feat: implement t-604 keyword prompt moderation

apps/moderation/services.py

@@ -0,0 +1,94 @@
+"""Prompt moderation orchestration.
+
+T-604 只做本地关键词 prompt 审核：在图片下载、定价、预扣点和上游调用之前执行。
+MVP 不做输出审核、不做图片审核，也不保存用户 prompt 原文。
+"""
+
+from __future__ import annotations
+
+import logging
+from dataclasses import dataclass, field
+
+from . import policy
+from .providers import ModerationError, ModerationResult, Verdict
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass(frozen=True)
+class ModerationOutcome:
+    stage: str
+    verdict: Verdict
+    blocked: bool
+    labels: tuple[str, ...] = ()
+    keywords: tuple[str, ...] = ()
+    matched_word_ids: tuple[int, ...] = ()
+    request_id: str = ""
+    reason: str = ""
+    result: ModerationResult | None = field(default=None, repr=False)
+
+
+def _passed(stage: str) -> ModerationOutcome:
+    return ModerationOutcome(stage=stage, verdict=Verdict.PASS, blocked=False)
+
+
+def _on_provider_failure(stage: str, exc: Exception) -> ModerationOutcome:
+    """provider 不可用时的兜底：fail-closed → BLOCK，fail-open → PASS。"""
+    if policy.fail_closed():
+        logger.warning("moderation fail-closed at %s: %s", stage, exc.__class__.__name__)
+        return ModerationOutcome(
+            stage=stage,
+            verdict=Verdict.BLOCK,
+            blocked=True,
+            reason=f"fail-closed: {exc.__class__.__name__}",
+        )
+    logger.warning("moderation fail-open at %s: %s", stage, exc.__class__.__name__)
+    return ModerationOutcome(stage=stage, verdict=Verdict.PASS, blocked=False, reason="fail-open")
+
+
+def _evaluate(stage: str, call) -> ModerationOutcome:
+    if not policy.moderation_enabled():
+        return _passed(stage)
+    try:
+        result = call()
+    except ModerationError as exc:
+        outcome = _on_provider_failure(stage, exc)
+        _record(outcome)
+        return outcome
+
+    outcome = ModerationOutcome(
+        stage=stage,
+        verdict=result.verdict,
+        blocked=policy.verdict_is_blocking(result.verdict),
+        labels=result.labels,
+        keywords=result.keywords,
+        matched_word_ids=tuple(result.raw.get("word_ids", ())) if isinstance(result.raw, dict) else (),
+        request_id=result.request_id,
+        result=result,
+    )
+    _record(outcome)
+    return outcome
+
+
+def _record(outcome: ModerationOutcome) -> None:
+    logger.info(
+        "moderation stage=%s verdict=%s blocked=%s labels=%s word_ids=%s request_id=%s",
+        outcome.stage,
+        outcome.verdict.value,
+        outcome.blocked,
+        ",".join(outcome.labels),
+        ",".join(str(word_id) for word_id in outcome.matched_word_ids),
+        outcome.request_id,
+    )
+
+
+def moderate_prompt(*, user=None, api_key=None, prompt: str) -> ModerationOutcome:
+    return _evaluate(
+        "prompt",
+        lambda: policy.get_text_provider().moderate_text(
+            prompt, biz_type=policy.biz_type("input")
+        ),
+    )
+
+def moderate_input(*, user=None, prompt: str, **kwargs) -> ModerationOutcome:
+    return moderate_prompt(user=user, prompt=prompt)