"""Implement application-layer logic for services."""

from __future__ import annotations

from app.domain.retrieval import RetrievalQuery, Retriever, RetrievedChunk
from app.domain.retrieval.ports import Reranker
# Keep orchestration logic centralized so use-case flow stays easy to trace.


class KnowledgeRetrievalService:
    """Provide the Knowledge Retrieval Service service."""

    def __init__(self, *, retriever: Retriever, reranker: Reranker | None = None, reranker_top_k: int = 5) -> None:
        """Initialize the Knowledge Retrieval Service instance."""
        self.retriever = retriever
        self.reranker = reranker
        self.reranker_top_k = reranker_top_k

    def retrieve(self, *, query: str, top_k: int, filters: str | None = None) -> list[RetrievedChunk]:
        """Retrieve and optionally rerank chunks for a query."""
        candidate_k = top_k if self.reranker is None else max(top_k * 4, 20)
        retrieval_query = RetrievalQuery(query=query, top_k=candidate_k, filters=filters)
        candidates = self.retriever.retrieve(retrieval_query)
        if self.reranker and candidates:
            return self.reranker.rerank(query, candidates, top_k=self.reranker_top_k)
        return candidates[:top_k]