure/settings.py
│   ├── api/
│   │   ├── schemas.py           # Pydantic models
│   │   ├── job_store.py         # in-memory background-job tracker
│   │   └── routers/             # health, brands, search, chat, catalog
│   ├── core/
│   │   ├── catalog_engine.py    # discovery + enrichment + image pipeline
│   │   └── ingestion.py         # thin wrapper used by API + CLI
│   └── services/
│       ├── embeddings_service.py  # sentence-transformers (lazy-loaded)
│       ├── ollama_service.py      # local LLM calls (catalog + RAG answers)
│       ├── vector_store.py        # pgvector reads/writes/SEMANTIC SEARCH
│       ├── rag_service.py         # RAG orchestration (NEW)
│       ├── image_search.py / s3_service.py / price_estimator.py / brand_registry.py
├── cli/ingest_brand.py           # CLI: ingest one brand end-to-end
├── scripts/seed_sample_data.py   # load bundled sample catalogs (no LLM needed)
├── data/seed_catalogs/*.json     # bundled sample catalogs (Parle, Cadbury, ...)
└── requirements.txt
```

## Running tests

```bash
pytest -q
```