"""GraphRAG 融合查询 API 端点。

提供向量检索 + 知识图谱的融合查询能力：
- POST /api/graphrag/query     — 完整 GraphRAG 查询（检索+生成）
- POST /api/graphrag/retrieve  — 仅检索（返回上下文，不调 LLM）
- POST /api/graphrag/query/stream — 流式 GraphRAG 查询（SSE）
"""

from __future__ import annotations

import uuid
from typing import Annotated

from fastapi import APIRouter, Depends, Header, HTTPException
from fastapi.responses import StreamingResponse

from app.core.logging import get_logger
from app.module.kg_graphrag.kb_access import KnowledgeBaseAccessValidator
from app.module.kg_graphrag.models import (
    GraphRAGQueryRequest,
    GraphRAGQueryResponse,
    RetrievalContext,
)
from app.module.kg_graphrag.retriever import GraphRAGRetriever
from app.module.kg_graphrag.generator import GraphRAGGenerator
from app.module.shared.schema import StandardResponse

router = APIRouter(prefix="/graphrag", tags=["graphrag"])
logger = get_logger(__name__)

# 延迟初始化
_retriever: GraphRAGRetriever | None = None
_generator: GraphRAGGenerator | None = None
_kb_validator: KnowledgeBaseAccessValidator | None = None


def _get_retriever() -> GraphRAGRetriever:
    global _retriever
    if _retriever is None:
        _retriever = GraphRAGRetriever.from_settings()
    return _retriever


def _get_generator() -> GraphRAGGenerator:
    global _generator
    if _generator is None:
        _generator = GraphRAGGenerator.from_settings()
    return _generator


def _get_kb_validator() -> KnowledgeBaseAccessValidator:
    global _kb_validator
    if _kb_validator is None:
        _kb_validator = KnowledgeBaseAccessValidator.from_settings()
    return _kb_validator


def _require_caller_id(
    x_user_id: Annotated[
        str,
        Header(min_length=1, description="调用方用户 ID，由上游 Java 后端传递"),
    ],
) -> str:
    caller = x_user_id.strip()
    if not caller:
        raise HTTPException(status_code=401, detail="Missing required header: X-User-Id")
    return caller


# ---------------------------------------------------------------------------
# P0: 完整 GraphRAG 查询
# ---------------------------------------------------------------------------


@router.post(
    "/query",
    response_model=StandardResponse[GraphRAGQueryResponse],
    summary="GraphRAG 查询",
    description="并行从向量库和知识图谱检索上下文，融合后调用 LLM 生成回答。",
)
async def query(
    req: GraphRAGQueryRequest,
    caller: Annotated[str, Depends(_require_caller_id)],
):
    trace_id = uuid.uuid4().hex[:16]
    logger.info(
        "[%s] GraphRAG query: graph_id=%s, collection=%s, caller=%s",
        trace_id, req.graph_id, req.collection_name, caller,
    )

    retriever = _get_retriever()
    generator = _get_generator()

    # 权限校验：验证用户是否有权访问该知识库
    kb_validator = _get_kb_validator()
    if not await kb_validator.check_access(
        req.knowledge_base_id, caller, collection_name=req.collection_name,
    ):
        logger.warning(
            "[%s] KB access denied: kb_id=%s, collection=%s, caller=%s",
            trace_id, req.knowledge_base_id, req.collection_name, caller,
        )
        raise HTTPException(
            status_code=403,
            detail=f"无权访问知识库 {req.knowledge_base_id}",
        )

    try:
        context = await retriever.retrieve(
            query=req.query,
            collection_name=req.collection_name,
            graph_id=req.graph_id,
            strategy=req.strategy,
            user_id=caller,
        )
    except Exception:
        logger.exception("[%s] Retrieval failed", trace_id)
        raise HTTPException(status_code=502, detail=f"检索服务暂不可用 (trace: {trace_id})")

    try:
        answer = await generator.generate(query=req.query, context=context.merged_text)
    except Exception:
        logger.exception("[%s] Generation failed", trace_id)
        raise HTTPException(status_code=502, detail=f"生成服务暂不可用 (trace: {trace_id})")

    result = GraphRAGQueryResponse(
        answer=answer,
        context=context,
        model=generator.model_name,
    )
    return StandardResponse(code=200, message="success", data=result)


# ---------------------------------------------------------------------------
# P1-1: 仅检索
# ---------------------------------------------------------------------------


