import json
import re
from typing import Any, Dict, List

from app.services.fusion_prompts import (
    ROUTER_SYSTEM_PROMPT,
    ROUTER_USER_PROMPT_TEMPLATE,
)

VALID_INTENTS = {"A", "B", "C", "D"}


def _extract_json_object(raw_text: str) -> Dict[str, str]:
    """Extract and parse the first JSON object from model output."""
    cleaned = raw_text.strip()
    cleaned = cleaned.replace("```json", "").replace("```", "").strip()

    match = re.search(r"\{[\s\S]*\}", cleaned)
    if not match:
        raise ValueError("No JSON object found in router output")

    data = json.loads(match.group(0))
    if not isinstance(data, dict):
        raise ValueError("Router output JSON is not an object")

    intent = str(data.get("intent", "")).strip().upper()
    reason = str(data.get("reason", "")).strip()
    if intent not in VALID_INTENTS:
        raise ValueError(f"Invalid intent: {intent}")

    if not reason:
        reason = "模型未提供理由，已按规则兜底。"

    return {"intent": intent, "reason": reason}


def _build_history_text(messages: dict, max_turns: int = 6) -> str:
    if not isinstance(messages, dict):
        return ""

    history = messages.get("messages", [])
    if not isinstance(history, list):
        return ""

    tail = history[-max_turns:]
    rows: List[str] = []
    for msg in tail:
        role = str(msg.get("role", "unknown")).strip()
        content = str(msg.get("content", "")).strip().replace("\n", " ")
        if content:
            rows.append(f"{role}: {content}")
    return "\n".join(rows)


def _heuristic_route(query: str) -> Dict[str, str]:
    text = query.strip().lower()

    general_chat_patterns = [
        "你好",
        "您好",
        "在吗",
        "谢谢",
        "早上好",
        "晚上好",
        "你是谁",
        "讲个笑话",
    ]
    global_patterns = [
        "总结",
        "综述",
        "整体",
        "全局",
        "趋势",
        "对比",
        "比较",
        "宏观",
        "共性",
        "差异",
    ]
    local_graph_patterns = [
        "关系",
        "依赖",
        "影响",
        "导致",
        "原因",
        "链路",
        "多跳",
        "传导",
        "耦合",
        "约束",
    ]

    if any(token in text for token in general_chat_patterns):
        return {"intent": "A", "reason": "命中通用对话关键词，且不依赖知识库检索。"}

    if any(token in text for token in global_patterns):
        return {"intent": "D", "reason": "问题指向全局总结或跨主题趋势分析。"}

    if any(token in text for token in local_graph_patterns):
        return {"intent": "C", "reason": "问题强调实体关系与链式推理。"}

    return {"intent": "B", "reason": "默认归入事实查询，适合混合检索链路。"}


async def route_intent(llm: Any, query: str, messages: dict) -> Dict[str, str]:
    """Route user query to A/B/C/D with LLM-first and heuristic fallback."""
    history_text = _build_history_text(messages)
    user_prompt = ROUTER_USER_PROMPT_TEMPLATE.format(
        chat_history=history_text or "无",
        query=query,
    )

    try:
        full_prompt = f"{ROUTER_SYSTEM_PROMPT}\n\n{user_prompt}"
        model_resp = await llm.ainvoke(full_prompt)
        content = getattr(model_resp, "content", model_resp)
        raw_text = content if isinstance(content, str) else str(content)
        return _extract_json_object(raw_text)
    except Exception:
        return _heuristic_route(query)