refactor: extract 'bitfinex' and 'BTC/EUR' magic strings to constants

Add SOURCE_BITFINEX and PAIR_BTC_EUR constants in price_fetcher.py and
use them consistently in routes/audit.py, worker.py, and tests.

backend/price_fetcher.py

@@ -7,6 +7,10 @@ import httpx
 BITFINEX_TICKER_URL = "https://api-pub.bitfinex.com/v2/ticker/tBTCEUR"
 LAST_PRICE_INDEX = 6
 
+# Constants for price history records
+SOURCE_BITFINEX = "bitfinex"
+PAIR_BTC_EUR = "BTC/EUR"
+
 
 async def fetch_btc_eur_price() -> tuple[float, datetime]:
     """

backend/routes/audit.py

@@ -23,7 +23,7 @@ from pagination import (
     calculate_total_pages,
     create_paginated_response,
 )
-from price_fetcher import fetch_btc_eur_price
+from price_fetcher import PAIR_BTC_EUR, SOURCE_BITFINEX, fetch_btc_eur_price
 from schemas import (
     CounterRecordResponse,
     PaginatedCounterRecords,
@@ -194,8 +194,8 @@ async def fetch_price_now(
     price, timestamp = await fetch_btc_eur_price()
 
     record = PriceHistory(
-        source="bitfinex",
+        source=SOURCE_BITFINEX,
-        pair="BTC/EUR",
+        pair=PAIR_BTC_EUR,
         price=price,
         timestamp=timestamp,
     )

backend/tests/test_price_history.py

@@ -7,7 +7,7 @@ from unittest.mock import AsyncMock, MagicMock, patch
 import pytest
 
 from models import PriceHistory
-from price_fetcher import fetch_btc_eur_price
+from price_fetcher import PAIR_BTC_EUR, SOURCE_BITFINEX, fetch_btc_eur_price
 from worker import process_bitcoin_price_job
 
 
@@ -134,8 +134,8 @@ class TestGetPriceHistory:
             now = datetime.now(UTC)
             for i in range(5):
                 record = PriceHistory(
-                    source="bitfinex",
+                    source=SOURCE_BITFINEX,
-                    pair="BTC/EUR",
+                    pair=PAIR_BTC_EUR,
                     price=90000.0 + i * 100,
                     timestamp=now.replace(second=i),
                 )
@@ -159,8 +159,8 @@ class TestGetPriceHistory:
             now = datetime.now(UTC)
             for i in range(25):
                 record = PriceHistory(
-                    source="bitfinex",
+                    source=SOURCE_BITFINEX,
-                    pair="BTC/EUR",
+                    pair=PAIR_BTC_EUR,
                     price=90000.0 + i,
                     timestamp=now.replace(microsecond=i),
                 )
@@ -209,8 +209,8 @@ class TestManualFetch:
 
         assert response.status_code == 200
         data = response.json()
-        assert data["source"] == "bitfinex"
+        assert data["source"] == SOURCE_BITFINEX
-        assert data["pair"] == "BTC/EUR"
+        assert data["pair"] == PAIR_BTC_EUR
         assert data["price"] == 95123.45
         assert "id" in data
         assert "timestamp" in data
@@ -280,8 +280,8 @@ class TestProcessBitcoinPriceJob:
         call_args = mock_conn.execute.call_args
 
         # Check the SQL parameters
-        assert call_args[0][1] == "bitfinex"  # source
+        assert call_args[0][1] == SOURCE_BITFINEX  # source
-        assert call_args[0][2] == "BTC/EUR"  # pair
+        assert call_args[0][2] == PAIR_BTC_EUR  # pair
         assert call_args[0][3] == 95000.0  # price
 
     @pytest.mark.asyncio

backend/worker.py

@@ -14,7 +14,7 @@ from pgqueuer.queries import Queries
 
 from database import ASYNCPG_DATABASE_URL
 from jobs import JOB_FETCH_BITCOIN_PRICE, JOB_RANDOM_NUMBER
-from price_fetcher import fetch_btc_eur_price
+from price_fetcher import PAIR_BTC_EUR, SOURCE_BITFINEX, fetch_btc_eur_price
 
 logging.basicConfig(
     level=logging.INFO,
@@ -116,8 +116,8 @@ async def process_bitcoin_price_job(db_pool: asyncpg.Pool) -> None:
                 VALUES ($1, $2, $3, $4, NOW())
                 ON CONFLICT (source, pair, timestamp) DO NOTHING
                 """,
-                "bitfinex",
+                SOURCE_BITFINEX,
-                "BTC/EUR",
+                PAIR_BTC_EUR,
                 price,
                 timestamp,
             )