@router.post(
    "/retrieve",
    response_model=StandardResponse[RetrievalContext],
    summary="GraphRAG 仅检索",
    description="并行从向量库和知识图谱检索上下文，返回结构化上下文（不调 LLM）。",
)
async def retrieve(
    req: GraphRAGQueryRequest,
    caller: Annotated[str, Depends(_require_caller_id)],
):
    trace_id = uuid.uuid4().hex[:16]
    logger.info(
        "[%s] GraphRAG retrieve: graph_id=%s, collection=%s, caller=%s",
        trace_id, req.graph_id, req.collection_name, caller,
    )

    retriever = _get_retriever()

    # 权限校验：验证用户是否有权访问该知识库
    kb_validator = _get_kb_validator()
    if not await kb_validator.check_access(
        req.knowledge_base_id, caller, collection_name=req.collection_name,
    ):
        logger.warning(
            "[%s] KB access denied: kb_id=%s, collection=%s, caller=%s",
            trace_id, req.knowledge_base_id, req.collection_name, caller,
        )
        raise HTTPException(
            status_code=403,
            detail=f"无权访问知识库 {req.knowledge_base_id}",
        )

    try:
        context = await retriever.retrieve(
            query=req.query,
            collection_name=req.collection_name,
            graph_id=req.graph_id,
            strategy=req.strategy,
            user_id=caller,
        )
    except Exception:
        logger.exception("[%s] Retrieval failed", trace_id)
        raise HTTPException(status_code=502, detail=f"检索服务暂不可用 (trace: {trace_id})")

    return StandardResponse(code=200, message="success", data=context)


# ---------------------------------------------------------------------------
# P1-4: 流式查询 (SSE)
# ---------------------------------------------------------------------------


@router.post(
    "/query/stream",
    summary="GraphRAG 流式查询",
    description="并行检索后，通过 SSE 流式返回 LLM 生成内容。",
)
async def query_stream(
    req: GraphRAGQueryRequest,
    caller: Annotated[str, Depends(_require_caller_id)],
):
    trace_id = uuid.uuid4().hex[:16]
    logger.info(
        "[%s] GraphRAG stream: graph_id=%s, collection=%s, caller=%s",
        trace_id, req.graph_id, req.collection_name, caller,
    )

    retriever = _get_retriever()
    generator = _get_generator()

    # 权限校验：验证用户是否有权访问该知识库
    kb_validator = _get_kb_validator()
    if not await kb_validator.check_access(
        req.knowledge_base_id, caller, collection_name=req.collection_name,
    ):
        logger.warning(
            "[%s] KB access denied: kb_id=%s, collection=%s, caller=%s",
            trace_id, req.knowledge_base_id, req.collection_name, caller,
        )
        raise HTTPException(
            status_code=403,
            detail=f"无权访问知识库 {req.knowledge_base_id}",
        )

    try:
        context = await retriever.retrieve(
            query=req.query,
            collection_name=req.collection_name,
            graph_id=req.graph_id,
            strategy=req.strategy,
            user_id=caller,
        )
    except Exception:
        logger.exception("[%s] Retrieval failed", trace_id)
        raise HTTPException(status_code=502, detail=f"检索服务暂不可用 (trace: {trace_id})")

    import json

    async def event_stream():
        try:
            async for token in generator.generate_stream(
                query=req.query, context=context.merged_text
            ):
                yield f"data: {json.dumps({'token': token}, ensure_ascii=False)}\n\n"
            # 结束事件：附带检索上下文
            yield f"data: {json.dumps({'done': True, 'context': context.model_dump()}, ensure_ascii=False)}\n\n"
        except Exception:
            logger.exception("[%s] Stream generation failed", trace_id)
            yield f"data: {json.dumps({'error': '生成服务暂不可用'})}\n\n"

    return StreamingResponse(event_stream(), media_type="text/event-stream")


# ---------------------------------------------------------------------------
# 缓存管理
# ---------------------------------------------------------------------------


@router.get(
    "/cache/stats",
    response_model=StandardResponse[dict],
    summary="缓存统计",
    description="返回 GraphRAG 检索缓存的命中率和容量统计。",
)
async def cache_stats():
    from app.module.kg_graphrag.cache import get_cache

    return StandardResponse(code=200, message="success", data=get_cache().stats())


@router.post(
    "/cache/clear",
    response_model=StandardResponse[dict],
    summary="清空缓存",
    description="清空所有 GraphRAG 检索缓存。",
)
async def cache_clear():
    from app.module.kg_graphrag.cache import get_cache

    get_cache().clear()
    return StandardResponse(code=200, message="success", data={"cleared": True})