hyungi_document_server/app/api/search.py

"""하이브리드 검색 API — orchestrator (Phase 1.1: thin endpoint).

retrieval / fusion / rerank 등 실제 로직은 services/search/* 모듈로 분리.
이 파일은 mode 분기, 응답 직렬화, debug 응답 구성, BackgroundTask dispatch만 담당.
"""

import time
from typing import Annotated

from fastapi import APIRouter, BackgroundTasks, Depends, Query
from pydantic import BaseModel
from sqlalchemy.ext.asyncio import AsyncSession

from core.auth import get_current_user
from core.database import get_session
from core.utils import setup_logger
from models.user import User
from services.search.fusion_service import DEFAULT_FUSION, get_strategy, normalize_display_scores
from services.search.rerank_service import (
    MAX_CHUNKS_PER_DOC,
    MAX_RERANK_INPUT,
    apply_diversity,
    rerank_chunks,
)
from services.search.retrieval_service import compress_chunks_to_docs, search_text, search_vector
from services.search_telemetry import (
    compute_confidence,
    compute_confidence_hybrid,
    compute_confidence_reranked,
    record_search_event,
)

# logs/search.log + stdout 동시 출력 (Phase 0.4)
logger = setup_logger("search")

router = APIRouter()


class SearchResult(BaseModel):
    """검색 결과 단일 행.

    Phase 1.2-C: chunk-level vector retrieval 도입으로 chunk 메타 필드 추가.
    text 검색 결과는 chunk_id 등이 None (doc-level).
    vector 검색 결과는 chunk_id 등이 채워짐 (chunk-level).
    """

    id: int  # doc_id (text/vector 공통)
    title: str | None
    ai_domain: str | None
    ai_summary: str | None
    file_format: str
    score: float
    snippet: str | None
    match_reason: str | None = None
    # Phase 1.2-C: chunk 메타 (vector 검색 시 채워짐)
    chunk_id: int | None = None
    chunk_index: int | None = None
    section_title: str | None = None


# ─── Phase 0.4: 디버그 응답 스키마 ─────────────────────────


class DebugCandidate(BaseModel):
    """단계별 후보 (debug=true 응답에서만 노출)."""
    id: int
    rank: int
    score: float
    match_reason: str | None = None


class SearchDebug(BaseModel):
    timing_ms: dict[str, float]
    text_candidates: list[DebugCandidate] | None = None
    vector_candidates: list[DebugCandidate] | None = None
    fused_candidates: list[DebugCandidate] | None = None
    confidence: float
    notes: list[str] = []
    # Phase 1/2 도입 후 채워질 placeholder
    query_analysis: dict | None = None
    reranker_scores: list[DebugCandidate] | None = None


class SearchResponse(BaseModel):
    results: list[SearchResult]
    total: int
    query: str
    mode: str
    debug: SearchDebug | None = None


def _to_debug_candidates(rows: list[SearchResult], n: int = 20) -> list[DebugCandidate]:
    return [
        DebugCandidate(
            id=r.id, rank=i + 1, score=r.score, match_reason=r.match_reason
        )
        for i, r in enumerate(rows[:n])
    ]


@router.get("/", response_model=SearchResponse)
async def search(
    q: str,
    user: Annotated[User, Depends(get_current_user)],
    session: Annotated[AsyncSession, Depends(get_session)],
    background_tasks: BackgroundTasks,
    mode: str = Query("hybrid", pattern="^(fts|trgm|vector|hybrid)$"),
    limit: int = Query(20, ge=1, le=100),
    fusion: str = Query(
        DEFAULT_FUSION,
        pattern="^(legacy|rrf|rrf_boost)$",
        description="hybrid 모드 fusion 전략 (legacy=기존 가중합, rrf=RRF k=60, rrf_boost=RRF+강한신호 boost)",
    ),
    rerank: bool = Query(
        True,
        description="bge-reranker-v2-m3 활성화 (Phase 1.3, hybrid 모드만 동작)",
    ),
    debug: bool = Query(False, description="단계별 candidates + timing 응답에 포함"),
):
    """문서 검색 — FTS + ILIKE + 벡터 결합 (Phase 0.5: RRF fusion)"""
    timing: dict[str, float] = {}
    notes: list[str] = []
    text_results: list[SearchResult] = []
    vector_results: list[SearchResult] = []  # doc-level (압축 후, fusion 입력)
    raw_chunks: list[SearchResult] = []  # chunk-level (raw, Phase 1.3 reranker용)
    chunks_by_doc: dict[int, list[SearchResult]] = {}  # Phase 1.3 reranker용 보존

    t_total = time.perf_counter()

    if mode == "vector":
        t0 = time.perf_counter()
        raw_chunks = await search_vector(session, q, limit)
        timing["vector_ms"] = (time.perf_counter() - t0) * 1000
        if not raw_chunks:
            notes.append("vector_search_returned_empty (AI client error or no embeddings)")
        # vector 단독 모드도 doc 압축해서 다양성 확보 (chunk 중복 방지)
        vector_results, chunks_by_doc = compress_chunks_to_docs(raw_chunks, limit)
        results = vector_results
    else:
        t0 = time.perf_counter()
        text_results = await search_text(session, q, limit)
        timing["text_ms"] = (time.perf_counter() - t0) * 1000

        if mode == "hybrid":
            t1 = time.perf_counter()
            raw_chunks = await search_vector(session, q, limit)
            timing["vector_ms"] = (time.perf_counter() - t1) * 1000

