refactor: enforce market data quality contracts

backend/data/gateway.py

@@ -2,10 +2,12 @@ from __future__ import annotations
 
 from collections.abc import Callable
 from dataclasses import dataclass
+from datetime import datetime
 
 from backend.data.contracts import DataUsage
 from backend.data.policy import DataSourcePolicy
 from backend.data.providers import IfindProvider, TushareProvider
+from backend.data.quality import DataQualityGate, QualityEvidence, QualityReport
 from chart_data_provider import EastmoneyChartClient, MarketChartClient
 from ifind_client import IfindHttpClient
 from realtime_aggregator import WebRealtimeAggregator
@@ -15,6 +17,7 @@ from tushare_client import TushareClient
 @dataclass(frozen=True)
 class DataGateway:
     policy: DataSourcePolicy
+    quality: DataQualityGate
     tushare_provider: TushareProvider
     ifind_provider: IfindProvider
     chart_data: MarketChartClient
@@ -36,6 +39,27 @@ class DataGateway:
     def assert_source(self, dataset_id: str, provider_id: str, usage: DataUsage) -> None:
         self.policy.assert_allowed(dataset_id, provider_id, usage)
 
+    def provider_chain(self, dataset_id: str, usage: DataUsage) -> tuple[str, ...]:
+        dataset = self.policy.dataset(dataset_id)
+        allowed = []
+        for provider_id in dataset.providers:
+            try:
+                self.policy.assert_allowed(dataset_id, provider_id, usage)
+            except Exception:
+                continue
+            allowed.append(provider_id)
+        if not allowed:
+            raise RuntimeError(f"No permitted provider for {dataset_id} ({usage})")
+        return tuple(allowed)
+
+    def require_quality(
+        self,
+        evidence: QualityEvidence,
+        usage: DataUsage,
+        as_of: str | datetime | None = None,
+    ) -> QualityReport:
+        return self.quality.require(evidence, usage, as_of)
+
 
 def build_data_gateway(
     credentials: dict[str, object],
@@ -48,8 +72,10 @@ def build_data_gateway(
     token_supplier = tushare_token_supplier or (
         lambda: str(credentials.get("tushare_token") or "")
     )
+    policy = DataSourcePolicy.load()
     return DataGateway(
-        policy=DataSourcePolicy.load(),
+        policy=policy,
+        quality=DataQualityGate.load(policy),
         tushare_provider=TushareProvider(token_supplier),
         ifind_provider=IfindProvider(ifind),
         chart_data=MarketChartClient(ifind, EastmoneyChartClient()),