Add configurable data providers and localize frontend UI

backend/config/data_config.py

@@ -1,29 +1,77 @@
 # -*- coding: utf-8 -*-
-"""
-Centralized Data Source Configuration
+"""Centralized data source configuration and fallback ordering."""
 
-Auto-detects and manages data source based on available API keys.
-Priority: FINNHUB_API_KEY > FINANCIAL_DATASETS_API_KEY
-"""
 import os
 from dataclasses import dataclass
 from typing import Literal, Optional
 
-DataSource = Literal["finnhub", "financial_datasets"]
+DataSource = Literal["finnhub", "financial_datasets", "yfinance", "local_csv"]
+_KNOWN_SOURCES: tuple[DataSource, ...] = (
+    "finnhub",
+    "financial_datasets",
+    "yfinance",
+    "local_csv",
+)
 
 
 @dataclass
 class DataSourceConfig:
-    """Immutable data source configuration"""
+    """Resolved data source configuration."""
 
     source: DataSource
     api_key: str
+    sources: list[DataSource]
 
 
 # Module-level cache for the resolved configuration
 _config_cache: Optional[DataSourceConfig] = None
 
 
+def _parse_enabled_sources() -> list[DataSource]:
+    """Parse optional enabled source allowlist from the environment."""
+    raw_value = os.getenv("ENABLED_DATA_SOURCES", "").strip().lower()
+    if not raw_value:
+        return []
+
+    enabled: list[DataSource] = []
+    for item in raw_value.split(","):
+        candidate = item.strip()
+        if not candidate or candidate not in _KNOWN_SOURCES:
+            continue
+        if candidate not in enabled:
+            enabled.append(candidate)
+    return enabled
+
+
+def _ordered_sources() -> list[DataSource]:
+    """Resolve source preference and available fallbacks."""
+    preferred = os.getenv("FIN_DATA_SOURCE", "").strip().lower()
+    finnhub_key = os.getenv("FINNHUB_API_KEY", "").strip()
+    fd_key = os.getenv("FINANCIAL_DATASETS_API_KEY", "").strip()
+    enabled_sources = _parse_enabled_sources()
+    wants_yfinance = preferred == "yfinance" or "yfinance" in enabled_sources
+
+    available: list[DataSource] = []
+    if finnhub_key:
+        available.append("finnhub")
+    if fd_key:
+        available.append("financial_datasets")
+    if wants_yfinance:
+        available.append("yfinance")
+    available.append("local_csv")
+
+    if enabled_sources:
+        filtered = [source for source in enabled_sources if source in available]
+        if filtered:
+            available = filtered
+
+    if preferred in available:
+        ordered = [preferred]
+        ordered.extend(source for source in available if source != preferred)
+        return ordered
+    return available
+
+
 def _resolve_config() -> DataSourceConfig:
     """
     Resolve data source configuration based on available API keys.
@@ -33,21 +81,22 @@ def _resolve_config() -> DataSourceConfig:
     2. FINANCIAL_DATASETS_API_KEY (if set)
     3. Raises error if neither is available
     """
-    # Check for Finnhub API key first (higher priority)
-    finnhub_key = os.getenv("FINNHUB_API_KEY")
-    if finnhub_key:
-        return DataSourceConfig(source="finnhub", api_key=finnhub_key)
-
-    # Fallback to Financial Datasets API
-    fd_key = os.getenv("FINANCIAL_DATASETS_API_KEY")
-    if fd_key:
-        return DataSourceConfig(source="financial_datasets", api_key=fd_key)
-
-    # No API key available
-    raise ValueError(
-        "No API key found. Please set either FINNHUB_API_KEY or "
-        "FINANCIAL_DATASETS_API_KEY in your .env file.",
-    )
+    sources = _ordered_sources()
+    if "finnhub" in sources:
+        return DataSourceConfig(
+            source="finnhub",
+            api_key=os.getenv("FINNHUB_API_KEY", "").strip(),
+            sources=sources,
+        )
+    if "financial_datasets" in sources:
+        return DataSourceConfig(
+            source="financial_datasets",
+            api_key=os.getenv("FINANCIAL_DATASETS_API_KEY", "").strip(),
+            sources=sources,
+        )
+    if "yfinance" in sources:
+        return DataSourceConfig(source="yfinance", api_key="", sources=sources)
+    return DataSourceConfig(source="local_csv", api_key="", sources=sources)
 
 
 def get_config() -> DataSourceConfig:
@@ -71,6 +120,11 @@ def get_data_source() -> DataSource:
     return get_config().source
 
 
+def get_data_sources() -> list[DataSource]:
+    """Get preferred source ordering including fallbacks."""
+    return get_config().sources
+
+
 def get_api_key() -> str:
     """Get the API key for the configured data source."""
     return get_config().api_key