"""
app/core/retriever.py — Semantischer/Hybrid-Retriever (WP-04 / Step 4a, Schritt 1)

Aktueller Stand:
- Reine Chunk-Vektorsuche gegen *_chunks (Qdrant)
- Zwei Modi:
  - semantic_retrieve: used_mode = "semantic"
  - hybrid_retrieve:  used_mode = "hybrid" (aktuell gleiche Kandidatenliste)
- Noch keine Edge-Expansion, kein retriever_weight

Wichtige Design-Entscheidung:
- Wir importieren die benötigten Funktionen NICHT direkt,
  sondern die Module (qdr, qp, ec). Dadurch funktionieren
  Monkeypatches in den Tests (monkeypatch.setattr(qp, "..."), etc.).
"""

from __future__ import annotations

import time
from typing import Any, Dict, List, Tuple

from app.config import get_settings
from app.models.dto import QueryRequest, QueryResponse, QueryHit
import app.core.qdrant as qdr
import app.core.qdrant_points as qp
import app.services.embeddings_client as ec


def _get_client_and_prefix() -> Tuple[Any, str]:
    """
    Liefert (QdrantClient, prefix) basierend auf QdrantConfig.from_env().
    """
    cfg = qdr.QdrantConfig.from_env()
    client = qdr.get_client(cfg)
    return client, cfg.prefix


def _get_query_vector(req: QueryRequest) -> List[float]:
    """
    Liefert den Query-Vektor aus dem Request.

    - Falls req.query_vector gesetzt ist, wird dieser unverändert genutzt.
    - Falls req.query (Text) gesetzt ist, wird ec.embed_text(req.query) aufgerufen.
    - Andernfalls: ValueError.
    """
    if req.query_vector is not None:
        if not isinstance(req.query_vector, list):
            raise ValueError("query_vector muss eine Liste von floats sein")
        return req.query_vector

    if req.query:
        return ec.embed_text(req.query)

    raise ValueError("Weder query_vector noch query gesetzt – mindestens eines ist erforderlich")


def _semantic_hits(
    client: Any,
    prefix: str,
    vector: List[float],
    top_k: int,
    filters: Dict | None,
):
    """
    Kapselt den Aufruf von qp.search_chunks_by_vector.

    Rückgabeformat laut qdrant_points.search_chunks_by_vector:
    [
        (point_id: str, score: float, payload: dict),
        ...
    ]
    """
    flt = filters or None
    hits = qp.search_chunks_by_vector(client, prefix, vector, top=top_k, filters=flt)
    return hits


def _build_hits_from_semantic(
    hits: List[Tuple[str, float, Dict[str, Any]]],
    top_k: int,
    used_mode: str,
) -> QueryResponse:
    """
    Formt rohe Treffer in QueryResponse um.

    Aktueller Step-1-Stand:
    - edge_bonus       = 0.0
    - centrality_bonus = 0.0
    - total_score      = semantic_score
    """
    t0 = time.time()
    # defensiv sortieren, auch wenn Qdrant selbst sortiert
    sorted_hits = sorted(hits, key=lambda h: float(h[1]), reverse=True)
    limited = sorted_hits[: max(1, top_k)]

    results: List[QueryHit] = []
    for pid, semantic_score, payload in limited:
        note_id = payload.get("note_id")
        path = payload.get("path")
        section = payload.get("section_title")

        edge_bonus = 0.0
        cent_bonus = 0.0
        total = float(semantic_score) + edge_bonus + cent_bonus

        results.append(
            QueryHit(
                node_id=str(pid),
                note_id=note_id,
                semantic_score=float(semantic_score),
                edge_bonus=edge_bonus,
                centrality_bonus=cent_bonus,
                total_score=total,
                paths=None,  # Edge-Paths kommen in einem späteren Schritt hinzu
                source={"path": path, "section": section},
            )
        )

    dt = int((time.time() - t0) * 1000)
    return QueryResponse(results=results, used_mode=used_mode, latency_ms=dt)


def _resolve_top_k(req: QueryRequest) -> int:
    """
    Ermittelt ein sinnvolles top_k:

    - bevorzugt req.top_k, falls > 0
    - sonst Settings.RETRIEVER_TOP_K (Default 10)
    """
    if isinstance(req.top_k, int) and req.top_k > 0:
        return req.top_k
    s = get_settings()
    return max(1, int(getattr(s, "RETRIEVER_TOP_K", 10)))


def semantic_retrieve(req: QueryRequest) -> QueryResponse:
    """
    Reiner semantischer Retriever (ohne Edge-Expansion).
    """
    top_k = _resolve_top_k(req)
    vector = _get_query_vector(req)
    client, prefix = _get_client_and_prefix()
    hits = _semantic_hits(client, prefix, vector, top_k=top_k, filters=req.filters)
    return _build_hits_from_semantic(hits, top_k=top_k, used_mode="semantic")


def hybrid_retrieve(req: QueryRequest) -> QueryResponse:
    """
    Hybrid-Retriever.

    Step-1-Implementierung:
    - nutzt die gleiche semantische Kandidatenliste wie semantic_retrieve
    - setzt lediglich used_mode = "hybrid"
    - Edge-Expansion & Score-Modifikationen folgen in den nächsten Schritten.
    """
    top_k = _resolve_top_k(req)
    vector = _get_query_vector(req)
    client, prefix = _get_client_and_prefix()
    hits = _semantic_hits(client, prefix, vector, top_k=top_k, filters=req.filters)
    return _build_hits_from_semantic(hits, top_k=top_k, used_mode="hybrid")