feat: 多专业小模型+路由模型系统 MVP（mock 全链路 + FastAPI 网关 + 论文调研）

router_system/difficulty.py

@@ -0,0 +1,52 @@
+"""查询难度估计器（启发式，纯标准库）。
+
+依据：RouterArena 用 Bloom 分类法把问题分为 easy/medium/hard。
+这里用查询长度、指令动词、数学/推理标记做轻量估计。
+"""
+from __future__ import annotations
+
+import re
+from typing import Tuple
+
+# 触发 hard 的指令动词 / 推理标记
+_HARD_MARKERS = [
+    "证明", "推导", "为什么", "如何", "对比", "比较", "分析", "评估", "设计", "优化",
+    "复杂度", "时间复杂度", "空间复杂度", "原理", "机制", "优缺点", "区别", "推论", "定理",
+    "proof", "prove", "derive", "explain why", "why", "how", "compare", "contrast",
+    "analy", "evaluate", "design", "optimize", "refactor", "architect",
+    "implement", "debug", "review", "plan", "synthesize",
+    "int", "sum", "sqrt", "lim", "log", "derivative", "integral",
+]
+# 触发 medium 的标记
+_MEDIUM_MARKERS = [
+    "用", "写", "计算", "求解", "生成", "翻译", "总结", "解释",
+    "注意", "建议", "是否", "实现", "步骤",
+    "write", "code", "function", "script", "calculate", "solve", "summarize",
+    "translate", "fix", "explain", "describe", "list",
+]
+
+
+def estimate_difficulty(query: str) -> Tuple[str, float]:
+    """返回 (difficulty, score)，score 属于 [0,1]。"""
+    q = query.lower()
+    hard_hits = sum(1 for m in _HARD_MARKERS if m in q)
+    medium_hits = sum(1 for m in _MEDIUM_MARKERS if m in q)
+    length = len(query)
+
+    score = 0.0
+    score += min(0.30, length / 600.0)          # 长度贡献
+    score += min(0.55, hard_hits * 0.25)        # 推理标记贡献
+    score += min(0.30, medium_hits * 0.08)      # 一般指令贡献
+
+    # 额外：代码 / 数学表达式（多步骤信号）
+    if "```" in query or re.search(r"\b(def|class|function|import)\b", q):
+        score += 0.15
+    if re.search(r"[0-9]+\s*[+\-*/^=]\s*[0-9xya-z]", q):
+        score += 0.15
+
+    score = max(0.0, min(1.0, score))
+    if score >= 0.55:
+        return "hard", score
+    if score >= 0.25:
+        return "medium", score
+    return "easy", score␍