            # chunk-level → doc-level 압축 (raw chunks는 chunks_by_doc에 보존)
            t1b = time.perf_counter()
            vector_results, chunks_by_doc = compress_chunks_to_docs(raw_chunks, limit)
            timing["compress_ms"] = (time.perf_counter() - t1b) * 1000

            if not vector_results:
                notes.append("vector_search_returned_empty — text-only fallback")

            t2 = time.perf_counter()
            strategy = get_strategy(fusion)
            # fusion은 doc 기준 — 더 넓게 가져옴 (rerank 후보용)
            fusion_limit = max(limit * 5, 100) if rerank else limit
            fused_docs = strategy.fuse(text_results, vector_results, q, fusion_limit)
            timing["fusion_ms"] = (time.perf_counter() - t2) * 1000
            notes.append(f"fusion={strategy.name}")
            notes.append(
                f"chunks raw={len(raw_chunks)} compressed={len(vector_results)} "
                f"unique_docs={len(chunks_by_doc)}"
            )

            if rerank:
                # Phase 1.3: reranker — chunk 기준 입력
                # fusion 결과 doc_id로 chunks_by_doc에서 raw chunks 회수
                t3 = time.perf_counter()
                rerank_input: list[SearchResult] = []
                for doc in fused_docs:
                    chunks = chunks_by_doc.get(doc.id, [])
                    if chunks:
                        # doc당 max 2 chunk (latency/VRAM 보호)
                        rerank_input.extend(chunks[:MAX_CHUNKS_PER_DOC])
                    else:
                        # text-only 매치 doc → doc 자체를 chunk처럼 wrap
                        rerank_input.append(doc)
                    if len(rerank_input) >= MAX_RERANK_INPUT:
                        break
                rerank_input = rerank_input[:MAX_RERANK_INPUT]
                notes.append(f"rerank input={len(rerank_input)}")

                reranked = await rerank_chunks(q, rerank_input, limit * 3)
                timing["rerank_ms"] = (time.perf_counter() - t3) * 1000

                # diversity (chunk → doc 압축, max_per_doc=2, top score>0.90 unlimited)
                t4 = time.perf_counter()
                results = apply_diversity(reranked, max_per_doc=MAX_CHUNKS_PER_DOC)[:limit]
                timing["diversity_ms"] = (time.perf_counter() - t4) * 1000
            else:
                # rerank 비활성: fused_docs를 그대로 (limit 적용)
                results = fused_docs[:limit]
        else:
            results = text_results

    # display score 정규화 — 프론트엔드는 score*100을 % 표시.
    # fusion 내부 score(RRF는 0.01~0.05 범위)를 그대로 노출하면 표시가 깨짐.
    normalize_display_scores(results)

    timing["total_ms"] = (time.perf_counter() - t_total) * 1000

    # confidence는 fusion 적용 전 raw 신호로 계산 (Phase 0.5 이후 fused score는 절대값 의미 없음)
    # rerank 활성 시 reranker score가 가장 신뢰할 수 있는 신호 → 우선 사용
    if mode == "hybrid":
        if rerank and "rerank_ms" in timing:
            confidence_signal = compute_confidence_reranked(results)
        else:
            confidence_signal = compute_confidence_hybrid(text_results, vector_results)
    elif mode == "vector":
        confidence_signal = compute_confidence(vector_results, "vector")
    else:
        confidence_signal = compute_confidence(text_results, mode)

    # 사용자 feedback: 모든 단계 timing은 debug 응답과 별도로 항상 로그로 남긴다
    timing_str = " ".join(f"{k}={v:.0f}" for k, v in timing.items())
    fusion_str = f" fusion={fusion}" if mode == "hybrid" else ""
    logger.info(
        "search query=%r mode=%s%s results=%d conf=%.2f %s",
        q[:80], mode, fusion_str, len(results), confidence_signal, timing_str,
    )

    # Phase 0.3: 실패 자동 로깅 (응답 latency에 영향 X — background task)
    background_tasks.add_task(
        record_search_event, q, user.id, results, mode, confidence_signal
    )

    debug_obj: SearchDebug | None = None
    if debug:
        debug_obj = SearchDebug(
            timing_ms=timing,
            text_candidates=_to_debug_candidates(text_results) if text_results or mode != "vector" else None,
            vector_candidates=_to_debug_candidates(vector_results) if vector_results or mode in ("vector", "hybrid") else None,
            fused_candidates=_to_debug_candidates(results) if mode == "hybrid" else None,
            confidence=confidence_signal,
            notes=notes,
        )

    return SearchResponse(
        results=results,
        total=len(results),
        query=q,
        mode=mode,
        debug=debug_obj,
    )