arbret/backend/price_fetcher.py

"""Bitfinex price fetcher for BTC/EUR pair."""

from datetime import UTC, datetime

import httpx

BITFINEX_TICKER_URL = "https://api-pub.bitfinex.com/v2/ticker/tBTCEUR"
LAST_PRICE_INDEX = 6
REQUEST_TIMEOUT_SECONDS = 30.0

# Constants for price history records
SOURCE_BITFINEX = "bitfinex"
PAIR_BTC_EUR = "BTC/EUR"


async def fetch_btc_eur_price() -> tuple[float, datetime]:
    """
    Fetch the current BTC/EUR price from Bitfinex.

    Returns:
        Tuple of (price, timestamp) where timestamp is the current UTC time.

    Raises:
        httpx.HTTPStatusError: If the API returns a non-2xx status code.
        httpx.RequestError: If a network error occurs (including timeout).
        ValueError: If the response format is unexpected.
    """
    async with httpx.AsyncClient(timeout=REQUEST_TIMEOUT_SECONDS) as client:
        response = await client.get(BITFINEX_TICKER_URL)
        response.raise_for_status()

        data = response.json()

        # Bitfinex ticker response is an array:
        # [BID, BID_SIZE, ASK, ASK_SIZE, DAILY_CHANGE, DAILY_CHANGE_RELATIVE,
        #  LAST_PRICE, VOLUME, HIGH, LOW]
        if not isinstance(data, list) or len(data) <= LAST_PRICE_INDEX:
            raise ValueError(f"Unexpected response format: {data}")

        price = float(data[LAST_PRICE_INDEX])
        timestamp = datetime.now(UTC)

        return price, timestamp