CLAUDE.md

Bitcoin price tracker UI — Python FastAPI web application. Serves the HTML/Tailwind UI and proxies live price data from btcdata over WebSocket.

Build & Development Commands

make run — Start dev server on port 4000; creates .venv and installs requirements.txt on first run (the venv target, keyed off requirements.txt)
cp .env.example .env — optional; .env is -included, so a missing one is not fatal
make run-local — Same, but with BTCDATA_URL=$BTCDATA_LOCAL_URL
make tailwind — Watch Tailwind CSS for changes
make test — Installs test-only dependencies from requirements-dev.txt and runs pytest tests/
make venv — Bootstrap the virtualenv without starting the server

Docker

Docker runs alongside local dev on different ports:

Service	Local dev	Docker
btcprice	localhost:4000	localhost:4041 (container port 4040)
btcdata	localhost:4100	localhost:4102

docker compose up -d here starts btcprice only. Both projects attach to the external btc-network (docker network create btc-network once), and btcdata must be started from ../btcdata. Inside the network btcprice reaches it at http://btcdata:${DOCKER_BTCDATA_PORT:-4102}.

The image does not set BTCDATA_URL; deployments must provide it. BUILD_SHA is embedded as APP_VERSION and exposed at /api/version. The port in CMD is hardcoded to 4040.

CI/CD

.gitea/workflows/build.yml tests pushes to main and v* tags, then publishes immutable linux/amd64 images to harbor.pmagnus.cloud/btcprice/btcprice. It embeds the short Git SHA as APP_VERSION. CI has no Kubernetes credentials; the planned Flux deployment belongs in magnus/deploy once the shared GitOps gate is complete.

Legacy deployment

./deploy-citadel.sh — build locally for the remote's arch, docker save | ssh docker load, docker compose up -d --no-build in /home/pmp/apps/btcprice on citadel (192.168.50.195). Mirrors ../elprice/deploy-citadel.sh; no registry.

docker-compose.citadel.yml → remote docker-compose.yml; .env.citadel → remote .env.
btcdata also runs on citadel, so both attach to the external btc-network there and BTCDATA_URL is http://btcdata:4102 (service name, not a LAN address). The deploy script creates the network on the remote if it is missing.
Live at http://192.168.50.195:4041.

Architecture

Framework: FastAPI
Server: Uvicorn
Templates: Inline HTML strings + HTMX (WebSocket extension)
Styling: Tailwind CSS v4
Data backend: btcdata (separate service at BTCDATA_URL, default http://localhost:4100)
No database — all data comes from btcdata
Probes: /api/health is process-only liveness; /api/ready checks btcdata with a 3-second timeout; /api/version exposes the build identifier

btcdata connection

The browser connects only to btcprice: ws-connect="/ws/price" and ws-connect="/ws/strike". Each endpoint runs _ws_proxy, which opens an upstream WebSocket to btcdata's /api/price/ws and /api/strike/ws, converts each JSON message to an HTML fragment (price_json_to_html, strike_json_to_html) and forwards it. BTCDATA_URL is the single point of contact; _btcdata_ws_url rewrites its scheme to ws/wss.

Source Layout

btcprice acts as a WebSocket proxy between the browser and btcdata:

Browser connects via HTMX WebSocket to /ws/price or /ws/strike
btcprice proxies to btcdata's /api/price/ws or /api/strike/ws
JSON from btcdata is transformed into HTML fragments (in price_json_to_html / strike_json_to_html)
HTMX swaps the HTML into the DOM by matching element IDs (price-display, strike-display)

Key Conventions

Numbers use Danish locale formatting (dots for thousands, commas for decimals) via da_fmt()
Price changes are color-coded: green (up), red (down), gray (unchanged)
All HTML is built as string concatenation in Python — no template engine

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